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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(Print or Type Responses)

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) 6409 GUADALUPE MINES ROAD 3. Date of Earliest Transaction (Month/Day/Year) 02/27/2007 (Street) SAN JOSE, CA 95120 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 02/28/2007(1)   M   50,000 A $ 1.32 952,144 D   Common Stock 02/28/2007   S   50,000 D $ 12.8758 (2) 902,144 D   Common Stock 02/28/2007(1)   M   25,000 A $ 1.32 927,144 D   Common Stock 02/28/2007   S   25,000 D $ 12.7342 (2) 902,144 D   Common Stock               270,897 I By Jointly w/Spouse Common Stock               133,040 I By S. Hsing 04 Trust 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

Incentive Stock Option (right to buy)

$ 1.32

02/28/2007(3)

M

50,000

07/17/2006

07/17/2007(4)

Common Stock

50,000

$ 12.8758

25,000

D

Incentive Stock Option (right to buy)

$ 1.32

02/28/2007(3)

M

25,000

07/17/2006

07/17/2007(4)

Common Stock

25,000

$ 12.7342

0

D

Non-Qualified Stock Option (right to buy)

$ 12.99

02/27/2007

A

125,000

02/27/2009(5)

02/27/2014

Common Stock

125,000

$ 12.99

125,000

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Hsing Michael 6409 GUADALUPE MINES ROAD SAN JOSE, CA 95120	X		CEO

Signatures

Michael Hsing		02/28/2007
**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)	Option shares will expire if not exercised on or before July 17, 2007.
(2)	Average price per share
(3)	Shares exercised are subject to expiration on July 17, 2007.
(4)	Option shares expire five years from grant date if not exercised.
(5)	Fifty percent (50%) of the Shares subject to the Option shall vest twenty-four (24) months after the Grant Date, and 1/48 of the Shares subject to the Option shall vest monthly thereafter on the same day of the month as the Grant Date, subject to the Optionee continuing to be a Service Provider on such dates.

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