FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Hsing Michael   2. Issuer Name and Ticker or Trading Symbol MONOLITHIC POWER SYSTEMS INC [MPWR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) CEO (Last) (First) (Middle) 79 GREAT OAKS BLVD 3. Date of Earliest Transaction (Month/Day/Year) 04/01/2015 (Street) SAN JOSE, CA 95119 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 04/01/2015   M(1)   14,117 A $ 15.03 1,052,008 D   Common Stock 04/01/2015   S(1)   9,438 D $ 52.0002 (2) 1,042,570 D   Common Stock 04/01/2015   M(1)   74,154 A $ 15.03 1,116,724 D   Common Stock 04/01/2015   S(1)   49,572 D $ 52.0151 (3) 1,067,152 D   Common Stock 04/02/2015   M(1)   107,030 A $ 15.03 1,174,182 D   Common Stock 04/02/2015   S(1)   71,550 D $ 52.0021 (4) 1,102,632 D   Common Stock               29,000 I Hsing Fam Foundation Common Stock               133,040 I by M Hsing 04 Trust

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Non-Qualified Stock Option (right to buy)

$ 15.03

04/01/2015

M(1)

14,117

12/28/2012(5)

10/28/2015

Common Stock

14,117

$ 0

0

D

Non-Qualified Stock Option (right to buy)

$ 15.03

04/01/2015

M(1)

74,154

10/28/2010(6)

10/28/2015

Common Stock

74,154

$ 0

225,846

D

Non-Qualified Stock Option (right to buy)

$ 15.03

04/02/2015

M(1)

107,030

10/28/2010(6)

10/28/2015

Common Stock

107,030

$ 0

118,816

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Hsing Michael 79 GREAT OAKS BLVD SAN JOSE, CA 95119	X		CEO

Signatures

/s/ Saria Tseng For: Michael Hsing		04/03/2015
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	In accordance with the reporting person's 10b5-1 trading plan.
(2)	The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $52.00 to $52.02. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
(3)	The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $52.00 to $52.60. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
(4)	The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $52.00 to $52.05. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
(5)	Original option grant was for 14,117 shares. One-hundred percent (100%) of the Shares subject to the Option shall vest immediately. All outstanding options have fully vested.
(6)	Original option grant was for 300,000 shares. Fifty percent (50%) of the Shares subject to the Option shall vest twenty-four (24) months after the Vesting Commencement Date, and 1/48 of the Shares subject to the Option shall vest monthly thereafter on the same day of the month as the Vesting Commencement Date, subject to the Optionee continuing to be a Service Provider on such dates. All outstanding options have fully vested.

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