Semtech (SMTC) 10-Q 5 Sep 14 2015 Q2 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	6 Months Ended
	Jul. 27, 2014	Aug. 29, 2014
Entity Information [Line Items]	'	'
Document Type	'10-Q	'
Document Period End Date	27-Jul-14	'
Amendment Flag	'false	'
Document Fiscal Year Focus	'2015	'
Document Fiscal Period Focus	'Q2	'
Entity Registrant Name	'SEMTECH CORP	'
Entity Central Index Key	'0000088941	'
Current Fiscal Year End Date	'--01-25	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	67,356,515

Condensed_Consolidated_Stateme

Condensed Consolidated Statements Of Income (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Net sales	$145,742	$165,010	$278,601	$327,417
Cost of sales	57,521	64,302	112,296	129,422
Gross profit	88,221	100,708	166,305	197,995
Operating costs and expenses:	'	'	'	'
Selling, general and administrative	31,547	33,315	63,243	68,109
Product development and engineering	28,173	33,125	55,986	67,684
Intangible amortization	6,444	7,211	12,869	15,067
Intangible asset impairments	0	2,600	0	2,600
Restructuring charge	0	0	1,001	0
Total operating costs and expenses	66,164	76,251	133,099	153,460
Operating income	22,057	24,457	33,206	44,535
Interest expense, net	-1,588	-10,584	-2,975	-14,644
Non-operating expense, net	-345	-198	-623	-1,005
Income before taxes	20,124	13,675	29,608	28,886
Provision (benefit) for taxes	2,226	-5,437	3,843	-5,003
Net income	$17,898	$19,112	$25,765	$33,889
Earnings per share:	'	'	'	'
Basic (in dollars per share)	$0.27	$0.28	$0.38	$0.50
Diluted (in dollars per share)	$0.26	$0.28	$0.38	$0.49
Weighted average number of shares used in computing earnings per share:	'	'	'	'
Basic (in shares)	67,208	67,614	67,254	67,285
Diluted (in shares)	67,850	69,090	67,888	68,812

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Net income	$17,898	$19,112	$25,765	$33,889
Other comprehensive (loss) income, before tax:	'	'	'	'
Change in unrealized holding loss on available-for-sale investments	-2	-7	-1	-8
Change in unrealized (loss) income on interest rate cap	-51	288	-161	47
Reclassification to interest expense	47	10	80	19
Other comprehensive (loss) income, before tax	-6	291	-82	58
(Provision) benefit for taxes related to items of other comprehensive loss	-16	-106	12	-21
Other comprehensive (loss) income, net of tax	-22	185	-70	37
Total comprehensive income, net of tax	$17,876	$19,297	$25,695	$33,926

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$238,667	$243,194
Accounts receivable, less allowances of $4,754 at July 27, 2014 and $3,825 at January 26, 2014	68,468	66,333
Inventories	54,479	60,267
Deferred tax assets	2,998	2,946
Prepaid taxes	2,387	4,993
Other current assets	20,824	15,863
Total current assets	387,823	393,596
Non-current assets:	'	'
Property, plant and equipment, net of accumulated depreciation of $130,690 at July 27, 2014 and $112,610 at January 26, 2014	111,576	110,121
Long-term investments	550	3,674
Deferred tax assets	84	348
Goodwill	276,898	276,898
Other intangible assets, net	128,301	140,944
Other assets	29,124	23,359
TOTAL ASSETS	934,356	948,940
Current liabilities:	'	'
Accounts payable	37,819	40,016
Accrued liabilities	40,519	44,148
Deferred revenue	6,427	7,267
Current portion - long-term debt	18,539	18,529
Deferred tax liabilities	927	930
Total current liabilities	104,231	110,890
Non-current liabilities:	'	'
Deferred tax liabilities	6,802	3,626
Long term debt, less current portion	239,022	273,293
Other long-term liabilities	27,881	25,288
Stockholders’ equity:	'	'
Common stock, $0.01 par value, 250,000,000 shares authorized, 78,136,144 issued and 67,139,327 outstanding on July 27, 2014 and 78,136,144 issued and 67,283,221 outstanding on January 26, 2014	785	785
Treasury stock, at cost, 10,996,817 shares as of July 27, 2014 and 10,852,923 shares as of January 26, 2014	-210,521	-201,152
Additional paid-in capital	366,372	362,121
Retained earnings	399,601	373,836
Accumulated other comprehensive income	183	253
Total stockholders’ equity	556,420	535,843
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$934,356	$948,940

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Allowance for doubtful accounts, receivables	$4,754	$3,825
Accumulated depreciation	$130,690	$112,610
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	78,136,144	78,136,144
Common stock, shares outstanding	67,139,327	67,283,221
Treasury stock, shares	10,996,817	10,852,923

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements Of Cash Flows (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013
Cash flows from operating activities:	'	'
Net income	$25,765	$33,889
Adjustments to reconcile net income to net cash provided by operating activities, net of effects of acquisitions:	'	'
Depreciation, amortization and impairments	24,030	28,937
Effect of acquisition fair value adjustments	0	2,529
Accretion of deferred financing costs and debt discount	511	1,010
Write off deferred financing costs & debt discount	0	8,773
Deferred income taxes	3,143	-6,529
Stock-based compensation	13,121	14,782
Gain on disposition of property, plant and equipment	-14	-27
Changes in assets and liabilities:	'	'
Accounts receivable, net	-2,135	-11,435
Inventories	5,816	-5,659
Prepaid expenses and other assets	-4,247	46
Accounts payable	-2,544	-2,479
Accrued liabilities	-1,681	-10,140
Deferred revenue	-840	1,532
Income taxes payable and prepaid taxes	-1,839	-1,389
Other liabilities	2,051	4,605
Net cash provided by operating activities	61,137	58,445
Cash flows from investing activities:	'	'
Purchases of available-for-sale investments	0	-1,050
Proceeds from sales and maturities of available-for-sale investments	3,124	8,998
Proceeds from sales of property, plant and equipment	71	57
Purchase of property, plant and equipment	-12,662	-23,565
Purchase of intangible assets	-1,000	-2,583
Purchase of cost method investment	-3,264	0
Net cash used in investing activities	-13,731	-18,143
Cash flows from financing activities:	'	'
Proceeds of debt issue, net of discount	0	326,448
Deferred financing cost	0	-2,085
Payment for employee stock-based compensation payroll taxes	-3,533	-5,148
Proceeds from exercises of stock options	5,975	13,476
Repurchase of outstanding common stock	-20,000	0
Payment of long term debt	-34,375	-359,125
Net cash used in financing activities	-51,933	-26,434
Net (decrease) increase in cash and cash equivalents	-4,527	13,868
Cash and cash equivalents at beginning of period	243,194	223,192
Cash and cash equivalents at end of period	$238,667	$237,060

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	6 Months Ended
	Jul. 27, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization and Basis of Presentation	'
	Organization and Basis of Presentation
	Nature of Business
	Semtech is a global supplier of high performance analog and mixed-signal semiconductor products. The end-customers for the Company’s products are primarily original equipment manufacturers (“OEMs”) that produce and sell electronics.
	The Company designs, develops and markets a wide range of products for commercial applications, the majority of which are sold into the enterprise computing, communications, high-end consumer and industrial end-markets. The Company’s classification of sales by end-market requires significant judgment by management, since many of its products are used across multiple platforms and support multiple end-markets.
	Enterprise Computing: datacenters, passive optical networks, storage networks, optical receiver and transceiver, servers, desktops, notebooks, servers, graphic boards, monitors, printers and other computer peripherals.
	Communications: base stations, backplane, optical networks, carrier networks, switches and routers, cable modems, signal conditioners, wireless local area network (“LAN”) and other communication infrastructure equipment.
	High-End Consumer: smart phones and other handheld products, set-top boxes, digital televisions, tablets, wearable devices, digital video recorders and other consumer equipment.
	Industrial: broadcast studio equipment, automated meter reading, military and aerospace, medical, security systems, automotive, industrial and home automation, video security and surveillance and other industrial equipment.
	Fiscal Year
	The Company reports results on the basis of 52 and 53 week periods and ends its fiscal year on the last Sunday in January. The other quarters generally end on the last Sunday of April, July and October. All quarters consist of 13 weeks except for one 14-week period in 53-week years. The second quarter of fiscal years 2015 and 2014 each consisted of 13 weeks.
	Principles of Consolidation
	The accompanying interim condensed consolidated financial statements of Semtech have been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). In the opinion of the Company, these unaudited statements contain all adjustments (consisting of normal recurring adjustments) necessary to present fairly, in all material respects, the financial position of Semtech for the interim periods presented. All significant intercompany balances have been eliminated. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been condensed or omitted pursuant to such rules and regulations, and the Company believes that the included disclosures are adequate to make the information presented not misleading. The Company evaluated all subsequent events through the date these condensed consolidated financial statements were issued.
	These interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended January 26, 2014. The results reported in these interim condensed consolidated financial statements should not be regarded as indicative of results that may be expected for any subsequent period or for the entire year.
	Segment Information
	In the second quarter of fiscal year 2015, the Company completed the reassessment of its operations in light of its recent restructuring efforts (discussed in Note 16). Based on this reassessment, the Company has identified four operating segments in total. Three of the operating segments aggregate into one reportable segment. The remaining operating segment could not be aggregated with the other operating segments and did not meet the criteria for a separate reportable segment as defined by the guidance regarding segment disclosure. The Company’s Chief Executive Officer (“CEO”) has been identified as the Chief Operating Decision Maker (“CODM”) as defined by the segment disclosure guidance (see Note 14 for further discussion) and now receives discrete financial information pertaining to the Systems Innovation group. As a result, beginning with the second quarter of fiscal 2015, the financial activity associated with the Systems Innovation group will be reported separately from the Company's reportable segment. This separate reporting is included in the "All others" category. The historical activity of the reportable segment has been recast for consistent presentation for the three and six months periods ended July 27, 2014 and July 28, 2013.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize revenue from the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance addresses, in particular, contracts with more than one performance obligation, as well as the accounting for some costs to obtain or fulfill a contract with a customer, and provides for additional disclosures with respect to revenues and cash flows arising from contracts with customers. Public entities are required to apply the amendments on either a full- or modified-retrospective basis for annual periods beginning after December 15, 2016 and for interim periods within those annual periods. Early adoption is not permitted. The Company is currently assessing the basis of adoption and evaluating the impact of the adoption of the update on its consolidated financial statements.

Earnings_Per_Share

Earnings Per Share	6 Months Ended
	Jul. 27, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Earnings per Share
	The computation of basic and diluted earnings per common share is as follows:
		Three Months Ended				Six Months Ended
	(in thousands, except per share amounts)	July 27,		July 28,		July 27,		July 28,
		2014		2013		2014		2013
	Net income	$	17,898	$	19,112	$	25,765	$	33,889
	Weighted average common shares outstanding - basic	67,208		67,614		67,254		67,285
	Dilutive effect of options and restricted stock units	642		1,476		634		1,527
	Weighted average common shares outstanding - diluted	67,850		69,090		67,888		68,812
	Basic earnings per common share	$	0.27	$	0.28	$	0.38	$	0.5
	Diluted earnings per common share	$	0.26	$	0.28	$	0.38	$	0.49
	Anti-dilutive shares not included in the above calculations	1,463		352		1,427		392
	Basic earnings per common share is computed by dividing income available to common stockholders by the weighted-average number of shares of common stock outstanding during the reporting period. Diluted earnings per common share incorporates the incremental shares issuable, calculated using the treasury stock method, upon the assumed exercise of stock options and the vesting of restricted stock.

Revenue_Recognition

Revenue Recognition	6 Months Ended
	Jul. 27, 2014
Revenue Recognition [Abstract]	'
Revenue Recognition	'
	Revenue Recognition
	The Company recognizes product revenue when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable and collectability is reasonably assured. Recovery of costs associated with product design and engineering services are recognized during the period in which services are performed. The product design and engineering recovery, when recognized, will be reported as a reduction to product development and engineering expense. Historically, these recoveries have not exceeded the cost of the related development efforts.
	The Company includes revenue related to granted technology licenses in “Net sales” within the condensed consolidated statements of income. Historically, revenue from these arrangements has not been significant though it is part of the Company’s recurring ordinary business.
	The Company defers revenue recognition on shipment of products to certain customers, principally distributors, under agreements which provide for limited pricing credits or return privileges, until these products are sold through to end-users or the return privileges lapse. For sales subject to certain pricing credits or return privileges, the amount of future pricing credits or inventory returns cannot be reasonably estimated given the relatively long period in which a particular product may be held by the customer. Therefore, the Company has concluded that sales to customers under these agreements are not fixed and determinable at the date of the sale and revenue recognition has been deferred. The Company estimates the deferred gross margin on these sales by applying an average gross profit margin to the actual gross sales. The average gross profit margin is calculated for each category of material using standard costs which is expected to approximate actual costs at the date of sale. The estimated deferred gross margins on these sales, where there are no outstanding receivables, are included in “Deferred revenue” within the condensed consolidated balance sheets.
	The Company records a provision for estimated sales returns and rebates in the same period as the related revenues are recorded. The Company bases these estimates on historical sales returns, rebates and other known factors. Actual returns could be different from Company estimates and current provisions for sales returns and allowances, resulting in future charges to earnings. There were no significant impairments of deferred cost of sales in the second quarter of fiscal year 2015 or fiscal year 2014.

