[Form 4] Monolithic Power Systems, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) – Form 4 insider transaction. EVP Global Operations Deming Xiao reported a single open-market sale on 08/01/2025.

• Shares sold: 39,999 common shares
• Price per share: $780
• Approx. proceeds: ~$31.2 million (39,999 × $780)
• Post-sale direct holding: 121,605 shares
• Indirect holdings: 20,455 shares held by spouse and 3,391 shares held in the Christopher Chao Xiao Trust

The transaction is coded “S” (open-market sale). No derivative activity was reported. After this disposition, Xiao retains a combined 145,451 shares (direct + indirect), indicating continued but reduced exposure. The form notes an additional 27 shares added on 02/17/2025 through the company’s ESPP.

Large executive sales can be perceived as a bearish signal if not offset by offsetting purchases or clear diversification rationale. No Rule 10b5-1 plan box was checked, suggesting the sale was not conducted under a pre-arranged trading plan.

Positive

• None.

Negative

• Executive divestiture of 39,999 shares (~$31 M) without a disclosed Rule 10b5-1 plan may signal reduced insider confidence and increase selling pressure.

Insights

Financial Analyst

TL;DR: EVP sold ~$31 M in stock; sizable reduction, mildly negative sentiment.

The sale of 39,999 shares at $780 represents roughly 25% of Xiao’s prior direct stake (assuming no interim changes), generating significant cash. Lack of a 10b5-1 plan makes timing discretionary, which investors may interpret as diminished short-term confidence. However, he still holds over 145 K shares, maintaining meaningful alignment. The transaction does not alter fundamentals but could add near-term supply pressure and modestly dampen sentiment.

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).

X

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)
08/01/2025

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	08/01/2025		S		39,999	D	$780	121,605(1)	D
Common Stock								20,455	I	by Spouse
Common Stock								3,391	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. Ending balance includes 27 shares acquired on February 17, 2025 through the Company's qualified ESPP program.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Mr. Deming Xiao	08/01/2025
	** 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

How many MPWR shares did EVP Deming Xiao sell on 08/01/2025?

39,999 shares of common stock were sold.

At what price were the MPWR shares sold?

The reported sale price was $780 per share.

What is Deming Xiao’s remaining direct ownership in MPWR after the sale?

He now directly owns 121,605 MPWR shares.

Does the filing indicate a Rule 10b5-1 trading plan?

No. The box for a Rule 10b5-1(c) plan was not checked.

Were any derivative securities involved in this Form 4?

No derivative securities were acquired or disposed of in this filing.