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Table of Contents

As filed with the Securities and Exchange Commission on December 4,11, 2017

Registration No. 333-221147


UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

AMENDMENT NO. 12
TO
FORM S-4
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933



LITTELFUSE, INC.
(Exact name of registrant as specified in its charter)



Delaware
(State or other jurisdiction of
incorporation or organization)
 3613
(Primary Standard Industrial
Classification Code Number)
 36-3795742
(I.R.S. Employer
Identification Number)



8755 West Higgins Road, Suite 500
Chicago, Illinois 60631
(773) 628-1000
Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

Ryan K. Stafford, Esq.
Executive Vice President, Chief Legal and
Human Resources Officer and Corporate Secretary
Littelfuse, Inc.
8755 West Higgins Road, Suite 500
Chicago, Illinois 60631
(773) 628-1000
(Name, address, including zip code, and telephone number, including area code, of agent for service)



With copies to:

Edward D. Herlihy, Esq.
Mark F. Veblen, Esq.
Wachtell, Lipton, Rosen & Katz
51 West 52nd Street
New York, New York 10019
(212) 403-1000

 

James R. Jones, Esq.
Vice President and General Counsel
IXYS Corporation
1590 Buckeye Drive
Milpitas, California 95035-7418
(408) 457-9000

 

Luke J. Bergstrom, Esq.
Chad G. Rolston, Esq.
Latham & Watkins LLP
140 Scott Drive
Menlo Park, California 94025
(650) 328-4600

Approximate date of commencement of proposed sale of the securities to the public:
As soon as practicable after this Registration Statement is declared effective and upon the satisfaction or waiver of all
other conditions to consummation of the transactions described herein.

           If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box.    o

           If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

           If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

           Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer ý Accelerated filer o Non-accelerated filer o
(Do not check if a
smaller reporting company)
 Smaller reporting company o

Emerging growth company o

           If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. o

           If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

           The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

   


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The information in this proxy statement/prospectus is subject to completion and amendment. A registration statement relating to the securities described in this proxy statement/prospectus has been filed with the Securities and Exchange Commission. These securities may not be sold nor may offers to buy these securities be accepted prior to the time the registration statement becomes effective. This proxy statement/prospectus shall not constitute an offer to sell or the solicitation of any offer to buy nor shall there be any sale of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration under the securities laws of any such jurisdiction.

PRELIMINARY—SUBJECT TO COMPLETION, DATED DECEMBER 4,11, 2017

LOGO

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

Dear IXYS Corporation Stockholder:

          On August 25, 2017, IXYS Corporation (referred to as IXYS), Littelfuse, Inc. (referred to as Littelfuse) and Iron Merger Co., Inc., a wholly owned subsidiary of Littelfuse (referred to as Merger Sub), entered into an Agreement and Plan of Merger that provides for the acquisition of IXYS by Littelfuse (such agreement, as amended by Amendment No. 1, dated as of December 4, 2017, by and among IXYS, Littelfuse, Merger Sub and IXYS Merger Co., LLC, a wholly owned subsidiary of Littelfuse (referred to as Merger Sub Two), as it may be further amended from time to time, is referred to as the merger agreement). Pursuant to the terms of the merger agreement, Merger Sub will merge with and into IXYS (referred to as the initial merger), with IXYS continuing as the surviving corporation in the initial merger and a wholly owned subsidiary of Littelfuse. Further to the terms of the merger agreement, IXYS, as the surviving corporation of the initial merger, will merge with and into Merger Sub Two (referred to as the follow-on merger, and collectively with the initial merger, the merger), with Merger Sub Two continuing as the surviving company in the follow-on merger and a wholly owned subsidiary of Littelfuse. The respective boards of directors of IXYS and Littelfuse have unanimously approved the merger agreement, the merger and the other transactions contemplated by the merger agreement.

          Upon the terms and subject to the conditions of the merger agreement, at the effective time of the initial merger (referred to as the effective time), each share of common stock, par value $0.01 per share, of IXYS that you own immediately prior to the effective time will be cancelled and extinguished and automatically converted into the right to receive, at your election and subject to proration, (i) $23.00 in cash (subject to applicable withholding tax), without interest (referred to as the cash consideration), or (ii) 0.1265 of a share of common stock, par value $0.01 per share, of Littelfuse (referred to as the stock consideration and together with the cash consideration, the merger consideration). You will receive cash in lieu of any fractional shares of Littelfuse common stock that you would otherwise be entitled to receive. Additionally, at the effective time, each outstanding option to purchase shares of IXYS common stock granted under an IXYS equity plan will be assumed by Littelfuse and converted into an option to acquire (i) a number of shares of Littelfuse common stock equal to the number of shares of IXYS common stock subject to such option immediately prior to the effective time multiplied by 0.1265, rounded down to the nearest whole share, with (ii) an exercise price per share of Littelfuse common stock equal to the exercise price of such IXYS stock option immediately prior to the effective time divided by 0.1265, rounded up to the nearest whole cent.

          Based on the closing stock price of Littelfuse common stock on August 25, 2017, the last full trading day before the announcement of the merger, the per share value of IXYS common stock implied by the stock consideration is $22.55. Based on the closing stock price of Littelfuse common stock on [    ·    ], 2017, the most recent practicable date prior to the date of the accompanying proxy statement/prospectus, the per share value implied by the stock consideration is $[    ·    ], which represents a premium of approximately [    ·    ]% over IXYS' closing stock price on August 25, 2017. The implied value of the stock consideration will fluctuate as the market price of Littelfuse common stock fluctuates because the stock consideration is payable in a fixed number of shares of Littelfuse common stock. As a result, the value of the stock consideration that IXYS stockholders will receive upon completion of the merger could be greater than, less than or the same as the value of the stock consideration on the date of the accompanying proxy statement/prospectus or at the time of the special meeting of the IXYS stockholders described in the accompanying proxy statement/prospectus (referred to as the special meeting). Accordingly, you should obtain current stock price quotations for Littelfuse common stock and IXYS common stock before deciding how to vote with respect to the approval of the merger proposal. Littelfuse common stock and IXYS common stock trade on The NASDAQ Global Select Market under the symbols "LFUS" and "IXYS," respectively.

          Based on the number of shares of Littelfuse common stock and IXYS common stock outstanding on November 29,December 6, 2017, upon completion of the merger, former IXYS stockholders will own approximately 8% of the outstanding shares of Littelfuse common stock and Littelfuse stockholders immediately prior to the merger will own approximately 92% of the outstanding shares of Littelfuse common stock.

          The IXYS board of directors unanimously determined that the merger and the merger agreement are fair to and in the best interests of IXYS and its stockholders, and approved and declared it advisable to enter into the merger agreement.

          At the special meeting, you will be asked to approve the merger proposal and to vote on other merger-related matters.The IXYS board of directors unanimously recommends that IXYS stockholders vote "FOR" the merger proposal and "FOR" each of the other proposals described in the accompanying proxy statement/prospectus.

          Your vote is very important.    Littelfuse and IXYS cannot complete the merger without the approval of the merger proposal by IXYS stockholders holding at least a majority of the shares of IXYS common stock outstanding at the close of business on [    ·    ],December 6, 2017, the record date for the special meeting. The failure of any stockholder to vote will have the same effect as a vote against the approval of the merger proposal. It is important that your shares of IXYS common stock be represented and voted regardless of the size of your holdings. Whether or not you plan to attend the special meeting, IXYS urges you to submit a proxy in advance of the special meeting to have your shares voted by using one of the methods described in the accompanying proxy statement/prospectus.

          More information about Littelfuse, IXYS, the special meeting, the merger and the other proposals for consideration at the special meeting is contained in the accompanying proxy statement/prospectus.Please carefully read the entire proxy statement/prospectus, including the section titled "Risk Factors" beginning on page 32, for a discussion of the risks relating to the proposed merger, and the annexes and documents incorporated by reference.

On behalf of the IXYS board of directors, thank you for your continued support.

Sincerely,

Uzi Sasson
President and Chief Executive Officer

          NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED THE MERGER OR OTHER TRANSACTIONS DESCRIBED IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS OR THE SECURITIES TO BE ISSUED PURSUANT TO THE MERGER UNDER THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS NOR HAVE THEY DETERMINED IF THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS IS ACCURATE OR ADEQUATE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

          The accompanying proxy statement/prospectus is dated [    ·    ], 2017 and is first being mailed to IXYS stockholders on or about [    ·    ], 2017.


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LOGO

IXYS CORPORATION
1590 Buckeye Drive
Milpitas, California 95035-7418

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS TO BE HELD ON [    ·    ], 2018

        This is a notice that the special meeting of stockholders of IXYS Corporation (referred to as IXYS) will be held on [    ·    ], 2018, beginning at [    ·    ],9:00 a.m., local time, at IXYS' principal executive offices at the above address, unless postponed to a later date. The special meeting will be held for the following purposes:

        The accompanying proxy statement/prospectus describes the proposals listed above in more detail. Please refer to the accompanying proxy statement/prospectus, including the merger agreement and the other annexes and documents included in, or incorporated by reference into, the accompanying proxy statement/prospectus for further information with respect to the business to be transacted at the special meeting. You are encouraged to read the entire proxy statement/prospectus carefully before voting.In particular, see the section titled "Risk Factors" beginning on page 32.

        The IXYS board of directors unanimously determined that the terms of the merger agreement and the merger are fair to, and in the best interests of, IXYS and its stockholders, and that it is in the best interests of IXYS and its stockholders, and declared it advisable, for IXYS to enter into the merger agreement. The IXYS board of directors recommends that IXYS stockholders vote "FOR" the merger proposal and "FOR" each of the other proposals listed above and described in more detail in the accompanying proxy statement/prospectus.

        The IXYS board of directors has fixed the close of business on [    ·    ],December 6, 2017 as the record date for determination of IXYS stockholders entitled to receive notice of, and to vote at, the special meeting or any adjournments or postponements thereof. Only holders of record of IXYS common stock as of the close of business on the record date are entitled to receive notice of, and to vote at, the special meeting.


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        YOUR VOTE IS VERY IMPORTANT, REGARDLESS OF THE NUMBER OF SHARES THAT YOU OWN.

        The merger cannot be completed unless the merger proposal is approved by the affirmative vote, in person or by proxy, of holders of a majority of the outstanding shares of IXYS common stock entitled to vote thereon.

        The affirmative vote of holders of a majority of the shares of IXYS common stock present in person or represented by proxy at the special meeting and entitled to vote thereon is required to approve the merger-related compensation proposal and the adjournment proposal.

        Whether or not you expect to attend the special meeting in person, IXYS urges you to submit a proxy to have your shares voted as promptly as possible by either: (1) logging onto the website shown on your proxy card and following the instructions to submit a proxy online; (2) dialing the toll-free number shown on your proxy card and following the instructions to submit a proxy by phone; or (3) signing and returning the enclosed proxy card in the postage-paid envelope provided, so that your shares may be represented and voted at the special meeting. If your shares are held in the name of a bank, brokerage firm or other nominee, please follow the instructions on the voting instruction card furnished by such bank, brokerage firm or other nominee. Any stockholder of record attending the special meeting may vote in person even if such stockholder has returned a proxy card.

        If you have any questions about the special meeting, the merger, the proposals or the accompanying proxy statement/prospectus, would like additional copies of the proxy statement/prospectus, need to obtain proxy cards or other information related to this proxy solicitation or need help submitting a proxy or voting your shares of IXYS common stock, you should contact:

IXYS Corporation
1590 Buckeye Drive
Milpitas, CA 95035
(408) 457-9000
Attention: Investor Relations

or

D.F. King & Co., Inc.
48 Wall Street
New York, NY 10005

Banks and Brokerage Firms Call: (212) 493-3910
Stockholders Call Toll Free: (800) 334-0384
Email: ixys@dfking.com

By order of the board of directors

Uzi Sasson
President and Chief Executive Officer

Dated: [    ·    ], 2017
Milpitas, California


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ADDITIONAL INFORMATION

        This proxy statement/prospectus incorporates important business and financial information about Littelfuse and IXYS from other documents that Littelfuse and IXYS have filed with the U.S. Securities and Exchange Commission (referred to in this proxy statement/prospectus as the SEC) and that are contained in or incorporated by reference into this proxy statement/prospectus. For a listing of documents incorporated by reference into this proxy statement/prospectus, please see the section titled "Where You Can Find More Information" beginning on page 151. This information is available for you to review at the SEC's public reference room located at 100 F Street, N.E., Room 1580, Washington, DC 20549, and through the SEC's website at www.sec.gov.

        You can obtain copies of this proxy statement/prospectus and the documents incorporated by reference into this proxy statement/prospectus free of charge by requesting them in writing or by telephone at the following addresses and telephone numbers:

For Information Regarding Littelfuse: For Information Regarding IXYS:

Littelfuse, Inc.

 

IXYS Corporation
8755 West Higgins Road, Suite 500 1590 Buckeye Drive
Chicago, Illinois 60631 Milpitas, California 95035
(773) 628-1000 (408) 457-9000
Attention: Investor Relations Attention: Investor Relations

        In addition, if you have questions about the special meeting, the merger, the proposals or this proxy statement/prospectus, would like additional copies of the proxy statement/prospectus, need to obtain proxy cards or other information related to the proxy solicitation or need help submitting a proxy or voting your shares of IXYS common stock, you may contact D.F. King & Co., Inc. (referred to in this proxy statement/prospectus as D.F. King or IXYS' proxy solicitor), at the address and telephone number listed below. You will not be charged for any of these documents that you request.

D.F. King & Co., Inc.
48 Wall Street
New York, NY 10005

Banks and Brokerage Firms Call: (212) 493-3910
Stockholders Call Toll Free: (800) 334-0384
Email: ixys@dfking.com

        If you would like to request any documents, please do so by [    ·    ], 2018, which is the date that is five business days prior to the date of the special meeting, in order to receive them before the special meeting.