StockBased_Compensation

Stock-Based Compensation	6 Months Ended
	Jul. 27, 2014
Share-based Compensation [Abstract]	'
Stock-Based Compensation	'
	Stock-Based Compensation
	Financial Statement Effects and Presentation. The following table summarizes pre-tax, stock-based compensation expense included in the unaudited condensed consolidated statements of income captions for the three and six months ended July 27, 2014 and July 28, 2013.
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,				July 28,
		2014				2013				2014				2013
	Cost of sales	$	355			$	405			$	718			$	733
	Selling, general and administrative	3,448				3,548				7,513				8,430
	Product development and engineering	2,472				2,203				4,891				5,619
	Stock-based compensation, pre-tax	$	6,274			$	6,156			$	13,121			$	14,782
	Net change in stock-based compensation capitalized into inventory	$	37			$	8			$	28			$	85
	Share-based Payment Arrangements
	The Company has various equity award plans that provide for granting stock-based awards to employees and non-employee directors of the Company. The plans provide for the granting of several available forms of stock-based compensation. As of July 27, 2014, the Company has granted stock options, restricted stock and restricted stock units under the plans and has also issued some stock-based compensation outside of the plans, including stock options, restricted stock and restricted stock units issued as inducements to join the Company.
	Grant Date Fair Values and Underlying Assumptions; Contractual Terms
	The Company uses the Black-Scholes pricing model to value stock options. The estimated fair value of restricted stock units, for which vesting is not linked to a market condition, is calculated based on the market price of the Company’s common stock on the date of grant. For restricted stock units that vest according to a market condition, the Company uses a Monte Carlo simulation model to value the award.
	Some of the restricted stock units granted in the first six months of fiscal year 2015 and prior years are classified as liabilities rather than equity. For grants classified as equity, stock-based compensation cost is measured at the grant date, based on the fair value of the award, and is recognized as an expense over the grantee’s requisite service period. For grants classified as liabilities, stock-based compensation cost is measured at fair value at the end of each reporting date until the date of settlement, and is recognized as an expense over the grantee’s requisite service period. Expected volatilities are based on historical volatility using daily and monthly stock price observations.
	The following table summarizes the assumptions used in the Black-Scholes model to determine the fair value of stock options granted in the three and six months ended July 27, 2014 and July 28, 2013:
		Three Months Ended				Six Months Ended
		July 27,		July 28,		July 27,		July 28,
		2014		2013		2014		2013
	Expected lives, in years	4.3 - 4.4		4.7		3.0 - 4.4		4.2 - 4.7
	Estimated volatility	33%		33%		33% - 34%		33% - 35%
	Dividend yield	—		—		—		—
	Risk-free interest rate	1.30% - 1.43%		1.30%		1.26% - 1.43%		0.65% - 1.30%
	Weighted average fair value on grant date	$7.43		$10.59		$7.26		$9.33
	Stock Option Awards. The Company has historically granted stock options to both employees and non-employee directors. The fair value of these grants was measured on the grant date and is being recognized as an expense over the requisite vesting period (typically 3-4 years).
	The following table summarizes the activity for stock options for the six months ended July 27, 2014:
	(in thousands, except for per share amounts)	Number			Weighted				Aggregate				Aggregate				Number of	Weighted
		of			Average				Intrinsic				Unrecognized				Shares	Average
		Shares			Exercise				Value				Compensation				Exercisable	Contractual
					Price													Term
					(per share)													(in years)
	Balance at January 26, 2014	1,935			$	21.33			$	7,722			$	4,354			1,275
	Options granted	261			24.92
	Options exercised	(353	)		16.94				3,102
	Options cancelled/forfeited	(31	)		26.71
	Balance at July 27, 2014	1,812			22.61				4,425				$	4,846			1,112
	Exercisable at July 27, 2014	1,112			$	19.58			$	4,383								2.4
	Restricted Stock. The Company has not granted any restricted stock to employees since fiscal year 2009. There is no outstanding and unvested restricted stock as of July 27, 2014.
	Performance-based Restricted Stock Units. The Company grants performance-based restricted stock units to select employees. These awards have a performance condition in addition to a service condition. The performance metrics are determined based on a pre-defined cumulative three-year performance of the Company’s revenue and operating income measured against internal goals. The performance-based unit which is granted in any fiscal year will be tied to the Company’s performance of that fiscal year and the succeeding two fiscal years.  The performance-based unit award recipient must be employed for the entire three-year period, which is the requisite service period, and be an active employee at the time of vesting of the awards (cliff vesting at the end of the third year). Under the terms of these awards, assuming the highest performance level of 200% with no cancellations due to forfeitures, the maximum number of shares that can be earned would be 522,532 shares and an additional 522,532 shares would be settled in cash. The Company would have a liability accrued under “Other liabilities” within the condensed consolidated balance sheets equal to the value of 522,532 shares on the settlement date, which would be settled in cash. Only cash performance-based unit awards are classified as liabilities and the value of these awards is re-measured at each reporting date. At July 27, 2014, the performance metrics associated with the outstanding awards issued in fiscal years 2015, 2014 and 2013 are expected to be met at a level which would result in a grant at 100%, 87%, and 0% of target, respectively.
	The following table summarizes the activity for performance-based restricted stock units for the first six months ended July 27, 2014:
					Subject to			Subject to							Weighted			Aggregate		Period Over
					Share Settlement			Cash Settlement							Average					Which Expected
															Grant Date
	(in thousands, except for per unit amounts)	Total			Units			Units			Recorded				Fair Value			Unrecognized		to be Recognized
		Units									Liability				(per unit)			Compensation		(in years)
	Balance at January 26, 2014	376			192			184			$	1,305			$	28.5		$	3,893	1.3
	Performance-based units granted	256			128			128							24.74
	Performance-based units vested	(93	)		(52	)		(41	)						23.36
	Performance-based units cancelled/forfeited	(17	)		(9	)		(8	)						25.51
	Change in liability										(318		)
	Balance at July 27, 2014	522			259			263			$	987			$	27.57		$	7,577	1.9
	The liability associated with performance-based restricted stock units, which is recorded in “Other liabilities” within the condensed consolidated balance sheets, has been reduced by $0.3 million in the first six months of fiscal year 2015 due to vesting in the first quarter of fiscal year 2014, forfeitures, re-measurement adjustments and change in the expected performance results.
	Market Performance Units. On February 26, 2014, the Company granted its CEO restricted stock units with a market performance condition. The award is eligible to vest during the period commencing February 26, 2014 and ending February 26, 2019 (the “Performance Period”) as follows: 30% of the restricted stock units covered by the award will vest if, during any consecutive 120 calendar day period that commences and ends during the Performance Period, the average per-share closing price of the Company’s common stock equals or exceeds $35.00 (“Tranche 1”) and the award will vest in full if, during any consecutive 120 calendar day period that commences and ends during the Performance Period, the average per-share closing price of the Company’s common stock equals or exceeds $40.00 (“Tranche 2”). The award will also vest if a majority change in control of the Company occurs during the Performance Period and, in connection with such event, the Company’s stockholders become entitled to receive per-share consideration having a value equal to or greater than $40.00.
	The following tables summarize the assumptions used in the Monte Carlo simulation model to determine the fair value of restricted stock units granted in the first quarter of fiscal year 2015 for both Tranche 1 and Tranche 2. The Company did not grant any restricted stock units that vest according to a market performance conditions in the second quarter of fiscal year 2015. The Company did not grant any restricted stock units that vest according to a market performance condition in the three and six months ended July 28, 2013.
	Tranche 1:
		Six Months Ended
		July 27, 2014
	Expected lives, in years	1.6
	Estimated volatility	34%
	Dividend yield	—
	Risk-free interest rate	1.50%
	Fair value on grant date	$17.26
	Tranche 2:
	Six Months Ended
	July 27, 2014
Expected lives, in years	2.1
Estimated volatility	34%
Dividend yield	—
Risk-free interest rate	1.50%
Fair value on grant date	$14.88
The following table summarizes the activity for market performance units for the six months ended July 27, 2014:
				Weighted				Aggregate				Period Over
				Average								Which Expected
				Grant Date
(in thousands, except for per unit amounts)	Total			Fair Value				Unrecognized				to be Recognized
	Units			(per unit)				Compensation				(in years)
Balance at January 26, 2014	—			$	—			$	—			0
Market performance units granted	220			15.59
Market performance units vested	—			—
Market performance units cancelled/forfeited	—			—
Balance at July 27, 2014	220			$	15.59			$	2,664			1.5
Restricted Stock Units, Employees. The Company grants restricted stock units to employees which are expected to be settled with stock. The grant date for these awards is equal to the measurement date. These awards are valued as of the measurement date and recognized as an expense over the requisite vesting period (typically 4 years).
The following table summarizes the employees’ restricted stock unit activity for the six months ended July 27, 2014:
(in thousands, except for per unit amounts)	Number of			Weighted Average				Aggregate				Aggregate				Weighted Average
	Units			Grant Date				Intrinsic				Unrecognized				Period Over
				Fair Value				Value (1)				Compensation				Which Expected
				(per unit)												to be Recognized
																(in years)
Balance at January 26, 2014	2,195			$	27.18							$	49,563			2.5
Restricted stock units granted	333			24.18
Restricted stock units vested	(319	)		27.37				$	7,905
Restricted stock units forfeited	(142	)		26.65
Balance at July 27, 2014	2,067			$	26.71							$	44,313			2.3
-1	Reflects the value of Semtech stock on the date that the restricted stock unit vested.
Restricted Stock Units, Non-Employee Directors. The Company grants restricted stock units to non-employee directors. These restricted stock units are accounted for as liabilities and accrued under “Other liabilities” in the condensed consolidated balance sheets because they are cash settled. These awards are vested after 1 year of service. However, because these awards are not typically settled until a non-employee director’s separation from service, the value of these awards is re-measured at the end of each reporting period until settlement.
The following table summarizes the non-employee directors’ activity for stock units for the six months ended July 27, 2014:
(in thousands, except for per unit amounts)	Number of			Recorded				Weighted Average				Aggregate				Period Over
	Units			Liability				Grant Date				Unrecognized				Which Expected
								Fair Value				Compensation				to  be Recognized
								(per unit)								(in years)
Balance at January 26, 2014	18			$	3,981			$	35.17			$	177			0.4
Restricted stock units granted	24							26.59
Restricted stock units vested	(18	)						35.17
Restricted stock units forfeited	—							—
Change in liability				(39		)
Balance at July 27, 2014	24			$	3,942			$	26.59			$	478			0.9
As of July 27, 2014, the total number of vested but unsettled restricted stock units for non-employee directors is 179,092 units. The liability associated with these awards as of July 27, 2014 and January 26, 2014, respectively, is included in “Other liabilities” within the condensed consolidated balance sheets.

Investments

Investments	6 Months Ended
	Jul. 27, 2014
Investments [Abstract]	'
Investments	'
	Investments
	Investments that have original maturities of three months or less are accounted for as cash equivalents. This includes money market funds, time deposits and United States (“U.S.”) government obligations. Temporary and long-term investments consist of government, bank and corporate obligations, and bank time deposits with original maturity dates in excess of three months. Temporary investments have original maturities in excess of three months, but mature within twelve months of the balance sheet date. Long-term investments have original maturities in excess of twelve months. The Company determines the cost of securities sold based on the specific identification method. Realized gains or losses are reported in “Non-operating expense, net” within the condensed consolidated statements of income.
	The Company classifies its investments as “available-for-sale” because it may sell some securities prior to maturity. The Company’s investments are subject to market risk, primarily interest rate and credit risks. The Company’s investments are managed by a limited number of outside professional managers that operate within investment guidelines set by the Company. These guidelines include specified permissible investments, minimum credit quality ratings and maximum average duration restrictions and are intended to limit market risk by restricting the Company’s investments to high quality debt instruments with relatively short-term maturities.
	As of July 27, 2014, all of the Company’s long-term investments mature on various dates through fiscal year 2016.
	The following table summarizes the Company’s available-for-sale investments:
		July 27, 2014								January 26, 2014
	(in thousands)	Market Value			Adjusted			Gross		Market Value			Adjusted		Gross
					Cost			Unrealized Gain					Cost		Unrealized
															Gain
	Agency securities	$	550		$	550		$	—	$	3,674		$	3,673	$	1
	Total investments	$	550		$	550		$	—	$	3,674		$	3,673	$	1
	Agency securities are specific securities that are issued by U.S. government agencies such as Ginnie Mae, Fannie Mae, Freddie Mac or the Federal Home Loan Banks. Due to the expectation of federal backing, these securities usually hold the highest credit rating possible.
	The following table summarizes the maturities of the Company’s available-for-sale investments:
		27-Jul-14						January 26, 2014
	(in thousands)	Market Value			Adjusted Cost			Market Value		Adjusted Cost
	Within 1 year	$	—		$	—		$	—	$	—
	After 1 year through 5 years	550			550			3,674		3,673
	Total investments	$	550		$	550		$	3,674	$	3,673
	Unrealized gains and losses are the result of fluctuations in the market value of the Company’s available-for-sale investments and are included in “Accumulated other comprehensive income” within the condensed consolidated balance sheets. The following table summarizes net unrealized losses arising in the periods presented in addition to the tax associated with these comprehensive income items:
		Three Months Ended						Six Months Ended
	(in thousands)	July 27,			July 28,			July 27,		July 28,
		2014			2013			2014		2013
	Unrealized loss, net of tax	$	(1	)	$	(4	)	$	—	$	(5	)
	Increase to deferred tax liability	(1		)	(3		)	—		(3		)
	The following table summarizes interest income generated from investments and cash and cash equivalents:
		Three Months Ended						Six Months Ended
	(in thousands)	July 27,			July 28,			July 27,		July 28,
		2014			2013			2014		2013
	Interest income	$	12		$	91		$	20	$	191
	The Company has investments in two privately held companies. The Company accounts for these equity investments under the cost method of accounting since it does not have the ability to exercise significant influence over the investees. These equity investment interests are included in “Other assets” within the condensed consolidated balance sheet as of July 27, 2014.
	(in thousands)	Equity Investment
	Balance at January 26, 2014	$	5,000
	Additions	3,264
	Balance at July 27, 2014	$	8,264

Fair_Value_Measurements

Fair Value Measurements	6 Months Ended
	Jul. 27, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Instruments Measured at Fair Value on a Recurring Basis
	Financial assets measured and recorded at fair value on a recurring basis consisted of the following types of instruments:
		Fair Value as of July 27, 2014								Fair Value as of January 26, 2014
	(in thousands)	Total		(Level 1)		(Level 2)		(Level 3)		Total		(Level 1)		(Level 2)		(Level 3)
	Agency securities	$	550	$	—	$	550	$	—	$	3,674	$	—	$	3,674	$	—
	Total available-for-sale securities	550		—		550		—		3,674		—		3,674		—
	Interest rate cap	155		—		155		—		316		—		316		—
	Total financial assets	$	705	$	—	$	705	$	—	$	3,990	$	—	$	3,990	$	—
	Available-for-sale securities included in Level 2 are valued utilizing inputs obtained from an independent service (the “Service”), which uses quoted market prices for identical or comparable instruments rather than direct observations of quoted prices in active markets. The Service gathers observable inputs for all of our fixed income securities from a variety of industry data providers, for example, large custodial institutions and other third-party sources. Once the observable inputs are gathered by the Service, all data points are considered and an average price is determined. The Service’s providers utilize a variety of inputs to determine their quoted prices. The Company reviews and evaluates the values provided by the Service and agrees with the valuation methods and assumptions used in determining the fair value of investments. The Company believes this method provides a reasonable estimate for fair value.
	The fair value of the interest rate cap at July 27, 2014 is estimated as described in Note 10 and is included in “Other assets” within the condensed consolidated balance sheets.
	Financial assets measured and recorded at fair value on a recurring basis were presented on the Company’s condensed consolidated balance sheets as follows:
		Fair Value as of July 27, 2014								Fair Value as of January 26, 2014
	(in thousands)	Total		(Level 1)		(Level 2)		(Level 3)		Total		(Level 1)		(Level 2)		(Level 3)
	Long-term investments	$	550	$	—	$	550	$	—	$	3,674	$	—	$	3,674	$	—
	Other assets	155		—		155		—		316		—		316		—
	Total financial assets	$	705	$	—	$	705	$	—	$	3,990	$	—	$	3,990	$	—
	During the six months ended July 27, 2014, the Company had no transfers of financial assets or liabilities between Level 1, Level 2 or Level 3. As of July 27, 2014 and January 26, 2014, the Company had not elected the fair value option for any financial assets and liabilities for which such an election would have been permitted.
	Instruments Not Recorded at Fair Value on a Recurring Basis
	Some of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts that approximate fair value due to their liquid or short-term nature. Such financial assets and financial liabilities include cash and cash equivalents, receivables, net, certain other assets, accounts payable, accrued expenses, accrued personnel costs, and other current liabilities.
	The Company’s long-term debt is not recorded at fair value on a recurring basis, but is measured at fair value for disclosure purposes. The fair value of the Company’s Term Loans (as defined herein) is $105.0 million and $114.3 million and Revolving Commitments (as defined herein) is $152.6 million and $177.5 million at July 27, 2014 and January 26, 2014, respectively. These are based on Level 2 inputs which are derived from transactions with similar amounts, maturities, credit ratings and payment terms.
	Assets and Liabilities Recorded at Fair Value on a Non-Recurring Basis
	The Company reduces the carrying amounts of its goodwill, intangible assets, long-lived assets and non-marketable equity securities to fair value when held for sale or determined to be impaired.
	For its investment in equity interests, the Company has not identified events or changes in circumstances that may have a significant adverse effect on the fair value of its cost method investments during the first six months of fiscal year 2015.

