Alpha and Omega Semiconductor Limited (AOSL) 10-Q 6 Feb 15 2015 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Dec. 31, 2014	Jan. 31, 2015
Entity Information [Line Items]
Entity Registrant Name	ALPHA & OMEGA SEMICONDUCTOR Ltd
Entity Central Index Key	1387467
Current Fiscal Year End Date	-24
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q2
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		26,656,866

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$120,647	$117,788
Restricted cash	203	244
Accounts receivable, net	26,704	36,535
Inventories	69,982	66,560
Deferred income tax assets	2,906	2,842
Other current assets	3,697	3,810
Total current assets	224,139	227,779
Property, plant and equipment, net	118,600	123,254
Intangible assets, net	18	229
Goodwill	269	269
Deferred income tax assets - long term	10,950	10,854
Other long-term assets	1,771	1,963
Total assets	355,747	364,348
Current liabilities:
Short term debt	7,143	13,821
Accounts payable	33,731	38,760
Accrued liabilities	18,559	17,376
Income taxes payable	1,389	1,933
Deferred margin	654	665
Capital leases	966	1,061
Total current liabilities	62,442	73,616
Income taxes payable - long term	2,357	2,315
Deferred income tax liabilities	3,220	3,234
Capital leases - long term	550	1,005
Other long term liabilities	1,053	1,143
Total liabilities	69,622	81,313
Commitments and contingencies (Note 9)
Preferred shares, par value $0.002 per share:
Authorized: 10,000 shares, issued and outstanding: none at December 31, 2014 and June 30, 2014	0	0
Common shares, par value $0.002 per share:
Authorized: 50,000 shares, issued and outstanding: 26,988 shares and 26,651 shares at December 31, 2014 and 26,644 shares and 26,304 shares at June 30, 2014	54	53
Treasury shares at cost, 337 shares at December 31, 2014 and 340 shares at June 30, 2014	-2,854	-2,889
Additional paid-in capital	178,052	174,084
Accumulated other comprehensive income	887	1,033
Retained earnings	109,986	110,754
Total shareholders’ equity	286,125	283,035
Total liabilities and shareholders’ equity	$355,747	$364,348

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2014	Jun. 30, 2014
Common shares, par value (in dollars per share)	$0.00	$0.00
Common shares, authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	26,988,000	26,644,000
Common stock, shares outstanding (in shares)	26,651,000	26,304,000
Preferred stock, par value (in dollars per share)	$0.00	$0.00
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Treasury shares (in shares)	337,000	340,000

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Revenue	$81,328	$76,265	$169,545	$160,386
Cost of goods sold	66,086	62,646	136,143	129,616
Gross profit	15,242	13,619	33,402	30,770
Operating expenses
Research and development	6,430	4,972	13,226	11,819
Selling, general and administrative	9,135	7,309	18,739	16,249
Total operating expenses	15,565	12,281	31,965	28,068
Operating income (loss)	-323	1,338	1,437	2,702
Interest income and other, net	26	14	74	38
Interest expense	-43	-69	-116	-148
Income (loss) before income taxes	-340	1,283	1,395	2,592
Income tax expense	957	1,123	2,128	2,125
Net income (loss)	($1,297)	$160	($733)	$467
Net income (loss) per share
Basic (in dollars per share)	($0.05)	$0.01	($0.03)	$0.02
Diluted (in dollars per share)	($0.05)	$0.01	($0.03)	$0.02
Weighted average number of common shares used to compute net income (loss) per share
Basic (in shares)	26,577	25,846	26,481	25,765
Diluted (in shares)	26,577	26,462	26,481	26,385

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Net income (loss)	($1,297)	$160	($733)	$467
Foreign currency translation adjustment, net of tax	-98	-5	-146	49
Total comprehensive income (loss)	($1,395)	$155	($879)	$516

CONDENSED_CONSOLIDATED_STATEME2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net income (loss)	($733)	$467
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	13,911	13,748
Amortization	139	200
Allowance for doubtful accounts	0	-363
Share-based compensation expense	2,379	1,314
Deferred income taxes, net	-174	497
(Gain) loss on disposal of property and equipment	36	-120
Government grant via forgiven loan	-250	0
Changes in assets and liabilities:
Accounts receivable	9,830	-341
Inventories	-3,422	5,572
Other current and long-term assets	307	-292
Accounts payable	-6,940	-5,961
Income taxes payable	-502	-287
Accrued and other liabilities	471	607
Net cash provided by operating activities	15,052	15,041
Cash flows from investing activities
Purchases of property and equipment	-6,938	-3,282
Proceeds from sale of property and equipment	0	244
Restricted cash released (placed)	-40	2
Net cash used in investing activities	-6,898	-3,040
Cash flows from financing activities
Proceeds from exercise of stock options and ESPP	1,759	930
Repayments of borrowings	-6,429	-2,143
Principal payments on capital leases	-551	-667
Net cash used in financing activities	-5,221	-1,880
Effect of exchange rate changes on cash and cash equivalents	-74	6
Net increase in cash and cash equivalents	2,859	10,127
Cash and cash equivalents at beginning of period	117,788	92,406
Cash and cash equivalents at end of period	120,647	102,533
Supplemental disclosures of non-cash investing and financing information:
Property and equipment purchased but not yet paid	5,673	1,808
Re-issuance of treasury stock	$35	$41