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ABOUT THIS PROXY STATEMENT/PROSPECTUS

        This proxy statement/prospectus, which forms part of a registration statement on Form S-4 (Registration No. 333-221147) filed with the SEC by Littelfuse, constitutes a prospectus of Littelfuse under the Securities Act of 1933, as amended (referred to in this proxy statement/prospectus as the Securities Act), with respect to the Littelfuse common stock to be issued to IXYS stockholders pursuant to the merger. This proxy statement/prospectus also constitutes a proxy statement for IXYS under the Securities Exchange Act of 1934, as amended (referred to in this proxy statement/prospectus as the Exchange Act), and a notice of meeting with respect to the special meeting of IXYS stockholders.

        You should rely only on the information contained in or incorporated by reference into this proxy statement/prospectus. No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this proxy statement/prospectus. This proxy statement/prospectus is dated [    ·    ], 2017, and you should assume that the information contained in this proxy statement/prospectus is accurate only as of such date. You should also assume that the information incorporated by reference into this proxy statement/prospectus is accurate only as of the date of such information.

        This proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Information contained in this proxy statement/prospectus regarding Littelfuse has been provided by Littelfuse, and information contained in this proxy statement/prospectus regarding IXYS has been provided by IXYS.


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TABLE OF CONTENTS

QUESTIONS AND ANSWERS

  1 

SUMMARY

  12 

The Parties

  12 

The Merger and the Merger Agreement

  13 

Merger Consideration

  13 

IXYS Special Meeting

  14 

How Proxies Are Counted; Failure to Vote; Abstentions and Broker Non-Votes

  15 

IXYS' Reasons for the Merger; Recommendation of IXYS Board of Directors

  15 

Opinion of IXYS' Financial Advisor

  15 

Interests of IXYS' Directors and Executive Officers in the Merger

  16 

Material U.S. Federal Income Tax Consequences

  16 

Accounting Treatment of the Merger

  17 

Regulatory Approvals Required to Complete the Merger

  17 

Expected Timing of Merger

  17 

Treatment of IXYS Stock Options

  18 

Listing of Littelfuse Common Stock; Delisting of IXYS Common Stock

  18 

Appraisal Rights

  18 

No Solicitation of Company Takeover Proposals

  18 

Changes in Board Recommendation

  19 

Conditions to Completion of the Merger

  20 

Termination of the Merger Agreement

  20 

Expenses and Termination Fees Relating to the Merger

  21 

Comparison of Rights of Common Stockholders of Littelfuse and IXYS

  21 

Risk Factors

  21 

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA

  22 

Selected Historical Consolidated Financial Data of Littelfuse

  22 

Selected Historical Consolidated Financial Data of IXYS

  24 

UNAUDITED COMPARATIVE PER SHARE INFORMATION

  27 

COMPARATIVE STOCK PRICE DATA AND DIVIDENDS

  28 

Stock Prices

  28 

Littelfuse Common Stock

  28 

IXYS Common Stock

  29 

Dividends

  29 

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

  30 

RISK FACTORS

  32 

Risks Relating to the Merger

  32 

Other Risk Factors of Littelfuse and IXYS

  39 

INFORMATION ABOUT IXYS

  40 

INFORMATION ABOUT LITTELFUSE

  40 

INFORMATION ABOUT THE IXYS SPECIAL MEETING

  41 

General

  41 

Date, Time and Place of the Special Meeting

  41 

Purposes of the Special Meeting

  41 

Only the approval of the merger proposal is required for completion of the merger. 

  41 

Attendance at the Special Meeting

  41 

Record Date

  42 

Outstanding Shares As of Record Date

  42 

Shares and Voting of IXYS' Directors and Executive Officers

  42 

Quorum and Broker Non-Votes

  43 

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Required Vote

  43 

How To Vote or Have Your Shares Voted

  44 

Revocation of Proxies

  45 

Solicitation of Proxies

  45 

Adjournments

  45 

Questions and Additional Information

  46 

PROPOSAL 1: THE MERGER PROPOSAL

  47 

PROPOSAL 2: THE MERGER-RELATED COMPENSATION PROPOSAL

  48 

PROPOSAL 3: THE ADJOURNMENT PROPOSAL

  49 

THE MERGER

  50 

Merger Consideration

  50 

Background of the Merger

  51 

IXYS' Reasons for the Merger; Recommendation of IXYS Board of Directors

  56 

Certain Financial Projections Utilized by the IXYS Board of Directors and IXYS' Financial Advisor

  61 

Opinion of IXYS' Financial Advisor

  65 

Form of Merger

  74 

Interests of IXYS' Directors and Executive Officers in the Merger

  75 

Quantification of Potential Payments and Benefits to IXYS' Named Executive Officers in Connection with the Merger

  78 

Narrative Disclosure to Golden Parachute Compensation Table

  79 

Accounting Treatment of the Merger

  80 

Material U.S. Federal Income Tax Consequences

  80 

Regulatory Approvals

  84 

Exchange of Shares; Elections As to Form of Consideration

  85 

Dividend Policy

  87 

Listing of Littelfuse Common Stock; Delisting of IXYS Common Stock

  87 

THE MERGER AGREEMENT

  88 

Closing; Effective Time

  88 

Effect of the Merger on Capital Stock

  89 

Election Procedures

  92 

Exchange and Payment Procedures

  93 

Treatment of IXYS Equity Awards

  95 

Representations and Warranties

  96 

Conduct of Businesses of IXYS and Littelfuse Prior to Completion of the Merger

  98 

No Solicitation of Company Takeover Proposals

  101 

No Change in Recommendation or Termination For a Superior Proposal

  103 

IXYS Stockholder Meeting

  105 

Actions with Respect to IXYS Debt

  105 

Access to Information

  105 

Employee Matters

  106 

Indemnification and Insurance

  106 

Littelfuse Board of Directors

  107 

Certain Additional Covenants

  107 

Conditions to Completion of the Merger

  108 

Regulatory Approvals

  109 

Termination of the Merger Agreement

  109 

Amendment and Assignment

  111 

Jurisdiction; Specific Enforcement

  111 

THE VOTING AGREEMENT

  113 

OTHER MATTERS

  113 

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LITIGATION RELATING TO THE MERGER

  114 

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

  115 

NOTES TO THE UNAUDTED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS GIVING EFFECT TO THE TRANSACTION

  119 

DESCRIPTION OF LITTELFUSE CAPITAL STOCK

  126 

Common Stock

  126 

Potential Anti-Takeover Effects of Various Provisions of Delaware Law and Littelfuse's Certificate of Incorporation and Bylaws

  126 

COMPARISON OF RIGHTS OF COMMON STOCKHOLDERS OF LITTELFUSE AND IXYS

  128 

APPRAISAL RIGHTS OF IXYS STOCKHOLDERS

  143 

LEGAL MATTERS

  148 

EXPERTS

  148 

Littelfuse

  148 

IXYS

  148 

IXYS 2018 STOCKHOLDER PROPOSALS

  149 

HOUSEHOLDING OF PROXY STATEMENT/PROSPECTUS

  150 

WHERE YOU CAN FIND MORE INFORMATION

  151 

Annex A—Agreement and Plan of Merger, dated as of August 25, 2017, by and among IXYS Corporation, Littelfuse, Inc. and Iron Merger Co., Inc. with Amendment No. 1 to the Agreement and Plan of Merger, dated as of December 4, 2017, by and among IXYS Corporation, Littelfuse, Inc., Iron Merger Co.,  Inc. and IXYS Merger Co., LLC

  
 

Annex B—Voting Agreement, dated as of August 25, 2017, by and between Littelfuse,  Inc. and Dr. Nathan Zommer, Sharkz, L.P., The Nathan Zommer Dynasty Trust Dated July 17, 2006 and the Nathan Zommer TTEE FBO Nathan Zommer Trust U/A/D 04-08-2003

    

Annex C—Opinion of Needham & Company, LLC

    

Annex D—General Corporation Law of the State of Delaware, Section 262

    

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QUESTIONS AND ANSWERS

        The following questions and answers are intended to briefly address some commonly asked questions regarding the merger, the merger agreement and the special meeting. These questions and answers may not address all questions that may be important to you as an IXYS stockholder. Please refer to the section titled "Summary" beginning on page 12 and the more detailed information contained elsewhere in this proxy statement/prospectus, the annexes to this proxy statement/prospectus and the documents referred to in this proxy statement/prospectus, which you should read carefully and in their entirety. You may obtain the information incorporated by reference into this proxy statement/prospectus without charge by following the instructions under the section titled "Where You Can Find More Information" beginning on page 151.

Q:    Why am I receiving this proxy statement/prospectus?

A:
IXYS Corporation (referred to in this proxy statement/prospectus as IXYS) is sending these materials to IXYS stockholders to help them decide how to vote their shares of IXYS common stock with respect to the adoption of the Agreement and Plan of Merger, dated as of August 25, 2017, as amended by Amendment No. 1, dated as of December 4, 2017, by and among IXYS, Littelfuse, Inc. (referred to in this proxy statement/prospectus as Littelfuse), Iron Merger Co., Inc., a wholly owned subsidiary of Littelfuse (referred to in this proxy statement/prospectus as Merger Sub), and IXYS Merger Co., LLC, a wholly owned subsidiary of Littelfuse (referred to in this proxy statement/prospectus as Merger Sub Two), which agreement provides for the acquisition of IXYS by Littelfuse (such agreement, as it may be further amended from time to time, is referred to in this proxy statement/prospectus as the merger agreement) and with respect to the other proposals to be considered at the special meeting of IXYS stockholders to be held on [    ·    ], 2018 (referred to in this proxy statement/prospectus as the special meeting).

Q:    What is the merger?

A:
IXYS has agreed to be acquired by Littelfuse under the terms of the merger agreement, which is further described in this proxy statement/prospectus. If the merger agreement is adopted by IXYS stockholders and the other conditions to closing under the merger agreement are satisfied or waived, Merger Sub will merge with and into IXYS (referred to in this proxy statement/prospectus as the initial merger), with IXYS continuing as the surviving corporation in the initial merger and a wholly owned subsidiary of Littelfuse. Further to the terms of the merger agreement, IXYS, as the surviving corporation of the initial merger, will merge with and into Merger Sub Two (referred to in this proxy statement/prospectus as the follow-on merger, and collectively with the initial merger, the merger), with Merger Sub Two continuing as the surviving company in the follow-on merger and a wholly owned subsidiary of Littelfuse.

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Q:    Are there any risks that I should consider in deciding whether to vote for the approval of the merger proposal?

A:
Yes. You should read and carefully consider the risk factors set forth in the section titled "Risk Factors" beginning on page 32. You should also read and carefully consider the risk factors of Littelfuse and IXYS contained in the documents that are incorporated by reference into this proxy statement/prospectus.

Q:    What will IXYS stockholders receive for their shares if the merger is completed?

A:
At the effective time of the initial merger (referred to in this proxy statement/prospectus as the effective time), you will be entitled to receive, at your election and subject to proration, for each share of IXYS common stock that you hold, merger consideration equal to $23.00 in cash, without interest, less any applicable withholding taxes (referred to in this proxy statement/prospectus as the cash consideration), or 0.1265 of a share of Littelfuse common stock (referred to in this proxy statement/prospectus as the stock consideration and together with the cash consideration, the merger consideration). The exchange ratio was derived by dividing the cash consideration of $23.00 by the volume weighted average price per share of Littelfuse common stock for a pre-determined trading period prior to the signing of the merger agreement. You will receive cash in lieu of any fractional shares of Littelfuse common stock that you would otherwise be entitled to receive.

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Implied Value, Per Share of IXYS Common Stock, of Stock Consideration
Based on Range of Hypothetical Littelfuse Share Prices(1)

GRAPHICGRAPHIC


(1)
The implied value, per share of IXYS common stock, of the stock consideration, at each hypothetical Littelfuse share price, is equal to 0.1265, the exchange ratio for the stock consideration, multiplied by the hypothetical Littelfuse share price.

Q:    What happens if I am eligible to receive a fraction of a share of Littelfuse common stock as part of the stock consideration?

A:
If the aggregate number of shares of Littelfuse common stock that you are entitled to receive as part of the stock consideration otherwise would include a fraction of a share of Littelfuse common stock, you will receive cash in lieu of that fractional share. See the section titled "The Merger—Exchange of Shares; Elections As to Form of Consideration" beginning on page 85.

Q:    What will holders of IXYS stock options receive in the merger?

A:
At the effective time, each outstanding and unexercised option to purchase shares of IXYS common stock granted by IXYS under one of its equity plans (each, an IXYS stock option) will be assumed by Littelfuse and converted into an option (each, a Littelfuse stock option) to acquire (i) that number of whole shares of Littelfuse common stock (rounded down to the nearest whole share) equal to the product of (x) the number of shares of IXYS common stock subject to such IXYS stock option immediately prior to the effective time multiplied by (y) 0.1265, (ii) at an exercise price per share of Littelfuse common stock (rounded up to the nearest whole cent) equal

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Q:    How will IXYS stockholders make their election to receive either the cash consideration or the stock consideration in the merger?

A:
An election form will be mailed to each holder of record of IXYS common stock as of the business day immediately preceding the mailing. The mailing will occur at least 20 business days prior to the anticipated election deadline, which is expected to be 5:00 p.m. local time (in the city in which the principal office of the exchange agent is located) on the date Littelfuse and IXYS expect to be two business days before the closing date. Littelfuse will also make an election form available to each IXYS stockholder who requests such form before the election deadline. Each IXYS stockholder should complete and return the election form, along with IXYS stock certificate(s) (or a properly completed notice of guaranteed delivery, as set forth in the election form), according to the instructions included with the form. The election form will be provided to IXYS stockholders under separate cover and is not being provided with this document.

Q:    What happens if an IXYS stockholder does not make a valid election to receive either the cash consideration or the stock consideration?

A:
If an IXYS stockholder does not return a properly completed election form by the election deadline specified in the election form, such stockholder's shares of IXYS common stock will be considered "non-election" shares and will be converted into the right to receive the stock consideration or the cash consideration according to the allocation procedures specified in the merger agreement. Generally, in the event one form of merger consideration (i.e., cash or shares of Littelfuse common stock) is undersubscribed, shares of IXYS common stock for which no election was validly made will be allocated to that form of merger consideration before shares of IXYS common stock electing the oversubscribed form of merger consideration will be allocated to the undersubscribed form of merger consideration pursuant to the proration and adjustment procedures. Accordingly, although electing one form of merger consideration will not guarantee you will receive that form of merger consideration for all of your shares of IXYS common stock, in the event proration is necessary, electing shares will be allocated the undersubscribed form of consideration only after such consideration is allocated to "non-election" shares.