Inventories

Inventories	6 Months Ended
	Jul. 27, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	Inventories
	Inventories, consisting of material, material overhead, labor, and manufacturing overhead, are stated at the lower of cost (first-in, first-out) or market and consist of the following:
	(in thousands)	July 27, 2014		January 26, 2014
	Raw materials	$	1,769	$	1,971
	Work in progress	37,256		45,508
	Finished goods	15,454		12,788
	Inventories	$	54,479	$	60,267
	During the first six months of fiscal year 2015 and in the fourth quarter of fiscal year 2014, the Company reduced the cost basis of inventories by $1.1 million and $15.0 million, respectively, as a result of its strategic decision made in the fourth quarter of fiscal year 2014 to reduce investments in the long-haul optical market.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	6 Months Ended
	Jul. 27, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets	'
	Goodwill and Intangible Assets
	Goodwill – Changes in the carrying amount of goodwill were as follows:
	(in thousands)	Signal Integrity				Signal, Integrity and Timing				Wireless and Sensing				Wireless, Sensing and Timing				Total
	Balance as of January 26, 2014	$	—			$	261,891			$	15,007			$	—			$	276,898
	Transfers	261,891				(261,891		)		(15,007		)		15,007				—
	Balance at July 27, 2014	$	261,891			$	—			$	—			$	15,007			$	276,898
	On January 27, 2014, the Timing product line was integrated with the Wireless and Sensing reporting unit to form the Wireless, Sensing and Timing reporting unit. Simultaneously, the Signal, Integrity and Timing reporting unit was reorganized into the Signal Integrity reporting unit. No portion of the goodwill associated with the previous Signal, Integrity and Timing reporting unit, which originated with the March 2012 acquisition of Gennum Corporation, was allocated to the Timing product line as it was never integrated into the Signal, Integrity and Timing reporting unit. In reaching this conclusion, the Company considered the events leading up to the multiple reorganizations and the short time span between the December 2013 and January 27, 2014 reorganizations.
	Goodwill is not amortized, but is tested for impairment using a two-step method on an annual basis and whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The recoverability of goodwill is measured at the reporting unit level by comparing the reporting unit’s carrying amount, including goodwill, to the fair market value of the reporting unit.
	Goodwill is allocated to two reporting units (Signal Integrity and Wireless, Sensing and Timing). These reporting units also represent the related operating segment since segment management who report to the CODM regularly review operating results and make resource allocation decisions at this level. The difference between the fair value and the carrying amount of these reporting units is one of several factors the Company will consider before reaching its conclusion about whether to perform the first step of the goodwill impairment test. No Goodwill is allocated to the newly identified Systems Innovation Group operating segment (see Note 14).
	Goodwill was tested for impairment as of November 30, 2013 at the reporting unit level, the date of the Company’s annual impairment review. The Company estimated the fair values using an income approach, as well as other generally accepted valuation methodologies. The cash flows for each reporting unit were based on discrete financial forecasts developed by management for planning purposes. Cash flows beyond the discrete forecasts were estimated using a terminal value calculation, which incorporated historical and forecasted financial trends for each identified reporting unit and considered perpetual earnings growth rates for publicly traded peer companies.
	Goodwill is measured at fair value on a non-recurring basis. That is, goodwill is not measured at fair value on an ongoing basis, but is subject to fair value adjustments using Level 3 inputs in certain circumstances (e.g. when there is evidence of impairment). At July 27, 2014, the Company concluded that there were no indicators of such impairment.
	Purchased Intangibles – The following table sets forth the Company’s finite-lived intangible assets resulting from business acquisitions and technology licenses purchased, which continue to be amortized:
				July 27, 2014												January 26, 2014
	(in thousands)	Estimated		Gross				Accumulated				Net Carrying				Gross				Accumulated			Net Carrying
		Useful Life		Carrying				Amortization				Amount				Carrying				Amortization			Amount
				Amount												Amount
	Core technologies	2-10 years		$	146,925			$	(45,817	)		$	101,108			$	146,925			$	(35,357	)	$	111,568
	Customer relationships	7-10 years		28,630				(9,579		)		19,051				28,630				(7,505		)	21,125
	Technology licenses (1)	5-10 years		4,842				(1,103		)		3,739				3,842				(367		)	3,475
	Other intangibles assets	1-5 years		6,600				(6,197		)		403				6,600				(5,824		)	776
	Total finite-lived intangible assets			$	186,997			$	(62,696	)		$	124,301			$	185,997			$	(49,053	)	$	136,944
	-1	Technology licenses relate to in-license agreements for intellectual property that is used by the Company in research and development activities and also has alternative future uses. Amortization expense related to technology licenses is reported as “Product development and engineering” in the condensed consolidated statements of income.
	The Company’s finite-lived intangible assets resulting from purchases, additions from acquisitions, and transfers from In-process Research and Development (“IPR&D”) was $187.0 million and $186.0 million as of July 27, 2014 and January 26, 2014, respectively.
	For the three months ended July 27, 2014 and July 28, 2013, amortization expense related to acquired finite-lived intangible assets was $6.4 million and $7.2 million, respectively. For the six months ended July 27, 2014 and July 28, 2013, amortization expense related to finite-lived intangible assets was $12.9 million and $15.1 million, respectively. Amortization expense related to acquired finite-lived intangible assets is reported as “Intangible amortization and impairments” in the condensed consolidated statements of income.
	The estimated annual amount of future amortization expense for all finite-lived intangible assets will be as follows:
	(in thousands)
	To be recognized in:	Core Technologies				Customer Relationships				Technology Licenses				Other Intangibles				Total
	Remaining six months of fiscal year 2015	$	10,459			$	2,075			$	898			$	310			$	13,742
	Fiscal year 2016	20,919				4,149				1,798				93				26,959
	Fiscal year 2017	20,919				4,149				1,043				—				26,111
	Fiscal year 2018	20,919				4,130				—				—				25,049
	Fiscal year 2019	17,507				4,000				—				—				21,507
	Thereafter	10,385				548				—				—				10,933
	Total expected amortization expense	$	101,108			$	19,051			$	3,739			$	403			$	124,301
	At July 27, 2014 and January 26, 2014, the Company had a total of $4.0 million of indefinite-lived intangible assets consisting of IPR&D from previous acquisitions for which development is continuing.
	The Company reviews indefinite-lived intangible assets for impairment annually or whenever events or changes in circumstances indicate the carrying value may not be recoverable. Recoverability of indefinite-lived intangible assets is measured by comparing the carrying amount of the asset to the future discounted cash flows the asset is expected to generate.
	Indefinite-lived intangible assets are measured at fair value on a non-recurring basis using Level 3 inputs in certain circumstances (e.g. when there is evidence of impairment). At July 27, 2014 the Company concluded that there were no indicators of impairment. During the three month period ending July 28, 2013, the Company made the strategic decision to discontinue development of microwave products which resulted in the Company recording a $2.6 million impairment to IPR&D from the acquisition of Sierra Monolithics, Inc.

Credit_Facilities

Credit Facilities	6 Months Ended
	Jul. 27, 2014
Debt Instruments [Abstract]	'
Credit Facilities	'
	Credit Facilities
	On March 20, 2012, Semtech Corporation entered into a credit agreement with certain lenders (the “Prior Lenders”) and Jefferies Finance LLC, as administrative and collateral agent (the “Prior Credit Agreement”). Pursuant to the Prior Credit Agreement, the Prior Lenders provided the Company with senior secured first lien credit facilities in an aggregate principal amount of $350.0 million (the “Prior Credit Facilities”), consisting of term A loans in an aggregate principal amount of $100.0 million (the “Term A Loans”) and term B loans in an aggregate principal amount of $250.0 million (the “Term B Loans”). The initial carrying amounts totaled $99.5 million (net of original issue discount of $0.5 million) for the Term A Loans and $247.5 million (net of original issue discount of $2.5 million) for the Term B Loans.
	On May 2, 2013 (the “Closing Date”), Semtech Corporation, with each of its domestic subsidiaries as guarantors (the “Guarantors”), entered into a new Credit Agreement (the “New Credit Agreement”) with the lenders referred to therein (the “Lenders”) and HSBC Bank USA, National Association, as administrative agent and as swing line lender and letter of credit issuer. In accordance with the New Credit Agreement, the Lenders provided Semtech with senior secured first lien credit facilities in an aggregate principal amount of $400.0 million (the “New Facilities”) for a five year term, consisting of term loans in an aggregate principal amount of $150.0 million (the “Term Loans”) and revolving line of credit commitments in an aggregate principal amount of $250.0 million (the “Revolving Commitments”). The Revolving Commitments can be used as follows: up to $40.0 million for letters of credit, up to $25.0 million for swing line loans (as defined below), and up to $40.0 million for revolving loans and letters of credit in certain currencies other than U.S. Dollars (“Alternative Currencies”). Swing line loans are Base Rate (as defined below) loans made in immediately available funds denominated in dollars by a swing line lender in its sole and absolute discretion. As of July 27, 2014, there were no amounts outstanding under the letters of credit, swing line loans, and Alternative Currencies.
	At the Closing Date, $326.6 million of borrowings were outstanding under the New Facilities consisting of $149.3 million of Term Loans and $177.3 million of Revolving Commitments, net of $1.4 million of debt discounts resulting from amounts paid to the Lenders. As a result of debt refinancing and changes in some of the Lenders, $0.8 million of debt discounts were expensed in the second quarter of fiscal year 2014 and $0.6 million was capitalized as of May 2, 2013 and is being amortized using the effective interest method over the five year term of the New Credit Agreement. The expense is included in “Interest expense, net” in the condensed consolidated statements of income. The proceeds from the New Credit Facilities were used to repay in full the outstanding obligations of $327.5 million under the Prior Credit Facilities, which was terminated. The portion of the transaction associated with Prior Lenders was accounted for as a debt modification.
	Deferred financing costs incurred in the second quarter of fiscal year 2014, in connection with the New Facilities, were approximately $2.2 million, of which $1.0 million was expensed, inclusive of certain legal costs directly related to the refinancing. Of this amount $1.2 million was capitalized and is being amortized using the effective interest method over the five year term of the New Facilities. The expense is included in “Interest expense, net” in the condensed consolidated statements of income for the six months ended July 27, 2014.
	As a result of the debt refinancing, the Company recorded a $7.1 million loss on debt modification of unamortized deferred financing costs and original issue discount associated with the Prior Credit Facilities in the fiscal year ended January 26, 2014. The remaining $1.7 million of unamortized deferred financing costs and original issue discount associated with the Prior Credit Facilities is being amortized over the five year terms of the New Facilities. The expense is included in “Interest expense, net” within the condensed consolidated statements of income for the six months ended July 27, 2014.
	The New Credit Agreement provides that, subject to certain conditions, Semtech Corporation may request, at any time and from time to time, the establishment of one or more additional term loan facilities and/or increases to the Revolving Commitments in an aggregate principal amount not to exceed $100.0 million, the proceeds of which may be used for working capital and general corporate purposes; however the Lenders are not required to provide such increase upon our request.
	Interest on loans made under the New Credit Agreement in U.S. Dollars accrues, at Semtech’s option, at a rate per annum equal to (1) the Base Rate plus a margin ranging from 0.25% to 1.25% depending upon Semtech’s consolidated leverage ratio or (2) London Interbank Offered Rate (“LIBOR”) (determined with respect to deposits in U.S. Dollars) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio. The “Base Rate” is equal to a fluctuating rate equal to the highest of (a) the prime rate (as published by The Wall Street Journal), (b) ½ of 1% above the federal funds effective rate or (c) one-month LIBOR (determined with respect to deposits in U.S. Dollars) plus 1%. Alternative Currencies, other than Canadian Dollars, accrues at a rate per annum equal to LIBOR (determined with respect to deposits in the applicable Alternative Currency) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio. Interest on loans in Canadian Dollars accrues at a rate per annum equal to the CDOR Rate (as defined below) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio. The “CDOR Rate” for any interest period is the rate equal to the sum of: (a) the rate determined by the administrative agent with reference to the arithmetic average of the discount rate quotations of all institutions listed for CAD Dollar-denominated bankers’ acceptances displayed and identified on the “Reuters Screen CDOR Page” and (b) 0.10% per annum. CDOR Commitment fees on the unused portion of the Revolving Commitments accrue at a rate per annum ranging from 0.20% to 0.45% depending upon Semtech’s consolidated leverage ratio. Interest is paid monthly for a Base Rate loan and swing line loan and quarterly for a Euro dollar rate loan. Interest is payable on the revolving line of credit maturity date in the case of Revolving Commitments and the additional term maturity date in the case of additional Term Loans, respectively. As of July 27, 2014, the interest rates payable on both the Term Loans and the Revolving Commitments was 1.90%.
	As of July 27, 2014, there was $105.3 million outstanding under the Term Loans. Under the terms of the New Credit Agreement, the Company is required to make $4.7 million in quarterly principal payment on the Term Loans through the second quarter of fiscal year 2018. Beginning in the third quarter of fiscal year 2018, the required quarterly principal payment will increase to $7.5 million. Quarterly principal payments for Term Loans are due beginning on the last day of the Company’s fiscal quarter-end months, beginning on October 27, 2013 and ending on April 30, 2018. The principal payments related to the Term Loans are due as follows: $9.4 million remaining in fiscal year 2015; $18.8 million in fiscal year 2016; $18.8 million in fiscal year 2017; $24.4 million in fiscal year 2018. The final remaining principal payment is due on the maturity date of May 1, 2018.
	There are no scheduled principal payments for the Revolving Commitments which had an outstanding balance of $153.0 million at July 27, 2014 and is due on or before May 1, 2018. The Company may, upon notice to the administrative agent, at any time or from time to time voluntarily prepay the Term Loans or Revolving Commitments in whole or in part without premium or penalty. On June 3, 2013, the Company made an early prepayment of $26.0 million against the Term Loans. On July 14, 2014, the Company made a voluntary payment of $25.0 million against the Revolving Commitments.
	All obligations of Semtech Corporation under the New Facilities are unconditionally guaranteed by each of the Guarantors and are secured by a first priority security interest in substantially all of the assets of Semtech and the Guarantors, subject to certain customary exceptions.
	Semtech Corporation and the Guarantors are subject to customary covenants under the New Facilities, including the maintenance of a minimum interest ratio of 3.50:1.00 as of July 27, 2014 and a maximum total consolidated leverage ratio of 3.00:1.00 as of July 27, 2014. Semtech Corporation was in compliance with such financial covenants as of July 27, 2014.
	The New Facilities also contain customary provisions pertaining to events of default. If any event of default occurs, the principal, interest, and any other monetary obligations on all the then outstanding amounts can become due and payable immediately.

Interest_Rate_Derivative_Agree

Interest Rate Derivative Agreement	6 Months Ended
	Jul. 27, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Interest Rate Derivative Agreement	'
	Interest Rate Derivative Agreement
	In June 2012, in connection with the Prior Credit Agreement (see Note 9), the Company entered into an interest rate cap agreement (“Cap Agreement”) with a $175.0 million notional amount and an upfront payment of $1.1 million. The Cap Agreement matures on February 22, 2016 and caps interest rates on one-month LIBOR at 1.00%.
	The purpose of the Cap Agreement is to hedge the Company’s exposure to fluctuations in LIBOR-indexed interest payments. Although the Prior Credit Agreement was terminated on May 2, 2013, the New Credit Agreement, in an aggregate principal amount of $400.0 million (see Note 9), permits the Company to elect LIBOR or Base Rate loans. Since the Company intends to make interest payments based on one-month LIBOR-indexed rates and will not elect interest rates based on alternative indices during the term of the Cap Agreement, the Cap Agreement was re-designated as a hedge of one month LIBOR-indexed interest payments associated with the New Credit Agreement. The effectiveness of the interest rate cap was assessed and the Cap Agreement continues to be an effective cash flow hedge of interest rate risk for the Company. No ineffectiveness was recorded during the six months ended July 27, 2014.
	The Cap Agreement is recorded at estimated fair value at the end of each reporting period. The fair value of the Cap Agreement at July 27, 2014 was determined using Level 2 inputs, including observable market-based inputs such as interest rate curves and implied volatilities for similar instruments with similar contractual terms.
	The Company has determined that the Cap Agreement is highly effective in offsetting future variable interest payments associated with the hedged portion of the Company’s New Credit Agreement. Gains or losses associated with the value of the Cap Agreement are initially reported in other comprehensive income or loss and amortized as an increase to interest expense through the maturity of the Cap Agreement. The amount of unrealized losses on the Cap Agreement recorded in “Accumulated other comprehensive income” at July 27, 2014 that is expected to be reclassified into interest expense in the next twelve months, if interest rates remain unchanged, is approximately $0.4 million.