The_Company_and_Significant_Ac

The Company and Significant Accounting Policies	6 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Significant Accounting Policies	The Company and Significant Accounting Policies
	The Company
	Alpha and Omega Semiconductor Limited and its subsidiaries (the “Company,” "AOS," "we" or "us") design, develop and supply a broad range of power semiconductors. The Company's portfolio of products targets high-volume applications, including portable computers, flat panel TVs, LED lighting, smart phones, battery packs, consumer and industrial motor controls and power supplies for TVs, computers, servers and telecommunications equipment. The Company conducts its operations primarily in the United States of America (“USA”), Hong Kong, Macau, China, Taiwan, Korea and Japan.
	Basis of Preparation
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and with the instructions to Article 10 of Securities and Exchange Commission Regulation S-X, as amended. They do not include all information and footnotes necessary for a fair presentation of financial position, results of operations and cash flows in conformity with U.S. GAAP for complete financial statements. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes contained in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2014. All significant intercompany balances and transactions have been eliminated in consolidation. In the opinion of management, all adjustments (consisting of normal recurring adjustments and accruals) considered necessary for a fair presentation of the results of operations for the period presented have been included in the interim periods. Operating results for the three and six months ended December 31, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending June 30, 2015. The condensed consolidated balance sheet at June 30, 2014 is derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2014.
	Use of Estimates
	The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Company to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses. To the extent there are material differences between these estimates and actual results, the Company's condensed consolidated financial statements will be affected. On an ongoing basis, the Company evaluates the estimates, judgments and assumptions including those related to stock rotation returns, price adjustments, allowance for doubtful accounts, inventory reserves, warranty accrual, income taxes, share-based compensation, and useful lives for property, plant and equipment and intangible assets.
	Fair Value of Financial Instruments
	The fair value of cash equivalents are based on observable market prices and have been categorized in Level 1 in the fair value hierarchy. Cash equivalents consist primarily of short term bank deposits. The carrying values of financial instruments such as cash and cash equivalents, accounts receivable and accounts payable approximate their carrying values due to their short-term maturities. The carrying value of the Company's debt is considered a reasonable estimate of fair value which is estimated by considering the current rates available to the Company for debt of the same remaining maturities, structure and terms of the debts.
	Comprehensive Income (Loss)
	Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company's accumulated other comprehensive income (loss) consists of cumulative foreign currency translation adjustments. Total comprehensive income (loss) is presented in the condensed consolidated statements of comprehensive income (loss).
	Recent Accounting Pronouncements
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016. Early adoption is not permitted. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements.
	In August 2014, the FASB issued amended standards No. 2014-15, Presentation of Financial Statements - Going Concern ('ASU 2014-15"), to provide guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures requirement. The amendments (1) provide a definition of the term substantial doubt, (2) require an evaluation for each annual and interim reporting period, (3) provide principles for considering the mitigating effect of management’s plans, (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans, (5) require an express statement and other disclosures when substantial doubt is not alleviated, and (6) require an assessment for a period of one year after the date that the financial statements are issued (or available to be issued). ASU 2014-15 is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early adoption is permitted. The Company does not expect the adoption of this guidance will have a material impact on its consolidated financial position, results of operations or cash flows.

Net_Income_Per_Share

Net Income Per Share	6 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Income Per Share	Net Income (Loss) Per Share
	The following table presents the calculation of basic and diluted net income (loss) per share:
		Three Months Ended December 31,							Six Months Ended December 31,
		2014				2013			2014			2013
		(in thousands, except per share data)
	Numerator:
	Net income (loss)	$	(1,297	)		$	160		$	(733	)	$	467
	Denominator:
	Basic:
	Weighted average number of common shares used to compute basic net income per share	26,577				25,846			26,481			25,765
	Diluted:
	Weighted average number of common shares used to compute basic net income per share	26,577				25,846			26,481			25,765
	Effect of potentially dilutive securities:
	Stock options, RSUs and ESPP shares	—				616			—			620
	Weighted average number of common shares used to compute diluted net income per share	26,577				26,462			26,481			26,385
	Net income (loss) per share:
	Basic	$	(0.05	)		$	0.01		$	(0.03	)	$	0.02
	Diluted	$	(0.05	)		$	0.01		$	(0.03	)	$	0.02
	The following potential dilutive securities were excluded from the computation of diluted net income per share as their effect would have been anti-dilutive:
		Three Months Ended December 31,						Six Months Ended December 31,
		2014			2013			2014		2013
		(in thousands)
	Employee stock options and RSUs	3,694			2,700			3,758		2,742
	ESPP to purchase common shares	462			302			441		304
	Total potential dilutive securities	4,156			3,002			4,199		3,046

Concentration_of_Credit_Risk_a

Concentration of Credit Risk and Significant Customers	6 Months Ended
	Dec. 31, 2014
Risks and Uncertainties [Abstract]
Concentration of Credit Risk and Significant Customers	Concentration of Credit Risk and Significant Customers
	The Company manages its credit risk associated with exposure to distributors and direct customers on outstanding accounts receivable through the application of credit approvals, credit ratings and other monitoring procedures. In some instances, the Company also obtains letters of credit from certain customers.
	Credit sales, which are mainly on credit terms of 30 to 60 days, are only made to customers who meet the Company's credit requirements, while sales to new customers or customers with low credit ratings are usually made on an advance payment basis. The Company considers its trade accounts receivable to be of good credit quality because its key distributors and direct customers have long-standing business relationships with the Company and the Company has not experienced any significant bad debt write-offs of accounts receivable in the past. The Company closely monitors the aging of accounts receivable from its distributors and direct customers, and regularly reviews their financial positions, when available.
	Summarized below are individual customers whose revenue or accounts receivable balances were 10% or higher than the respective total consolidated amounts:
		Three Months Ended December 31,				Six Months Ended December 31,
	Percentage of revenue	2014		2013		2014		2013
	Customer A	24.2	%	22.7	%	24.2	%	21.6	%
	Customer B	37.1	%	42.2	%	38.4	%	43.3	%
	Customer C	11.5	%	13	%	12.2	%	12.4	%
		December 31,		June 30,
	Percentage of accounts receivable	2014		2014
	Customer A	22.6	%	23.1	%
	Customer B	19.6	%	30.5	%
	Customer C	21.7	%	17.4	%

Balance_Sheet_Components

Balance Sheet Components	6 Months Ended
	Dec. 31, 2014
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components
	Accounts receivable:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Accounts receivable	$	43,208		$	51,128
	Less: Allowance for price adjustments	(16,474		)	(14,563		)
	Less: Allowance for doubtful accounts	(30		)	(30		)
	Accounts receivable, net	$	26,704		$	36,535
	Inventories:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Raw materials	$	18,944		$	18,996
	Work in-process	34,464			36,003
	Finished goods	16,574			11,561
		$	69,982		$	66,560
	Property, plant and equipment, net:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Land	$	4,950		$	4,950
	Building	4,241			4,106
	Manufacturing machinery and equipment	168,131			161,354
	Equipment and tooling	10,821			10,486
	Computer equipment and software	20,360			19,319
	Office furniture and equipment	1,609			1,643
	Leasehold improvements	25,727			25,154
		235,839			227,012
	Less: Accumulated depreciation	(128,400		)	(114,658		)
		107,439			112,354
	Equipment and construction in progress	11,161			10,900
	Property, plant and equipment, net	$	118,600		$	123,254
	Other long-term assets:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Prepayments for property and equipment	$	1,239		$	1,435
	Investment in a privately held company	100			100
	Office leases deposits	432			428
		$	1,771		$	1,963
	Accrued liabilities:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Accrued compensation and benefit	$	5,337		$	4,879
	Accrued vacation	1,666			1,777
	Accrued bonuses	2,170			1,873
	Warranty accrual	1,188			1,346
	Stock rotation accrual	1,663			1,645
	Accrued professional fees	1,094			1,001
	ESPP payable	345			323
	Customer deposits	56			104
	Accrued inventory	672			590
	Accrued facilities related expenses	1,602			1,353
	Other accrued expenses	2,766			2,485
		$	18,559		$	17,376
	The activities in the warranty accrual, included in accrued liabilities, are as follows:
		Six Months Ended December 31,
		2014			2013
		(in thousands)
	Beginning balance	$	1,346		$	1,428
	Additions	910			1,239
	Utilization	(1,068		)	(1,171		)
Ending balance	$	1,188		$	1,496
The activities in the stock rotation accrual, included in accrued liabilities, are as follows:
	Six Months Ended December 31,
	2014			2013
	(in thousands)
Beginning balance	$	1,645		$	1,572
Additions	2,820			2,332
Utilization	(2,802		)	(2,424		)
Ending balance	$	1,663		$	1,480
Other Long-term liabilities:
	December 31,			June 30,
	2014			2014
	(in thousands)
Deferred rent	$	1,050		$	1,143
Customer deposit	3			—
	$	1,053		$	1,143

