Monolithic Power CEO Reports 20,231-Share Sale on Form 4

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) Form 4 shows insider sales by Michael R. Hsing, who is listed as CEO and a director. On 08/15/2025 the reporting person, via an attorney-in-fact, sold multiple blocks of common stock in separate transactions totaling 20,231 shares. The reported sale prices per line are weighted averages ranging from about $825.06 to $836.50. After these transactions the filings show direct beneficial ownership levels on each line declining to a final reported direct holding of 814,667 shares. The filing also discloses indirect holdings of 133,040 shares held by the M Hsing 04 Trust and 12,825 shares held by the ZH Family 2020 Trust. The Form 4 is signed by an attorney-in-fact for Mr. Hsing and provides weighted-average price ranges for each sale line.

Positive

• Transparent disclosure of multiple sale transactions with weighted-average price ranges and commitment to provide per-price details upon request
• Proper form execution including signature by attorney-in-fact and clear reporting of direct and indirect holdings

Negative

• Insider sales totaling 20,231 shares by the CEO/director on 08/15/2025, reducing direct holdings
• No stated reason or explicit 10b5-1 plan details are included in the filing to explain the sales

Insights

Financial Analyst

TL;DR: CEO and director sold 20,231 MPWR shares on one day at prices around $825–$836; direct holdings remain substantial.

The Form 4 documents routine open-market dispositions totaling 20,231 shares executed on 08/15/2025 with weighted-average sale price ranges disclosed per trade line. The filing shows continuing significant direct ownership (final reported line: 814,667 shares) plus material indirect trust holdings. From an investor-analysis perspective, the transaction is clearly disclosed and quantifiable in size and price; it reduces direct share count but does not eliminate ownership. The form does not state the reason for the sales or provide a trading plan reference beyond the submission checkbox fields.

Corporate Governance Expert

TL;DR: Form 4 is properly executed and signed by an attorney-in-fact; it reports multiple same-day sales and identifies trusts holding indirect shares.

The filing is detailed: each sale line includes a weighted-average price range and a commitment to provide per-price quantities on request, and the signature block is completed by an attorney-in-fact. Indirect beneficial ownership is disclosed for two trusts, which is important for understanding aggregate insider exposure. The filing does not indicate an amended Form or a 10b5-1 plan reference checkbox checked with specifics, so no further procedural context is provided within the document.

Insider Trade Summary

Net Seller: 20,231 shares ($16,773,550)

Net Sell 13 txns

Insider Hsing Michael

Role CEO

Sold 20,231 shs ($16.77M)

Type	Security	Shares	Price	Value
Sale	Common Stock	2,603	$825.69	$2.15M
Sale	Common Stock	2,555	$826.64	$2.11M
Sale	Common Stock	3,878	$827.72	$3.21M
Sale	Common Stock	396	$828.64	$328K
Sale	Common Stock	4,101	$829.45	$3.40M
Sale	Common Stock	2,100	$830.46	$1.74M
Sale	Common Stock	1,953	$831.57	$1.62M
Sale	Common Stock	1,510	$832.57	$1.26M
Sale	Common Stock	535	$833.37	$446K
Sale	Common Stock	200	$834.92	$167K
Sale	Common Stock	400	$836.40	$335K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 832,295 shares (Direct); Common Stock — 133,040 shares (Indirect, by M Hsing 04 Trust)

Footnotes (1)

1. 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 $825.06 to $825.86. 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. 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 $826.12 to $826.98. 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. 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 $827.06 to $827.98. 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. 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 $828.07 to $828.84. 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. 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 $829.23 to $829.86. 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. 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 $830.01 to $830.97. 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. 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 $831.00 to $831.87. 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. 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 $832.05 to $832.90. 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. 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 $833.20 to $833.50. 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. 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 $836.11 to $836.50. 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.

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^*

Hsing Michael

(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
X	Officer (give title below)		Other (specify below)
	CEO

3. Date of Earliest Transaction (Month/Day/Year)
08/15/2025

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	08/15/2025		S		2,603	D	$825.69(1)	832,295	D
Common Stock	08/15/2025		S		2,555	D	$826.64(2)	829,740	D
Common Stock	08/15/2025		S		3,878	D	$827.72(3)	825,862	D
Common Stock	08/15/2025		S		396	D	$828.64(4)	825,466	D
Common Stock	08/15/2025		S		4,101	D	$829.45(5)	821,365	D
Common Stock	08/15/2025		S		2,100	D	$830.46(6)	819,265	D
Common Stock	08/15/2025		S		1,953	D	$831.57(7)	817,312	D
Common Stock	08/15/2025		S		1,510	D	$832.57(8)	815,802	D
Common Stock	08/15/2025		S		535	D	$833.37(9)	815,267	D
Common Stock	08/15/2025		S		200	D	$834.92	815,067	D
Common Stock	08/15/2025		S		400	D	$836.4(10)	814,667	D
Common Stock								133,040	I	by M Hsing 04 Trust
Common Stock								12,825	I	ZH Family 2020 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 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 $825.06 to $825.86. 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.

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 $826.12 to $826.98. 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 $827.06 to $827.98. 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 $828.07 to $828.84. 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 $829.23 to $829.86. 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 $830.01 to $830.97. 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 $831.00 to $831.87. 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 $832.05 to $832.90. 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 $833.20 to $833.50. 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 $836.11 to $836.50. 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.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Mr. Michael R. Hsing	08/15/2025
	** 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 Michael R. Hsing report on Form 4?

The Form 4 reports that Michael R. Hsing, listed as CEO and director, sold multiple blocks totaling 20,231 shares on 08/15/2025.

How many shares did the insider hold after the reported sales?

The filing shows direct beneficial ownership on the final reported line of 814,667 shares, plus indirect holdings of 133,040 shares (M Hsing 04 Trust) and 12,825 shares (ZH Family 2020 Trust).

At what prices were the MPWR shares sold?

Each sale line lists weighted-average price ranges; the reported ranges across lines run approximately from $825.06 to $836.50.

Was the Form 4 signed and properly filed?

Yes. The document is signed by Saria Tseng, attorney-in-fact for Mr. Michael R. Hsing with a signature date of 08/15/2025.

Does the filing indicate the sales were made under a 10b5-1 trading plan?

The form includes checkbox language for 10b5-1 plans but does not provide explicit plan details or indicate the sales were made pursuant to such a plan in the body of the filing.