Income_Taxes

Income Taxes	6 Months Ended
	Jul. 27, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The Company’s effective tax rate differs from the statutory federal income tax rate of 35% due primarily to regional mix of income and certain undistributed foreign earnings for which no U.S. taxes are provided because such earnings are intended to be indefinitely reinvested outside of the U.S.
	The Company uses a two-step approach to recognize and measure uncertain tax positions (“UTP”). The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon ultimate settlement.
	A reconciliation of the beginning and ending amount of gross unrecognized tax benefits (before federal impact of state items) is as follows:
	(in thousands)	July 27, 2014
	Balance as of January 26, 2014	14,414
	Reductions for settlements with tax authorities	(4,513	)
	Balance as of July 27, 2014	9,901
	The gross unrecognized tax benefit (before federal impact of state items) was $9.9 million and $14.4 million at July 27, 2014 and January 26, 2014, respectively. Included in the balance of unrecognized tax benefits at July 27, 2014 and January 26, 2014, is $7.8 million and $12.3 million of net tax benefit (after federal impact of state items), respectively, that, if recognized, would impact the effective tax rate, subject to the valuation allowance.
	The liability for UTP is reflected within the consolidated balance sheets as follows:
	(in thousands)	July 27, 2014		January 26, 2014
	Deferred tax assets - non-current	$	7,582	$	12,095
	Other long-term liabilities	252		252
	Total accrued taxes	$	7,834	$	12,347
	The Company’s policy is to include net interest and penalties related to unrecognized tax benefits within the provision for taxes on the condensed consolidated statements of income. The Company had approximately $293,000 of net interest and penalties accrued at July 27, 2014 and January 26, 2014.
	Tax years prior to 2010 (the Company’s fiscal year 2011) are generally not subject to examination by the Internal Revenue Service (“IRS”) except for items involving tax attributes that have been carried forward to tax years whose statute of limitations remains open. The Company is currently under IRS audit for fiscal years 2011, 2012 and 2013. The Company is also currently under audit by the Canadian Revenue Agency for fiscal years 2010, 2011 and the short-year ended March 19, 2012. For state returns, the Company is generally not subject to income tax examinations for years prior to 2008 (the Company’s fiscal year 2009). The Company has a significant tax presence in Switzerland for which Swiss tax filings have been examined through fiscal year 2013. The Company is also subject to routine examinations by various foreign tax jurisdictions in which it operates.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jul. 27, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments And Contingencies	'
	Commitments and Contingencies
	From time to time in the ordinary course of its business, the Company is involved in various claims, litigation, and other legal actions that are normal to the nature of its business, including with respect to Intellectual Property (“IP”), contract, product liability, employment, and environmental matters.
	In accordance with accounting standards regarding loss contingencies, the Company accrues an undiscounted liability for those contingencies where the incurrence of a loss is probable and the amount can be reasonably estimated. The Company also discloses the amount accrued and the amount of a reasonably possible loss in excess of the amount accrued, if such disclosure is necessary for its financial statements not to be misleading. The Company does not record liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated, or when the liability is believed to be only reasonably possible or remote. The Company evaluates, at least quarterly, developments in its legal matters that could affect the amount of liability that has been previously accrued, and makes adjustments as appropriate. Significant judgment is required to determine both probability and the estimated amount. The Company may be unable to estimate a possible loss or range of possible loss due to various reasons, including, among others: (i) if the damages sought are indeterminate; (ii) if the proceedings are in early stages, (iii) if there is uncertainty as to the outcome of pending appeals, motions or settlements, (iv) if there are significant factual issues to be determined or resolved, and (v) if there are novel or unsettled legal theories presented. In such instances, there is considerable uncertainty regarding the ultimate resolution of such matters, including a possible eventual loss, if any.
	Because litigation outcomes are inherently unpredictable, the Company’s evaluation of legal proceedings often involves a series of complex assessments by management about future events and can rely heavily on estimates and assumptions. While the consequences of certain unresolved proceedings are not presently determinable, and an estimate of the probable and reasonably possible loss or range of loss in excess of amounts accrued for such proceedings cannot be reasonably made, an adverse outcome from such proceedings could have a material adverse effect on the Company’s earnings in any given reporting period. However, in the opinion of management, after consulting with legal counsel, and taking into account insurance coverage, any ultimate liability related to current outstanding claims and lawsuits, individually or in the aggregate, is not expected to have a material adverse effect on the Company’s financial statements, as a whole. However, legal matters are inherently unpredictable and subject to significant uncertainties, some of which are beyond the Company’s control. As such, even though the Company intends to vigorously defend itself with respect to its legal matters, there can be no assurance that the final outcome of these matters will not materially and adversely affect the Company’s business, financial condition, results of operations, or cash flows.
	Environmental Matters
	In 2001, the Company was notified by the California Department of Toxic Substances Control (“State”) that it may have liability associated with the clean-up of the one-third acre Davis Chemical Company site in Los Angeles, California. The Company has been included in the clean-up program because it was one of the companies that used the Davis Chemical Company site for waste recycling and/or disposal between 1949 and 1990. The Company joined with other potentially responsible parties and entered into a Consent Order with the State that required the group to perform a soils investigation at the site and submit a remediation plan. The State has approved the remediation plan, which addressed the group’s obligations under the Consent Order. Although the Consent Order does not require the group to remediate the site and the State has indicated it intends to look to other parties for remediation, the State has not yet issued “no further action” letters to the group members and has not been able to obtain reimbursement from the former site owner. To date, the Company’s share of the group’s expenses has not been material and has been expensed as incurred.
	The Company has used an environmental firm, specializing in hydrogeology, to perform monitoring of the groundwater at the Company’s former facility in Newbury Park, California that was leased for approximately forty years. The Company vacated the building in May 2002. Certain contaminants have been found in the local groundwater and site soils. Responsibility for soil contamination remains under investigation. The location of key soil contamination (and some related site groundwater impact associated with the soil contamination) is concentrated in and found to emanate from an area of an underground storage tank that the Company believes to have been installed and primarily used in the early 1960s by a former tenant at the site who preceded the Company’s tenancy. There are no claims pending with respect to environmental matters at the Newbury Park site. The Los Angeles Regional Water Quality Control Board having authority over the site issued joint instructions in November 2008, ordering the Company and the current owner of the site to perform additional assessments and surveys, and to create ongoing groundwater monitoring plans before any final regulatory action for “no further action” may be approved. In September 2009, the regulatory agency issued supplemental instructions to the Company and the current site owner regarding previously ordered site assessments, surveys and groundwater monitoring. In October 2013, an order was issued including a scope of proposed additional site work, monitoring, and proposed remediation activities. The Company has filed an appeal of the October 2013 order seeking reconsideration of the removal of two other potentially responsible parties, and seeking clarification of certain other factual findings by the regulatory agency. Other parties have filed their own responses to the October 2013 order. The parties are expected to work cooperatively in responding to and determining the appropriate scope and extent of additional site investigative and categorization work, as well as in relation to any ultimate proposed clean up and abatement work. The Company has retained the services of an environmental firm which has engaged with the regulatory agency and has begun activities to comply with the order.
	The Company has accrued liabilities where it is probable that a loss will be incurred and the cost or amount of loss can be reasonably estimated. Based on the Company’s preliminary assessment following a November 2012 draft cleanup and abatement order, which has been reviewed under the October 2013 order pending the current appeal by the Company and other impacted parties, the Company has determined a likely range of probable loss between $2.5 million and $5.7 million. Given the yet unresolved status of the clean up and abatement order and uncertainties associated with environmental assessment and the remediation activities, the Company is unable to determine a best estimate within the range of loss. Therefore, the Company recorded the minimum amount of $2.5 million in the third quarter of fiscal year 2013, and such reserve remains on the Company’s books under “Other long-term liabilities” on the condensed consolidated balance sheets. These estimates could change as a result of changes in planned remedial actions, further actions from the regulatory agency, remediation technology, and other factors.
	Commercial Disputes
	The Company periodically is involved in disputes arising in the normal course of business regarding products or services provided to the Company by vendors or service providers. Historically, the cost of commercial disputes has been immaterial to the Company’s consolidated financial statements.
	Indemnification
	The Company has entered into agreements with its current executive and some former officers and directors indemnifying them against certain liabilities incurred in connection with the performance of their duties. The Company’s Certificate of Incorporation and Bylaws contain comparable indemnification obligations with respect to the Company’s current directors and employees.
	Product Warranties
	The Company’s general warranty policy provides for repair or replacement of defective parts. In some cases, a refund of the purchase price is offered. In certain instances the Company has agreed to other warranty terms, including some indemnification provisions.
	The product warranty accrual reflects the Company’s best estimate of probable liability under its product warranties. The Company accrues for known warranty issues if a loss is probable and can be reasonably estimated, and accrues for estimated incurred but unidentified issues based on historical experience. Historically, warranty expense has been immaterial to the Company’s consolidated financial statements.
	Earnout Liability
	Pursuant to the earn-out arrangement with stockholders of Cycleo SAS (“Cycleo”), which the Company acquired on March 7, 2012, the Company potentially may make payments totaling up to approximately $16.0 million based on the achievement of a combination of certain revenue and operating income milestones by Cycleo over a period of four years beginning on April 30, 2012. For certain of the Cycleo stockholders, payment of the earn-out liability is contingent upon employment at the end of the four-year period and is accounted for as post-acquisition compensation expense over the service period. The portion of the earn-out liability that is not dependent on continued employment was included in the purchase price allocation at March 7, 2012. The Company has recorded a cumulative liability of $0.9 million and $0.9 million as of July 27, 2014 and January 26, 2014, respectively.

Concentration_of_Risk

Concentration of Risk	6 Months Ended
	Jul. 27, 2014
Risks and Uncertainties [Abstract]	'
Concentration of Risk	'
	Concentration of Risk
	Sales to the Company’s customers are generally made on open account, subject to credit limits the Company may impose, and the receivables are subject to the risk of being uncollectible.
	The following significant customer accounted for at least 10% of net sales in all but one of the periods indicated:
		Three Months Ended				Six Months Ended
	(percentage of net sales)	July 27,		July 28,		July 27,		July 28,
		2014		2013		2014		2013
	Samsung Electronics (and affiliates)	9	%	11	%	11	%	13	%
	The following table shows the customer that has an outstanding receivable balance that represents at least 10% of total net receivables for the periods indicated:
		Balance as of
	(percentage of net accounts receivable)	July 27,		January 26,
		2014		2014
	Samsung Electronics (and affiliates)	10	%	13	%
	Outside Subcontractors and Suppliers
	The Company relies on a limited number of outside subcontractors and suppliers for the production of silicon wafers, packaging and certain other tasks. Disruption or termination of supply sources or subcontractors, due to natural disasters such as an earthquake or other causes, could delay shipments and could have a material adverse effect on the Company. Although there are generally alternate sources for these materials and services, qualification of the alternate sources could cause delays sufficient to have a material adverse effect on the Company. Several of the Company’s outside subcontractors and suppliers, including third-party foundries that supply silicon wafers, are located in foreign countries, including China, Taiwan, Europe and Israel. The Company’s largest source of silicon wafers is an outside foundry located in China and a significant amount of the Company’s assembly and test operations are conducted by third-party contractors in China, Malaysia, Taiwan, Thailand, Korea and the Philippines. For the second quarter of fiscal years 2015 and 2014, respectively, approximately 43% and 35% of the Company’s silicon in terms of cost of wafers was supplied by a third-party foundry in China, and this percentage could be higher in future periods.
	In the second quarter of fiscal year 2015, authorized distributors accounted for approximately 60% of the Company’s net sales compared to 44% in the second quarter of fiscal year 2014. Generally, the Company does not have long-term contracts with its distributors and most can terminate their agreement with little or no notice. For the second quarter of fiscal year 2015, the Company’s two largest distributors were based in Asia.

Segment_Information

Segment Information	6 Months Ended
	Jul. 27, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	Segment information
	Segment Information
	In the second quarter of fiscal year 2015, the Company completed the reassessment of its operations in light of its restructuring efforts (discussed in Note 16). Based on this reassessment, the Company identified four operating segments. The Company’s CEO continues to function as the CODM. The Company’s CODM makes operating decisions and assesses performance based on these operating segments. Three of the operating segments: Protection, Power and High Reliability Products; Signal Integrity Products; and Wireless, Sensing and Timing Products, all have similar economic characteristics and have been aggregated into one reportable segment identified in the table below as the “Semiconductor Products Group”. The Company concluded that the remaining operating segment, the Systems Innovation Group, could not be aggregated with the other operating segments and did not meet the thresholds for a separate reportable segment as defined by the guidance regarding segment disclosure. Therefore the Company has classified it as “All others” in the tables below. Historically, the Company has shown “All others” as part of the Company’s one reportable segment for the three and six month periods ended July 28, 2013. The reportable segment has been reclassified for comparison purposes for the three and six month periods ended July 28, 2013. The Company’s assets are commingled among the various reporting units and the CODM does not use that information in making operating decisions or assessing performance. Therefore, the Company has not included asset information by segment below.
	Net sales by segment are as follows:
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,			July 28,
		2014				2013				2014			2013
	Semiconductor Products Group	$	145,451			$	158,149			$	277,195		$	316,708
	All others	291				6,861				1,406			10,709
	Total	$	145,742			$	165,010			$	278,601		$	327,417
	Income (loss) by segment and reconciliation to consolidated operating income:
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,			July 28,
		2014				2013				2014			2013
	Semiconductor Products Group	$	36,517			$	39,137			$	66,478		$	81,160
	All others	(1,345		)		2,131				(4,049		)	346
	Operating Income by segment	35,172				41,268				62,429			81,506
	Items to reconcile segment operating income (loss) to consolidated income before taxes
	Intangible amortization and impairments	6,444				9,811				12,869			17,667
	Stock-based compensation expense	6,274				6,156				13,121			14,782
	Inventory write-down	—				—				1,052			—
	Restructuring charges	—				—				1,001			—
	Other non-segment related expenses	58				506				502			1,437
	Amortization of fair value adjustments related to acquired PP&E	339				338				678			3,085
	Interest expense, net	1,588				10,584				2,975			14,644
	Non-operating expense, net	345				198				623			1,005
	Income before taxes	$	20,124			$	13,675			$	29,608		$	28,886
	Geographic Information
	The Company generates virtually all of its sales from its Semiconductor Products Group through sales of analog and mixed-signal devices.
	Net sales activity by geographic region is as follows:
		Three Months Ended						Six Months Ended
		July 27,			July 28,			July 27,			July 28,
		2014			2013			2014			2013
	Asia-Pacific	77	%		72	%		76	%		73	%
	North America	13	%		17	%		13	%		16	%
	Europe	10	%		11	%		11	%		11	%
		100	%		100	%		100	%		100	%
	The Company generally attributes sales to a country based on the ship-to address. The table below summarizes sales activity to countries that represented greater than 10% of total net sales for one or more of the periods presented:
		Three Months Ended						Six Months Ended
	(percentage of total sales)	July 27,			July 28,			July 27,			July 28,
		2014			2013			2014			2013
	China (including Hong Kong)	36	%		32	%		35	%		33	%
	United States	12	%		15	%		13	%		15	%
	Japan	12	%		13	%		11	%		12	%
	South Korea	8	%		11	%		10	%		11	%
	Income (loss) from continuing operations before income taxes is as follows:
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,			July 28,
		2014				2013				2014			2013
	Domestic	$	(6,002	)		$	(11,831	)		$	(11,139	)	$	(18,245	)
	Foreign	26,126				25,506				40,747			47,131
	Total	$	20,124			$	13,675			$	29,608		$	28,886

Stock_Repurchase_Program

Stock Repurchase Program	6 Months Ended
	Jul. 27, 2014
Equity [Abstract]	'
Stock Repurchase Program	'
	Stock Repurchase Program
	The Company maintains an active stock repurchase program which was approved by the Company’s Board of Directors (the “Program”). The Program does not have an expiration date and the Board of Directors has authorized expansion of the program over the years. In November 2011 the Board of Directors authorized the Company to repurchase up to $50.0 million of shares of the Company’s common stock from time to time through negotiated or open market transactions, and in August 2013 the Company announced an additional $50.0 million expansion of the Program, for a total authorized Program of $100.0 million, such authorization being subject to certain limitations, guidelines and conditions as directed by the Board of Directors. As of July 27, 2014, the Company had repurchased $57.5 million shares of common stock under the Program.
	In the first six months of fiscal year 2015, we repurchased 761,294 shares for $20.0 million. There were no shares repurchased in the first six months of fiscal year 2014.
	The Company currently intends to hold the repurchased shares as treasury stock. The Company typically reissues treasury shares to settle stock option exercises and vested restricted stock units.

Restructuring

Restructuring	6 Months Ended
	Jul. 27, 2014
Restructuring and Related Activities [Abstract]	'
Restructuring	'
	Restructuring
	In the fourth quarter of fiscal year 2014, the Company made a strategic decision to reduce its investment in the long-haul optical market, realign its product groupings and align spending to current demand levels. As a result of these actions, the Company recorded restructuring charges of $1.0 million in the first quarter of fiscal year 2015. The Company recorded no restructuring charges in the second quarter of fiscal year 2015. Restructuring related liabilities are included in “Accrued liabilities” within the condensed consolidated balance sheet as of July 27, 2014.
	The following table summarizes the restructuring activity for the six months ended July 27, 2014:
	(in thousands)	One-time employee termination benefits			Contract commitments			Total
	Balance at January 26, 2014	1,387			1,245			2,632
	Charges	378			623			1,001
	Cash payments	(1,702		)	(1,586		)	(3,288		)
	Reclassifications	—			(115		)	(115		)
	Balance at July 27, 2014	$	63		$	167		$	230
	Restructuring charges are presented in “Restructuring charge” within the condensed consolidated statements of income. The Company does not expect to incur additional costs related to this restructuring event.