Debt

Debt	6 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	Debt
	On May 11, 2012, the Company entered into a loan agreement with a financial institution that provides a term loan of $20.0 million for general purposes and a $10.0 million non-revolving credit line for the purchase of equipment. Both the term loan and equipment line will be fully repayable in May 2015. The borrowings may be made in the form of either Eurodollar loans or Base Rate loans. Eurodollar loans accrue interest based on an adjusted London Interbank Offered Rate ("LIBOR") as defined in the agreement, plus a margin of 1.00% to 1.75%. Base Rate loans accrue interest at the highest of (a) the lender's Prime Rate, (b) the Federal Funds Rate plus 0.5% and (c) the Eurodollar Rate (for a one-month interest period) plus 1%; plus a margin of -0.5% to 0.25%. The applicable margins for both Eurodollar loans and Base Rate loans will vary from time to time in the foregoing ranges based on the cash and cash equivalent balances maintained by the Company and its subsidiaries with the lender. In May 2013, the equipment credit line expired and there was no outstanding balance. As of December 31, 2014 and June 30, 2014, the outstanding balances of the term loan were $7.1 million and $13.6 million, respectively.
	The obligations under the loan agreement are secured by substantially all assets of two subsidiaries of the Company, including, but not limited to, certain real property and related assets located at the Oregon fab. In addition, the Company and certain subsidiaries of the Company have agreed to guarantee full repayment and performance of the obligations under the loan agreement. The loan agreement contains customary restrictive covenants and includes certain financial covenants that require the Company to maintain on a consolidated basis specified financial ratios including total liabilities to tangible net worth, fixed charge coverage and current assets to current liabilities. As of December 31, 2014, the Company was in compliance with these covenants.
	During July 2012, the Company entered into a loan agreement with the State of Oregon for an amount of $0.3 million. The loan was required to be used for training new and re-training existing employees of the Oregon fab. The loan bore a compound annual interest rate of 5.0% and was to be repaid in April 2014 if the required conditions were not met. In September 2014, the State of Oregon forgave the outstanding balance in full as we had satisfied the conditions. The $0.3 million loan forgiven was recorded as a reduction of costs of goods sold in our condensed consolidated statements of operations.

Shareholders_Equity_and_Shareb

Shareholders' Equity and Share-based Compensation	6 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Shareholders' Equity and Share-based Compensation	Shareholders' Equity and Share-based Compensation
	Share Repurchase
	On May 8, 2014, our Board of Directors approved to reactivate the share repurchase program which was originally authorized on October 22, 2010 for a total amount of $25.0 million.  The Board authorized management to repurchase, subject to oversight by the Board, our common shares up to the remaining balance of the program, or $22.7 million.  The repurchases may be made from the open market or through privately negotiated transactions. Open market repurchases will be made pursuant to a pre-established 10b5-1 trading plan with specified amount of shares and price for the repurchases. The amount and timing of any repurchases will depend on a number of factors, including but not limited to, the trading price, volume and availability of our common shares, applicable legal requirements, our business and financial conditions and general market environment. The Company accounts for treasury stock under the cost method. Shares repurchased are accounted for as treasury shares and the total cost of shares repurchased is recorded as a reduction of shareholders' equity. From time to time, treasury shares may be reissued as part of the Company's stock-based compensation programs. Gains on re-issuance of treasury stock are credited to additional paid-in capital; losses are charged to additional paid-in capital to offset the net gains, if any, from previous sales or re-issuance of treasury stock. Any remaining balance of the losses are charged to retained earnings.
	During the six months ended December 31, 2014, the Company did not repurchase any shares under the share repurchase program.  Since the inception of the program in 2010, the Company repurchased an aggregate of 361,364 shares from the open market for a total cost of $3.2 million, at an average price of $8.82 per share.  No repurchased shares have been retired. Of the 361,364 repurchased shares, 24,150 shares with a weighted average repurchase price of $13.82 per share, were reissued at an average price of $2.69 per share for option exercises and vested RSU.
	Stock Options
	The following table summarizes the Company's stock option activities for the six months ended December 31, 2014:
				Weighted
				Average
		Number of		Exercise Price				Aggregate
		Shares		Per Share				Intrinsic Value
	Outstanding at June 30, 2014	3,238,784		$	10.28			$	3,258,607
	Granted	10,000		$	9.07
	Exercised	(163,731	)	$	5.97			$	585,449
	Canceled or forfeited	(41,650	)	$	13.66
	Outstanding at December 31, 2014	3,043,403		$	10.47			$	2,139,768
	Information with respect to stock options outstanding and exercisable at December 31, 2014 is as follows:
		Options Outstanding								Options Vested and Exercisable
		Number Outstanding		Weighted-Average		Weighted-Average				Number Exercisable		Weighted-Average
				Remaining Contractual Life (years)		Exercise Price						Exercise Price
	Total options outstanding	3,043,403		5.51		$	10.47			2,161,744		$	11.34
	Options vested and expected to vest	2,963,102		5.42		$	10.54
	Options expected to vest are the result of applying the pre-vesting forfeiture rate assumption to total outstanding options.
	The fair value of stock options granted were estimated at the date of grant using the Black-Scholes option valuation model for the six months ended December 31, 2014 with the following weighted average assumptions:
		Six Months Ended December 31,
		2014
	Volatility rate	41.90%
	Risk-free interest rate	1.7% - 1.8%
	Expected term	5.5 years
	Dividend yield	0%
	Historically, the Company estimates its expected volatility based on that of the publicly traded shares of industry peers over a period equivalent to the expected term of the stock awards granted. Beginning in July 2015, the Company estimates its expected volatility based on a weighted average calculation of both the Company's volatility of its publicly traded share prices since its IPO and that of the publicly traded shares of industry peers over a period equivalent to the expected term of the stock awards granted.
	Restricted Stock Units ("RSU")
	The following table summarizes the Company's RSU activities for the six months ended December 31, 2014:
		Number of Restricted Stock		Weighted Average				Weighted Average		Aggregate Intrinsic Value
		Units		Grant Date Fair				Remaining
				Value Per Share				Recognition
								Period (Years)
	Nonvested at June 30, 2014	656,374		$	8.4			1.77		$	6,084,587
	Granted	78,642		$	9.18
	Vested	(75,423	)	$	9.19
	Forfeited	(31,250	)	$	8.53
	Nonvested at December 31, 2014	628,343		$	8.4			1.52		$	5,560,836
	RSUs vested and expected to vest	555,613						1.43		$	4,917,176
	The fair value of RSU is estimated based on the market price of the Company's share on the date of grant.
	Employee Share Purchase Plan ("ESPP")
	The assumptions used to estimate the fair values of common shares issued under the ESPP were as follows:
		Six Months Ended December 31,
		2014
	Volatility rate	50%
	Risk-free interest rate	0.1% - 0.5%
	Expected term	1.3 years
	Dividend yield	0%
	Share-based Compensation Expense
	The total share-based compensation expense related to stock options, ESPP and RSUs described above, recognized in the condensed consolidated statements of operations for the periods presented was as follows:
		Three Months Ended December 31,							Six Months Ended December 31,
		2014			2013				2014			2013
		(in thousands)							(in thousands)
	Cost of goods sold	$	174		$	142			$	328		$	338
	Research and development	293			(32		)		499			263
	Selling, general and administrative	810			(5		)		1,552			713
		$	1,277		$	105			$	2,379		$	1,314
	Total unrecognized stock-based compensation expense as of December 31, 2014 was $4.1 million, which includes estimated forfeitures and is expected to be recognized over a weighted-average period of 1.4 years.

