MPWR insider tax withholding; 201,637 shares remain direct

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) reported an insider tax-withholding transaction by its EVP, Global Operations. On 10/30/2025, the officer had 54,543 shares of common stock withheld at $1,096.63 per share (Form 4 code F) to cover income taxes tied to the earnout and vesting of market-based RSUs granted in October 2022.

After the transaction, the reporting person beneficially owns 201,637 shares directly, plus 20,455 shares held by a spouse and 4,336 shares held by the Christopher Chao Xiao Trust.

Insider Trade Summary

3 transactions reported

Mixed 3 txns

Insider Xiao Deming

Role EVP, Global Operations

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock	54,543	$1,096.63	$59.81M
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 201,637 shares (Direct); Common Stock — 20,455 shares (Indirect, by Spouse)

Footnotes (1)

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Form 4 Insider Transactions: What Each Field Means →

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
Estimated average burden
hours per response:			0.5

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)
10/30/2025

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	10/30/2025		F		54,543(1)	D	$1,096.63	201,637	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. The sales transaction reported in this Form 4 represents shares of common stock withheld by the Company to satisfy the income tax obligations in connection with the earnout and vesting of the market-based restricted stock units granted in October 2022, previously reported in a Form 4.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Mr. Deming Xiao	10/30/2025
	** 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 disclose in this Form 4?

An officer reported a code F transaction: 54,543 shares were withheld at $1,096.63 to satisfy tax obligations from RSU vesting.

When did the MPWR insider transaction occur?

The transaction date was 10/30/2025.

Why were the shares withheld for the MPWR officer?

They were withheld to cover taxes related to the earnout and vesting of market-based RSUs granted in October 2022.

How many MPWR shares does the insider own after the transaction?

Post-transaction holdings are 201,637 shares direct, 20,455 by spouse, and 4,336 by the Christopher Chao Xiao Trust.

What does Form 4 code F indicate?

Code F indicates shares were withheld by the issuer to satisfy tax obligations upon vesting or delivery of equity awards.

What role does the reporting person hold at MPWR?

The reporting person is an Officer, titled EVP, Global Operations.