Organization_and_Basis_of_Pres1

Organization and Basis of Presentation (Policy)	6 Months Ended
	Jul. 27, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Fiscal Year	'
	Fiscal Year
	The Company reports results on the basis of 52 and 53 week periods and ends its fiscal year on the last Sunday in January. The other quarters generally end on the last Sunday of April, July and October. All quarters consist of 13 weeks except for one 14-week period in 53-week years. The second quarter of fiscal years 2015 and 2014 each consisted of 13 weeks.
Principles of Consolidation	'
	Principles of Consolidation
	The accompanying interim condensed consolidated financial statements of Semtech have been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). In the opinion of the Company, these unaudited statements contain all adjustments (consisting of normal recurring adjustments) necessary to present fairly, in all material respects, the financial position of Semtech for the interim periods presented. All significant intercompany balances have been eliminated. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been condensed or omitted pursuant to such rules and regulations, and the Company believes that the included disclosures are adequate to make the information presented not misleading. The Company evaluated all subsequent events through the date these condensed consolidated financial statements were issued.
	These interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended January 26, 2014. The results reported in these interim condensed consolidated financial statements should not be regarded as indicative of results that may be expected for any subsequent period or for the entire year.
Segment Information	'
	Segment Information
	In the second quarter of fiscal year 2015, the Company completed the reassessment of its operations in light of its recent restructuring efforts (discussed in Note 16). Based on this reassessment, the Company has identified four operating segments in total. Three of the operating segments aggregate into one reportable segment. The remaining operating segment could not be aggregated with the other operating segments and did not meet the criteria for a separate reportable segment as defined by the guidance regarding segment disclosure. The Company’s Chief Executive Officer (“CEO”) has been identified as the Chief Operating Decision Maker (“CODM”) as defined by the segment disclosure guidance (see Note 14 for further discussion) and now receives discrete financial information pertaining to the Systems Innovation group. As a result, beginning with the second quarter of fiscal 2015, the financial activity associated with the Systems Innovation group will be reported separately from the Company's reportable segment. This separate reporting is included in the "All others" category. The historical activity of the reportable segment has been recast for consistent presentation for the three and six months periods ended July 27, 2014 and July 28, 2013
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize revenue from the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance addresses, in particular, contracts with more than one performance obligation, as well as the accounting for some costs to obtain or fulfill a contract with a customer, and provides for additional disclosures with respect to revenues and cash flows arising from contracts with customers. Public entities are required to apply the amendments on either a full- or modified-retrospective basis for annual periods beginning after December 15, 2016 and for interim periods within those annual periods. Early adoption is not permitted. The Company is currently assessing the basis of adoption and evaluating the impact of the adoption of the update on its consolidated financial statements.
Earnings Per Share	'
	Basic earnings per common share is computed by dividing income available to common stockholders by the weighted-average number of shares of common stock outstanding during the reporting period. Diluted earnings per common share incorporates the incremental shares issuable, calculated using the treasury stock method, upon the assumed exercise of stock options and the vesting of restricted stock.
Revenue Recognition	'
	Revenue Recognition
	The Company recognizes product revenue when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable and collectability is reasonably assured. Recovery of costs associated with product design and engineering services are recognized during the period in which services are performed. The product design and engineering recovery, when recognized, will be reported as a reduction to product development and engineering expense. Historically, these recoveries have not exceeded the cost of the related development efforts.
	The Company includes revenue related to granted technology licenses in “Net sales” within the condensed consolidated statements of income. Historically, revenue from these arrangements has not been significant though it is part of the Company’s recurring ordinary business.
	The Company defers revenue recognition on shipment of products to certain customers, principally distributors, under agreements which provide for limited pricing credits or return privileges, until these products are sold through to end-users or the return privileges lapse. For sales subject to certain pricing credits or return privileges, the amount of future pricing credits or inventory returns cannot be reasonably estimated given the relatively long period in which a particular product may be held by the customer. Therefore, the Company has concluded that sales to customers under these agreements are not fixed and determinable at the date of the sale and revenue recognition has been deferred. The Company estimates the deferred gross margin on these sales by applying an average gross profit margin to the actual gross sales. The average gross profit margin is calculated for each category of material using standard costs which is expected to approximate actual costs at the date of sale. The estimated deferred gross margins on these sales, where there are no outstanding receivables, are included in “Deferred revenue” within the condensed consolidated balance sheets.
	The Company records a provision for estimated sales returns and rebates in the same period as the related revenues are recorded. The Company bases these estimates on historical sales returns, rebates and other known factors. Actual returns could be different from Company estimates and current provisions for sales returns and allowances, resulting in future charges to earnings. There were no significant impairments of deferred cost of sales in the second quarter of fiscal year 2015 or fiscal year 2014.
Share-based Compensation, Option and Incentive Plans	'
	Share-based Payment Arrangements
	The Company has various equity award plans that provide for granting stock-based awards to employees and non-employee directors of the Company. The plans provide for the granting of several available forms of stock-based compensation. As of July 27, 2014, the Company has granted stock options, restricted stock and restricted stock units under the plans and has also issued some stock-based compensation outside of the plans, including stock options, restricted stock and restricted stock units issued as inducements to join the Company.
	Grant Date Fair Values and Underlying Assumptions; Contractual Terms
	The Company uses the Black-Scholes pricing model to value stock options. The estimated fair value of restricted stock units, for which vesting is not linked to a market condition, is calculated based on the market price of the Company’s common stock on the date of grant. For restricted stock units that vest according to a market condition, the Company uses a Monte Carlo simulation model to value the award.
	Some of the restricted stock units granted in the first six months of fiscal year 2015 and prior years are classified as liabilities rather than equity. For grants classified as equity, stock-based compensation cost is measured at the grant date, based on the fair value of the award, and is recognized as an expense over the grantee’s requisite service period. For grants classified as liabilities, stock-based compensation cost is measured at fair value at the end of each reporting date until the date of settlement, and is recognized as an expense over the grantee’s requisite service period. Expected volatilities are based on historical volatility using daily and monthly stock price observations.
Investments	'
	Investments that have original maturities of three months or less are accounted for as cash equivalents. This includes money market funds, time deposits and United States (“U.S.”) government obligations. Temporary and long-term investments consist of government, bank and corporate obligations, and bank time deposits with original maturity dates in excess of three months. Temporary investments have original maturities in excess of three months, but mature within twelve months of the balance sheet date. Long-term investments have original maturities in excess of twelve months. The Company determines the cost of securities sold based on the specific identification method. Realized gains or losses are reported in “Non-operating expense, net” within the condensed consolidated statements of income.
	The Company classifies its investments as “available-for-sale” because it may sell some securities prior to maturity. The Company’s investments are subject to market risk, primarily interest rate and credit risks. The Company’s investments are managed by a limited number of outside professional managers that operate within investment guidelines set by the Company. These guidelines include specified permissible investments, minimum credit quality ratings and maximum average duration restrictions and are intended to limit market risk by restricting the Company’s investments to high quality debt instruments with relatively short-term maturities.
Fair Value of Financial Instruments	'
	Available-for-sale securities included in Level 2 are valued utilizing inputs obtained from an independent service (the “Service”), which uses quoted market prices for identical or comparable instruments rather than direct observations of quoted prices in active markets. The Service gathers observable inputs for all of our fixed income securities from a variety of industry data providers, for example, large custodial institutions and other third-party sources. Once the observable inputs are gathered by the Service, all data points are considered and an average price is determined. The Service’s providers utilize a variety of inputs to determine their quoted prices. The Company reviews and evaluates the values provided by the Service and agrees with the valuation methods and assumptions used in determining the fair value of investments. The Company believes this method provides a reasonable estimate for fair value.
	Instruments Not Recorded at Fair Value on a Recurring Basis
	Some of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts that approximate fair value due to their liquid or short-term nature. Such financial assets and financial liabilities include cash and cash equivalents, receivables, net, certain other assets, accounts payable, accrued expenses, accrued personnel costs, and other current liabilities.
	The Company’s long-term debt is not recorded at fair value on a recurring basis, but is measured at fair value for disclosure purposes. The fair value of the Company’s Term Loans (as defined herein) is $105.0 million and $114.3 million and Revolving Commitments (as defined herein) is $152.6 million and $177.5 million at July 27, 2014 and January 26, 2014, respectively. These are based on Level 2 inputs which are derived from transactions with similar amounts, maturities, credit ratings and payment terms.
	Assets and Liabilities Recorded at Fair Value on a Non-Recurring Basis
	The Company reduces the carrying amounts of its goodwill, intangible assets, long-lived assets and non-marketable equity securities to fair value when held for sale or determined to be impaired.
	For its investment in equity interests, the Company has not identified events or changes in circumstances that may have a significant adverse effect on the fair value of its cost method investments during the first six months of fiscal year 2015.
	The fair value of the Cap Agreement at July 27, 2014 was determined using Level 2 inputs, including observable market-based inputs such as interest rate curves and implied volatilities for similar instruments with similar contractual terms.
Impairment or Disposal of Long-Lived Assets, Including Intangible Assets	'
	Goodwill is not amortized, but is tested for impairment using a two-step method on an annual basis and whenever events or changes in circumstances indicate that the carrying value may not be recoverable. The recoverability of goodwill is measured at the reporting unit level by comparing the reporting unit’s carrying amount, including goodwill, to the fair market value of the reporting unit.
	Goodwill is allocated to two reporting units (Signal Integrity and Wireless, Sensing and Timing). These reporting units also represent the related operating segment since segment management who report to the CODM regularly review operating results and make resource allocation decisions at this level. The difference between the fair value and the carrying amount of these reporting units is one of several factors the Company will consider before reaching its conclusion about whether to perform the first step of the goodwill impairment test. No Goodwill is allocated to the newly identified Systems Innovation Group operating segment (see Note 14).
	Goodwill was tested for impairment as of November 30, 2013 at the reporting unit level, the date of the Company’s annual impairment review. The Company estimated the fair values using an income approach, as well as other generally accepted valuation methodologies. The cash flows for each reporting unit were based on discrete financial forecasts developed by management for planning purposes. Cash flows beyond the discrete forecasts were estimated using a terminal value calculation, which incorporated historical and forecasted financial trends for each identified reporting unit and considered perpetual earnings growth rates for publicly traded peer companies.
	Goodwill is measured at fair value on a non-recurring basis. That is, goodwill is not measured at fair value on an ongoing basis, but is subject to fair value adjustments using Level 3 inputs in certain circumstances (e.g. when there is evidence of impairment). At July 27, 2014, the Company concluded that there were no indicators of such impairment.
	The Company reviews indefinite-lived intangible assets for impairment annually or whenever events or changes in circumstances indicate the carrying value may not be recoverable. Recoverability of indefinite-lived intangible assets is measured by comparing the carrying amount of the asset to the future discounted cash flows the asset is expected to generate.
	Indefinite-lived intangible assets are measured at fair value on a non-recurring basis using Level 3 inputs in certain circumstances (e.g. when there is evidence of impairment). At July 27, 2014 the Company concluded that there were no indicators of impairment.
Product Warranties	'
	Product Warranties
	The Company’s general warranty policy provides for repair or replacement of defective parts. In some cases, a refund of the purchase price is offered. In certain instances the Company has agreed to other warranty terms, including some indemnification provisions.
	The product warranty accrual reflects the Company’s best estimate of probable liability under its product warranties. The Company accrues for known warranty issues if a loss is probable and can be reasonably estimated, and accrues for estimated incurred but unidentified issues based on historical experience. Historically, warranty expense has been immaterial to the Company’s consolidated financial statements.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	6 Months Ended
	Jul. 27, 2014
Earnings Per Share [Abstract]	'
Computation of Basic and Diluted Earnings Per Common Share	'
	The computation of basic and diluted earnings per common share is as follows:
		Three Months Ended				Six Months Ended
	(in thousands, except per share amounts)	July 27,		July 28,		July 27,		July 28,
		2014		2013		2014		2013
	Net income	$	17,898	$	19,112	$	25,765	$	33,889
	Weighted average common shares outstanding - basic	67,208		67,614		67,254		67,285
	Dilutive effect of options and restricted stock units	642		1,476		634		1,527
	Weighted average common shares outstanding - diluted	67,850		69,090		67,888		68,812
	Basic earnings per common share	$	0.27	$	0.28	$	0.38	$	0.5
	Diluted earnings per common share	$	0.26	$	0.28	$	0.38	$	0.49
	Anti-dilutive shares not included in the above calculations	1,463		352		1,427		392

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	6 Months Ended
	Jul. 27, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Allocation Of Stock-Based Compensation	'
	The following table summarizes pre-tax, stock-based compensation expense included in the unaudited condensed consolidated statements of income captions for the three and six months ended July 27, 2014 and July 28, 2013.
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,				July 28,
		2014				2013				2014				2013
	Cost of sales	$	355			$	405			$	718			$	733
	Selling, general and administrative	3,448				3,548				7,513				8,430
	Product development and engineering	2,472				2,203				4,891				5,619
	Stock-based compensation, pre-tax	$	6,274			$	6,156			$	13,121			$	14,782
	Net change in stock-based compensation capitalized into inventory	$	37			$	8			$	28			$	85
Summary Of Fair Value Assumptions, Stock Options	'
	The following table summarizes the assumptions used in the Black-Scholes model to determine the fair value of stock options granted in the three and six months ended July 27, 2014 and July 28, 2013:
		Three Months Ended				Six Months Ended
		July 27,		July 28,		July 27,		July 28,
		2014		2013		2014		2013
	Expected lives, in years	4.3 - 4.4		4.7		3.0 - 4.4		4.2 - 4.7
	Estimated volatility	33%		33%		33% - 34%		33% - 35%
	Dividend yield	—		—		—		—
	Risk-free interest rate	1.30% - 1.43%		1.30%		1.26% - 1.43%		0.65% - 1.30%
	Weighted average fair value on grant date	$7.43		$10.59		$7.26		$9.33
Summary Of The Activity For Stock Option Awards	'
	The following table summarizes the activity for stock options for the six months ended July 27, 2014:
	(in thousands, except for per share amounts)	Number			Weighted				Aggregate				Aggregate				Number of	Weighted
		of			Average				Intrinsic				Unrecognized				Shares	Average
		Shares			Exercise				Value				Compensation				Exercisable	Contractual
					Price													Term
					(per share)													(in years)
	Balance at January 26, 2014	1,935			$	21.33			$	7,722			$	4,354			1,275
	Options granted	261			24.92
	Options exercised	(353	)		16.94				3,102
	Options cancelled/forfeited	(31	)		26.71
	Balance at July 27, 2014	1,812			22.61				4,425				$	4,846			1,112
	Exercisable at July 27, 2014	1,112			$	19.58			$	4,383								2.4
Schedule Of Fair Value Assumptions, Market Performance Units	'
	The following tables summarize the assumptions used in the Monte Carlo simulation model to determine the fair value of restricted stock units granted in the first quarter of fiscal year 2015 for both Tranche 1 and Tranche 2. The Company did not grant any restricted stock units that vest according to a market performance conditions in the second quarter of fiscal year 2015. The Company did not grant any restricted stock units that vest according to a market performance condition in the three and six months ended July 28, 2013.
	Tranche 1:
		Six Months Ended
		July 27, 2014
	Expected lives, in years	1.6
	Estimated volatility	34%
	Dividend yield	—
	Risk-free interest rate	1.50%
	Fair value on grant date	$17.26
	Tranche 2:
		Six Months Ended
		July 27, 2014
	Expected lives, in years	2.1
	Estimated volatility	34%
	Dividend yield	—
	Risk-free interest rate	1.50%
	Fair value on grant date	$14.88
Summary Of The Activity For Employee Stock Unit Awards	'
	The following table summarizes the employees’ restricted stock unit activity for the six months ended July 27, 2014:
	(in thousands, except for per unit amounts)	Number of			Weighted Average				Aggregate				Aggregate				Weighted Average
		Units			Grant Date				Intrinsic				Unrecognized				Period Over
					Fair Value				Value (1)				Compensation				Which Expected
					(per unit)												to be Recognized
																	(in years)
	Balance at January 26, 2014	2,195			$	27.18							$	49,563			2.5
	Restricted stock units granted	333			24.18
	Restricted stock units vested	(319	)		27.37				$	7,905
	Restricted stock units forfeited	(142	)		26.65
	Balance at July 27, 2014	2,067			$	26.71							$	44,313			2.3
	-1	Reflects the value of Semtech stock on the date that the restricted stock unit vested.
Summary Of The Activity For Non-Employee Directors Stock Unit Awards	'
	The following table summarizes the non-employee directors’ activity for stock units for the six months ended July 27, 2014:
	(in thousands, except for per unit amounts)	Number of			Recorded				Weighted Average				Aggregate				Period Over
		Units			Liability				Grant Date				Unrecognized				Which Expected
									Fair Value				Compensation				to  be Recognized
									(per unit)								(in years)
	Balance at January 26, 2014	18			$	3,981			$	35.17			$	177			0.4
	Restricted stock units granted	24							26.59
	Restricted stock units vested	(18	)						35.17
	Restricted stock units forfeited	—							—
	Change in liability				(39		)
	Balance at July 27, 2014	24			$	3,942			$	26.59			$	478			0.9
Performance shares [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Summary Of The Activity For Performance Unit Awards	'
	The following table summarizes the activity for performance-based restricted stock units for the first six months ended July 27, 2014:
					Subject to			Subject to							Weighted			Aggregate		Period Over
					Share Settlement			Cash Settlement							Average					Which Expected
															Grant Date
	(in thousands, except for per unit amounts)	Total			Units			Units			Recorded				Fair Value			Unrecognized		to be Recognized
		Units									Liability				(per unit)			Compensation		(in years)
	Balance at January 26, 2014	376			192			184			$	1,305			$	28.5		$	3,893	1.3
	Performance-based units granted	256			128			128							24.74
	Performance-based units vested	(93	)		(52	)		(41	)						23.36
	Performance-based units cancelled/forfeited	(17	)		(9	)		(8	)						25.51
	Change in liability										(318		)
	Balance at July 27, 2014	522			259			263			$	987			$	27.57		$	7,577	1.9
Market performance shares [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Summary Of The Activity For Performance Unit Awards	'
	The following table summarizes the activity for market performance units for the six months ended July 27, 2014:
					Weighted				Aggregate				Period Over
					Average								Which Expected
					Grant Date
	(in thousands, except for per unit amounts)	Total			Fair Value				Unrecognized				to be Recognized
		Units			(per unit)				Compensation				(in years)
	Balance at January 26, 2014	—			$	—			$	—			0
	Market performance units granted	220			15.59
	Market performance units vested	—			—
	Market performance units cancelled/forfeited	—			—
	Balance at July 27, 2014	220			$	15.59			$	2,664			1.5