Income_Taxes

Income Taxes	6 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The Company recognized income tax expense of approximately $1.0 million and $1.1 million for the three months ended December 31, 2014 and 2013, respectively. The Company recognized income tax expense of approximately $2.1 million and $2.1 million for the six months ended December 31, 2014 and 2013, respectively. The estimated effective tax rate for the three months ended December 31, 2014 was 281.5% compared to 87.5% for the three months ended December 31, 2013. The estimate effective tax rate was 152.5% and 82.0% for the six months ended December 31, 2014 and 2013, respectively. The effective tax rate for the three and the six months ended December 31, 2014 was higher than the effective tax rate for the same period last year primarily due to the changes in the mix of earnings in various geographic jurisdictions between the two periods.
	The Company files its income tax returns in the United States and in various foreign jurisdictions. The tax years 2001 to 2014 remain open to examination by U.S. federal and state tax authorities. The tax years 2005 to 2014 remain open to examination by foreign tax authorities.
	The Company's income tax returns are subject to examinations by the Internal Revenue Service and other tax authorities in various jurisdictions. In accordance with the guidance on the accounting for uncertainty in income taxes, the Company regularly assesses the likelihood of adverse outcomes resulting from these examinations to determine the adequacy of its provision for income taxes. These assessments can require considerable estimates and judgments. As of December 31, 2014, the gross amount of unrecognized tax benefits was approximately $7.0 million, of which $4.9 million, if recognized, would reduce the effective income tax rate in future periods. If the Company's estimate of income tax liabilities proves to be less than the ultimate assessment, then a further charge to expense would be required. If events occur and the payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities would result in tax benefits being recognized in the period when the Company determines the liabilities are no longer necessary. The Company does not anticipate any material changes to its uncertain tax positions during the next twelve months.

Segment_and_Geographic_Informa

Segment and Geographic Information	6 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment and Geographic Information	Segment and Geographic Information
	The Company is organized as, and operates in, one operating segment: the design, development and supply of power semiconductor products for computing, consumer electronics, communication and industrial applications. The chief operating decision-maker is the Chief Executive Officer. The financial information presented to the Company's Chief Executive Officer is on a consolidated basis, accompanied by information about revenue by customer and geographic region, for purposes of evaluating financial performance and allocating resources. The Company has one business segment, and there are no segment managers who are held accountable for operations, operating results and plans for products or components below the consolidated unit level. Accordingly, the Company reports as a single operating segment.
	The Company sells its products primarily to distributors in the Asia Pacific region, who in turn sell these products to end customers. Because the Company's distributors sell their products to end customers which may have a global presence, revenue by geographical location is not necessarily representative of the geographical distribution of sales to end user markets.
	The revenue by geographical location in the following tables is based on the country or region to which the products were shipped to:
		Three Months Ended December 31,				Six Months Ended December 31,
		2014		2013		2014		2013
		(in thousands)				(in thousands)
	Hong Kong	$	70,278	$	64,229	$	145,525	$	135,485
	China	8,823		10,156		19,780		21,048
	South Korea	524		745		1,163		1,542
	United States	881		425		1,564		898
	Other countries	822		710		1,513		1,413
		$	81,328	$	76,265	$	169,545	$	160,386
	The following is a summary of revenue by product type:
		Three Months Ended December 31,				Six Months Ended December 31,
		2014		2013		2014		2013
		(in thousands)				(in thousands)
	Power discrete	$	61,203	$	58,946	$	126,094	$	124,091
	Power IC	16,109		13,226		$	35,265	$	26,838
	Packaging and testing services	4,016		4,093		$	8,186	$	9,457
		$	81,328	$	76,265	$	169,545	$	160,386
	Long-lived assets, net consisting of property, plant and equipment, by geographical area are as follows:
		December 31,		June 30,
		2014		2014
		(in thousands)
	China	$	76,118	$	80,736
	United States	41,988		42,106
	Other Countries	494		412
		$	118,600	$	123,254

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Purchase Commitments
	As of December 31, 2014 and June 30, 2014, the Company had approximately $21.7 million and $34.5 million, respectively, of outstanding purchase commitments primarily for purchases of semiconductor raw materials, wafers, spare parts and packaging and testing services, and approximately $9.9 million and $4.6 million, respectively, of capital commitments for the purchase of property and equipment.
	Contingencies and Indemnities
	The Company is currently not a party to any pending material legal proceedings. The Company has in the past, and may from time to time in the future, become involved in legal proceedings arising from the normal course of business activities.  The semiconductor industry is characterized by frequent claims and litigation, including claims regarding patent and other intellectual property rights as well as improper hiring practices. Irrespective of the validity of such claims, the Company could incur significant costs in the defense of such claims and suffer adverse effects on its operations.
	The Company is a party to a variety of agreements that it has contracted with various third parties. Pursuant to these agreements, the Company may be obligated to indemnify another party to such an agreement with respect to certain matters. Typically, these obligations arise in the context of contracts entered into by the Company, under which the Company customarily agrees to hold the other party harmless against losses arising from a breach of representations and covenants related to such matters as title to assets sold, certain intellectual property rights, specified environmental matters and certain income taxes. In these circumstances, payment by the Company is customarily conditioned on the other party making a claim pursuant to the procedures specified in the particular contract, which procedures typically allow the Company to challenge the other party's claim. Further, the Company's obligations under these agreements may be limited in time and/or amount, and in some instances, the Company may have recourse against third parties for certain payments made by it under these agreements. The Company has not historically paid or recorded any material indemnifications and no accrual has been made at December 31, 2014 and June 30, 2014.
	The Company has agreed to indemnify its directors and certain employees as permitted by law and pursuant to its bye-laws, and has entered into indemnification agreements with its directors and executive officers. The Company has not recorded a liability associated with these indemnification arrangements, as it historically has not incurred any material costs associated with such indemnification obligations. Costs associated with such indemnification obligations may be mitigated by insurance coverage that the Company maintains. However, such insurance may not cover any, or may cover only a portion of, the amounts the Company may be required to pay. In addition, the Company may not be able to maintain such insurance coverage in the future.

