UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 2)

MICROSEMI CORP
(Name of Issuer)

COMMON STOCK
(Title of Class of Securities)

595137100
(CUSIP NUMBER)

December 31, 2017
(Date of Event which Requires Filing of Statement)

Check the appropriate box to designate the Rule pursuant to which this
Schedule is filed:
[x]  Rule 13d - 1(b)
     Rule 13d - 1(c)
     Rule 13d - 1(d)

1. Name of Reporting Person
   T. ROWE PRICE ASSOCIATES, INC.
   52-0556948

2. Check the Appropriate Box if a Member of a Group
   NOT APPLICABLE

3. SEC Use Only

4. Citizenship or Place of Organization
   Maryland

Number of Shares Beneficially Owned by Each Reporting Person With

5. Sole Voting Power*         2,175,344

6. Shared Voting Power*       0

7. Sole Dispositive Power*    8,589,829

8. Shared Dispositive Power   0

9. Aggregate Amount Beneficially Owned by Each Reporting Person
   8,589,829

10. Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares
	NOT APPLICABLE

11. Percent of Class Represented by Amount in Row 9
	7.3%

12. Type of Reporting Person
	IA

*Any shares reported in Items 5 and 6 are also reported in Item 7.


Item 1(a) Name of Issuer:
MICROSEMI CORP

Item 1(b) Address of Issuer's Principal Executive Offices:
ONE ENTERPRISE
ALISO VIEJO, CALIFORNIA 92656

Item 2(a) Name of Person(s) Filing:
(1) T. ROWE PRICE ASSOCIATES, INC. ("Price Associates")


Item 2(b) Address of Principal Business Office:
100 E. Pratt Street, Baltimore, MD 21202

Item 2(c) Citizenship or Place of Organization:
(1) Maryland

Item 2(d) Title of Class of Securities: COMMON STOCK

Item 2(e) Cusip Number: 595137100

Item 3: The person filing this Schedule 13G is an:
X   Investment Adviser registered under Section 203 of the Investment
    Advisers Act of 1940

Item 4: Reference is made to Items 5-11 on the preceding pages of this
        Schedule 13G.

Item 5: Ownership of Five Percent or Less of a Class
	Not Applicable

Item 6: Ownership of More than Five Percent on Behalf of Another Person

(1)     Price Associates does not serve as custodian of the assets of any of
        its clients; accordingly, in each instance only the client or the
        client's custodian or trustee bank has the right to receive dividends
        paid with respect to, and proceeds from the sale of, such securities.

        The ultimate power to direct the receipt of dividends paid with
        respect to, and the proceeds from the sale of, such securities, is
        vested in the individual and institutional clients which Price
        Associates serves as investment adviser. Any and all discretionary
        authority which has been delegated to Price Associates may be revoked
        in whole or in part at any time.

        Except as may be indicated if this is a joint filing with one of the
        registered investment companies sponsored by Price Associates which it
        also serves as investment adviser ("T. Rowe Price Funds"), not more
        than 5% of the class of such securities is owned by any one client
        subject to the investment advice of Price Associates.

(2)     With respect to securities owned by any one of the T. Rowe Price
        Funds, only the custodian for each of such Funds, has the right to
        receive dividends paid with respect to, and proceeds from the sale of,
        such securities. No other person is known to have such right, except
        that the shareholders of each such Fund participate proportionately
        in any dividends and distributions so paid.

Item 7: Identification and Classification of the Subsidiary Which Acquired the
        Security Being Reported on By the Parent Holding Company.
        Not Applicable

Item 8: Identification and Classification of Members of the Group
        Not Applicable

Item 9: Notice of Dissolution of Group
        Not Applicable

Item 10: Certification
         By signing below I certify that, to the best of my knowledge and
         belief, the securities referred to above were acquired in the
         ordinary course of business and were not acquired and are not
         held for the purpose of or with the effect of changing or
         influencing the control of the issuer of the securities and were
         not acquired and are not held in connection with or as a participant
         in any transaction having that purpose or effect. T. Rowe Price
         Associates, Inc. hereby declares and affirms that the filing
         of Schedule 13G shall not be construed as an admission that Price
         Associates is the beneficial owner of the securities referred to,
         which beneficial ownership is expressly denied.

         Signature.

         After reasonable inquiry and to the best of my knowledge and belief,
         I certify that the information set forth in this statement is true,
         complete and correct.

T. ROWE PRICE ASSOCIATES, INC.
Date: February 14, 2018
Signature: /s/ David Oestreicher
Name & Title: David Oestreicher, Vice President

12/31/2017