Q:    How will I receive the merger consideration to which I am entitled?

A:
After receiving the proper documentation from you, following completion of the initial merger, the exchange agent for the merger (referred to in this proxy statement/prospectus as the exchange agent) will forward to you the stock consideration and/or cash consideration to which you are entitled. More information on the documentation you are required to deliver to the exchange

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Q:    What will happen to IXYS as a result of the merger?

A:
If the merger is completed, IXYS, as the surviving corporation of the initial merger, will merge with and into Merger Sub Two, with Merger Sub Two continuing as the surviving company in the follow-on merger and a wholly owned subsidiary of Littelfuse. As a result of the merger, IXYS will no longer be a publicly held company. Following the merger, IXYS common stock will be delisted from The NASDAQ Global Select Market and deregistered under the Exchange Act.

Q:    Will the Littelfuse common stock received at the time of completion of the merger be traded on an exchange?

A:
It is a condition to the consummation of the merger that the shares of Littelfuse common stock to be issued to IXYS stockholders in the merger be approved for listing on The NASDAQ Global Select Market, subject to official notice of issuance.

Q:    When is the merger expected to be completed?

A:
Littelfuse and IXYS currently expect the merger to be completed during the first quarter of calendar year 2018, subject to the affirmative vote of the holders of a majority of the outstanding shares of IXYS common stock in favor of adoption of the merger agreement and the satisfaction or waiver of the other conditions to closing contained in the merger agreement. However, Littelfuse and IXYS cannot predict the actual date on which the merger will be completed because completion is subject to conditions beyond their control and it is possible that such conditions could result in the merger being completed earlier or later or not being completed at all. See the sections titled "The Merger—Regulatory Approvals" beginning on page 84 and "The Merger Agreement—Conditions to Completion of the Merger" beginning on page 108.

Q:    What am I being asked to vote on?

A:
IXYS stockholders are being asked to vote upon the following proposals:

1.
Proposal 1—The Merger Proposal:    the proposal to adopt the merger agreement, which is further described in the sections titled "The Merger" beginning on page 50 and "The Merger Agreement" beginning on page 88 and a copy of which is attached to this proxy statement/prospectus asAnnex A;

2.
Proposal 2—The Merger-Related Compensation Proposal:    the proposal to approve on an advisory (non-binding) basis the compensation that may be paid or become payable to IXYS' named executive officers that is based on or otherwise relates to the merger; and

3.
Proposal 3—The Adjournment Proposal:    the proposal to approve the adjournment of the special meeting, if necessary, to solicit additional proxies if there are not sufficient votes to approve the merger proposal.

Q:    How does the IXYS board of directors recommend that I vote at the special meeting?

A:
The IXYS board of directors unanimously recommends that IXYS stockholders vote "FOR" the merger proposal and "FOR" each of the other proposals described in this proxy statement/prospectus.

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Q:    What do I need to do now?

A:
After carefully reading and considering the information contained in this proxy statement/prospectus, please submit your proxy as soon as possible so that your shares of IXYS common stock will be represented and voted at the special meeting. Please follow the instructions set forth on the proxy card or on the voting instruction form provided by the record holder if your shares are held in "street name" by your bank, brokerage firm or other nominee.

Q:    Should I send in my IXYS stock certificates now?

A:
No.Please do not send in your IXYS stock certificates with your proxy. You should submit your IXYS stock certificates with your election form. Any IXYS stockholder who has not submitted its, his or her physical stock certificate(s) with a form of election will be sent materials after the merger closes to effect the exchange of such stockholder's IXYS common stock for the merger consideration. See "The Merger Agreement—Exchange and Payment Procedures."

Q:    When and where is the special meeting of the IXYS stockholders?

        

A:
The special meeting will be held on [    ·    ], 2018, beginning at [    ·    ],9:00 a.m., local time, at IXYS' principal executive offices at 1590 Buckeye Drive, Milpitas, California 95035, unless postponed to a later date.

Q:    Who can vote at the special meeting?

A:
Only IXYS stockholders who held shares of record as of the close of business on [    ·    ],December 6, 2017, the record date for the special meeting, are entitled to receive notice of and to vote at the special meeting. IXYS' official stock ownership records will conclusively determine whether a stockholder is a "holder of record" as of the record date.

Q:    How many votes do I have?

A:
Each IXYS stockholder is entitled to one vote on each matter properly brought before the special meeting for each share of IXYS common stock held of record as of the close of business on the record date. As of the close of business on the record date, there were [    ·    ]32,935,335 shares of IXYS common stock outstanding and owned by stockholders (i.e., excluding shares of IXYS common stock held in treasury by IXYS), held by [    ·    ]216 holders of record.

Q:    What constitutes a quorum for the special meeting?

A:
The presence at the special meeting, in person or by proxy, of the holders of a majority of the outstanding shares of IXYS common stock as of the record date entitled to vote at the special meeting constitutes a quorum for the purposes of the special meeting. The Inspector of Elections at the special meeting will determine whether or not a quorum is present. Abstentions are considered present for purposes of establishing a quorum, but will not be counted as votes cast "FOR" any matter. Broker non-votes are considered present for purposes of establishing a quorum, but will not be counted as votes cast "FOR" any matter.

Q:    What vote is required to approve each proposal to be considered at the IXYS special meeting?

A:
The votes required for each proposal are as follows:

1.
The Merger Proposal:    The affirmative vote, in person or by proxy, of holders of a majority of the outstanding shares of IXYS common stock entitled to vote on the merger proposal is required to approve the merger proposal.

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Q:    How are proxies counted and what results from a failure to vote, abstention or broker non-vote?

A:
The Merger Proposal:    If you are an IXYS stockholder on the record date and take any action other than voting (or causing your shares to be voted) "FOR" the merger proposal, it will have the same effect as a vote "AGAINST" the merger proposal. For example, if you fail to instruct your bank, brokerage firm or other nominee to vote, it will have the same effect as a vote "AGAINST" the merger proposal.

Q:    What will happen if the merger-related compensation proposal is not approved?

A:
The merger-related compensation proposal is advisory only and not binding on IXYS or Littelfuse, whether or not the merger is completed. The vote on the merger-related compensation proposal is separate and apart from the vote to adopt the merger agreement and not a condition to the

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Q:    How do I vote or have my shares voted?

A:
If you are an IXYS stockholder of record, you may vote in person at the special meeting or vote by proxy using the enclosed proxy card. Whether or not you plan to attend the meeting, we urge you to vote by proxy to ensure your vote is counted. You may still attend the meeting and vote in person even if you have already voted by proxy.

To vote in person, come to the special meeting and we will give you a ballot when you arrive.

To vote using the proxy card, simply complete, sign and date the enclosed proxy card and return it promptly in the envelope provided. If you return your signed proxy card to us before the special meeting, we will vote your shares as you direct.

To vote by telephone, submit your proxy by dialing the following number: [    ·    ].1-800-652-VOTE (8683). Telephone voting is available 24 hours a day and will be accessible until [    ·    ], local11:59 p.m., Pacific time, on [    ·    ], 2018, the day before the special meeting.

To vote via the Internet, submit your proxy by going to the following website: [    ·    ].www.investorvote.com/IXYS. Internet voting is available 24 hours a day and will be accessible until [    ·    ], local11:59 p.m., Pacific time, on [    ·    ], 2018, the day before the special meeting.

Q:    How will my proxy be voted?

A:
If you are a holder of record and submit your proxy via the Internet, by telephone or by completing, signing, dating and returning the enclosed proxy card, your shares will be voted in accordance with your instructions contained in the proxy. If you are a holder of record and submit your proxy without specifying how your shares should be voted in one or more matters, your shares will be voted on those matters as the IXYS board of directors recommends.

Q:    What must I bring to attend the special meeting?

A:
Only stockholders of record as of the record date, non-record owners as of the record date, holders of valid proxies for the special meeting and invited guests of IXYS may attend the special meeting. All attendees should be prepared to present picture identification for admittance. The additional items, if any, that attendees must bring depend on whether they are stockholders of record, non-record owners or proxy holders.

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Q:    If my shares are held in "street name" by my bank, brokerage firm or other nominee, will my bank, brokerage firm or other nominee vote my shares for me?

A:
No. If your shares are held in "street name" by your bank, brokerage firm or other nominee, you must direct your bank, brokerage firm or other nominee on how to vote and you will receive instructions from your bank, brokerage firm or other nominee describing how to vote your shares of IXYS common stock. The availability of Internet or telephonic voting will depend on the nominee's voting process. Please check with your bank, brokerage firm or other nominee and follow the voting procedures your bank, brokerage firm or other nominee provides.

Q:    What is the difference between holding shares as a stockholder of record and in "street name"?

A:
If your shares of IXYS common stock are registered directly in your name with the transfer agent of IXYS, Computershare Inc., you are considered the stockholder of record with respect to those shares. As the stockholder of record, you have the right to vote or to grant a proxy for your vote directly to IXYS or to a third party to vote at the special meeting.

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Q:    What should I do if I receive more than one set of voting materials for the special meeting?

A:
You may receive more than one set of voting materials for the special meeting, including multiple copies of this proxy statement/prospectus and multiple proxy cards or voting instruction cards. For example, if you hold your IXYS common stock in more than one brokerage account, you will receive a separate voting instruction card for each brokerage account in which you hold shares. If you are a stockholder of record and your shares are registered in more than one name, you will receive more than one proxy card. Please submit each separate proxy or voting instruction card that you receive by following the instructions set forth in each separate proxy or voting instruction card.

Q:    What do I do if I am an IXYS stockholder and I want to revoke my proxy?

A:
IXYS stockholders of record may revoke their proxies at any time prior to the voting at the special meeting in any of the following ways:

submitting another properly completed proxy card with a later date;

sending timely written notice that you are revoking your proxy to IXYS Corporation's Secretary, Uzi Sasson, at 1590 Buckeye Drive, Milpitas, California 95035;

submitting a proxy via the Internet or by telephone at a later date but before the voting at the special meeting (in which case only the later-dated proxy is counted and the earlier proxy is revoked); or

attending the special meeting and voting in person. Attendance at the special meeting will not, however, in and of itself, constitute a vote or revocation of a prior proxy.

Q:    What happens if I sell my shares of IXYS common stock before the special meeting?

A:
The record date is earlier than both the date of the special meeting and the closing of the merger. If you transfer your shares of IXYS common stock after the record date but before the special meeting, you will, unless the transferee requests a proxy from you, retain your right to vote at the special meeting but will transfer the right to receive the merger consideration to the person to whom you transfer your shares. In order to receive the merger consideration, you must hold your shares upon completion of the merger.

Q:    Do IXYS stockholders have appraisal rights?

A:
Yes. IXYS stockholders are entitled to appraisal rights under Section 262 of the General Corporation Law of the State of Delaware (referred to in this proxy statement/prospectus as the DGCL), provided they follow the procedures and satisfy the conditions set forth in Section 262 of the DGCL. For more information regarding appraisal rights, see the section titled "Appraisal Rights of IXYS Stockholders" beginning on page 143. In addition, a copy of Section 262 of the DGCL is attached asAnnex D to this proxy statement/prospectus. Failure to strictly comply with Section 262 of the DGCL may result in your waiver of, or inability to, exercise appraisal rights.

Q:    Who will solicit and pay the cost of soliciting proxies?

A:
IXYS will pay for the proxy solicitation costs related to the special meeting. IXYS has engaged D.F. King to assist in the solicitation of proxies for the special meeting. IXYS estimates that it will pay D.F. King a fee of approximately $10,500, plus reasonable out-of-pocket expenses. IXYS will also reimburse banks, brokerage firms, custodians, trustees, nominees and fiduciaries who hold

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Q:    How can I find more information about Littelfuse and IXYS?

A:
You can find more information about Littelfuse and IXYS from various sources described in the section titled "Where You Can Find More Information" beginning on page 151.

Q:    Who can answer any questions I may have about the special meeting or the proxy materials?

A:
If you have any questions about the special meeting, the merger, the proposals or this proxy statement/prospectus, would like additional copies of the proxy statement/prospectus, need to obtain proxy cards or other information related to this proxy solicitation or need help submitting a proxy or voting your shares of IXYS common stock, you should contact:

IXYS Corporation
1590 Buckeye Drive
Milpitas, CA 95035
(408) 457-9000
Attention: Investor Relations

or
D.F. King & Co., Inc.

48 Wall Street
New York, NY 10005

Banks and Brokerage Firms Call: (212) 493-3910
Stockholders Call Toll Free: (800) 334-0384
Email: ixys@dfking.com


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SUMMARY

        The following summary highlights selected information described in more detail elsewhere in this proxy statement/prospectus and the documents incorporated by reference into this proxy statement/prospectus, and may not contain all the information that may be important to you. To understand the merger and the matters being voted on by IXYS stockholders at the special meeting more fully, and to obtain a more complete description of the legal terms of the merger agreement, you should carefully read this entire proxy statement/prospectus, including the annexes, and the documents to which Littelfuse and IXYS refer you. Each item in this summary includes a page reference directing you to a more complete description of that topic. See the section titled "Where You Can Find More Information" beginning on page 151.

The Parties

        (see page 40)

IXYS Corporation

        IXYS Corporation, a Delaware corporation (referred to in this proxy statement/prospectus as IXYS), has been developing technology-driven products to improve energy conversion efficiency, generate clean energy, advance automation and provide solutions for the transportation, medical and telecommunication industries since its founding in Silicon Valley. IXYS, with its subsidiaries, has developed power semiconductors, solid state relays, high voltage integrated circuits and microcontrollers that are used in conserving energy and in reducing the world's dependence on fossil fuels. Diminishing natural resources, demand for renewable energy and environmental directives for energy efficiency represent a significant challenge. IXYS' power semiconductors and mixed-signal integrated circuits can reduce energy costs and consumption by improving the energy efficiency of everyday products. IXYS semiconductors are also used in medical devices and systems that provide diagnostics and therapy by medical equipment OEMs worldwide. IXYS common stock trades on The NASDAQ Global Select Market under the symbol "IXYS". The principal executive offices of IXYS are located at 1590 Buckeye Drive, Milpitas, California 95035, and its telephone number is (408) 457-9000.