The_Company_and_Significant_Ac1

The Company and Significant Accounting Policies (Policies)	6 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Concentration Risk, Credit Risk, Policy [Policy Text Block]	The Company manages its credit risk associated with exposure to distributors and direct customers on outstanding accounts receivable through the application of credit approvals, credit ratings and other monitoring procedures. In some instances, the Company also obtains letters of credit from certain customers.
	Credit sales, which are mainly on credit terms of 30 to 60 days, are only made to customers who meet the Company's credit requirements, while sales to new customers or customers with low credit ratings are usually made on an advance payment basis. The Company considers its trade accounts receivable to be of good credit quality because its key distributors and direct customers have long-standing business relationships with the Company and the Company has not experienced any significant bad debt write-offs of accounts receivable in the past. The Company closely monitors the aging of accounts receivable from its distributors and direct customers, and regularly reviews their financial positions, when available.
Basis of Preparation	Basis of Preparation
	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and with the instructions to Article 10 of Securities and Exchange Commission Regulation S-X, as amended. They do not include all information and footnotes necessary for a fair presentation of financial position, results of operations and cash flows in conformity with U.S. GAAP for complete financial statements. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes contained in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2014. All significant intercompany balances and transactions have been eliminated in consolidation. In the opinion of management, all adjustments (consisting of normal recurring adjustments and accruals) considered necessary for a fair presentation of the results of operations for the period presented have been included in the interim periods. Operating results for the three and six months ended December 31, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending June 30, 2015. The condensed consolidated balance sheet at June 30, 2014 is derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the fiscal year ended June 30, 2014.
Use of Estimates	Use of Estimates
	The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires the Company to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses. To the extent there are material differences between these estimates and actual results, the Company's condensed consolidated financial statements will be affected. On an ongoing basis, the Company evaluates the estimates, judgments and assumptions including those related to stock rotation returns, price adjustments, allowance for doubtful accounts, inventory reserves, warranty accrual, income taxes, share-based compensation, and useful lives for property, plant and equipment and intangible assets.
Fair Value of Financial Instruments	Fair Value of Financial Instruments
	The fair value of cash equivalents are based on observable market prices and have been categorized in Level 1 in the fair value hierarchy. Cash equivalents consist primarily of short term bank deposits. The carrying values of financial instruments such as cash and cash equivalents, accounts receivable and accounts payable approximate their carrying values due to their short-term maturities. The carrying value of the Company's debt is considered a reasonable estimate of fair value which is estimated by considering the current rates available to the Company for debt of the same remaining maturities, structure and terms of the debts.
Comprehensive Income (Loss)	Comprehensive Income (Loss)
	Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. The Company's accumulated other comprehensive income (loss) consists of cumulative foreign currency translation adjustments. Total comprehensive income (loss) is presented in the condensed consolidated statements of comprehensive income (loss).
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). The standard provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016. Early adoption is not permitted. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements.
	In August 2014, the FASB issued amended standards No. 2014-15, Presentation of Financial Statements - Going Concern ('ASU 2014-15"), to provide guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures requirement. The amendments (1) provide a definition of the term substantial doubt, (2) require an evaluation for each annual and interim reporting period, (3) provide principles for considering the mitigating effect of management’s plans, (4) require certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans, (5) require an express statement and other disclosures when substantial doubt is not alleviated, and (6) require an assessment for a period of one year after the date that the financial statements are issued (or available to be issued). ASU 2014-15 is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early adoption is permitted. The Company does not expect the adoption of this guidance will have a material impact on its consolidated financial position, results of operations or cash flows.

Net_Income_Per_Share_Tables

Net Income Per Share (Tables)	6 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted net income (loss) per share:
		Three Months Ended December 31,							Six Months Ended December 31,
		2014				2013			2014			2013
		(in thousands, except per share data)
	Numerator:
	Net income (loss)	$	(1,297	)		$	160		$	(733	)	$	467
	Denominator:
	Basic:
	Weighted average number of common shares used to compute basic net income per share	26,577				25,846			26,481			25,765
	Diluted:
	Weighted average number of common shares used to compute basic net income per share	26,577				25,846			26,481			25,765
	Effect of potentially dilutive securities:
	Stock options, RSUs and ESPP shares	—				616			—			620
	Weighted average number of common shares used to compute diluted net income per share	26,577				26,462			26,481			26,385
	Net income (loss) per share:
	Basic	$	(0.05	)		$	0.01		$	(0.03	)	$	0.02
	Diluted	$	(0.05	)		$	0.01		$	(0.03	)	$	0.02
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following potential dilutive securities were excluded from the computation of diluted net income per share as their effect would have been anti-dilutive:
		Three Months Ended December 31,						Six Months Ended December 31,
		2014			2013			2014		2013
		(in thousands)
	Employee stock options and RSUs	3,694			2,700			3,758		2,742
	ESPP to purchase common shares	462			302			441		304
	Total potential dilutive securities	4,156			3,002			4,199		3,046

Concentration_of_Credit_Risk_a1

Concentration of Credit Risk and Significant Customers (Tables)	6 Months Ended
	Dec. 31, 2014
Risks and Uncertainties [Abstract]
Schedules of Concentration of Risk, by Risk Factor	Summarized below are individual customers whose revenue or accounts receivable balances were 10% or higher than the respective total consolidated amounts:
		Three Months Ended December 31,				Six Months Ended December 31,
	Percentage of revenue	2014		2013		2014		2013
	Customer A	24.2	%	22.7	%	24.2	%	21.6	%
	Customer B	37.1	%	42.2	%	38.4	%	43.3	%
	Customer C	11.5	%	13	%	12.2	%	12.4	%
		December 31,		June 30,
	Percentage of accounts receivable	2014		2014
	Customer A	22.6	%	23.1	%
	Customer B	19.6	%	30.5	%
	Customer C	21.7	%	17.4	%

