Monolithic Power EVP reports 135,520-share MSU award; direct stake 256,180

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) executive Deming Xiao, EVP, Global Operations, reported the acquisition of 135,520 shares of common stock on October 25, 2025 at $0 per share. The shares were awarded upon certification of performance for market-based restricted stock units (MSUs) granted on October 25, 2022, tied to five stock price targets and relative total stockholder return over a three-year period; all shares vested on October 25, 2025.

Following the transaction, the filing shows 256,180 shares beneficially owned directly, plus 20,455 shares indirectly by spouse and 4,336 shares indirectly by the Christopher Chao Xiao Trust.

SEC Form 4

FORM 4

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

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Xiao Deming

(Last) (First) (Middle)

5808 LAKE WASHINGTON BLVD NE

(Street)

KIRKLAND WA 98033

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MONOLITHIC POWER SYSTEMS INC [ MPWR ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	EVP, Global Operations

3. Date of Earliest Transaction (Month/Day/Year)
10/25/2025

4. If Amendment, Date of 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

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	10/25/2025		A		135,520(1)	A	$0	256,180	D
Common Stock								20,455	I	by Spouse
Common Stock								4,336	I	Christopher Chao Xiao Trust

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 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: 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

Explanation of Responses:

1. On October 25, 2022, the reporting person was granted market-based restricted stock units ("MSUs") subject to the achievement of five stock price targets and relative total stockholder return percentile rank over a three-year performance and vesting period. On October 25, 2025, the Company's Compensation Committee of the Board of Directors certified and approved the achievement of the performance criteria for the MSUs, which resulted in 135,520 shares being awarded to the reporting person. All of the shares fully vested on October 25, 2025, pursuant to the grant agreement.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Mr. Deming Xiao	10/27/2025
	** 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 Number.

FAQ

What did MPWR report in this Form 4 filing?

An executive reported receiving 135,520 shares of common stock on October 25, 2025 from performance-based MSUs that fully vested.

What are the performance conditions for the awarded MSUs at MPWR?

The MSUs, granted on October 25, 2022, were tied to five stock price targets and relative total stockholder return over a three-year period.

What is the transaction price for the awarded shares?

The reported transaction lists a price of $0 per share, consistent with vesting of stock units.

How many MPWR shares does the reporting person own after the transaction?

The filing shows 256,180 shares directly owned, plus 20,455 indirectly by spouse and 4,336 indirectly by a trust.

Who is the reporting person and their role at MPWR?

The reporting person is Deming Xiao, serving as EVP, Global Operations.

When did the MSUs fully vest?

All shares fully vested on October 25, 2025 after the Compensation Committee certified performance.