Littelfuse, Inc.

        Littelfuse, Inc., a Delaware corporation (referred to in this proxy statement/prospectus as Littelfuse), is the world leader in circuit protection with growing global platforms in power control and sensing. The company serves customers in the electronics, automotive and industrial markets with technologies including fuses, semiconductors, polymers, ceramics, relays and sensors. Littelfuse has over 10,000 employees in more than 40 locations throughout the Americas, Europe and Asia. Littelfuse common stock trades on The NASDAQ Global Select Market under the symbol "LFUS". The principal executive offices of Littelfuse are located at 8755 West Higgins Road, Suite 500, Chicago, Illinois 60631, and its telephone number is (773) 628-1000.

Iron Merger Co., Inc.

        Iron Merger Co., Inc., a Delaware corporation (referred to in this proxy statement/prospectus as Merger Sub), is a wholly owned subsidiary of Littelfuse. Merger Sub was formed by Littelfuse solely in contemplation of the merger, has not conducted any business and has no assets, liabilities or obligations of any nature other than in connection with the merger. The principal executive offices of Merger Sub are located at c/o Littelfuse, Inc., 8755 West Higgins Road, Suite 500, Chicago, Illinois 60631, and its telephone number is (773) 628-1000.


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IXYS Merger Co., LLC

        IXYS Merger Co., LLC, a Delaware limited liability company (referred to in this proxy statement/prospectus as Merger Sub Two), is a wholly owned subsidiary of Littelfuse. Merger Sub Two was formed by Littelfuse solely in contemplation of the merger, has not conducted any business and has no assets, liabilities or obligations of any nature other than in connection with the merger. The principal executive offices of Merger Sub Two are located at c/o Littelfuse, Inc., 8755 West Higgins Road, Suite 500, Chicago, Illinois 60631, and its telephone number is (773) 628-1000.

The Merger and the Merger Agreement

        (see pages 50 and 88)

        The terms and conditions of the merger are contained in the merger agreement, a copy of which is attached asAnnex A to this proxy statement/prospectus. IXYS encourages you to read the merger agreement carefully and in its entirety, as it is the legal document that governs the merger.

        The merger agreement provides that, subject to the terms and conditions of the merger agreement, Merger Sub will merge with and into IXYS, with IXYS continuing as the surviving corporation in the initial merger and a wholly owned subsidiary of Littelfuse. Further to the terms of the merger agreement, IXYS, as the surviving corporation of the initial merger, will merge with and into Merger Sub Two, with Merger Sub Two continuing as the surviving company in the follow-on merger and a wholly owned subsidiary of Littelfuse.

Merger Consideration

        (see page 50)

        At the effective time, each issued and outstanding share of IXYS common stock (other than shares (i) owned or held in treasury by IXYS or owned by Littelfuse or Merger Sub (referred to in this proxy statement/prospectus as cancelled shares) or (ii) owned by stockholders that did not vote in favor of the adoption of the merger agreement and have validly made a demand for appraisal and not validly withdrawn such demand or otherwise lost their rights of appraisal with respect to such shares pursuant to Section 262 of the DGCL) (referred to in this proxy statement/prospectus as dissenting shares) will be converted into the right to receive, at the election of the holder of such share and subject to proration, $23.00 in cash, less any applicable withholding taxes and without interest, or 0.1265 of a share of Littelfuse common stock.stock (which exchange ratio was derived by dividing the cash consideration of $23.00 by the volume weighted average price per share of Littelfuse common stock for a pre-determined trading period prior to the signing of the merger agreement). No fractional shares of Littelfuse common stock will be issued in the merger, and holders of IXYS common stock will instead receive cash in lieu of fractional shares of Littelfuse common stock.

        The merger consideration is subject to proration so that 50% of IXYS common stock issued and outstanding immediately prior to the effective time will be converted into cash consideration and the remaining IXYS common stock will be converted into stock consideration, based on an exchange ratio of 0.1265 of a share of Littelfuse common stock for each share of IXYS common stock entitled to receive stock consideration. A holder of IXYS common stock who does not make an election will be treated as having elected to receive cash consideration or stock consideration in accordance with the proration methodology in the merger agreement, which is described in the section titled "The Merger Agreement—Effect of the Merger on Capital Stock—Proration and Allocation of Merger Consideration" beginning on page 90.

        Based on the closing stock price of Littelfuse common stock on August 25, 2017, the last full trading day before the announcement of the merger, the per share value of IXYS common stock implied by the stock consideration is $22.55. Based on the closing stock price of Littelfuse common


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stock on [    ·    ], 2017, the most recent practicable date prior to the date of this proxy statement/prospectus, the per share value of IXYS common stock implied by the stock consideration is $[    ·    ].


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The implied value of the stock consideration will fluctuate as the market price of Littelfuse common stock fluctuates because the stock consideration is payable in a fixed number of shares of Littelfuse common stock. As a result, the value of the stock consideration that IXYS stockholders will receive upon completion of the merger could be greater than, less than or the same as the value of the stock consideration on the date of this proxy statement/prospectus or at the time of the IXYS special meeting. Accordingly, Littelfuse and IXYS encourage you to obtain current stock price quotations for Littelfuse common stock and IXYS common stock before deciding how to vote with respect to approval of the merger proposal. Littelfuse common stock and IXYS common stock trade on The NASDAQ Global Select Market under the symbols "LFUS" and "IXYS," respectively.

IXYS Special Meeting

        (see page 41)

Purposes of the Special Meeting

        At the special meeting, IXYS stockholders will be asked to vote upon the following proposals:

Record Date

        The record date for the determination of IXYS stockholders entitled to notice of and to vote at the special meeting is [    ·    ],December 6, 2017. Only IXYS stockholders who held shares of record as of the close of business on [    ·    ],December 6, 2017 are entitled to receive notice of and vote at the special meeting and any adjournment or postponement of the special meeting, as long as such shares remain outstanding on the date of the special meeting.

Required Vote

        As of [    ·    ],December 6, 2017, the record date, IXYS directors and executive officers, as a group, owned and were entitled to vote [    ·    ]6,917,562 shares of IXYS common stock, or approximately [    ·    ]%21.0% of the outstanding shares of IXYS common stock. IXYS currently expects that these directors and executive officers will vote their shares in favor of approving the merger proposal and each of the other proposals described in this proxy statement/prospectus, although none of them, other than Dr. Nathan Zommer, has entered into any agreement obligating them to do so.


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        Concurrently with the execution of the merger agreement, each of Dr. Nathan Zommer (the current Chairman and Chief Executive Officer of IXYS) and certain of his controlled affiliates entered


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into the voting agreement with Littelfuse pursuant to which each party agreed, among other things, to vote the shares of IXYS common stock held by such party in favor of the merger proposal. See the section titled "The Voting Agreement" beginning on page 113.

        As of [    ·    ],December 6, 2017, the record date, approximately [    ·    ]%20.5% of the outstanding shares of IXYS common stock were subject to the voting agreement, a copy of which is attached to this proxy statement/prospectus asAnnex B.

How Proxies Are Counted; Failure to Vote; Abstentions and Broker Non-Votes

        The Merger Proposal:    If you are an IXYS stockholder on the record date and take any action other than voting (or causing your shares to be voted) "FOR" the merger proposal, it will have the same effect as a vote "AGAINST" the merger proposal. For example, if you fail to instruct your bank, brokerage firm or other nominee to vote, it will have the same effect as a vote "AGAINST" the merger proposal.

        The Merger-Related Compensation Proposal:    If you are an IXYS stockholder on the record date and attend the IXYS special meeting in person but fail to vote, or you are a stockholder and mark your proxy or voting instructions to abstain, it will have the same effect as a vote "AGAINST" the merger-related compensation proposal. If you are an IXYS stockholder and fail to vote by not attending the IXYS special meeting, in person or by proxy, or you fail to instruct your bank, brokerage firm or other nominee to vote, it will have no effect on the merger-related compensation proposal (assuming a quorum is present).

        The Adjournment Proposal:    If you are an IXYS stockholder on the record date and attend the IXYS special meeting in person but fail to vote, or you are a stockholder and mark your proxy or voting instructions to abstain, it will have the same effect as a vote "AGAINST" the adjournment proposal. If you are an IXYS stockholder and fail to vote by not attending the IXYS special meeting, in person or by proxy, or you fail to instruct your bank, brokerage firm or other nominee to vote, it will have no effect on the adjournment proposal (assuming a quorum is present).

IXYS' Reasons for the Merger; Recommendation of IXYS Board of Directors

        (see page 56)

        After careful evaluation of the merger agreement and the transactions contemplated thereby, the IXYS board of directors unanimously determined that the terms of the merger agreement and the merger are fair to, and in the best interests of, IXYS and its stockholders, and that it is in the best interests of IXYS and its stockholders, and declared it advisable, for IXYS to enter into the merger agreement.

        The IXYS board of directors unanimously recommends that IXYS stockholders vote "FOR" the merger proposal, and "FOR" each of the other proposals described in this proxy statement/prospectus.

        In the course of reaching its recommendation, the IXYS board of directors consulted with IXYS' senior management and financial advisor, Needham & Company, LLC (referred to in this proxy statement/prospectus as Needham & Company) and outside legal counsel and considered a number of factors. See the section titled "The Merger—IXYS' Reasons for the Merger; Recommendation of IXYS Board of Directors" beginning on page 56.

Opinion of IXYS' Financial Advisor

        (see page 65)


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        In connection with the merger, on August 25, 2017, Needham & Company delivered its oral opinion, which it subsequently confirmed in writing, that as of such date, and based upon and subject


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to the assumptions, qualifications, limitations and other matters set forth in its written opinion, the consideration of $23.00 in cash or 0.1265 of a share of Littelfuse common stock per share of IXYS common stock to be received by the holders of IXYS common stock (other than the holders of cancelled shares and dissenting shares) pursuant to the merger agreement was fair, from a financial point of view, to such holders.

        The full text of Needham & Company's written opinion, dated August 25, 2017, is attached as Annex C to this proxy statement/prospectus and is incorporated into this proxy statement/prospectus by reference. Needham & Company provided its opinion to the IXYS board of directors for the information and assistance of the IXYS board of directors (in its capacity as such) in connection with and for the purpose of the IXYS board of directors' evaluation of the transactions contemplated by the merger agreement. Needham & Company's opinion does not address any other aspect of the merger, or any related transaction, and does not constitute a recommendation to any stockholder of IXYS as to whether that stockholder should elect to receive the cash consideration or the stock consideration, or make no such election, or how that stockholder should vote or act on any matter relating to the merger.

Interests of IXYS' Directors and Executive Officers in the Merger

        (see page 75)

        When considering the recommendation of the IXYS board of directors with respect to the merger proposal and the merger-related compensation proposal, you should be aware that IXYS' directors and executive officers may have interests in the merger that are different from, or in addition to, those of IXYS stockholders more generally. The IXYS board of directors was aware of these interests during its deliberations on the merits of the merger and considered them in deciding to recommend that IXYS stockholders vote in favor of the merger proposal and the merger-related compensation proposal. These interests include, among others, the rights to accelerated vesting of stock options and certain payments and benefits in connection with the merger and/or a qualifying termination of employment following the merger, as described in more detail in the section titled "The Merger—Interests of IXYS' Directors and Executive Officers in the Merger" beginning on page 75.

Material U.S. Federal Income Tax Consequences

        (see page 80)

        The initial merger and the follow-on merger, taken together, are intended to qualify as a "reorganization" within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended (referred to in this proxy statement/prospectus as the Code). The completion of the initial merger and the follow-on merger is conditioned upon the delivery by each of Wachtell, Lipton, Rosen & Katz (or other nationally recognized outside counsel), counsel to Littelfuse, and Latham & Watkins LLP (or other nationally recognized outside counsel), counsel to IXYS, of its opinion to the effect that the initial merger and the follow-on merger, taken together, will qualify as a "reorganization" within the meaning of Section 368(a) of the Code. If the initial merger and the follow-on merger, taken together, qualify as a "reorganization" within the meaning of Section 368(a) of the Code, the U.S. federal income tax consequences to IXYS stockholders who are U.S. holders (as defined in the section titled "Material U.S. Federal Income Tax Consequences") and receive stock consideration and/or cash consideration in exchange for their shares of IXYS common stock pursuant to the merger agreement generally will be as follows:


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        Each IXYS stockholder should read the discussion under the section titled "Material U.S. Federal Income Tax Consequences" and should consult his, her or its own tax advisor for a full understanding of the tax consequences of the merger to such stockholder.

Accounting Treatment of the Merger

        (see page 80)

        Littelfuse prepares its financial statements in accordance with accounting principles generally accepted in the United States of America (referred to in this proxy statement/prospectus as GAAP). The merger will be accounted for using the acquisition method of accounting. Littelfuse will be treated as the acquiror for accounting purposes.

Regulatory Approvals Required to Complete the Merger

        (see pages 84 and 109)

        Littelfuse, IXYS and Merger Sub have each agreed to use their respective reasonable best efforts to take, or cause to be taken, all reasonable actions, and to do, or cause to be done, all reasonable things necessary, proper or advisable under any applicable laws to consummate the merger and obtain (and to cooperate with each other in obtaining) the required regulatory approvals, as described in the section titled "The Merger—Regulatory Approvals" beginning on page 84.

        The obligations of Littelfuse and IXYS to consummate the merger were subject to, among other matters, the termination or expiration of the waiting period (and any extension thereof) applicable to the merger under the HSR Act and the receipt of the clearances and approvals applicable to the merger under the antitrust/merger control laws of Germany. On October 2, 2017, Littelfuse and IXYS received early termination of the applicable waiting period under the HSR Act in the United States, and on October 6, 2017, Littelfuse and IXYS received the required German clearance. There are no other known regulatory approvals required before the closing of the merger.