Balance_Sheet_Components_Table

Balance Sheet Components (Tables)	6 Months Ended
	Dec. 31, 2014
Balance Sheet Related Disclosures [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	Accounts receivable:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Accounts receivable	$	43,208		$	51,128
	Less: Allowance for price adjustments	(16,474		)	(14,563		)
	Less: Allowance for doubtful accounts	(30		)	(30		)
	Accounts receivable, net	$	26,704		$	36,535
Schedule of Inventory, Current	Inventories:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Raw materials	$	18,944		$	18,996
	Work in-process	34,464			36,003
	Finished goods	16,574			11,561
		$	69,982		$	66,560
Property, Plant and Equipment	Property, plant and equipment, net:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Land	$	4,950		$	4,950
	Building	4,241			4,106
	Manufacturing machinery and equipment	168,131			161,354
	Equipment and tooling	10,821			10,486
	Computer equipment and software	20,360			19,319
	Office furniture and equipment	1,609			1,643
	Leasehold improvements	25,727			25,154
		235,839			227,012
	Less: Accumulated depreciation	(128,400		)	(114,658		)
		107,439			112,354
	Equipment and construction in progress	11,161			10,900
	Property, plant and equipment, net	$	118,600		$	123,254
Schedule of Other Assets, Noncurrent	Other long-term assets:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Prepayments for property and equipment	$	1,239		$	1,435
	Investment in a privately held company	100			100
	Office leases deposits	432			428
		$	1,771		$	1,963
Schedule of Accrued Liabilities	Accrued liabilities:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Accrued compensation and benefit	$	5,337		$	4,879
	Accrued vacation	1,666			1,777
	Accrued bonuses	2,170			1,873
	Warranty accrual	1,188			1,346
	Stock rotation accrual	1,663			1,645
	Accrued professional fees	1,094			1,001
	ESPP payable	345			323
	Customer deposits	56			104
	Accrued inventory	672			590
	Accrued facilities related expenses	1,602			1,353
	Other accrued expenses	2,766			2,485
		$	18,559		$	17,376
Schedule of Product Warranty Liability	The activities in the warranty accrual, included in accrued liabilities, are as follows:
		Six Months Ended December 31,
		2014			2013
		(in thousands)
	Beginning balance	$	1,346		$	1,428
	Additions	910			1,239
	Utilization	(1,068		)	(1,171		)
	Ending balance	$	1,188		$	1,496
Stock Rotation Accrual	The activities in the stock rotation accrual, included in accrued liabilities, are as follows:
		Six Months Ended December 31,
		2014			2013
		(in thousands)
	Beginning balance	$	1,645		$	1,572
	Additions	2,820			2,332
	Utilization	(2,802		)	(2,424		)
	Ending balance	$	1,663		$	1,480
Schedule of Other Noncurrent Liabilities	Other Long-term liabilities:
		December 31,			June 30,
		2014			2014
		(in thousands)
	Deferred rent	$	1,050		$	1,143
	Customer deposit	3			—
		$	1,053		$	1,143

Shareholders_Equity_and_Shareb1

Shareholders' Equity and Share-based Compensation (Tables)	6 Months Ended
	Dec. 31, 2014
Share-based Compensation [Abstract]
Summary of Stock Option Activities	Stock Options
	The following table summarizes the Company's stock option activities for the six months ended December 31, 2014:
				Weighted
				Average
		Number of		Exercise Price				Aggregate
		Shares		Per Share				Intrinsic Value
	Outstanding at June 30, 2014	3,238,784		$	10.28			$	3,258,607
	Granted	10,000		$	9.07
	Exercised	(163,731	)	$	5.97			$	585,449
	Canceled or forfeited	(41,650	)	$	13.66
	Outstanding at December 31, 2014	3,043,403		$	10.47			$	2,139,768
	Information with respect to stock options outstanding and exercisable at December 31, 2014 is as follows:
		Options Outstanding								Options Vested and Exercisable
		Number Outstanding		Weighted-Average		Weighted-Average				Number Exercisable		Weighted-Average
				Remaining Contractual Life (years)		Exercise Price						Exercise Price
	Total options outstanding	3,043,403		5.51		$	10.47			2,161,744		$	11.34
	Options vested and expected to vest	2,963,102		5.42		$	10.54
	Options expected to vest are the result of applying the pre-vesting forfeiture rate assumption to total outstanding options.
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The fair value of stock options granted were estimated at the date of grant using the Black-Scholes option valuation model for the six months ended December 31, 2014 with the following weighted average assumptions:
		Six Months Ended December 31,
		2014
	Volatility rate	41.90%
	Risk-free interest rate	1.7% - 1.8%
	Expected term	5.5 years
	Dividend yield	0%
Restricted Stock Units Activity	Restricted Stock Units ("RSU")
	The following table summarizes the Company's RSU activities for the six months ended December 31, 2014:
		Number of Restricted Stock		Weighted Average				Weighted Average		Aggregate Intrinsic Value
		Units		Grant Date Fair				Remaining
				Value Per Share				Recognition
								Period (Years)
	Nonvested at June 30, 2014	656,374		$	8.4			1.77		$	6,084,587
	Granted	78,642		$	9.18
	Vested	(75,423	)	$	9.19
	Forfeited	(31,250	)	$	8.53
	Nonvested at December 31, 2014	628,343		$	8.4			1.52		$	5,560,836
	RSUs vested and expected to vest	555,613						1.43		$	4,917,176
	The fair value of RSU is estimated based on the market price of the Company's share on the date of grant.
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]	Employee Share Purchase Plan ("ESPP")
	The assumptions used to estimate the fair values of common shares issued under the ESPP were as follows:
		Six Months Ended December 31,
		2014
	Volatility rate	50%
	Risk-free interest rate	0.1% - 0.5%
	Expected term	1.3 years
	Dividend yield	0%
Share-based Compensation, Allocation of Recognized Period Costs	Share-based Compensation Expense
	The total share-based compensation expense related to stock options, ESPP and RSUs described above, recognized in the condensed consolidated statements of operations for the periods presented was as follows:
		Three Months Ended December 31,							Six Months Ended December 31,
		2014			2013				2014			2013
		(in thousands)							(in thousands)
	Cost of goods sold	$	174		$	142			$	328		$	338
	Research and development	293			(32		)		499			263
	Selling, general and administrative	810			(5		)		1,552			713
		$	1,277		$	105			$	2,379		$	1,314

Segment_and_Geographic_Informa1

Segment and Geographic Information (Tables)	6 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas	Long-lived assets, net consisting of property, plant and equipment, by geographical area are as follows:
		December 31,		June 30,
		2014		2014
		(in thousands)
	China	$	76,118	$	80,736
	United States	41,988		42,106
	Other Countries	494		412
		$	118,600	$	123,254
	The revenue by geographical location in the following tables is based on the country or region to which the products were shipped to:
		Three Months Ended December 31,				Six Months Ended December 31,
		2014		2013		2014		2013
		(in thousands)				(in thousands)
	Hong Kong	$	70,278	$	64,229	$	145,525	$	135,485
	China	8,823		10,156		19,780		21,048
	South Korea	524		745		1,163		1,542
	United States	881		425		1,564		898
	Other countries	822		710		1,513		1,413
		$	81,328	$	76,265	$	169,545	$	160,386
Revenue from External Customers by Products and Services	The following is a summary of revenue by product type:
		Three Months Ended December 31,				Six Months Ended December 31,
		2014		2013		2014		2013
		(in thousands)				(in thousands)
	Power discrete	$	61,203	$	58,946	$	126,094	$	124,091
	Power IC	16,109		13,226		$	35,265	$	26,838
	Packaging and testing services	4,016		4,093		$	8,186	$	9,457
		$	81,328	$	76,265	$	169,545	$	160,386

