Monolithic Power (MPWR) EVP/CFO Executes 10b5-1 Sales Reducing Holdings

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) Form 4 reports multiple open-market sales by EVP and CFO Theodore Blegen executed on 10/01/2025 under a Rule 10b5-1 trading plan adopted 02/26/2025. The schedule shows a sequence of sales at weighted-average prices ranging from $902.61 to $917.17 per share across separate blocks, reducing Mr. Blegen's direct holdings from earlier reported balances down to 37,940 shares held directly. The filing also discloses indirect ownership of 5,331 shares in an irrevocable trust for Theodore F. Blegen and 5,331 shares in an irrevocable trust for Sarah N. Blegen. The form is signed by an attorney-in-fact.

Positive

• Transactions were executed under a Rule 10b5-1 trading plan, indicating pre-established, compliant disposition methodology
• Detailed weighted-average prices and offer to provide per-price breakdowns improve transparency for regulators and investors
• Indirect trust holdings remain disclosed, preserving visibility into continued insider economic exposure

Negative

• Significant reduction in direct holdings to 37,940 shares following multiple sales on 10/01/2025
• All reported activity are dispositions; no purchases or option grants reported that would offset dilution or indicate accumulation

Insights

Financial Analyst

TL;DR: Senior officer sold a material tranche of shares via a pre-established 10b5-1 plan; holdings decreased but indirect trust ownership remains.

The reported trades consist solely of planned dispositions under a Rule 10b5-1 plan adopted on 02/26/2025, with multiple execution lines on 10/01/2025 at weighted-average prices between $902.61 and $917.17. The direct position following the transactions is reported as 37,940 shares, with two identical irrevocable trust holdings of 5,331 shares each disclosed as indirect. For investors, this is a disclosure of insider liquidity rather than an operational signal; absence of purchases or option exercises in this filing suggests no concurrent increasing insider accumulation.

Corporate Governance Expert

TL;DR: Sales were executed under a documented 10b5-1 plan, which supports compliance but reduces insider free float.

The filing transparently cites the 10b5-1 plan as the basis for the transactions and provides weighted-average price ranges and an undertaking to supply per-price breakdowns on request, which aligns with good governance disclosure practices. The signature by an attorney-in-fact is noted. These sales lower the reporting person’s direct ownership and should be viewed as scheduled liquidity rather than discretionary trades based on nonpublic information, per the plan disclosure.

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).

1. Name and Address of Reporting Person^*

BLEGEN THEODORE

(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 and CFO

3. Date of Earliest Transaction (Month/Day/Year)
10/01/2025

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	10/01/2025		S		6(1)	D	$902.61	40,933	D
Common Stock	10/01/2025		S		40(1)	D	$903.82	40,893	D
Common Stock	10/01/2025		S		60(1)	D	$904	40,833	D
Common Stock	10/01/2025		S		115(1)	D	$905.37(2)	40,718	D
Common Stock	10/01/2025		S		250(1)	D	$907.36(3)	40,468	D
Common Stock	10/01/2025		S		80(1)	D	$909.52(4)	40,388	D
Common Stock	10/01/2025		S		65(1)	D	$911.27(5)	40,323	D
Common Stock	10/01/2025		S		676(1)	D	$912.73(6)	39,647	D
Common Stock	10/01/2025		S		138(1)	D	$913.87(7)	39,509	D
Common Stock	10/01/2025		S		390(1)	D	$914.71(8)	39,119	D
Common Stock	10/01/2025		S		440(1)	D	$915.43(9)	38,679	D
Common Stock	10/01/2025		S		580(1)	D	$916.37(10)	38,099	D
Common Stock	10/01/2025		S		160(1)	D	$917.17(11)	37,940(12)	D
Common Stock								5,331	I	Irrevocable Trust FBO Theodore F. Blegen
Common Stock								5,331	I	Irrevocable Trust FBO Sarah N. Blegen

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. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 2/26/2025.

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 $905.35 to $905.40. 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 $907.30 to $907.37. 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 $909.22 to $909.82. 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. 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 $911.04 to $911.66. 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.

6. 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 $912.39 to $912.82. 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.

7. 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 $913.84 to $913.87. 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.

8. 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 $914.59 to $914.77. 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.

9. 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 $915.01 to $915.68. 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.

10. 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 $916.09 to $916.49. 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.

11. 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 $917.08 to $917.28. 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.

12. Ending balance includes 1 share acquired on August 15, 2025 through the Company's qualified ESPP program.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Mr. Bernie Blegen	10/01/2025
	** 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

What did MPWR insider Theodore Blegen report on Form 4?

The filing reports multiple sales of Monolithic Power Systems common stock on 10/01/2025 executed under a Rule 10b5-1 plan adopted 02/26/2025.

How many shares does Theodore Blegen own after the reported transactions?

Directly owned: 37,940 shares. Additionally, 5,331 shares are held indirectly in an irrevocable trust for Theodore F. Blegen and 5,331 shares in an irrevocable trust for Sarah N. Blegen.

At what prices were the MPWR shares sold?

Weighted-average sale prices ranged from $902.61 to $917.17 per share across the reported transaction lines; per-line ranges are provided in the filing explanations.

Was the Form 4 trading activity part of a planned trading program?

Yes. The filing states the transactions were made pursuant to a Rule 10b5-1 trading plan adopted 02/26/2025.

Who signed the Form 4 filing for Theodore Blegen?

The form is signed by Saria Tseng, attorney-in-fact for Mr. Bernie Blegen with the signature date 10/01/2025 as shown in the filing.