Expected Timing of Merger

        Littelfuse and IXYS currently expect the merger to be completed during the first quarter of calendar year 2018, subject to the affirmative vote of the holders of a majority of the outstanding shares of IXYS common stock in favor of adoption of the merger agreement and the satisfaction or waiver of the other conditions to closing contained in the merger agreement. However, Littelfuse and IXYS cannot predict the actual date on which the merger will be completed because completion is subject to conditions beyond their control and it is possible that such conditions could result in the merger being completed earlier or later or not being completed at all. See the sections titled "The


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Merger—Regulatory Approvals" beginning on page 84 and "The Merger Agreement—Conditions to Completion of the Merger" beginning on page 108.


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Treatment of IXYS Stock Options

        (see pages 75 and 95)

        At the effective time, each outstanding and unexercised IXYS stock option will be assumed by Littelfuse and converted into a Littelfuse stock option to acquire (i) that number of whole shares of Littelfuse common stock (rounded down to the nearest whole share) equal to the product of (x) the number of shares of IXYS common stock subject to such IXYS stock option immediately prior to the effective time multiplied by (y) 0.1265, (ii) at an exercise price per share of Littelfuse common stock (rounded up to the nearest whole cent) equal to the quotient of (x) the exercise price per share of IXYS common stock of such IXYS stock option divided by (y) 0.1265. Each IXYS stock option assumed and converted into a Littelfuse stock option will continue to have, and will be subject to, the same vesting schedule (including any accelerated vesting terms) and all other terms and conditions as applied to such IXYS stock option immediately prior to the effective time.

Listing of Littelfuse Common Stock; Delisting of IXYS Common Stock

        (see page 87)

        It is a condition to the consummation of the merger that the shares of Littelfuse common stock to be issued to IXYS stockholders in the merger be approved for listing on The NASDAQ Global Select Market, subject to official notice of issuance. As a result of the merger, shares of IXYS common stock will cease to be listed on The NASDAQ Global Select Market.

Appraisal Rights

        (see page 143)

        IXYS stockholders who do not vote in favor of approval of the merger proposal, who continuously hold their shares of IXYS common stock through the effective time and who otherwise comply precisely with the applicable provisions of Section 262 of the DGCL will be entitled to seek appraisal of the fair value of their shares of IXYS common stock, as determined by the Delaware Court of Chancery, if the merger is completed. The "fair value" of your shares of IXYS common stock as determined by the Delaware Court of Chancery could be greater than, the same as, or less than the value of the merger consideration that you would otherwise be entitled to receive under the terms of the merger agreement. IXYS stockholders who wish to exercise the right to seek an appraisal of their shares must so advise IXYS by submitting a written demand for appraisal in the form described in this proxy statement/prospectus prior to the vote to approve the merger proposal, and must otherwise follow the procedures prescribed by Section 262 of the DGCL. A person having a beneficial interest in shares of IXYS common stock held of record in the name of another person, such as a nominee or intermediary, must act promptly to cause the record holder to follow the steps summarized in this proxy statement/prospectus and in a timely manner to perfect appraisal rights.

        The text of Section 262 of the DGCL is attached asAnnex D to this proxy statement/prospectus. You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising appraisal rights, IXYS stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel and their financial advisors. Failure to strictly comply with these provisions may result in the loss of appraisal rights.

No Solicitation of Company Takeover Proposals

        (see page 101)


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        As more fully described in this proxy statement/prospectus and in the merger agreement, and subject to the exceptions summarized below, IXYS has agreed that it will not (1) solicit, initiate,


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knowingly encourage or knowingly facilitate any inquiry, proposal or offer that constitutes, or would reasonably be expected to lead to, a company takeover proposal (as defined on page 102), (2) engage in, continue or otherwise participate in any discussions or negotiations regarding any company takeover proposal, or (3) approve, recommend, or enter into, or propose to approve, recommend, or enter into, any agreement with respect to a company takeover proposal.

        Notwithstanding these restrictions, if at any time prior to obtaining the approval by IXYS stockholders of the merger proposal, IXYS receives a written, bona fide, unsolicited company takeover proposal that did not result from a breach of the merger agreement and that the IXYS board of directors determines in good faith (after consultation with its advisors) constitutes or would reasonably be expected to lead to a company superior proposal (as defined on page 102), IXYS may (1) furnish information with respect to IXYS to the party making the company takeover proposal (subject to certain conditions and obligations in the merger agreement) and (2) engage in discussions or negotiations with the party making the company takeover proposal.

        IXYS has agreed to notify Littelfuse within one business day of the receipt of any company takeover proposal or any request for information that is reasonably likely to lead to a company takeover proposal, or of any determination by the IXYS board of directors that a company takeover proposal constitutes or would be reasonably expected to lead to a company superior proposal. IXYS has also agreed to keep Littelfuse reasonably informed, on a reasonably current basis, as to the status of any company takeover proposal, and to promptly provide Littelfuse with any draft agreements relating to a company takeover proposal.

Changes in Board Recommendation

        (see page 103)

        The merger agreement provides that, subject to certain exceptions, the IXYS board of directors will not (i) fail to include its recommendation in favor of the merger proposal in this proxy statement/prospectus, (ii) change, qualify, withhold, withdraw or modify, or publicly propose to change, qualify, withhold, withdraw or modify (in each case in a manner adverse to Littelfuse) its recommendation in favor of the merger proposal, or (iii) adopt, approve or recommend to IXYS stockholders, or publicly propose or announce its intention to adopt, approve or recommend to IXYS stockholders, any company takeover proposal or agreement relating to a company takeover proposal (any of the foregoing, an adverse recommendation change). Notwithstanding these restrictions, at any time prior to obtaining the approval by IXYS stockholders of the merger proposal, the IXYS board of directors may, if it determines in good faith (after consultation with its advisors) that a company takeover proposal is a company superior proposal (and subject to compliance with certain obligations set forth in the merger agreement, including providing Littelfuse with prior notice and the right under certain circumstances to negotiate to match the terms of any company superior proposal), make an adverse recommendation change or terminate the merger agreement in order to enter into a binding agreement with respect to the company superior proposal.

        In addition, the IXYS board of directors is permitted under certain circumstances, prior to obtaining the approval by IXYS stockholders of the merger proposal and subject to compliance with certain obligations set forth in the merger agreement (including providing Littelfuse with prior notice and the right under certain circumstances to negotiate to amend the terms of the merger agreement) to make an adverse recommendation change in response to an intervening event (as defined on page 104) if the IXYS board of directors determines in good faith (after consultation with its advisors) that the failure to do so would be inconsistent with its fiduciary duties.


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Conditions to Completion of the Merger

        (see page 108)

        The obligations of each of IXYS and Littelfuse to effect the merger are subject to the satisfaction or waiver of the following conditions:

        In addition, Littelfuse's obligations to effect the merger are subject to IXYS' repayment of all of its outstanding debt obligations and delivery to Littelfuse of evidence of such repayment.

        Neither Littelfuse nor IXYS can be certain when, or if, the conditions to the merger will be satisfied or waived, or that the merger will be completed.

Termination of the Merger Agreement

        (see page 109)

        Littelfuse and IXYS may mutually agree to terminate the merger agreement before completing the merger, whether before or after the receipt of IXYS stockholder approval of the merger proposal.

        Either Littelfuse or IXYS may terminate the merger agreement, whether before or after the receipt of IXYS stockholder approval of the merger proposal:


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        IXYS may also terminate the merger agreement, prior to the receipt of IXYS stockholder approval of the merger proposal, in order to enter into an agreement for a company superior proposal, provided that IXYS has complied with its non-solicitation obligations under the merger agreement and pays a termination fee of $28.5 million to Littelfuse prior to or concurrently with such termination.

        Littelfuse may also terminate the merger agreement, prior to the receipt of IXYS stockholder approval of the merger proposal, if IXYS has made an adverse recommendation change or if IXYS is in willful breach of its non-solicitation obligations. Following such termination, IXYS must pay Littelfuse a termination fee of $28.5 million.

Expenses and Termination Fees Relating to the Merger

        (see page 110)

        IXYS must pay Littelfuse a termination fee of $28.5 million if the merger agreement is terminated in certain circumstances involving a company takeover proposal, an adverse recommendation change or a willful breach of IXYS' non-solicitation obligations under the merger agreement.

        All other expenses relating to the merger will generally be paid by the party incurring the expense.

Comparison of Rights of Common Stockholders of Littelfuse and IXYS

        (see page 128)

        IXYS stockholders receiving shares of Littelfuse common stock in the initial merger will have different rights once they become stockholders of Littelfuse due to differences between the governing corporate documents applicable to IXYS and Littelfuse.

Risk Factors

        (see page 32)

        You should consider all the information contained in or incorporated by reference into this proxy statement/prospectus in deciding how to vote for the proposals presented in this proxy statement/prospectus.


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SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA

Selected Historical Consolidated Financial Data of Littelfuse

        The following selected historical consolidated financial data of Littelfuse for each of the fiscal years during the three-year period ended December 31, 2016 and the selected historical consolidated balance sheet data as of December 31, 2016 and January 2, 2016 have been derived from Littelfuse's audited consolidated financial statements as of and for the fiscal year ended December 31, 2016 contained in Littelfuse's Annual Report on Form 10-K for the fiscal year ended December 31, 2016, which is incorporated by reference into this proxy statement/prospectus. The selected historical consolidated financial data for each of the fiscal years ended December 28, 2013 and December 29, 2012 and the selected balance sheet data as of December 27, 2014, December 28, 2013 and December 29, 2012 have been derived from Littelfuse's audited consolidated financial statements as of and for such years contained in Littelfuse's other reports filed with the SEC, which are not incorporated by reference into this proxy statement/prospectus.

        The unaudited selected financial data for Littelfuse as of September 30, 2017, and for the nine months ended September 30, 2017 and October 1, 2016, are derived from Littelfuse's unaudited condensed consolidated financial statements and accompanying notes, which are contained in Littelfuse's Quarterly Report on Form 10-Q for the quarter ended September 30, 2017, which is incorporated by reference into this proxy statement/prospectus. The selected financial data as of October 1, 2016 is derived from Littelfuse's unaudited condensed consolidated financial statements for the quarter ended October 1, 2016, which have previously been filed with the SEC but which are not incorporated by reference into this proxy statement/prospectus. The unaudited financial data presented have been prepared on a basis consistent with Littelfuse's audited consolidated financial statements. In the opinion of Littelfuse's management, such unaudited financial data reflect all adjustments, consisting only of normal and recurring adjustments, necessary for a fair presentation of the results for those periods. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the full year or any future period.

        The information set forth below is only a summary and is not necessarily indicative of the results of future operations of Littelfuse, including following completion of the merger, and you should read the following information together with Littelfuse's consolidated financial statements, the related notes and the sections titled "Management's Discussion and Analysis of Financial Condition and Results of Operations" contained in Littelfuse's Annual Report on Form 10-K for the fiscal year ended December 31, 2016 and in its Quarterly Report on Form 10-Q for the quarter ended September 30, 2017, which are incorporated by reference into this proxy statement/prospectus, and in Littelfuse's other reports filed with the SEC. For more information, see the section titled "Where You Can Find More Information" beginning on page 151.


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LITTELFUSE, INC.
SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA
(Dollar Amounts in Thousands, Except Per Share Data)

 
 Nine Months Ended or As of  
  
  
  
  
 
 
 Fiscal Years Ended 
 
 September 30,
2017
 October 1,
2016
 
 
 2016 2015 2014 2013 2012 
 
 (Unaudited)
 (Unaudited)
  
  
  
  
  
 

Net sales

 $916,685 $771,641 $1,056,159 $867,864 $851,995 $757,853 $667,913 

Gross profit

  379,909  298,780  413,117  330,499  324,428  296,232  258,467 

Operating income

  167,731  89,656  130,644  104,157  133,830  129,881  106,870 

Net income

  130,338  77,243  104,488  80,866  98,100  87,814  74,370 

Per share of common stock:

  
 
  
 
  
 
  
 
  
 
  
 
  
 
 

Income from continuing operations

                      

Basic

  5.75  3.43  4.63  3.58  4.35  3.94  3.41 

Diluted

  5.69  3.41  4.60  3.56  4.32  3.90  3.37 

Cash dividends paid

  0.99  0.91  1.24  1.08  0.94  0.84  0.76 

Cash and cash equivalents

  
372,828
  
194,494
  
275,124
  
328,786
  
297,571
  
305,192
  
235,404
 

Total assets

  1,702,192  1,458,103  1,491,194  1,065,475  1,069,859  1,024,373  777,728 

Short-term debt

  9,375  6,250  6,250  87,000  88,500  126,000  84,000 

Long-term debt, less current portion

  492,272  434,206  447,892  83,753  105,691  93,750   

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Selected Historical Consolidated Financial Data of IXYS

        The following selected historical consolidated financial data of IXYS for the fiscal years ended March 31, 2017, March 31, 2016 and March 31, 2015 and the selected historical consolidated balance sheet data as of March 31, 2017 and March 31, 2016 have been derived from IXYS' audited consolidated financial statements contained in IXYS' Annual Report on Form 10-K for the fiscal year ended March 31, 2017, which is incorporated by reference into this proxy statement/prospectus. The selected historical consolidated financial data for the fiscal years ended March 31, 2014 and March 31, 2013 and the selected balance sheet data as of March 31, 2015, March 31, 2014 and March 31, 2013 have been derived from IXYS' audited consolidated financial statements as of and for such years, which statements are not incorporated by reference into this proxy statement/prospectus.

        The unaudited selected financial data for IXYS as of September 30, 2017, and for the six months ended September 30, 2017 and September 30, 2016, are derived from IXYS' unaudited condensed consolidated financial statements and accompanying notes, which are contained in IXYS' Quarterly Report on Form 10-Q for the quarter ended September 30, 2017, which is incorporated by reference into this proxy statement/prospectus. The selected financial data as of September 30, 2016 is derived from IXYS' unaudited condensed consolidated financial statements for the quarter ended September 30, 2016, which have previously been filed with the SEC but which are not incorporated by reference into this proxy statement/prospectus. The unaudited financial data presented have been prepared on a basis consistent with IXYS' audited consolidated financial statements. In the opinion of IXYS' management, such unaudited financial data reflect all adjustments, consisting only of normal and recurring adjustments, necessary for a fair presentation of the results for those periods. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the full year or any future period.