Investments_Tables

Investments (Tables)	6 Months Ended
	Jul. 27, 2014
Investments [Abstract]	'
Summary Of Investments	'
	The following table summarizes the Company’s available-for-sale investments:
		July 27, 2014								January 26, 2014
	(in thousands)	Market Value			Adjusted			Gross		Market Value			Adjusted		Gross
					Cost			Unrealized Gain					Cost		Unrealized
															Gain
	Agency securities	$	550		$	550		$	—	$	3,674		$	3,673	$	1
	Total investments	$	550		$	550		$	—	$	3,674		$	3,673	$	1
Schedule Of Investments, Classified By Maturity Period	'
	The following table summarizes the maturities of the Company’s available-for-sale investments:
		27-Jul-14						January 26, 2014
	(in thousands)	Market Value			Adjusted Cost			Market Value		Adjusted Cost
	Within 1 year	$	—		$	—		$	—	$	—
	After 1 year through 5 years	550			550			3,674		3,673
	Total investments	$	550		$	550		$	3,674	$	3,673
Summary Of Unrealized Gains (Losses) On Investments	'
	The following table summarizes net unrealized losses arising in the periods presented in addition to the tax associated with these comprehensive income items:
		Three Months Ended						Six Months Ended
	(in thousands)	July 27,			July 28,			July 27,		July 28,
		2014			2013			2014		2013
	Unrealized loss, net of tax	$	(1	)	$	(4	)	$	—	$	(5	)
	Increase to deferred tax liability	(1		)	(3		)	—		(3		)
Schedule Of Interest Income Generated From Investments	'
	The following table summarizes interest income generated from investments and cash and cash equivalents:
		Three Months Ended						Six Months Ended
	(in thousands)	July 27,			July 28,			July 27,		July 28,
		2014			2013			2014		2013
	Interest income	$	12		$	91		$	20	$	191
Schedule of Cost Method Equity Investments	'
	The Company has investments in two privately held companies. The Company accounts for these equity investments under the cost method of accounting since it does not have the ability to exercise significant influence over the investees. These equity investment interests are included in “Other assets” within the condensed consolidated balance sheet as of July 27, 2014.
	(in thousands)	Equity Investment
	Balance at January 26, 2014	$	5,000
	Additions	3,264
	Balance at July 27, 2014	$	8,264

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jul. 27, 2014
Fair Value Disclosures [Abstract]	'
Financial Assets And Liabilities Measured And Recorded At Fair Value On A Recurring Basis	'
	Financial assets measured and recorded at fair value on a recurring basis consisted of the following types of instruments:
		Fair Value as of July 27, 2014								Fair Value as of January 26, 2014
	(in thousands)	Total		(Level 1)		(Level 2)		(Level 3)		Total		(Level 1)		(Level 2)		(Level 3)
	Agency securities	$	550	$	—	$	550	$	—	$	3,674	$	—	$	3,674	$	—
	Total available-for-sale securities	550		—		550		—		3,674		—		3,674		—
	Interest rate cap	155		—		155		—		316		—		316		—
	Total financial assets	$	705	$	—	$	705	$	—	$	3,990	$	—	$	3,990	$	—
Financial Assets And Liabilities Measured And Recorded At Fair Value On A Recurring Basis, Presented On The Consolidated Condensed Balance Sheets	'
	Financial assets measured and recorded at fair value on a recurring basis were presented on the Company’s condensed consolidated balance sheets as follows:
		Fair Value as of July 27, 2014								Fair Value as of January 26, 2014
	(in thousands)	Total		(Level 1)		(Level 2)		(Level 3)		Total		(Level 1)		(Level 2)		(Level 3)
	Long-term investments	$	550	$	—	$	550	$	—	$	3,674	$	—	$	3,674	$	—
	Other assets	155		—		155		—		316		—		316		—
	Total financial assets	$	705	$	—	$	705	$	—	$	3,990	$	—	$	3,990	$	—

Inventories_Tables

Inventories (Tables)	6 Months Ended
	Jul. 27, 2014
Inventory Disclosure [Abstract]	'
Summary Of Inventories	'
	Inventories, consisting of material, material overhead, labor, and manufacturing overhead, are stated at the lower of cost (first-in, first-out) or market and consist of the following:
	(in thousands)	July 27, 2014		January 26, 2014
	Raw materials	$	1,769	$	1,971
	Work in progress	37,256		45,508
	Finished goods	15,454		12,788
	Inventories	$	54,479	$	60,267

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jul. 27, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Changes in Carrying Amounts of Goodwill	'
	Changes in the carrying amount of goodwill were as follows:
	(in thousands)	Signal Integrity				Signal, Integrity and Timing				Wireless and Sensing				Wireless, Sensing and Timing				Total
	Balance as of January 26, 2014	$	—			$	261,891			$	15,007			$	—			$	276,898
	Transfers	261,891				(261,891		)		(15,007		)		15,007				—
	Balance at July 27, 2014	$	261,891			$	—			$	—			$	15,007			$	276,898
Schedule of Finite-Lived Intangible Assets	'
	The following table sets forth the Company’s finite-lived intangible assets resulting from business acquisitions and technology licenses purchased, which continue to be amortized:
				July 27, 2014												January 26, 2014
	(in thousands)	Estimated		Gross				Accumulated				Net Carrying				Gross				Accumulated			Net Carrying
		Useful Life		Carrying				Amortization				Amount				Carrying				Amortization			Amount
				Amount												Amount
	Core technologies	2-10 years		$	146,925			$	(45,817	)		$	101,108			$	146,925			$	(35,357	)	$	111,568
	Customer relationships	7-10 years		28,630				(9,579		)		19,051				28,630				(7,505		)	21,125
	Technology licenses (1)	5-10 years		4,842				(1,103		)		3,739				3,842				(367		)	3,475
	Other intangibles assets	1-5 years		6,600				(6,197		)		403				6,600				(5,824		)	776
	Total finite-lived intangible assets			$	186,997			$	(62,696	)		$	124,301			$	185,997			$	(49,053	)	$	136,944
	-1	Technology licenses relate to in-license agreements for intellectual property that is used by the Company in research and development activities and also has alternative future uses. Amortization expense related to technology licenses is reported as “Product development and engineering” in the condensed consolidated statements of income.
Future Amortization Expense for Intangible Assets	'
	The estimated annual amount of future amortization expense for all finite-lived intangible assets will be as follows:
	(in thousands)
	To be recognized in:	Core Technologies				Customer Relationships				Technology Licenses				Other Intangibles				Total
	Remaining six months of fiscal year 2015	$	10,459			$	2,075			$	898			$	310			$	13,742
	Fiscal year 2016	20,919				4,149				1,798				93				26,959
	Fiscal year 2017	20,919				4,149				1,043				—				26,111
	Fiscal year 2018	20,919				4,130				—				—				25,049
	Fiscal year 2019	17,507				4,000				—				—				21,507
	Thereafter	10,385				548				—				—				10,933
	Total expected amortization expense	$	101,108			$	19,051			$	3,739			$	403			$	124,301

Income_Taxes_Tables

Income Taxes (Tables)	6 Months Ended
	Jul. 27, 2014
Income Tax Disclosure [Abstract]	'
Summary of Income Tax Contingencies	'
	A reconciliation of the beginning and ending amount of gross unrecognized tax benefits (before federal impact of state items) is as follows:
	(in thousands)	July 27, 2014
	Balance as of January 26, 2014	14,414
	Reductions for settlements with tax authorities	(4,513	)
	Balance as of July 27, 2014	9,901
Liability For Uncertain Tax Positions	'
	The liability for UTP is reflected within the consolidated balance sheets as follows:
	(in thousands)	July 27, 2014		January 26, 2014
	Deferred tax assets - non-current	$	7,582	$	12,095
	Other long-term liabilities	252		252
	Total accrued taxes	$	7,834	$	12,347

Concentration_of_Risk_Tables

Concentration of Risk (Tables)	6 Months Ended
	Jul. 27, 2014
Risks and Uncertainties [Abstract]	'
Schedule Of Significant Customers Accounting For At Least 10% Of Net Sales During Period	'
	The following significant customer accounted for at least 10% of net sales in all but one of the periods indicated:
		Three Months Ended				Six Months Ended
	(percentage of net sales)	July 27,		July 28,		July 27,		July 28,
		2014		2013		2014		2013
	Samsung Electronics (and affiliates)	9	%	11	%	11	%	13	%
Schedule Of Significant Customers Having An Outstanding Receivable Balance That Represents At Least 10% Of Total Net Receivables During Period	'
	The following table shows the customer that has an outstanding receivable balance that represents at least 10% of total net receivables for the periods indicated:
		Balance as of
	(percentage of net accounts receivable)	July 27,		January 26,
		2014		2014
	Samsung Electronics (and affiliates)	10	%	13	%

Segment_Information_Tables

Segment Information (Tables)	6 Months Ended
	Jul. 27, 2014
Segment Reporting [Abstract]	'
Net Sales by Segment	'
	Net sales by segment are as follows:
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,			July 28,
		2014				2013				2014			2013
	Semiconductor Products Group	$	145,451			$	158,149			$	277,195		$	316,708
	All others	291				6,861				1,406			10,709
	Total	$	145,742			$	165,010			$	278,601		$	327,417
Income (loss) by Segment and Reconciliation to Consolidated Operating Income	'
	Income (loss) by segment and reconciliation to consolidated operating income:
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,			July 28,
		2014				2013				2014			2013
	Semiconductor Products Group	$	36,517			$	39,137			$	66,478		$	81,160
	All others	(1,345		)		2,131				(4,049		)	346
	Operating Income by segment	35,172				41,268				62,429			81,506
	Items to reconcile segment operating income (loss) to consolidated income before taxes
	Intangible amortization and impairments	6,444				9,811				12,869			17,667
	Stock-based compensation expense	6,274				6,156				13,121			14,782
	Inventory write-down	—				—				1,052			—
	Restructuring charges	—				—				1,001			—
	Other non-segment related expenses	58				506				502			1,437
	Amortization of fair value adjustments related to acquired PP&E	339				338				678			3,085
	Interest expense, net	1,588				10,584				2,975			14,644
	Non-operating expense, net	345				198				623			1,005
	Income before taxes	$	20,124			$	13,675			$	29,608		$	28,886
Net Sales Activity By Geographic Region	'
	Net sales activity by geographic region is as follows:
		Three Months Ended						Six Months Ended
		July 27,			July 28,			July 27,			July 28,
		2014			2013			2014			2013
	Asia-Pacific	77	%		72	%		76	%		73	%
	North America	13	%		17	%		13	%		16	%
	Europe	10	%		11	%		11	%		11	%
		100	%		100	%		100	%		100	%
Summary Of Sales Activity To Countries That Represented Greater Than 10% Of Total Net Sales	'
	The table below summarizes sales activity to countries that represented greater than 10% of total net sales for one or more of the periods presented:
		Three Months Ended						Six Months Ended
	(percentage of total sales)	July 27,			July 28,			July 27,			July 28,
		2014			2013			2014			2013
	China (including Hong Kong)	36	%		32	%		35	%		33	%
	United States	12	%		15	%		13	%		15	%
	Japan	12	%		13	%		11	%		12	%
	South Korea	8	%		11	%		10	%		11	%
Income (Loss) From Continuing Operations Before Income Taxes	'
	Income (loss) from continuing operations before income taxes is as follows:
		Three Months Ended								Six Months Ended
	(in thousands)	July 27,				July 28,				July 27,			July 28,
		2014				2013				2014			2013
	Domestic	$	(6,002	)		$	(11,831	)		$	(11,139	)	$	(18,245	)
	Foreign	26,126				25,506				40,747			47,131
	Total	$	20,124			$	13,675			$	29,608		$	28,886

Restructuring_Tables

Restructuring (Tables)	6 Months Ended
	Jul. 27, 2014
Restructuring and Related Activities [Abstract]	'
Schedule of Restructuring Related Liabilities	'
	The following table summarizes the restructuring activity for the six months ended July 27, 2014:
	(in thousands)	One-time employee termination benefits			Contract commitments			Total
	Balance at January 26, 2014	1,387			1,245			2,632
	Charges	378			623			1,001
	Cash payments	(1,702		)	(1,586		)	(3,288		)
	Reclassifications	—			(115		)	(115		)
	Balance at July 27, 2014	$	63		$	167		$	230

Organization_and_Basis_of_Pres2

Organization and Basis of Presentation (Fiscal Year) (Details)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014
	weeks	weeks	weeks
52 Week Fiscal Year [Member]	'	'	'
Organization And Basis Of Presentation [Line Items]	'	'	'
Number of weeks in the fiscal year reporting period	'	'	52
Number of weeks in a quarter for 52 week fiscal period	13	13	13
53 Week Fiscal Year [Member]	'	'	'
Organization And Basis Of Presentation [Line Items]	'	'	'
Number of weeks in the fiscal year reporting period	'	'	53
Number of weeks in the 4th quarter for 53 week fiscal period	'	'	14

Organization_and_Basis_of_Pres3

Organization and Basis of Presentation (Segment Information) (Details)	6 Months Ended
	Jul. 27, 2014
	operating_segment
	reportable_segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Number of reportable segments	1
Number of operating segments	4
Number of operating segments that aggregate into one reportable segment	3

Earnings_Per_Share_Computation

Earnings Per Share - Computation Of Basic And Diluted Earnings Per Common Share (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Earnings Per Share [Abstract]	'	'	'	'
Net income	$17,898	$19,112	$25,765	$33,889
Weighted average common shares outstanding - basic	67,208	67,614	67,254	67,285
Dilutive effect of options and restricted stock units	642	1,476	634	1,527
Weighted average common shares outstanding - diluted	67,850	69,090	67,888	68,812
Basic earnings per common share	$0.27	$0.28	$0.38	$0.50
Diluted earnings per common share	$0.26	$0.28	$0.38	$0.49
Anti-dilutive shares not included in the above calculations	1,463	352	1,427	392

StockBased_Compensation_Narrat

Stock-Based Compensation - Narrative (Details) (USD $)	6 Months Ended							0 Months Ended
In Thousands, except Share data, unless otherwise specified	Jul. 27, 2014	Jul. 27, 2014	Jul. 27, 2014	Jul. 27, 2014	Jul. 27, 2014	Jul. 27, 2014	Jul. 27, 2014	Feb. 26, 2014	Feb. 26, 2014	Feb. 26, 2014	Feb. 26, 2014
	Minimum [Member]	Stock options [Member]	Stock options [Member]	Performance shares [Member]	Employee stock unit awards [Member]	Non-employee director stock unit awards [Member]	Subject To Cash Settlement [Member]	CEO [Member]	CEO [Member]	CEO [Member]	CEO [Member]
		Minimum [Member]	Maximum [Member]				Performance shares [Member]	Market Performance Units, Tranche 1 [Member]	Market Performance Units, Tranche 1 [Member]	Market Performance Units, Tranche 2 [Member]	Market Performance Units, Tranche 2 [Member]
									Minimum [Member]		Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Vesting period	'	'3 years	'4 years	'	'4 years	'1 year	'	'	'	'	'
Performance condition, highest potential performance level	'	'	'	200.00%	'	'	'	'	'	'	'
Maximum number of shares which would be settled in shares	'	'	'	522,532	'	'	'	'	'	'	'
Maximum number of shares which would be settled in cash	'	'	'	522,532	'	'	'	'	'	'	'
Target performance metrics for performance unit awards, fiscal year 2015	'	'	'	100.00%	'	'	'	'	'	'	'
Target performance metrics for performance unit awards, fiscal year 2014	'	'	'	87.00%	'	'	'	'	'	'	'
Target performance metrics for performance unit awards, fiscal year 2013	'	'	'	0.00%	'	'	'	'	'	'	'
Change in liability	'	'	'	'	'	($39)	($318)	'	'	'	'
Award vesting percentage	'	'	'	'	'	'	'	30.00%	'	'	'
Award performance period	'	'	'	'	'	'	'	'120 days	'	'120 days	'
Average per share closing price used to determine vesting rights (in dollars per share)	'	'	'	'	'	'	'	'	$35	'	$40
Potential per share consideration due upon change in control	$40	'	'	'	'	'	'	'	'	'	'
Vested but unsettled stock units	'	'	'	'	'	179,092	'	'	'	'	'