Net_Income_Per_Share_Basic_and

Net Income Per Share - Basic and Diluted Income Per Share (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income (loss)	($1,297)	$160	($733)	$467
Basic:
Weighted average number of common shares used to compute basic net income per share	26,577	25,846	26,481	25,765
Effect of potentially dilutive securities:
Stock options, RSUs and ESPP shares (in shares)	0	616	0	620
Weighted average number of common shares used to compute diluted net income per share	26,577	26,462	26,481	26,385
Net income (loss) per share:
Basic (in dollars per share)	($0.05)	$0.01	($0.03)	$0.02
Diluted (in dollars per share)	($0.05)	$0.01	($0.03)	$0.02

Net_Income_Per_Share_Potential

Net Income Per Share - Potential Dilutive Shares (Details)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities (in shares)	4,156	3,002	4,199	3,046
Employee stock options and RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities (in shares)	3,694	2,700	3,758	2,742
ESPP to purchase common shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities (in shares)	462	302	441	304

Concentration_of_Credit_Risk_a2

Concentration of Credit Risk and Significant Customers - (Details)	6 Months Ended	3 Months Ended		6 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013	Jun. 30, 2014
Minimum
Concentration Risk
Terms of credit sales, (in days)	30 days
Maximum
Concentration Risk
Terms of credit sales, (in days)	60 days
Customer A | Sales Revenue, Goods, Net | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	24.20%	24.20%	22.70%	21.60%
Customer A | Accounts Receivable | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total		22.60%			23.10%
Customer B | Sales Revenue, Goods, Net | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	38.40%	37.10%	42.20%	43.30%
Customer B | Accounts Receivable | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total		19.60%			30.50%
Customer C | Sales Revenue, Goods, Net | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total	12.20%	11.50%	13.00%	12.40%
Customer C | Accounts Receivable | Customer Concentration Risk
Concentration Risk
Customers greater than 10% of total		21.70%			17.40%

Balance_Sheet_Components_Accou

Balance Sheet Components - Accounts receivable (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Balance Sheet Related Disclosures [Abstract]
Accounts receivable	$43,208	$51,128
Less: Allowance for price adjustments	-16,474	-14,563
Less: Allowance for doubtful accounts	-30	-30
Accounts receivable, net	$26,704	$36,535

Balance_Sheet_Components_Inven

Balance Sheet Components - Inventories (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Balance Sheet Related Disclosures [Abstract]
Raw materials	$18,944	$18,996
Work in-process	34,464	36,003
Finished goods	16,574	11,561
Inventory, net	$69,982	$66,560

Balance_Sheet_Components_Prope

Balance Sheet Components - Property, plant, and equipment (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	$235,839	$227,012
Less: Accumulated depreciation	-128,400	-114,658
Property, plant and equipment excluding equipment and construction in progress, net	107,439	112,354
Equipment and construction in progress	11,161	10,900
Property, plant and equipment, net	118,600	123,254
Land
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	4,950	4,950
Building
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	4,241	4,106
Manufacturing machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	168,131	161,354
Equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	10,821	10,486
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	20,360	19,319
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	1,609	1,643
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant, and equipment excluding equipment and construction In progress, gross	$25,727	$25,154

Balance_Sheet_Components_Other

Balance Sheet Components - Other long term assets (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Balance Sheet Related Disclosures [Abstract]
Prepayments for property and equipment	$1,239	$1,435
Investment in a privately held company	100	100
Office leases deposits	432	428
Other long-term assets	$1,771	$1,963

Balance_Sheet_Components_Accru

Balance Sheet Components - Accrued liabilities (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
In Thousands, unless otherwise specified
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and benefit	$5,337	$4,879
Accrued vacation	1,666	1,777
Accrued bonuses	2,170	1,873
Warranty accrual	1,188	1,346	1,496	1,428
Stock rotation accrual	1,663	1,645	1,480	1,572
Accrued professional fees	1,094	1,001
ESPP payable	345	323
Customer deposits	56	104
Accrued inventory	672	590
Accrued facilities related expenses	1,602	1,353
Other accrued expenses	2,766	2,485
Accrued liabilities	$18,559	$17,376

Balance_Sheet_Components_Produ

Balance Sheet Components - Product Warranty Accrual (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Beginning balance	$1,346	$1,428
Additions	910	1,239
Utilization	-1,068	-1,171
Ending balance	$1,188	$1,496

Balance_Sheet_Components_Stock

Balance Sheet Components - Stock Rotation Accrual (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Stock Rotation Accrual Increae (Decrease) [Roll Forward]
Beginning balance	$1,645	$1,572
Additions	2,820	2,332
Utilization	-2,802	-2,424
Ending balance	$1,663	$1,480

Balance_Sheet_Components_Other1

Balance Sheet Components - Other Long Term Liability (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Balance Sheet Related Disclosures [Abstract]
Deferred rent	$1,050	$1,143
Customer deposit	3	0
Other long term liabilities	$1,053	$1,143

Debt_Details

Debt - (Details) (USD $)	3 Months Ended	6 Months Ended		0 Months Ended
	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	11-May-12	Jun. 30, 2014	Jul. 17, 2012
Debt Instrument [Line Items]
Forgiveness of loan	$250,000	($250,000)	$0
Variable Interest Rate Term Loan Maturing May 2015 | Notes Payable to Banks
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		0
Loan, principal amount				20,000,000
Line of Credit Facility, Maximum Borrowing Capacity				10,000,000
Outstanding balance of loan		7,100,000			13,600,000
Number of subsidiaries securing obligations under loan agreement		2
State of Oregon Loan | Loans Payable
Debt Instrument [Line Items]
Loan, principal amount						$250,000
Interest rate on loan						5.00%
London Interbank Offered Rate (LIBOR) [Member] | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				1.00%
London Interbank Offered Rate (LIBOR) [Member] | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				1.75%
Federal Funds Rate [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				0.50%
Eurodollar [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				1.00%
Eurodollar [Member] | Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				-0.50%
Eurodollar [Member] | Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				0.25%

