[Form 4] MONOLITHIC POWER SYSTEMS INC Insider Trading Activity

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) director Carintia Martinez reported a sale of common stock under a 10b5-1 plan. On 09/18/2025 the reporting person sold 1,400 shares of Monolithic Power Systems common stock for a price reported as $900. After the sale the reporting person beneficially owned 878 shares. The filing states the transaction was executed pursuant to a Rule 10b5-1 trading plan adopted on 11/27/2024 and the Form 4 was signed by an attorney-in-fact on 09/18/2025.

Insights

Securities Analyst

TL;DR: Director sale of 1,400 shares executed under a 10b5-1 plan; ownership reduced to 878 shares.

The filing documents a non-derivative sale executed on 09/18/2025 under a pre-established Rule 10b5-1 plan adopted 11/27/2024. The report lists the transaction code S and shows the reporting person disposed of 1,400 shares at a price reported as $900, leaving 878 shares beneficially owned. As a single-reporting-person Form 4 by a director, this is a routine disclosure of insider liquidity rather than a corporate action or change in ownership control. The filing contains no additional context such as total prior holdings or reason beyond the 10b5-1 plan.

Corporate Governance Expert

TL;DR: Director sale appears compliant with Rule 10b5-1; disclosure shows reduced holdings to 878 shares.

The disclosure specifies the sale was made pursuant to a written 10b5-1 trading plan, which is a common mechanism for insiders to transact while providing affirmative defense against insider trading claims. The Form 4 was executed by an attorney-in-fact and includes the required information: transaction date, code, share amount, price, and resulting beneficial ownership. The filing does not indicate any amendment or other governance developments. Material governance implications are limited given the small absolute share count disclosed.

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^*

Martinez Carintia

(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)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
09/18/2025

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	09/18/2025		S		1,400(1)	D	$900	878	D

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. This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 11/27/2024.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Ms. Carintia Martinez	09/18/2025
	** 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.