Is the Monolithic Power interim CFO’s share sale part of a trading plan?

The provided disclosure notes the sale was to cover tax withholding on vested restricted stock units. It does not reference a Rule 10b5-1 trading plan in the excerpt, instead emphasizing the tax-related nature of the transaction.

How significant is the 22-share sale by Monolithic Power’s interim CFO?

The sale involved only 22 shares compared with 5,878 shares held directly afterward. Given its small size and stated purpose of satisfying tax withholding, it appears as a routine compensation-related transaction rather than a sizable change in insider ownership.

Monolithic Power (MPWR) interim CFO sells 22 shares to cover taxes

Filing Impact

(Neutral)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Monolithic Power Systems’ interim CFO Robert W. Dean II reported a small, tax-related share sale. On 2026-05-26, he sold 22 shares of common stock at a weighted average price of $1,649.56 per share to cover tax withholding obligations tied to vested restricted stock units. After this transaction, he directly held 5,878 common shares and indirectly held 65 additional shares through an account noted as held by parent and daughter. The filing indicates a routine tax-withholding event rather than a discretionary reduction of his ownership stake.

Insider Trade Summary

Net Seller: 22 shares ($36,290)

Net Sell 2 txns

Insider DEAN ROBERT W II

Role Interim CFO

Sold 22 shs ($36K)

Type	Security	Shares	Price	Value
Sale	Common Stock	22	$1,649.56	$36K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 5,878 shares (Direct, null); Common Stock — 65 shares (Indirect, Held by Parent & Daughter)

Footnotes (1)

The reported sale was to cover tax withholding obligations upon the vesting of restricted stock units. 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 $1,647.84 to $1,650.16. 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.

Key Figures

Shares sold: 22 shares Weighted average sale price: $1,649.56 per share Direct holdings after transaction: 5,878 shares +2 more

5 metrics

Shares sold 22 shares Common stock sold on 2026-05-26

Weighted average sale price $1,649.56 per share Open-market sale to cover tax withholding

Direct holdings after transaction 5,878 shares Common stock directly held post-sale

Indirect holdings after transaction 65 shares Held by Parent & Daughter

Sale price range $1,647.84–$1,650.16 Range for trades included in weighted average

Key Terms

restricted stock units, weighted average sale price, tax withholding obligations

3 terms

restricted stock units financial

"The reported sale was to cover tax withholding obligations upon the vesting of restricted stock units."

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

weighted average sale price financial

"The price is the weighted average sale price for the transactions reported on this line."

tax withholding obligations financial

"The reported sale was to cover tax withholding obligations upon the vesting of restricted stock units."

Form 4 Insider Transactions: What Each Field Means →

05/28/2026 - 07:46 PM

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^*

DEAN ROBERT W II

(Last)

(First)

(Middle)

1555 PALM BEACH LAKES BLVD.

(Street)

WEST PALM BEACH

FLORIDA

33401

(City)

(State)

(Zip)

UNITED STATES

(Country)

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)
	Interim CFO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/26/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	05/26/2026		S		22⁽¹⁾	D	$1,649.56⁽²⁾	5,878	D
Common Stock								65	I	Held by Parent & Daughter

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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. The reported sale was to cover tax withholding obligations upon the vesting of restricted stock units.

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 $1,647.84 to $1,650.16. 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. Robert W. Dean II	05/28/2026
	** 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.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR

FAQ

What insider transaction did Monolithic Power (MPWR) report for its interim CFO?

Monolithic Power’s interim CFO reported selling 22 common shares. The sale was made to cover tax withholding obligations from vested restricted stock units, according to the Form 4 disclosure and its accompanying footnotes.

At what price did the Monolithic Power interim CFO sell his MPWR shares?

The interim CFO sold 22 shares at a weighted average price of $1,649.56 per share. Footnotes state individual trades occurred between $1,647.84 and $1,650.16, with detailed breakdowns available on request from the company or regulators.

Why did the Monolithic Power interim CFO sell 22 MPWR shares?

The shares were sold specifically to cover tax withholding obligations from the vesting of restricted stock units. This type of sale is generally mechanical, reflecting tax requirements on equity compensation rather than a discretionary decision to reduce ownership.

How many Monolithic Power shares does the interim CFO hold after this Form 4?

Following the reported transaction, the interim CFO directly held 5,878 shares of Monolithic Power common stock. He also indirectly held 65 additional shares in an account described as "Held by Parent & Daughter" in the ownership details.