        The information set forth below is only a summary and is not necessarily indicative of the results of future operations of IXYS, and you should read the following information together with IXYS' consolidated financial statements, the related notes and the sections titled "Management's Discussion and Analysis of Financial Condition and Results of Operations" contained in IXYS' Annual Report on Form 10-K for the fiscal year ended March 31, 2017, which is incorporated by reference into this proxy statement/prospectus, and in IXYS' other reports filed with the SEC. For more information, see the section titled "Where You Can Find More Information" beginning on page 151.


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IXYS CORPORATION
SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA
(Dollar Amounts in Thousands, Except Per Share Data)

 
 Six Months
Ended September 30
 Years Ended March 31, 
 
 2017 2016 2017 2016 2015 2014(1) 2013 
 
 (Unaudited)
  
  
  
  
  
 

Statement of operations data:

                      

Net revenues

 $171,226 $159,267 $322,123 $317,209 $338,767 $336,330 $280,014 

Cost of goods sold

  117,893  109,818  216,541  217,451  236,802  236,120  195,134 

Gross profit

  53,333  49,449  105,582  99,758  101,965  100,210  84,880 

Operating expenses

                      

Research, development and engineering

  15,804  15,758  30,538  29,986  26,667  30,884  28,022 

Selling, general and administrative

  22,897  20,178  41,733  38,384  41,810  41,983  39,287 

Amortization of acquisition-related intangible assets

  1,193  1,713  3,068  5,555  5,978  10,521  2,244 

Impairment of acquisition-related intangible assets

      1,391         

Total operating expenses

  39,894  37,649  76,730  73,925  74,455  83,388  69,553 

Operating income

  13,439  11,800  28,852  25,833  27,510  16,822  15,327 

Other income (expense):

                      

Interest income

  168  115  265  212  240  157  334 

Interest expense

  (1,128) (1,250) (2,545) (1,641) (1,397) (1,579) (938)

Other income (expense), net

  (705) 1,401  2,328  (915) 4,077  (1,941) (41)

Income before income tax provision

  11,774  12,066  28,900  23,489  30,430  13,459  14,682 

Provision for income tax

  (2,817) (5,112) (7,552) (8,748) (6,690) (7,413) (7,034)

Net income

  8,957  6,954  21,348  14,741  23,740  6,046  7,648 

Net income per share:

                      

Basic

  0.28  0.22  0.68  0.47  0.75  0.19  0.25 

Diluted

  0.27  0.22  0.66  0.46  0.74  0.19  0.24 

Cash dividends per common share

    0.040  0.040  0.155  0.135  0.120  0.060 

Weighted average shares used in per share calculation:

                      

Basic

  32,364  31,447  31,544  31,579  31,531  31,146  31,025 

Diluted

  33,572  32,074  32,248  32,381  32,239  31,916  31,695 

(1)
During fiscal 2014, IXYS acquired a microcontroller product line from Samsung Electronics Co., Ltd.

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 Six Months Ended
September 30
 Years Ended March 31, 
 
 2017 2016 2017 2016 2015 2014(1) 2013 
 
 (Unaudited)
  
  
  
  
  
 

Balance sheet data:

                      

Cash and cash equivalents

 $168,771 $153,804 $167,904 $155,806 $121,164 $98,438 $107,116 

Working capital

  275,601  250,418  266,000  253,820  169,096  177,684  188,111 

Total assets

  462,978  422,700  433,979  422,701  373,855  383,182  333,476 

Total long-term obligations

  99,179  100,369  98,310  108,896  27,760  43,204  31,640 

Total stockholders' equity

  324,332  285,789  297,855  279,295  267,301  270,632  253,608 

 

 
 Six Months Ended
September 30
 Years Ended March 31, 
 
 2017 2016 2017 2016 2015 2014(1) 2013 
 
 (Unaudited)
  
  
  
  
  
 

Cash flow data:

                      

Cash provided by (used in) operating activities

 $6,389 $13,398 $34,537 $29,593 $48,194 $19,329 $31,637 

Cash used in investing activities(2)

  (15,076) (6,351) (11,193) (22,185) (15,148) (27,111) (11,277)

Cash provided by (used in) financing activities

  5,088  (8,132) (6,998) 25,977  (5,129) (3,344) (10,856)

(1)
During fiscal 2014, IXYS acquired a microcontroller product line from Samsung Electronics Co., Ltd.

(2)
Cash used in investing activities has been restated in accordance with the amended guidance we adopted in fiscal 2017 which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and restricted cash. See Note 2, "Summary of Significant Accounting Policies" in the Notes to Consolidated Financial Statements in Item 8 of the IXYS Annual Report on Form 10-K for further information regarding the amended guidance.

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UNAUDITED COMPARATIVE PER SHARE INFORMATION

        The following tables summarize unaudited per share data for (i) Littelfuse on a historical basis for the fiscal year ended December 31, 2016 and the nine months ended September 30, 2017; (ii) Littelfuse on a pro forma condensed combined basis, assuming that the merger occurred on the dates indicated; (iii) IXYS on a historical basis for the fiscal year ended March 31, 2017 and the six months ended September 30, 2017; and (iv) IXYS on a pro forma equivalent basis, which was calculated by multiplying the corresponding pro forma condensed combined data by the exchange ratio of 0.1265 of a share of Littelfuse common stock to 1.0 share of IXYS common stock. It has been assumed for purposes of the pro forma condensed combined financial information provided below that the pro forma events occurred on January 3, 2016 for earnings per share purposes and on September 30, 2017 for book value per share purposes.

        The historical earnings per share information should be read in conjunction with the historical consolidated financial statements and notes thereto of Littelfuse and IXYS incorporated by reference into this proxy statement/prospectus. See the section titled "Where You Can Find More Information" on page 151. The unaudited pro forma condensed combined earnings per share information is derived from, and should be read in conjunction with, the section titled "Unaudited Pro Forma Condensed Combined Financial Information" and related notes included in this proxy statement/prospectus beginning on page 115. The pro forma information is presented for illustrative purposes only and is not necessarily indicative of the operating results or financial position of Littelfuse following the merger.

 
 Littelfuse Twelve
Months Ended
December 31, 2016
 IXYS Twelve Months
Ended March 31, 2017
 
 
 Historical Pro Forma
Condensed
Combined
 Historical Pro Forma
Equivalent(1)
 

Basic earnings per share

 $4.63 $4.43 $0.68 $0.09 

Diluted earnings per share

  4.60  4.38  0.66  0.08 

Cash dividends per share(2)

  1.24  1.24  0.04  0.01 

Book value per share(3)

  36.02  N/A  9.33  N/A 

 

 
 Littelfuse Nine
Months Ended
September 30, 2017
 IXYS Six
Months Ended
September 30, 2017
 
 
 Historical Pro Forma
Condensed
Combined
 Historical Pro Forma
Equivalent(1)
 

Basic earnings per share

 $5.75 $5.73 $0.28 $0.04 

Diluted earnings per share

  5.69  5.63  0.27  0.03 

Cash dividends per share(2)

  0.99  0.99     

Book value per share(3)

  41.09  60.80  9.90  1.25 

(1)
The pro forma equivalent share amounts were calculated by multiplying the pro forma condensed combined per share amounts by the exchange ratio of 0.1265 of a share of Littelfuse common stock per share of IXYS common stock. This information shows how each share of IXYS common stock would have participated in the combined company's net income and book value if the pro forma events had occurred on the relevant dates.

(2)
For the twelve months ended December 31, 2016 and the nine months ended September 30, 2017, Littelfuse paid a cash dividend of $1.24 and $0.99 per share, respectively, to its stockholders. The pro forma dividends per share are based solely on Littelfuse's historical dividends.

(3)
Amount is calculated by dividing stockholders' equity by common shares outstanding at the end of the period.

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COMPARATIVE STOCK PRICE DATA AND DIVIDENDS

Stock Prices

        Littelfuse common stock trades on The NASDAQ Global Select Market under the symbol "LFUS." IXYS common stock trades on The NASDAQ Global Select Market under the symbol "IXYS."

        The following table sets forth the closing sales prices per share of Littelfuse common stock and IXYS common stock on The NASDAQ Global Select Market, and the implied value per share of one share of IXYS common stock, on the following dates:

 
 Littelfuse
Common
Stock
 IXYS
Common
Stock
 Implied Value
Per Share of
Stock
Consideration(1)
 

August 25, 2017

 $178.26 $15.95 $22.55 

[·], 2017

  [·]  [·]  [·] 

(1)
The implied value per share of the stock consideration, as of each date, is equal to 0.1265, the exchange ratio for the stock consideration, multiplied by the closing market price of one share of Littelfuse common stock on such date.

        The following table sets forth, for the periods indicated, the high and low sales prices per share of Littelfuse common stock and of IXYS common stock as reported on The NASDAQ Global Select Market.

Littelfuse Common Stock


 Price Range  
  Price Range  
 

 Cash
Dividends
  Cash
Dividends
 

 High Low  High Low 

Fiscal Year ending December 30, 2017

              

Fourth Quarter (through December 1, 2017)

 $215.00 $182.03 $0.37 

Fourth Quarter (through December 6, 2017)

 $215.00 $182.03 $0.37 

Third Quarter

 $199.26 $161.65 $0.37  $199.26 $161.65 $0.37 

Second Quarter

 $173.14 $149.81 $0.33  $173.14 $149.81 $0.33 

First Quarter

 $167.21 $146.94 $0.33  $167.21 $146.94 $0.33 

Fiscal Year ended December 31, 2016

              

Fourth Quarter

 $156.54 $124.32 $0.33  $156.54 $124.32 $0.33 

Third Quarter

 $130.79 $113.42 $0.33  $130.79 $113.42 $0.33 

Second Quarter

 $123.15 $106.26 $0.29  $123.15 $106.26 $0.29 

First Quarter

 $124.59 $90.61 $0.29  $124.59 $90.61 $0.29 

Fiscal Year ended January 2, 2016

              

Fourth Quarter

 $114.90 $87.32 $0.29  $114.90 $87.32 $0.29 

Third Quarter

 $97.96 $82.53 $0.29  $97.96 $82.53 $0.29 

Second Quarter

 $102.78 $93.31 $0.25  $102.78 $93.31 $0.25 

First Quarter

 $103.08 $89.11 $0.25  $103.08 $89.11 $0.25 

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IXYS Common Stock


 Price Range  
  Price Range  
 

 Cash
Dividends
  Cash
Dividends
 

 High Low  High Low 

Fiscal Year ending March 31, 2018

              

Third Quarter (through December 1, 2017)

 $24.96 $22.90  

Third Quarter (through December 6, 2017)

 $24.96 $22.90  

Second Quarter

 $23.95 $14.90   $23.95 $14.90  

First Quarter

 $16.95 $13.50   $16.95 $13.50  

Fiscal Year ended March 31, 2017

              

Fourth Quarter

 $14.60 $11.10   $14.60 $11.10  

Third Quarter

 $12.25 $10.06   $12.25 $10.06  

Second Quarter

 $12.24 $10.08   $12.24 $10.08  

First Quarter

 $12.02 $9.59 $0.04  $12.02 $9.59 $0.04 

Fiscal Year ended March 31, 2016

              

Fourth Quarter

 $12.60 $10.03 $0.04  $12.60 $10.03 $0.04 

Third Quarter

 $14.00 $10.84 $0.04  $14.00 $10.84 $0.04 

Second Quarter

 $15.62 $10.00 $0.04  $15.62 $10.00 $0.04 

First Quarter

 $16.76 $11.05 $0.035  $16.76 $11.05 $0.035 

        As of [    ·    ],December 6, 2017, the lastrecord date beforefor the date of this proxy statement/prospectus for which it was practicable to obtain this information,special meeting, there were [    ·    ]22,713,798 shares of Littelfuse common stock outstanding and approximately [    ·    ]70 holders of record of Littelfuse common stock, and [    ·    ]32,935,335 shares of IXYS common stock outstanding and approximately [    ·    ]216 holders of record of IXYS common stock.

        Because the number of shares of Littelfuse common stock issuable for each share of IXYS Common Stock in the merger will not be adjusted for changes in the market price of either Littelfuse common stock or IXYS common stock, the market value of the shares of Littelfuse common stock that holders of IXYS common stock will have the right to receive on the date the merger is completed may vary significantly from the market value of the shares of Littelfuse common stock that holders of IXYS common stock would receive if the merger were completed on the date of this proxy statement/prospectus.

        As a result, you should obtain recent market prices of Littelfuse common stock and IXYS common stock prior to voting your shares. See the section titled "Risk Factors—Risks Relating to the Merger" beginning on page 32.

Dividends

        Littelfuse currently pays regular quarterly cash dividends on its common stock. Littelfuse most recently paid a cash dividend on September 7, 2017, of $0.37 per share. Littelfuse currently expects to continue to pay quarterly cash dividends, although they remain subject to determination and declaration by Littelfuse's board of directors. The payment of future dividends, if any, will be based on several factors, including Littelfuse's financial performance, outlook and liquidity.

        IXYS pays quarterly cash dividends on its common stock at the discretion of its board of directors. IXYS most recently paid a cash dividend on July 5, 2016 of $0.04 per share. The payment of future dividends, if any, will be based on IXYS' financial performance.

        Under the terms of the merger agreement, during the period before the closing of the merger, Littelfuse is not permitted to pay any dividends or make any distributions on its capital stock other than quarterly cash dividends not exceeding $0.37 per share, and IXYS is not permitted to pay any dividends or make any distributions on its capital stock, in each case without the consent of the other party.


