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
                                                                                  
OMB APPROVAL
OMB Number: 3235-0287
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      

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 (MM/DD/YYYY)

4/1/2015
(Street)

SAN JOSE, CA 95119
(City)        (State)        (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)

 
6. Individual or Joint/Group Filing (Check Applicable Line)

_ X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3) 		2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. 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   4/1/2015     M (1)    14117   A $15.03   1052008   D    
Common Stock   4/1/2015     S (1)    9438   D $52.0002   (2) 1042570   D    
Common Stock   4/1/2015     M (1)    74154   A $15.03   1116724   D    
Common Stock   4/1/2015     S (1)    49572   D $52.0151   (3) 1067152   D    
Common Stock   4/2/2015     M (1)    107030   A $15.03   1174182   D    
Common Stock   4/2/2015     S (1)    71550   D $52.0021   (4) 1102632   D    
Common Stock                  29000   I   Hsing Fam Foundation  
Common Stock                  133040   I   by M Hsing 04 Trust  

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3) 		2. Conversion or Exercise Price of Derivative Security 3. Trans. Date 3A. Deemed Execution Date, if any 4. Trans. 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 7. Title and Amount of Securities Underlying Derivative Security
(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   4/1/2015     M   (1)       14117    12/28/2012   (5) 10/28/2015   Common Stock   14117   $0.00   0   D    
Non-Qualified Stock Option (right to buy)   $15.03   4/1/2015     M   (1)       74154    10/28/2010   (6) 10/28/2015   Common Stock   74154   $0.00   225846   D    
Non-Qualified Stock Option (right to buy)   $15.03   4/2/2015     M   (1)       107030    10/28/2010   (6) 10/28/2015   Common Stock   107030   $0.00   118816   D    

Explanation of Responses:
( 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.

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 4/3/2015
** Signature of Reporting Person Date


Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.
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