StockBased_Compensation_Alloca

Stock-Based Compensation - Allocation of Stock-Based Compensation (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated Share-based Compensation Expense	$6,274	$6,156	$13,121	$14,782
Inventories [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Increase In Stock Based Compensation Capitalized Into Inventory	37	8	28	85
Cost of Sales [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated Share-based Compensation Expense	355	405	718	733
General and Administrative Expense [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated Share-based Compensation Expense	3,448	3,548	7,513	8,430
Product Development And Engineering [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated Share-based Compensation Expense	$2,472	$2,203	$4,891	$5,619

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Fair Value Assumptions (Details) (Stock options [Member], USD $)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Expected lives	'	'4 years 8 months	'	'
Estimated volatility	33.00%	33.00%	'	'
Dividend yield	0.00%	0.00%	0.00%	0.00%
Risk-free interest rate, minimum	'	1.30%	'	'
Weighted average fair value on grant date	$7.43	$10.59	$7.26	$9.33
Minimum [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Expected lives	'4 years 4 months	'	'3 years 0 months	'4 years 2 months
Estimated volatility, minimum	'	'	33.00%	33.00%
Risk-free interest rate, minimum	1.30%	'	1.26%	0.65%
Maximum [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Expected lives	'4 years 5 months	'	'4 years 5 months	'4 years 8 months
Estimated volatility, maximum	'	'	34.00%	35.00%
Risk-free interest rate, maximum	1.43%	'	1.43%	1.30%

StockBased_Compensation_Summar1

Stock-Based Compensation - Summary of the Activity for Stock Option Awards (Details) (Stock options [Member], USD $)	6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014
Stock options [Member]	'
Number of Shares	'
Beginning balance (in shares)	1,935
Options granted (in shares)	261
Options exercised (in shares)	-353
Options cancelled/forfeited (in shares)	-31
Ending balance (in shares)	1,812
Exercisable at end of period (in shares)	1,112
Weighted Average Exercise Price (per share)	'
Beginning balance (in dollars per share)	$21.33
Options granted (in dollars per share)	$24.92
Options exercised (in dollars per share)	$16.94
Options cancelled/forfeited (in dollars per share)	$26.71
Ending balance (in dollars per share)	$22.61
Exercisable at end of period (in dollars per share)	$19.58
Aggregate Intrinsic Value	'
Beginning balance	$7,722
Options exercised	3,102
Ending balance	4,425
Exercisable at end of period	4,383
Aggregate Unrecognized Compensation	'
Beginning balance	4,354
Ending balance	$4,846
Number of Shares Exercisable	'
Exercisable at beginning of period (in shares)	1,275
Exercisable at end of period (in shares)	1,112
Weighted Average Contractual Term (in years)	'
Exercisable at end of period	'2 years 5 months

StockBased_Compensation_Summar2

Stock-Based Compensation - Summary of the Activity for Performance Unit Awards (Details) (Performance shares [Member], USD $)	6 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014	Jan. 26, 2014
Units	'	'
Beginning balance (in shares)	376	'
Performance units granted (in shares)	256	'
Performance units vested (in shares)	-93	'
Performance units cancelled/forfeited (in shares)	-17	'
Ending balance (in shares)	522	376
Weighted Average Grant Date Fair Value (per share)	'	'
Beginning balance (in dollars per share)	$28.50	'
Performance units granted (in dollars per share)	$24.74	'
Performance units vested (in dollars per share)	$23.36	'
Performance units forfeited (in dollars per share)	$25.51	'
Ending balance (in dollars per share)	$27.57	$28.50
Aggregate Unrecognized Compensation	'	'
Beginning balance	$3,893	'
Ending balance	7,577	3,893
Weighted Average Period Over Which Expected to be Recognized (in years)	'	'
Weighted average period over which expected to be recognized	'1 year 11 months	'1 year 4 months
Subject To Share Settlement [Member]	'	'
Units	'	'
Beginning balance (in shares)	192	'
Performance units granted (in shares)	128	'
Performance units vested (in shares)	-52	'
Performance units cancelled/forfeited (in shares)	-9	'
Ending balance (in shares)	259	'
Subject To Cash Settlement [Member]	'	'
Units	'	'
Beginning balance (in shares)	184	'
Performance units granted (in shares)	128	'
Performance units vested (in shares)	-41	'
Performance units cancelled/forfeited (in shares)	-8	'
Ending balance (in shares)	263	'
Recorded Liability	'	'
Beginning balance	1,305	'
Change in liability	-318	'
Ending balance	$987	'

StockBased_Compensation_Market

Stock-Based Compensation - Market Performance Units Valuation Assumptions (Details) (USD $)	6 Months Ended
	Jul. 27, 2014
Market Performance Units, Tranche 1 [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Expected lives, in years	'1 year 7 months
Estimated volatility	34.00%
Dividend yield	0.00%
Risk-free interest rate	1.50%
Stock units granted (in dollars per share)	$17.26
Market Performance Units, Tranche 2 [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Expected lives, in years	'2 years 1 month
Estimated volatility	34.00%
Dividend yield	0.00%
Risk-free interest rate	1.50%
Stock units granted (in dollars per share)	$14.88

StockBased_Compensation_Summar3

Stock-Based Compensation - Summary of the Activity for Market Performance Units Awards (Details) (Market performance shares [Member], USD $)	6 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014	Jan. 26, 2014
Market performance shares [Member]	'	'
Units	'	'
Beginning balance (in shares)	0	'
Performance units granted (in shares)	220	'
Performance units vested (in shares)	0	'
Performance units cancelled/forfeited (in shares)	0	'
Ending balance (in shares)	220	0
Weighted Average Grant Date Fair Value (per share)	'	'
Beginning balance (in dollars per share)	$0	'
Performance units granted (in dollars per share)	$15.59	'
Performance units vested (in dollars per share)	$0	'
Performance units forfeited (in dollars per share)	$0	'
Ending balance (in dollars per share)	$15.59	$0
Aggregate Unrecognized Compensation	'	'
Beginning balance	$0	'
Ending balance	$2,664	$0
Weighted Average Period Over Which Expected to be Recognized (in years)	'	'
Weighted average period over which expected to be recognized	'1 year 6 months	'0 years

StockBased_Compensation_Summar4

Stock-Based Compensation - Summary of the Activity for Employee Stock Unit Awards (Details) (Employee stock unit awards [Member], USD $)	6 Months Ended		12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014		Jan. 26, 2014
Employee stock unit awards [Member]	'		'
Number of Units	'		'
Beginning balance (in shares)	2,195		'
Stock units granted (in shares)	333		'
Stock units vested (in shares)	-319		'
Stock units forfeited (in shares)	-142		'
Ending balance (in shares)	2,067		2,195
Weighted Averaged Grant Date Fair Value (per unit)	'		'
Beginning balance (in dollars per share)	$27.18		'
Stock units granted (in dollars per share)	$24.18		'
Stock units vested (in dollars per share)	$27.37		'
Stock units forfeited (in dollars per share)	$26.65		'
Ending balance (in dollars per share)	$26.71		$27.18
Aggregate Intrinsic Value	'		'
Aggregate intrinsic value of stock units vested	$7,905	[1]	'
Aggregate Unrecognized Compensation	'		'
Beginning balance	49,563		'
Ending balance	$44,313		$49,563
Weighted Average Period Over Which Expected to be Recognized (in years)	'		'
Weighted average period over which expected to be recognized	'2 years 4 months		'2 years 6 months
[1]	Reflects the value of Semtech stock on the date that the restricted stock unit vested.

StockBased_Compensation_Summar5

Stock-Based Compensation - Summary of the Activity For Non-Employee Directors Stock Unit Awards (Details) (Non-employee director stock unit awards [Member], USD $)	6 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jul. 27, 2014	Jan. 26, 2014
Non-employee director stock unit awards [Member]	'	'
Number of Units	'	'
Beginning balance (in shares)	18	'
Stock units granted (in shares)	24	'
Stock units vested (in shares)	-18	'
Stock units forfeited (in shares)	0	'
Ending balance (in shares)	24	18
Recorded Liability	'	'
Beginning balance	$3,981	'
Change in liability	-39	'
Ending balance	3,942	3,981
Weighted Averaged Grant Date Fair Value (per unit)	'	'
Beginning balance (in dollars per share)	$35.17	'
Stock units granted (in dollars per share)	$26.59	'
Stock units vested (in dollars per share)	$35.17	'
Stock units forfeited (in dollars per share)	$0	'
Ending balance (in dollars per share)	$26.59	$35.17
Aggregate Unrecognized Compensation	'	'
Beginning balance	177	'
Ending balance	$478	$177
Period Over Which Expected to be Recognized (in years)	'	'
Weighted average period over which expected to be recognized	'11 months	'5 months

Investments_Narrative_Details

Investments - Narrative (Details)	6 Months Ended
	Jul. 27, 2014
Investment [Line Items]	'
Number of investments in privately held companies	2
Minimum [Member]	'
Investment [Line Items]	'
Investment maturity period	'3 months
Temporary Investments [Member] | Minimum [Member]	'
Investment [Line Items]	'
Investment maturity period	'3 months
Temporary Investments [Member] | Maximum [Member]	'
Investment [Line Items]	'
Investment maturity period	'12 months
Long-Term Investments [Member] | Minimum [Member]	'
Investment [Line Items]	'
Investment maturity period	'12 months
Long-Term Investments [Member] | Maximum [Member]	'
Investment [Line Items]	'
Investment maturity date, fiscal year	'2016

Investments_Summary_Of_Investm

Investments - Summary Of Investments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jan. 26, 2014
Investment [Line Items]	'	'
Market Value	$550	$3,674
Adjusted Cost	550	3,673
Gross Unrealized Gain	0	1
Agency Securities [Member]	'	'
Investment [Line Items]	'	'
Market Value	550	3,674
Adjusted Cost	550	3,673
Gross Unrealized Gain	$0	$1

Investments_Schedule_Of_Invest

Investments - Schedule Of Investments, Classified By Maturity Period (Details) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, unless otherwise specified
Investment [Line Items]	'	'
Market Value	$550	$3,674
Adjusted Cost	550	3,673
Within 1 Year [Member]	'	'
Investment [Line Items]	'	'
Market Value	0	0
Adjusted Cost	0	0
After 1 Year Through 5 Years [Member]	'	'
Investment [Line Items]	'	'
Market Value	550	3,674
Adjusted Cost	$550	$3,673

Investments_Summary_Of_Unreali

Investments - Summary Of Unrealized Gains (Losses) On Investments (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Investments [Abstract]	'	'	'	'
Unrealized loss, net of tax	($1)	($4)	$0	($5)
Increase to deferred tax liability	($1)	($3)	$0	($3)

Investments_Schedule_Of_Intere

Investments - Schedule Of Interest Income Generated From Investments (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Investments [Abstract]	'	'	'	'
Interest income	$12	$91	$20	$191

Investments_Cost_Method_Equity

Investments - Cost Method Equity Investments (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014
Cost Method Investments [Roll Forward]	'
Balance at January 26, 2014	$5,000
Additions	3,264
Balance at July 27, 2014	$8,264

Fair_Value_Measurements_Narrat

Fair Value Measurements - Narrative (Details) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Millions, unless otherwise specified
New credit facilities, Term Loan [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Fair value of debt	$105	$114.30
Revolving Credit Facility [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Fair value of debt	$152.60	$177.50

Fair_Value_Measurements_Financ

Fair Value Measurements - Financial Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis (Details) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, unless otherwise specified
Fair Value, Assets Measured On A Recurring Basis [Line Items]	'	'
Available-for-sale securities	$550	$3,674
Interest rate cap	155	316
Total financial assets	705	3,990
Level 1 [Member]	'	'
Fair Value, Assets Measured On A Recurring Basis [Line Items]	'	'
Available-for-sale securities	0	0
Interest rate cap	0	0
Total financial assets	0	0
Level 2 [Member]	'	'
Fair Value, Assets Measured On A Recurring Basis [Line Items]	'	'
Available-for-sale securities	550	3,674
Interest rate cap	155	316
Total financial assets	705	3,990
Level 3 [Member]	'	'
Fair Value, Assets Measured On A Recurring Basis [Line Items]	'	'
Available-for-sale securities	0	0
Interest rate cap	0	0
Total financial assets	$0	$0

Fair_Value_Measurements_Financ1

Fair Value Measurements - Financial Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis by Balance Sheet Line (Details) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Long-term investments	$550	$3,674
Other assets	155	316
Total financial assets	705	3,990
Level 1 [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Total financial assets	0	0
Level 2 [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Long-term investments	550	3,674
Other assets	155	316
Total financial assets	705	3,990
Level 3 [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Total financial assets	$0	$0

Inventories_Narrative_Details

Inventories - Narrative (Details) (USD $)	3 Months Ended	6 Months Ended
In Millions, unless otherwise specified	Jan. 26, 2014	Jul. 27, 2014
Inventory Disclosure [Abstract]	'	'
Cost of sales - lower of cost or market write-down	$15	$1.10

Inventories_Summary_of_Invento

Inventories - Summary of Inventories (Details) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials	$1,769	$1,971
Work in progress	37,256	45,508
Finished goods	15,454	12,788
Inventories	$54,479	$60,267

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets - Narrative (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013	Jan. 26, 2014
			reporting_unit
Goodwill and Intangible Assets Disclosure [Abstract]	'	'	'	'	'
Number of reporting units	'	'	2	'	'
Finite-lived intangible assets, gross	$186,997,000	'	$186,997,000	'	$185,997,000
Amortization expense related to finite-lived intangible assets	6,444,000	7,211,000	12,869,000	15,067,000	'
Indefinite-lived intangible assets	4,000,000	'	4,000,000	'	4,000,000
Intangible asset impairments	$0	$2,600,000	$0	$2,600,000	'

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets - Changes in Carrying Amounts of Goodwill (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014
Goodwill [Roll Forward]	'
Balance as of January 26, 2014	$276,898
Transfers	0
Balance at July 27, 2014	276,898
Signal Integrity [Member]	'
Goodwill [Roll Forward]	'
Balance as of January 26, 2014	0
Transfers	261,891
Balance at July 27, 2014	261,891
Signal Integrity and Timing [Member]	'
Goodwill [Roll Forward]	'
Balance as of January 26, 2014	261,891
Transfers	-261,891
Balance at July 27, 2014	0
Wireless and Sensing [Member]	'
Goodwill [Roll Forward]	'
Balance as of January 26, 2014	15,007
Transfers	-15,007
Balance at July 27, 2014	0
Wireless, Sensing and Timing [Member]	'
Goodwill [Roll Forward]	'
Balance as of January 26, 2014	0
Transfers	15,007
Balance at July 27, 2014	$15,007

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets - Schedule Of Finite-Lived Intangible Assets (Details) (USD $)

Jul. 27, 2014

Jan. 26, 2014

Jul. 27, 2014

Jan. 26, 2014

Jul. 27, 2014

Jul. 27, 2014

Jul. 27, 2014

Jan. 26, 2014

Jul. 27, 2014

Jul. 27, 2014

Jul. 27, 2014

Jan. 26, 2014

Jul. 27, 2014

Jul. 27, 2014

Jul. 27, 2014

Jan. 26, 2014

Jul. 27, 2014

Jul. 27, 2014

In Thousands, unless otherwise specified

Developed Technology [Member]

Developed Technology [Member]

Developed Technology [Member]

Developed Technology [Member]

Customer Relationships [Member]

Customer Relationships [Member]

Customer Relationships [Member]

Customer Relationships [Member]

Technology Licenses [Member]

Technology Licenses [Member]

Technology Licenses [Member]

Technology Licenses [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Finite-Lived Intangible Assets [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated useful life

'

'

'

'

'2 years

'10 years

'

'

'7 years

'10 years

'

'

'5 years

'10 years

'

'

'1 year

'5 years

Gross carrying amount

$186,997

$185,997

$146,925

$146,925

'

'

$28,630

$28,630

'

'

$4,842

[1]

$3,842

[1]

'

'

$6,600

$6,600

'

'

Accumulated amortization

-62,696

-49,053

-45,817

-35,357

'

'

-9,579

-7,505

'

'

-1,103

[1]

-367

[1]

'

'

-6,197

-5,824

'

'

Net carrying amount

$124,301

$136,944

$101,108

$111,568

'

'

$19,051

$21,125

'

'

$3,739

[1]

$3,475

[1]

'

'

$403

$776

'

'

[1]

Technology licenses relate to in-license agreements for intellectual property that is used by the Company in research and development activities and also has alternative future uses. Amortization expense related to technology licenses is reported as “Product development and engineering” in the condensed consolidated statements of income.