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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

        This proxy statement/prospectus and the documents incorporated by reference into this proxy statement/prospectus contain forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 that are not limited to historical facts but reflect Littelfuse's and IXYS' current beliefs, expectations or intentions regarding future events. Words such as "anticipate," "believe," "continue," "could," "estimate," "expect," "forecast," "guidance," "intend," "may," "plan," "possible," "potential," "predict," "project," "pursue," "will," "should," "target," and other similar words, phrases or expressions are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, Littelfuse's and IXYS' expectations with respect to the synergies, costs and other anticipated financial impacts of the merger; future financial and operating results of the combined company; the combined company's plans, objectives, expectations and intentions with respect to future operations and services; required adoption of the merger agreement by IXYS stockholders; required approvals of the merger by governmental regulatory authorities; the satisfaction of the closing conditions to the merger; and the timing of the completion of the merger.

        All forward-looking statements involve significant risks and uncertainties that could cause actual results to differ materially from those expressed or implied in the forward-looking statements, many of which are generally outside the control of Littelfuse and IXYS and difficult to predict. These risks and uncertainties include, among others, those set forth under "Risk Factors" beginning on page 32, as well as risks and uncertainties relating to:


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        Littelfuse and IXYS caution that the foregoing list of factors is not exhaustive. Additional information concerning these and other risk factors is contained in Littelfuse's and IXYS' most recently filed Annual Reports on Form 10-K and subsequently filed Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other SEC filings, as such filings may be amended from time to time. All of the forward-looking statements made by Littelfuse or IXYS contained or incorporated by reference in this proxy statement/prospectus and all subsequent written and oral forward-looking statements concerning Littelfuse, IXYS, the merger or other matters attributable to Littelfuse or IXYS or any person acting on either of their behalf are expressly qualified in their entirety by the cautionary statement above.

        Readers are cautioned not to place undue reliance on forward-looking statements contained in this proxy statement/prospectus, which speak only as of the date such statements were made. Neither Littelfuse nor IXYS undertakes any obligation to update or revise any of these forward-looking statements to reflect events or circumstances that may arise after the date hereof, even if experience or future changes make it clear that projected results expressed or implied in such statements will not be realized, except as may be required by applicable law. Neither Littelfuse nor IXYS intends to make any update or other revision to forward-looking statements, except as may be required by applicable law.


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RISK FACTORS

        In addition to the other information included in and incorporated by reference into this proxy statement/prospectus, including the matters addressed in the section titled "Cautionary Statement Regarding Forward-Looking Statements" beginning on page 30, you should carefully consider the following risk factors before deciding whether to vote for the merger proposal and the other proposals described in this proxy statement/prospectus. In addition, you should read and consider the risk factors associated with each of the businesses of Littelfuse and IXYS because these risk factors will relate to the combined company following the completion of the merger. These risk factors may be found in Littelfuse's Annual Report on Form 10-K for the fiscal year ended December 31, 2016 and IXYS' Annual Report on Form 10-K for the fiscal year ended March 31, 2017 and, in each case, any amendments thereto, as such risk factors may be updated or supplemented in each company's subsequently filed Quarterly Reports on Form 10-Q or Current Reports on Form 8-K, which are incorporated by reference into this proxy statement/prospectus. You should also consider the other information in this proxy statement/prospectus and the other documents incorporated by reference into this proxy statement/prospectus. See the section titled "Where You Can Find More Information" beginning on page 151.

Risks Relating to the Merger

Because the share-election exchange ratio is fixed and will not be adjusted for stock price changes and the market price of Littelfuse common stock has fluctuated and will continue to fluctuate, IXYS stockholders cannot be sure of the value of the consideration they will receive.

        Upon completion of the initial merger, each issued and outstanding share of IXYS common stock (other than (i) cancelled shares or (ii) dissenting shares) will be converted into the right to receive, at the election of the stockholder and subject to proration, $23.00 in cash, without interest, less any applicable withholding taxes or 0.1265 of a share of Littelfuse common stock.

        The share-election ratio was derived using the volume weighted average price per share of Littelfuse common stock for a pre-determined trading period prior to the signing of the merger agreement and will not change to reflect changes in the market price of IXYS and Littelfuse common stock. The market price of Littelfuse common stock at the time of completion of the merger may vary significantly from the market price of Littelfuse common stock on the date the merger agreement was executed, the date of this proxy statement/prospectus and the date of the IXYS special meeting. In addition, as discussed below, the merger consideration will be subject to proration. Accordingly, IXYS stockholders will not know or be able to calculate at the time of the IXYS special meeting the market value of the stock consideration they will receive upon completion of the merger.

        In addition, the merger might not be completed until a significant period of time has passed after the IXYS special meeting. Because the share-election exchange ratio will not be adjusted to reflect any changes in the market values of Littelfuse common stock and IXYS common stock, the market value of the Littelfuse common stock issued in connection with the merger and the IXYS common stock surrendered in connection with the merger may be higher or lower than the value of those shares on earlier dates. Stock price changes may result from a variety of factors, including, among others, general market and economic conditions, changes in Littelfuse's and IXYS' respective businesses, operations and prospects, market assessments of the likelihood that the merger will be completed, the timing of the merger, regulatory considerations and other risk factors set forth or incorporated by reference in this proxy statement/prospectus. Many of these factors are beyond Littelfuse's and IXYS' control.

IXYS common stockholders may not receive all consideration in the form elected.

        IXYS common stockholders electing to receive either the all-cash consideration or the all-stock consideration in the merger will be subject to proration so that 50% of IXYS common stock issued and outstanding immediately prior to the effective time will be converted into cash consideration and the


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remaining IXYS common stock will be converted into stock consideration. Accordingly, some of the merger consideration an IXYS common stockholder receives may differ from the type of consideration


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selected and such difference may be significant. This may result in, among other things, tax consequences that differ from those that would have resulted if the IXYS common stockholder had received solely the form of consideration elected. A discussion of the proration mechanism can be found under the section titled "The Merger—Merger Consideration" and a discussion of the material U.S. federal income tax consequences of the merger can be found under the section titled "Material U.S. Federal Income Tax Consequences."

The market price of Littelfuse common stock after the initial merger will continue to fluctuate and may be affected by factors different from those affecting shares of IXYS common stock currently.

        Upon completion of the initial merger, certain holders of IXYS common stock will become holders of Littelfuse common stock. The market price of Littelfuse common stock may fluctuate significantly following completion of the initial merger and holders of IXYS common stock could lose the value of their investment in Littelfuse common stock. In addition, any significant price and volume fluctuations of the stock markets could have a material adverse effect on the market for, or liquidity of, the Littelfuse common stock, regardless of Littelfuse's actual operating performance. In addition, Littelfuse's business differs in important respects from that of IXYS, and accordingly, the results of operations of the combined company and the market price of Littelfuse common stock after the completion of the merger may be affected by factors different from those currently affecting the independent results of operations of each of Littelfuse and IXYS. For a discussion of the businesses of Littelfuse and IXYS and of some important factors to consider in connection with those businesses, see the documents incorporated by reference into this proxy statement/prospectus and referred to under "Where You Can Find More Information" beginning on page 151.

Sales of shares of Littelfuse common stock after the completion of the merger may cause the market price of Littelfuse common stock to fall.

        Based on the number of outstanding shares of IXYS common stock as of November 29,December 6, 2017, Littelfuse would issue approximately 2.1 million shares of Littelfuse common stock in the initial merger. Many IXYS stockholders may decide not to hold the shares of Littelfuse common stock they will receive in the initial merger. Other IXYS stockholders, such as funds with limitations on their permitted holdings of stock in individual issuers, may be required to sell the shares of Littelfuse common stock that they receive in the initial merger. Such sales of Littelfuse common stock could have the effect of depressing the market price for Littelfuse common stock and may take place promptly following the initial merger.

Completion of the merger is subject to the conditions contained in the merger agreement and if these conditions are not satisfied or waived, the merger will not be completed.

        The obligations of Littelfuse and IXYS to complete the merger are subject to the satisfaction or waiver of a number of conditions, including the approval of the merger proposal by IXYS stockholders. For a more complete summary of the required regulatory approvals and the conditions to the closing of the merger, see the sections titled "The Merger—Regulatory Approvals" and "The Merger Agreement—Conditions to Completion of the Merger."

        Many of the conditions to the closing of the merger are not within Littelfuse's or IXYS' control, and neither company can predict when or if these conditions will be satisfied. If any of these conditions are not satisfied or waived prior to February 28, 2018, which deadline may be extended to May 28, 2018 under certain circumstances, it is possible that the merger agreement will be terminated. Although Littelfuse and IXYS have agreed in the merger agreement to use their reasonable best efforts to complete the merger as soon as practicable, these and other conditions to the completion of the merger


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may not be satisfied. The failure to satisfy all of the required conditions could delay the completion of the merger for a significant period of time or prevent it from occurring. Any delay in completing the


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merger could cause Littelfuse not to realize some or all of the benefits that Littelfuse expects to achieve if the merger is successfully completed within its expected timeframe. There can be no assurance that the conditions to the closing of the merger will be satisfied or waived or that the merger will be completed. See the risk factor titled "—Failure to complete the merger could negatively affect the stock price and the future business and financial results of IXYS," below.

The merger was subject to the expiration of applicable waiting periods and the receipt of approvals, consents or clearances from regulatory authorities in the United States and Germany. Those clearances have been received, but the merger may still be reviewed under antitrust statutes of other governmental authorities.

        Littelfuse and IXYS received early termination of the applicable waiting period under the HSR Act in the United States on October 2, 2017, and on October 6, 2017, they received the requisite clearance under the antitrust/merger control laws of Germany. The merger may still be reviewed under antitrust statutes of other governmental authorities, including U.S. state laws. In deciding whether to grant the required regulatory approval, consent or clearance, the relevant governmental entities will consider the effect of the merger on competition within their relevant jurisdiction. The terms and conditions of the approvals, consents and clearances that are granted may impose requirements, limitations or costs or place restrictions on the conduct of the combined company's business. Under the merger agreement, Littelfuse and IXYS have agreed to use their reasonable best efforts to obtain such approvals, consents and clearances and therefore may be required to comply with conditions or limitations imposed by governmental authorities. There can be no assurance that other regulators will not impose conditions, terms, obligations or restrictions and that such conditions, terms, obligations or restrictions will not have the effect of delaying completion of the merger or imposing additional material costs on or materially limiting the revenues of the combined company following the completion of the merger. In addition, neither Littelfuse nor IXYS can provide assurance that any such conditions, terms, obligations or restrictions will not result in the delay or abandonment of the merger. See the sections titled "The Merger—Regulatory Approvals" and "The Merger Agreement—Conditions to Completion of the Merger" beginning on pages 84 and 108, respectively, of this proxy statement/prospectus.

Combining the two companies may be more difficult, costly or time consuming than expected and the anticipated benefits and cost savings of the merger may not be realized.

        IXYS and Littelfuse have operated and, until the completion of the merger, will continue to operate, independently. The success of the merger, including anticipated benefits and cost savings, will depend, in part, on Littelfuse's ability to successfully combine and integrate the businesses of Littelfuse and IXYS. It is possible that the pendency of the merger and/or the integration process could result in the loss of key employees, higher than expected costs, diversion of management attention of both IXYS and Littelfuse, the disruption of either company's ongoing businesses or inconsistencies in standards, controls, procedures and policies that adversely affect the combined company's ability to maintain relationships with customers, vendors and employees or to achieve the anticipated benefits and cost savings of the merger. As part of the integration process, Littelfuse may also attempt to divest certain assets of the combined company, which may not be possible on favorable terms, or at all, or if successful, may change the profile of the combined company. If Littelfuse experiences difficulties with the integration process, the anticipated benefits of the merger may not be realized fully or at all, or may take longer to realize than expected. Littelfuse's management continues to refine its integration plan. These integration matters could have an adverse effect on (i) each of Littelfuse and IXYS during this transition period and (ii) the combined company for an undetermined period after completion of the merger. In addition, the actual cost savings of the merger could be less than anticipated.


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IXYS' directors and executive officers have interests in the merger that may be different from, or in addition to, your interests as a stockholder of IXYS more generally.

        When considering the recommendation of the IXYS board of directors that IXYS stockholders approve the merger proposal and the merger-related compensation proposal, IXYS stockholders should be aware that directors and executive officers of IXYS have certain interests in the merger that may be different from, or in addition to, the interests of IXYS stockholders more generally. These interests generally include, among others, rights to accelerated vesting of stock options and certain payments and benefits in connection with the merger and/or a qualifying termination of employment following the merger. See the section titled "The Merger—Interests of IXYS' Directors and Executive Officers in the Merger" beginning on page 75 for a more detailed description of these interests. The IXYS board of directors was aware of these interests during its deliberations on the merits of the merger and considered them in deciding to recommend that IXYS stockholders vote in favor of the merger proposal and the merger-related compensation proposal.

The merger agreement limits IXYS' ability to pursue alternatives to the merger and may discourage other companies from trying to acquire IXYS.

        The merger agreement contains provisions that make it more difficult for IXYS to sell its business to a party other than Littelfuse. These provisions include a general prohibition on IXYS soliciting any company takeover proposal or offer for a competing transaction. Further, there are only limited exceptions to (i) IXYS' agreement that the IXYS board of directors will not withdraw or modify in a manner adverse to Littelfuse the recommendation of the IXYS board of directors that IXYS stockholders vote in favor of the merger proposal and (ii) IXYS' agreement not to enter into an agreement with respect to a competing company takeover proposal. In addition, upon termination of the merger agreement, IXYS is required to pay Littelfuse a termination fee of $28.5 million if the merger agreement is terminated in certain circumstances involving a company takeover proposal, an adverse recommendation change or a willful breach of IXYS' non-solicitation obligations under the merger agreement.

        These provisions could discourage a third party that might have an interest in acquiring all or a significant part of IXYS from considering or proposing that acquisition, even if that party were prepared to pay consideration with a higher per share value than the value proposed to be received or realized in the merger. These provisions might also result in a potential competing acquirer proposing to pay a lower price than it might otherwise have proposed to pay because of the added expense of the termination fee that may become payable in certain circumstances.

The merger agreement subjects IXYS to restrictions on its business activities.

        The merger agreement subjects IXYS to restrictions on its business activities and obligates IXYS to generally operate its businesses in all material respects in the ordinary course. These restrictions could have an adverse effect on IXYS' results of operations, cash flows and financial position.