Shareholders_Equity_and_Shareb2

Shareholders' Equity and Share-based Compensation - Shares Repurchase (Details) (USD $)	0 Months Ended		6 Months Ended	50 Months Ended
In Millions, except Share data, unless otherwise specified	8-May-14	Oct. 22, 2010	Dec. 31, 2014	Dec. 31, 2014
Class of Stock [Line Items]
Share repurchase program, authorized amount (USD in Millions)		$25
Shares Repurchase Program Remaining Balance	22.7
Treasury stock acquired, shares repurchased (in shares)			0	361,364
Treasury Stock, Value, Acquired, Cost Method				$3.20
Treasury stock acquired, average price per share (in dollars per share)				$8.82
Treasury Stock, Shares, Retired				0
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures (in shares)				24,150
Treasury Stock Reissued, Average Price Per Share				$2.69
Treasury Stock Reissued
Class of Stock [Line Items]
Treasury stock acquired, average price per share (in dollars per share)				$13.82

Shareholders_Equity_and_Shareb3

Shareholders' Equity and Share-based Compensation - Share-based Compensation (Details) (USD $)	6 Months Ended	50 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury stock acquired, shares repurchased (in shares)	0	361,364
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at June 30, 2014 (in shares)	3,238,784
Granted (in shares)	10,000
Exercised (in shares)	-163,731
Canceled or forfeited (in shares)	-41,650
Outstanding at December 31, 2014 (in shares)	3,043,403	3,043,403
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding at June 30, 2014 (in dollars per share)	$10.28
Granted (in dollars per share)	$9.07
Exercised (in dollars per share)	$5.97
Canceled or forfeited (in dollars per share)	$13.66
Outstanding at December 31, 2014 (in dollars per share)	$10.47	$10.47
Options Outstanding Aggregate Intrinsic Value	$2,139,768	$2,139,768	$3,258,607
Options Exercised Aggregate Intrinsic Value	$585,449
Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility Rate	50.00%
Expected Term	1 year 3 months 18 days
Expected Dividend Rate	0.00%
Employee Share Purchase Plan [Member] | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk Free Interest Rate	0.10%
Employee Share Purchase Plan [Member] | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk Free Interest Rate	0.50%
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility Rate	41.90%
Expected Term	5 years 6 months
Expected Dividend Rate	0.00%
Stock Options [Member] | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk Free Interest Rate	1.70%
Stock Options [Member] | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk Free Interest Rate	1.80%

Shareholders_Equity_and_Shareb4

Shareholders' Equity and Share-based Compensation - Stock Options Outstanding and Exercisable (Details) (USD $)	6 Months Ended
	Dec. 31, 2014	Jun. 30, 2014
Share-based Compensation [Abstract]
Options, Number Outstanding (in shares)	3,043,403	3,238,784
Options, Weighted-Average Remaining Contractual Life (in years)	5 years 6 months 4 days
Options, Weighted-Average Exercise Price (in dollars per share)	$10.47	$10.28
Options, Number Exercisable (in shares)	2,161,744
Options, Weighted-Average Exercise Price (in dollars per share)	$11.34
Options vested and expected to vest, Number Outstanding (in shares)	2,963,102
Options vested and expected to vest, Weighted Average Remaining Contractual Life (in years)	5 years 5 months 1 day
Options vested and expected to vest, Weighted Average Exercise Price (in dollars per share)	$10.54

Shareholders_Equity_and_Shareb5

Shareholders' Equity and Share-based Compensation - Restricted Stock Activity (Details) (USD $)	3 Months Ended		6 Months Ended
	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Remaining Recognition Period (Years)	1 year 4 months 24 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested			656,374
Granted			78,642
Vested			-75,423
Forfeited			-31,250
Nonvested	628,343	656,374	628,343
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested			$8.40
Granted			$9.18
Vested			$9.19
Forfeited			$8.53
Nonvested	$8.40	$8.40	$8.40
Weighted Average Remaining Recognition Period (Years)	1 year 6 months 7 days	1 year 9 months 7 days
RSUs Nonvested Aggregate Intrinsic Value	$5,560,836	$6,084,587	$5,560,836
RSUs vested and expected to vest, Outstanding (in shares)	555,613		555,613
RSUs vested and expected to vest, Weighted Average Remaining Recognition Period (in years)	1 year 5 months 5 days
RSUs vested and expected to vest, Aggregate Intrinsic Value	$4,917,176		$4,917,176

Shareholders_Equity_and_Shareb6

Shareholders' Equity and Share-based Compensation - Share-based Compensation Expenses (Details) (USD $)	3 Months Ended		6 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$1,277,000	$105,000	$2,379,000	$1,314,000
Unrecognized compensation expense	4,100,000		4,100,000
Recognition period of share-based compensation expense (in years)	1 year 4 months 24 days
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	174,000	142,000	328,000	338,000
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	293,000	-32,000	499,000	263,000
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$810,000	($5,000)	$1,552,000	$713,000

Income_Taxes_Narrative_Details

Income Taxes - Narrative (Details) (USD $)	3 Months Ended		6 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax expense	$957,000	$1,123,000	$2,128,000	$2,125,000
Estimated effective income tax rate	281.50%	87.50%	152.50%	82.00%
Unrecognized tax benefits	7,000,000		7,000,000
Unrecognized tax benefit that would impact effective tax rate	$4,900,000		$4,900,000

Segment_and_Geographic_Informa2

Segment and Geographic Information - Revenue by Location and Product Type (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$81,328	$76,265	$169,545	$160,386
Power discrete
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	61,203	58,946	126,094	124,091
Power IC
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	16,109	13,226	35,265	26,838
Packaging and testing services
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	4,016	4,093	8,186	9,457
Hong Kong
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	70,278	64,229	145,525	135,485
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	8,823	10,156	19,780	21,048
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	524	745	1,163	1,542
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	881	425	1,564	898
Other Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$822	$710	$1,513	$1,413

Segment_and_Geographic_Informa3

Segment and Geographic Information - Long-lived Assets (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$118,600	$123,254
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	76,118	80,736
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	41,988	42,106
Other Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$494	$412

Segment_and_Geographic_Informa4

Segment and Geographic Information - Narratives (Details)	6 Months Ended
	Dec. 31, 2014
	Segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

Commitments_and_Contingencies_

Commitments and Contingencies - Purchase Commitments (Details) (USD $)	Dec. 31, 2014	Jun. 30, 2014
In Millions, unless otherwise specified
Raw materials, wafers, and packaging and testing services puchase commitments
Purchase Commitment, Excluding Long-term Committment [Line Items]
Purchase commitment, amount	$21.70	$34.50
Property and equipment purchase commitments
Purchase Commitment, Excluding Long-term Committment [Line Items]
Purchase commitment, amount	$9.90	$4.60

Commitments_and_Contingencies_1

Commitments and Contingencies - Guarantees (Details) (Indemnification Agreement, USD $)	Dec. 31, 2014	Jun. 30, 2014
Indemnification Agreement
Loss Contingencies [Line Items]
Indemnifications accrual	$0	$0