Goodwill_and_Intangible_Assets5

Goodwill and Intangible Assets - Future Amortization Expense For Intangible Assets (Details) (USD $)	Jul. 27, 2014		Jan. 26, 2014
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]	'		'
Remaining six months of fiscal year 2015	$13,742		'
Fiscal year 2016	26,959		'
Fiscal year 2017	26,111		'
Fiscal year 2018	25,049		'
Fiscal year 2019	21,507		'
Thereafter	10,933		'
Net carrying amount	124,301		136,944
Developed Technology [Member]	'		'
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]	'		'
Remaining six months of fiscal year 2015	10,459		'
Fiscal year 2016	20,919		'
Fiscal year 2017	20,919		'
Fiscal year 2018	20,919		'
Fiscal year 2019	17,507		'
Thereafter	10,385		'
Net carrying amount	101,108		111,568
Customer Relationships [Member]	'		'
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]	'		'
Remaining six months of fiscal year 2015	2,075		'
Fiscal year 2016	4,149		'
Fiscal year 2017	4,149		'
Fiscal year 2018	4,130		'
Fiscal year 2019	4,000		'
Thereafter	548		'
Net carrying amount	19,051		21,125
Technology Licenses [Member]	'		'
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]	'		'
Remaining six months of fiscal year 2015	898		'
Fiscal year 2016	1,798		'
Fiscal year 2017	1,043		'
Fiscal year 2018	0		'
Fiscal year 2019	0		'
Thereafter	0		'
Net carrying amount	3,739	[1]	3,475	[1]
Other Intangible Assets [Member]	'		'
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]	'		'
Remaining six months of fiscal year 2015	310		'
Fiscal year 2016	93		'
Fiscal year 2017	0		'
Fiscal year 2018	0		'
Fiscal year 2019	0		'
Thereafter	0		'
Net carrying amount	$403		$776
[1]	Technology licenses relate to in-license agreements for intellectual property that is used by the Company in research and development activities and also has alternative future uses. Amortization expense related to technology licenses is reported as “Product development and engineering” in the condensed consolidated statements of income.

Credit_Facilities_Narrative_De

Credit Facilities Narrative (Details) (USD $)

2-May-13

Mar. 20, 2012

Jul. 27, 2014

Jul. 27, 2014

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

Mar. 20, 2012

Mar. 20, 2012

Jun. 03, 2013

Jul. 27, 2014

2-May-13

Jul. 14, 2014

Jul. 27, 2014

2-May-13

2-May-13

2-May-13

2-May-13

Jul. 28, 2013

Jan. 26, 2014

2-May-13

Jul. 27, 2014

2-May-13

Jul. 27, 2014

2-May-13

Jul. 27, 2014

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

2-May-13

Jul. 27, 2014

Jul. 27, 2014

Minimum [Member]

Maximum [Member]

Base Rate [Member]

Base Rate [Member]

LIBOR [Member]

LIBOR [Member]

LIBOR [Member]

Federal Funds [Member]

CDOR [Member]

CDOR [Member]

CDOR [Member]

Prior credit facilities, Term A Loans [Member]

Prior credit facilities, Term B Loans [Member]

New credit facilities, Term Loan [Member]

New credit facilities, Term Loan [Member]

New credit facilities, Term Loan [Member]

New credit facilities, Revolving Credit Facility [Member]

New credit facilities, Revolving Credit Facility [Member]

New credit facilities, Revolving Credit Facility [Member]

New credit facilities, Revolving Credit Facility [Member]

New credit facilities, Revolving Credit Facility [Member]

New credit facilities [Member]

New credit facilities [Member]

Prior credit facilities [Member]

Prior credit facilities [Member]

New credit facilities, Letter of Credit [Member]

New credit facilities, Letter of Credit [Member]

New credit facilities, Swingline Loans [Member]

New credit facilities, Swingline Loans [Member]

New credit facilities, Revolving Loans and Non US Dollars LC [Member]

New credit facilities, Revolving Loans and Non US Dollars LC [Member]

Additional Term Loan or Increase in Revolver [Member]

Alternative Currencies, Except Canadian [Member]

United States of America, Dollars

Canada, Dollars

Base Rate [Member]

CDOR [Member]

Through second quarter of fiscal year 2018 [Domain]

Beginning third quarter of fiscal year 2018 [Domain]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Prior credit facilities, aggregate principal amount of term loans

'

$350,000,000

'

'

'

'

'

'

'

'

'

'

'

$100,000,000

$250,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Initial carrying amounts

'

'

'

'

'

'

'

'

'

'

'

'

'

99,500,000

247,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Original issue discount on debt

'

'

'

'

'

'

'

'

'

'

'

'

'

500,000

2,500,000

'

'

'

'

'

'

'

'

1,400,000

600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, maximum borrowing capacity

400,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

150,000,000

'

'

250,000,000

'

'

'

'

'

'

'

40,000,000

'

25,000,000

'

40,000,000

100,000,000

'

'

'

'

'

'

'

New credit facilities, amount outstanding

326,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

105,300,000

149,300,000

'

153,000,000

177,300,000

'

'

'

'

'

'

0

'

0

'

0

'

'

'

'

'

'

'

'

'

New credit facilities, debt discount expensed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Prior credit facilities, repayment of outstanding obligations

327,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, deferred financing cost

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, deferred financing costs expensed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Deferred finance costs capitalized

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,200,000

'

'

1,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, contractual term

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Prior credit facilities, loss on modification of debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-7,100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Description of variable rate basis

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'a rate per annum equal to LIBOR (determined with respect to deposits in the applicable Alternative Currency) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio.

'(1) the Base Rate plus a margin ranging from 0.25% to 1.25% depending upon Semtech’s consolidated leverage ratio or (2) LIBOR (determined with respect to deposits in U.S. Dollars) for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio.

'a rate per annum equal to the CDOR Rate for an interest period to be selected by Semtech plus a margin ranging from 1.25% to 2.25% depending upon Semtech’s consolidated leverage ratio.

'the highest of (a) the prime rate (as published by The Wall Street Journal), (b) ½ of 1% above the federal funds effective rate or (c) one-month LIBOR (determined with respect to deposits in U.S. Dollars) plus 1%.

'the sum of: (a) the rate determined by Administrative Agent with reference to the arithmetic average of the discount rate quotations of all institutions listed for CAD Dollar-denominated bankers’ acceptances displayed and identified on the “Reuters Screen CDOR Page” and (b) 0.10% per annum

'

'

Basis spread on variable rate

'

'

'

'

0.25%

1.25%

1.00%

1.25%

2.25%

1.00%

0.10%

1.25%

2.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, unused capacity, commitment fee percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.20%

0.45%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, Interest rate at period end

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.90%

'

'

1.90%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

New credit facilities, required quarterly principal payment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,700,000

7,500,000

Principal payments remaining in fiscal year 2015

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

9,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal payments in fiscal year 2016

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

18,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal payments in fiscal year 2017

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

18,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Principal payments in fiscal year 2018

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

24,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repayments of debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$26,000,000

'

'

$25,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest coverage ratio

'

'

3.5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total leverage ratio

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest_Rate_Derivative_Agree1

Interest Rate Derivative Agreement - Narrative (Details) (USD $)	0 Months Ended
	Jun. 20, 2012	Jul. 27, 2014	2-May-13
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'	'	'
Interest rate cap, notional amount	$175,000,000	'	'
Payment on interest rate cap	1,100,000	'	'
Description of variable rate basis	'one-month LIBOR	'	'
Interest rate cap, rate	1.00%	'	'
New credit facilities, maximum borrowing capacity	'	'	400,000,000
Interest rate cash flow hedge unrealized loss expected to be reclassified during next 12 months into interest expense, net	'	$400,000	'

Income_Taxes_Narrative_Details

Income Taxes - Narrative (Details) (USD $)	6 Months Ended
	Jul. 27, 2014	Jan. 26, 2014
Income Tax Disclosure [Abstract]	'	'
Statutory federal income tax rate	35.00%	'
Percentage of uncertain tax positions evaluating criteria	50.00%	'
Gross unrecognized tax benefits	$9,901,000	$14,414,000
Net tax benefits, if recognized, would impact the effective tax rate	7,800,000	12,300,000
Unrecognized tax benefits, interest and penalties	$293,000	$293,000

Income_Taxes_Summary_of_Income

Income Taxes Summary of Income Tax Contingencies (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014
Income Tax Contingency [Line Items]	'
Beginning balance	$14,414
Reductions for settlements with tax authorities	-4,513
Ending balance	$9,901

Income_Taxes_Liability_For_Unc

Income Taxes - Liability For Uncertain Tax Positions (Details) (USD $)	Jul. 27, 2014	Jan. 26, 2014
In Thousands, unless otherwise specified
Income Tax Contingency [Line Items]	'	'
Total accrued taxes	$7,834	$12,347
Non-current deferred tax asset [Member]	'	'
Income Tax Contingency [Line Items]	'	'
Other long-term liabilities	7,582	12,095
Other liabilities [Member]	'	'
Income Tax Contingency [Line Items]	'	'
Other long-term liabilities	$252	$252

Commitments_and_Contingencies_

Commitments and Contingencies - Narrative (Details) (USD $)	Jul. 27, 2014	Oct. 28, 2012	Jul. 27, 2014	Jan. 26, 2014
In Millions, unless otherwise specified			Cycleo [Member]	Cycleo [Member]
Loss Contingencies [Line Items]	'	'	'	'
Range of possible loss, minimum	$2.50	'	'	'
Range of possible loss, maximum	5.7	'	'	'
Environmental loss contingency accrual, at carrying value	2.5	2.5	'	'
Potential payments under earn-out arrangements, high estimate	'	'	16	'
Potential payments under earn-out arrangements, payout period	'	'	'4 years	'
Cumulative earn-out liability	'	'	$0.90	$0.90

Concentration_of_Risk_Narrativ

Concentration of Risk - Narrative (Details)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Sales Revenue, Goods, Net [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Minimum concentration risk threshold	10.00%	'	'	'
Net sales [Member] | Distributor concentration risk [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	60.00%	44.00%	'	'
China | Cost of Silicon Wafers [Member] | Supplier concentration risk [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	43.00%	35.00%	'	'

Concentration_of_Risk_Schedule

Concentration of Risk - Schedule Of Significant Customers Accounting For At Least 10% Of Net Sales During Period (Details)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Sales Revenue, Goods, Net [Member]	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Minimum concentration risk threshold	10.00%	'	'	'
Sales Revenue, Goods, Net [Member] | Samsung Electronics (and Affiliates)	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration risk, percentage	9.00%	11.00%	11.00%	13.00%

Concentration_of_Risk_Schedule1

Concentration of Risk - Schedule Of Significant Customers Having An Outstanding Receivable Balance That Represents At Least 10% Of Total Net (Details)	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 27, 2014	Jan. 26, 2014
					Accounts Receivable [Member]	Samsung Electronics (and Affiliates)	Samsung Electronics (and Affiliates)
						Accounts Receivable [Member]	Accounts Receivable [Member]
Concentration Risk [Line Items]	'	'	'	'	'	'	'
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%	'	10.00%	13.00%
Minimum concentration risk threshold	'	'	'	'	10.00%	'	'

Segment_Information_Net_Sales_

Segment Information Net Sales Activity by Segment (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Revenue from External Customer [Line Items]	'	'	'	'
Net sales	$145,742	$165,010	$278,601	$327,417
Semiconductor Products Group [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Net sales	145,451	158,149	277,195	316,708
All others [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Net sales	$291	$6,861	$1,406	$10,709

Segment_Information_Income_Los

Segment Information Income (Loss) by Segment and Reconciliation to Income Before Taxes (Details) (USD $)	3 Months Ended				6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Apr. 27, 2014	Jan. 26, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Segment Reporting Information [Line Items]	'	'	'	'	'	'
Operating income	$22,057	'	'	$24,457	$33,206	$44,535
Items to reconcile segment operating income (loss) to consolidated income before taxes	'	'	'	'	'	'
Stock-based compensation expense	6,274	'	'	6,156	13,121	14,782
Inventory write-down	'	'	15,000	'	1,100	'
Restructuring charge	0	1,001	'	0	1,001	0
Amortization of fair value adjustments related to acquired PP&E	'	'	'	'	0	2,529
Interest expense, net	1,588	'	'	10,584	2,975	14,644
Non-operating expense, net	345	'	'	198	623	1,005
Income before taxes	20,124	'	'	13,675	29,608	28,886
Corporate, Non-Segment [Member]	'	'	'	'	'	'
Items to reconcile segment operating income (loss) to consolidated income before taxes	'	'	'	'	'	'
Intangible amortization and impairments	6,444	'	'	9,811	12,869	17,667
Stock-based compensation expense	6,274	'	'	6,156	13,121	14,782
Inventory write-down	0	'	'	0	1,052	0
Restructuring charge	0	'	'	0	1,001	0
Other non-segment related expenses	58	'	'	506	502	1,437
Amortization of fair value adjustments related to acquired PP&E	339	'	'	338	678	3,085
Interest expense, net	1,588	'	'	10,584	2,975	14,644
Non-operating expense, net	345	'	'	198	623	1,005
Operating Segments [Member]	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'
Operating income	35,172	'	'	41,268	62,429	81,506
Semiconductor Products Group [Member]	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'
Operating income	36,517	'	'	39,137	66,478	81,160
All others [Member]	'	'	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'	'	'
Operating income	($1,345)	'	'	$2,131	($4,049)	$346

Segment_Information_Net_Sales_1

Segment Information Net Sales Activity by Geographic Region (Details)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Sales Revenue, Goods, Net [Member] | Asia-Pacific [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	77.00%	72.00%	76.00%	73.00%
Sales Revenue, Goods, Net [Member] | North America [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	13.00%	17.00%	13.00%	16.00%
Sales Revenue, Goods, Net [Member] | Europe [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	10.00%	11.00%	11.00%	11.00%

Segment_Information_Summary_of

Segment Information Summary of Sales Activity to Countries that Represented Greater than 10% of Total Net Sales (Details)	3 Months Ended		6 Months Ended
	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Sales Revenue, Goods, Net [Member] | China Including Hong Kong [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	36.00%	32.00%	35.00%	33.00%
Sales Revenue, Goods, Net [Member] | United States	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	12.00%	15.00%	13.00%	15.00%
Sales Revenue, Goods, Net [Member] | Japan	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	12.00%	13.00%	11.00%	12.00%
Sales Revenue, Goods, Net [Member] | South Korea	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Concentration risk, percentage	8.00%	11.00%	10.00%	11.00%

Segment_Information_Income_Los1

Segment Information Income (Loss) from Continuing Operations Before Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Segment Reporting [Abstract]	'	'	'	'
Domestic	($6,002)	($11,831)	($11,139)	($18,245)
Foreign	26,126	25,506	40,747	47,131
Income before taxes	$20,124	$13,675	$29,608	$28,886

Stock_Repurchase_Program_Narra

Stock Repurchase Program - Narrative (Details) (USD $)	0 Months Ended		6 Months Ended		21 Months Ended
	Aug. 21, 2013	Nov. 30, 2011	Jul. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Aug. 21, 2013
Equity, Class of Treasury Stock [Line Items]	'	'	'	'	'	'
Share repurchase program, authorized amount	'	$50,000,000	'	'	'	$100,000,000
Share repurchase program, additional amount authorized	50,000,000	'	'	'	'	'
Value of stock repurchased	'	'	'	'	57,500,000	'
Payments for repurchase of common stock	'	'	20,000,000	0	'	'
Two Thousand Eleven Repurchase Program [Member]	'	'	'	'	'	'
Equity, Class of Treasury Stock [Line Items]	'	'	'	'	'	'
Treasury stock, shares acquired	'	'	761,294	0	'	'
Payments for repurchase of common stock	'	'	$20,000,000	$0	'	'

Restructuring_Details

Restructuring (Details) (USD $)	3 Months Ended			6 Months Ended
In Thousands, unless otherwise specified	Jul. 27, 2014	Apr. 27, 2014	Jul. 28, 2013	Jul. 27, 2014	Jul. 28, 2013
Restructuring Reserve [Roll Forward]	'	'	'	'	'
Balance at January 26, 2014	'	$2,632	'	$2,632	'
Charges	0	1,001	0	1,001	0
Cash payments	'	'	'	-3,288	'
Reclassifications	'	'	'	-115	'
Balance at July 27, 2014	230	'	'	230	'
One-time employee termination benefits [Member]	'	'	'	'	'
Restructuring Reserve [Roll Forward]	'	'	'	'	'
Balance at January 26, 2014	'	1,387	'	1,387	'
Charges	'	'	'	378	'
Cash payments	'	'	'	-1,702	'
Reclassifications	'	'	'	0	'
Balance at July 27, 2014	63	'	'	63	'
Contract commitments [Member]	'	'	'	'	'
Restructuring Reserve [Roll Forward]	'	'	'	'	'
Balance at January 26, 2014	'	1,245	'	1,245	'
Charges	'	'	'	623	'
Cash payments	'	'	'	-1,586	'
Reclassifications	'	'	'	-115	'
Balance at July 27, 2014	$167	'	'	$167	'