The business relationships of Littelfuse and IXYS and their respective subsidiaries may be subject to disruption due to uncertainty associated with the merger, which could have an adverse effect on the results of operations, cash flows and financial position of Littelfuse, IXYS and, following the completion of the merger, the combined company.

        Parties with which Littelfuse and IXYS, or their respective subsidiaries, do business may be uncertain as to the effects on them of the merger and related transactions, including with respect to current or future business relationships with Littelfuse, IXYS, their respective subsidiaries or the combined company. These relationships may be subject to disruption as customers, suppliers and other persons with whom Littelfuse and IXYS have a business relationship may delay or defer certain


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business decisions or might decide to terminate, change or renegotiate their relationships with Littelfuse or IXYS, as applicable, or consider entering into business relationships with parties other than Littelfuse, IXYS, their respective subsidiaries or the combined company. These disruptions could have an adverse effect on the results of operations, cash flows and financial position of IXYS, Littelfuse or the combined company following the completion of the merger, including an adverse effect on Littelfuse's ability to realize the expected synergies and other benefits of the merger. The risk, and adverse effect, of any disruption could be exacerbated by a delay in completion of the merger or termination of the merger agreement.

Failure to complete the merger could negatively affect the stock price and the future business and financial results of IXYS.

        If the merger is not completed for any reason, including as a result of IXYS stockholders failing to approve the merger proposal, the ongoing business of IXYS may be adversely affected and, without realizing any of the benefits of having completed the merger, IXYS could be subject to a number of negative consequences, including the following:

        In addition, upon termination of the merger agreement, IXYS is required to pay Littelfuse a termination fee of $28.5 million if the merger agreement is terminated in certain circumstances involving a company takeover proposal, an adverse recommendation change or a willful breach of IXYS' non-solicitation obligations under the merger agreement. Finally, IXYS could be subject to litigation related to any failure to complete the merger or related to any enforcement proceeding commenced against IXYS to perform its obligations under the merger agreement. If the merger is not completed, any of these risks may materialize and may adversely affect IXYS' businesses, financial condition, financial results and stock price.


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The shares of Littelfuse common stock to be received by IXYS stockholders as a result of the merger will have rights different from the shares of IXYS common stock.

        Upon completion of the initial merger, IXYS stockholders will no longer be stockholders of IXYS. Former IXYS stockholders who receive stock consideration in the initial merger will become Littelfuse stockholders, and their rights as stockholders will be governed by the terms of the Littelfuse certificate of incorporation and bylaws and by the DGCL. See the section titled "Comparison of Rights of Common Stockholders of Littelfuse and IXYS" beginning on page 128 for a discussion of the different rights associated with Littelfuse common stock.

After the initial merger, IXYS stockholders will have a significantly lower ownership and voting interest in Littelfuse than they currently have in IXYS and will exercise less influence over management.

        Based on the number of shares of IXYS common stock outstanding as of November 29,December 6, 2017, and the number of shares of Littelfuse common stock outstanding as of November 29,December 6, 2017, it is expected that, immediately after completion of the initial merger, former IXYS stockholders will own approximately 8% of the outstanding shares of Littelfuse common stock. Consequently, former IXYS stockholders will have less influence over the management and policies of Littelfuse than they currently have over the management and policies of IXYS.

In connection with the merger, Littelfuse will incur new indebtedness, which could adversely affect Littelfuse, including by decreasing Littelfuse's business flexibility, and will increase its interest expense.

        Littelfuse's consolidated indebtedness as of July 1, 2017 was approximately $482 million. Littelfuse's pro forma indebtedness as of July 1, 2017, after giving effect to the merger and the anticipated incurrence of indebtedness in connection therewith, will be as much as $630 million. Littelfuse will have substantially increased indebtedness following completion of the merger in comparison to Littelfuse's indebtedness on a recent historical basis. In particular, in order to consummate the merger, Littelfuse expects to incur up to $150 million of new debt.

        This indebtedness could have the effect, among other things, of reducing Littelfuse's flexibility to respond to changing business and economic conditions and increasing Littelfuse's interest expense. The amount of cash required to pay interest on Littelfuse's increased indebtedness levels following completion of the merger, and thus the demands on Littelfuse's cash resources, will be greater than the amount of cash flows required to service the indebtedness of Littelfuse prior to the transaction. The cash resources required to service the increased levels of indebtedness following completion of the merger could also reduce funds available for working capital, capital expenditures, acquisitions and other general corporate purposes and may create competitive disadvantages for Littelfuse relative to other companies with lower debt levels. If Littelfuse does not achieve the expected benefits and cost savings from the merger, or if the financial performance of the combined company does not meet current expectations, then Littelfuse's ability to service its indebtedness may be adversely impacted.

        Certain of the indebtedness to be incurred in connection with the merger may bear interest at variable interest rates. If interest rates increase, variable rate debt will create higher debt service requirements, which could adversely affect Littelfuse's cash flows.

        Moreover, Littelfuse may be required to raise substantial additional financing to fund working capital, capital expenditures, acquisitions or other general corporate requirements. Littelfuse's ability to arrange additional financing or refinancing will depend on, among other factors, Littelfuse's financial position and performance, as well as prevailing market conditions and other factors beyond Littelfuse's control. Littelfuse cannot assure you that it will be able to obtain additional financing or refinancing on terms acceptable to Littelfuse or at all.


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The unaudited pro forma condensed combined financial information included in this proxy statement/prospectus is preliminary and the actual financial condition and results of operations after the merger may differ materially from them.

        The unaudited pro forma condensed combined financial information included in this proxy statement/prospectus is presented for illustrative purposes only and is not necessarily indicative of what Littelfuse's actual financial condition or results of operations would have been had the merger been completed on the dates indicated. The unaudited pro forma condensed combined financial information reflects adjustments, which are based upon assumptions, preliminary estimates and accounting reclassifications, to record the IXYS identifiable assets acquired and liabilities assumed at fair value and the resulting goodwill recognized. The purchase price allocation reflected in this proxy statement/prospectus is preliminary, and final allocation of the purchase price will be based upon the actual purchase price and the fair value of the assets and liabilities of IXYS as of the date of the completion of the merger. Accordingly, the final acquisition accounting adjustments may differ materially from the pro forma adjustments reflected in this proxy statement/prospectus. For more information, see the section titled "Unaudited Pro Forma Condensed Combined Financial Information" beginning on page 115.

The merger will involve substantial costs.

        IXYS and Littelfuse have incurred, and expect to continue to incur, a number of non-recurring costs associated with the merger and combining the operations of the two companies. The substantial majority of non-recurring expenses will be comprised of transaction costs related to the merger.

        Littelfuse also will incur transaction fees and costs related to formulating and implementing integration plans, including facilities and systems consolidation costs and employment-related costs. Littelfuse continues to assess the magnitude of these costs, and additional unanticipated costs may be incurred in the merger and the integration of the two companies' businesses. Although Littelfuse expects that the elimination of duplicative costs, as well as the realization of other efficiencies related to the integration of the businesses, should allow Littelfuse to offset integration-related costs over time, this net benefit may not be achieved in the near term, or at all. See the risk factor titled "—Combining the two companies may be more difficult, costly or time consuming than expected and the anticipated benefits and cost savings of the merger may not be realized" above.

Lawsuits may in the future be filed against IXYS, its directors, Littelfuse and Merger Sub challenging the merger, and an adverse ruling in any such lawsuit may prevent the merger from becoming effective or from becoming effective within the expected timeframe.

        Transactions like the merger are frequently the subject to litigation or other legal proceedings, including actions alleging that the board of directors of either IXYS or Littelfuse breached their respective fiduciary duties to their stockholders by entering into the merger agreement, by failing to obtain a greater value in the transaction for their stockholders or otherwise. Both IXYS and Littelfuse believe that any such litigation or proceedings would be without merit, but there can be no assurance that they will not be brought. If litigation or other legal proceedings are in fact brought against either IXYS or Littelfuse or against the board of directors of either company, they will defend against it, but they might not be successful in doing so. An adverse outcome in such matters, as well as the costs and efforts of a defense even if successful, could have a material adverse effect on the business, results of operation or financial position of IXYS, Littelfuse or the combined company, including through the possible diversion of either company's resources or distraction of key personnel.

        Further, one of the conditions to the completion of the merger is that no injunction by any court or other tribunal of competent jurisdiction will be in effect that temporarily or permanently prohibits, enjoins or makes illegal the consummation of the merger. As such, if any of the plaintiffs are successful


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in obtaining an injunction prohibiting the consummation of the merger, that injunction may prevent the merger from becoming effective or from becoming effective within the expected timeframe.

Uncertainties associated with the merger may cause a loss of management personnel and other key employees of IXYS or Littelfuse, which could adversely affect the future business and operations of the combined company following the merger.

        IXYS and Littelfuse are dependent on the experience and industry knowledge of their officers and other key employees to execute their business plans. The combined company's success after the merger will depend in part upon its ability to retain key management personnel and other key employees of IXYS and Littelfuse. Current and prospective employees of IXYS and Littelfuse may experience uncertainty about their future roles with the combined company following the merger, which may materially adversely affect the ability of each of IXYS and Littelfuse to attract and retain key personnel during the pendency of the merger. Accordingly, no assurance can be given that the combined company will be able to retain key management personnel and other key employees of IXYS and Littelfuse.

Other Risk Factors of Littelfuse and IXYS

        Littelfuse's and IXYS' businesses are and will be subject to the risks described above. In addition, Littelfuse and IXYS are, and will continue to be, subject to the risks described in Littelfuse's Annual Report for the fiscal year ended December 31, 2016 and IXYS' Annual Report on Form 10-K for the fiscal year ended March 31, 2017, as updated by subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, all of which are filed with the SEC and incorporated by reference into this proxy statement/prospectus. The risks described above and in those filings represent all known material risks with respect to Littelfuse's and IXYS' businesses. See the section titled "Where You Can Find More Information" beginning on page 151 for the location of information incorporated by reference into this proxy statement/prospectus.


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INFORMATION ABOUT IXYS

IXYS Corporation

        IXYS Corporation, a Delaware corporation (referred to in this proxy statement/prospectus as IXYS), has been developing technology-driven products to improve energy conversion efficiency, generate clean energy, advance automation and provide solutions for the transportation, medical and telecommunication industries since its founding in Silicon Valley. IXYS, with its subsidiaries, has developed power semiconductors, solid state relays, high voltage integrated circuits and microcontrollers that are used in conserving energy and in reducing the world's dependence on fossil fuels. Diminishing natural resources, demand for renewable energy and environmental directives for energy efficiency represent a significant challenge. IXYS' power semiconductors and mixed-signal integrated circuits can reduce energy costs and consumption by improving the energy efficiency of everyday products. IXYS semiconductors are also used in medical devices and systems that provide diagnostics and therapy by medical equipment OEMs worldwide. IXYS common stock trades on The NASDAQ Global Select Market under the symbol "IXYS". The principal executive offices of IXYS are located at 1590 Buckeye Drive, Milpitas, California 95035, and its telephone number is (408) 457-9000.


INFORMATION ABOUT LITTELFUSE

Littelfuse, Inc.

        Littelfuse, Inc., a Delaware corporation (referred to in this proxy statement/prospectus as Littelfuse), is the world leader in circuit protection with growing global platforms in power control and sensing. The company serves customers in the electronics, automotive and industrial markets with technologies including fuses, semiconductors, polymers, ceramics, relays and sensors. Littelfuse has over 10,000 employees in more than 40 locations throughout the Americas, Europe and Asia. Littelfuse common stock trades on The NASDAQ Global Select Market under the symbol "LFUS". The principal executive offices of Littelfuse are located at 8755 West Higgins Road, Suite 500, Chicago, Illinois 60631, and its telephone number is (773) 628-1000.

Iron Merger Co., Inc.

        Iron Merger Co., Inc., a Delaware corporation (referred to in this proxy statement/prospectus as Merger Sub), is a wholly owned subsidiary of Littelfuse. Merger Sub was formed by Littelfuse solely in contemplation of the merger, has not conducted any business and has no assets, liabilities or obligations of any nature other than in connection with the merger. The principal executive offices of Merger Sub are located at c/o Littelfuse, Inc., 8755 West Higgins Road, Suite 500, Chicago, Illinois 60631, and its telephone number is (773) 628-1000.

IXYS Merger Co., LLC

        IXYS Merger Co., LLC, a Delaware limited liability company (referred to in this proxy statement/prospectus as Merger Sub Two), is a wholly owned subsidiary of Littelfuse. Merger Sub Two was formed by Littelfuse solely in contemplation of the merger, has not conducted any business and has no assets, liabilities or obligations of any nature other than in connection with the merger. The principal executive offices of Merger Sub Two are located at c/o Littelfuse, Inc., 8755 West Higgins Road, Suite 500, Chicago, Illinois 60631, and its telephone number is (773) 628-1000.


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INFORMATION ABOUT THE IXYS SPECIAL MEETING

General

        This proxy statement/prospectus is being provided to IXYS stockholders as part of a solicitation of proxies by the board of directors of IXYS for use at the special meeting of IXYS stockholders and at any adjournments or postponements of such special meeting. This proxy statement/prospectus provides IXYS stockholders with information about the special meeting and should be read carefully in its entirety.

Date, Time and Place of the Special Meeting

        The special meeting will be held on [    ·    ], 2018, beginning at [    ·    ],9:00 a.m., local time, at IXYS' principal executive offices at [    ·    ],1590 Buckeye Drive, Milpitas, California 95035, unless postponed to a later date.

Purposes of the Special Meeting

        At the special meeting, IXYS stockholders will be asked to vote upon the following proposals:

Only the approval of the merger proposal is required for completion of the merger.

Attendance at the Special Meeting

        Only IXYS stockholders of record as of the record date, non-record owners as of the record date, holders of valid proxies for the special meeting and invited guests of IXYS may attend the special meeting.

        All attendees should be prepared to present picture identification for admittance. The additional items, if any, that attendees must bring depend on whether they are stockholders of record, non-record owners or proxy holders.


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