Deming Xiao (MPWR) unloads 30,000 shares but keeps large stake

Rhea-AI Filing Summary

Monolithic Power Systems EVP Deming Xiao reported sizable insider sales of common stock. On May 6, 2026, he executed open-market sales totaling 30,000 shares of MPWR common stock across four transactions at prices between $1,648.38 and $1,661.38 per share. Following these sales, Xiao directly holds 232,630 shares of common stock. The filing also reports indirect holdings of 4,336 shares held by the Christopher Chao Xiao Trust and 20,455 shares held by his spouse, reflecting additional exposure to the company’s stock. A footnote notes that the ending balance includes 27 shares acquired earlier through the company’s qualified employee stock purchase plan.

Insights

Equity compensation and insider-trading analyst

EVP Deming Xiao sold 30,000 MPWR shares but retains a large stake.

Deming Xiao, EVP of Global Operations at Monolithic Power Systems, reported open-market sales of 30,000 shares of common stock on May 6, 2026. Sale prices per share ranged from roughly $1,648 to $1,661, based on the individual transaction lines.

After these transactions, Xiao still directly owns 232,630 shares, plus indirect interests of 4,336 shares in the Christopher Chao Xiao Trust and 20,455 shares held by his spouse. With no option exercises or derivative activity disclosed, this filing reflects a straightforward reduction of an existing equity position rather than a compensation event.

Because the company’s total shares outstanding are not shown here, the relative size of this sale versus the overall float cannot be assessed from this data alone. Future company filings may provide additional context on aggregate insider ownership and any patterns in executive stock sales.

Insider Trade Summary

Net Seller: 30,000 shares ($49,636,560)

Net Sell 6 txns

Insider Xiao Deming

Role EVP, Global Operations

Sold 30,000 shs ($49.64M)

Type	Security	Shares	Price	Value
Sale	Common Stock	3,329	$1,648.38	$5.49M
Sale	Common Stock	14,167	$1,652.80	$23.42M
Sale	Common Stock	11,597	$1,657.93	$19.23M
Sale	Common Stock	907	$1,661.38	$1.51M
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 232,630 shares (Direct, null); Common Stock — 20,455 shares (Indirect, by Spouse)

Footnotes (1)

1. Ending balance includes 27 shares acquired on February 17, 2026 through the Company's qualified ESPP program. 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 $1,645.48 to $1,650.43. 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 $1,650.75 to $1,655.75. 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 $1,655.80 to $1,660.72. 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 $1,660.99 to $1,662 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

Total shares sold: 30,000 shares Sale block 1: 907 shares at $1,661.38 Sale block 2: 11,597 shares at $1,657.93 +5 more

8 metrics

Total shares sold 30,000 shares Open-market sales of MPWR common stock on May 6, 2026

Sale block 1 907 shares at $1,661.38 Open-market sale of common stock on May 6, 2026

Sale block 2 11,597 shares at $1,657.93 Open-market sale of common stock on May 6, 2026

Sale block 3 14,167 shares at $1,652.80 Open-market sale of common stock on May 6, 2026

Sale block 4 3,329 shares at $1,648.38 Open-market sale of common stock on May 6, 2026

Direct holdings after sale 232,630 shares Common stock directly owned by Deming Xiao after transactions

Trust indirect holdings 4,336 shares Common stock held via Christopher Chao Xiao Trust

Spouse indirect holdings 20,455 shares Common stock held indirectly by spouse

Key Terms

open-market sale, weighted average sale price, qualified ESPP program, indirect ownership

4 terms

open-market sale financial

"transaction_action: "open-market sale" for non-derivative common stock"

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

weighted average sale price financial

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

qualified ESPP program financial

"shares acquired on February 17, 2026 through the Company's qualified ESPP program."

indirect ownership financial

"ownership_type: "indirect" with nature_of_ownership "Christopher Chao Xiao Trust" and "by Spouse""

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^*

Xiao Deming

(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)
	EVP, Global Operations

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/06/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/06/2026		S		3,329	D	$1,648.38(2)	232,630(1)	D
Common Stock	05/06/2026		S		14,167	D	$1,652.8(3)	218,463	D
Common Stock	05/06/2026		S		11,597	D	$1,657.93(4)	206,866	D
Common Stock	05/06/2026		S		907	D	$1,661.38(5)	205,959	D
Common Stock								20,455	I	by Spouse
Common Stock								4,336	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, 2026 through the Company's qualified ESPP program.

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 $1,645.48 to $1,650.43. 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 $1,650.75 to $1,655.75. 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 $1,655.80 to $1,660.72. 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 $1,660.99 to $1,662 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. Deming Xiao	05/08/2026
	** 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)

FAQ

What did MPWR executive Deming Xiao report in this Form 4 filing?

Deming Xiao, EVP of Global Operations at MPWR, reported open-market sales totaling 30,000 shares of Monolithic Power Systems common stock on May 6, 2026. The filing also details his remaining direct and indirect shareholdings after these transactions.

How many MPWR shares does Deming Xiao still own after the May 6, 2026 sales?

After the reported sales, Deming Xiao directly owns 232,630 shares of Monolithic Power Systems common stock. The filing also shows indirect holdings of 4,336 shares in a family trust and 20,455 shares held by his spouse, indicating continued significant exposure.

At what prices did Deming Xiao sell MPWR stock in this Form 4?

The Form 4 shows four open-market sale transactions with per-share prices of $1,661.38, $1,657.93, $1,652.80, and $1,648.38. Footnotes indicate these are weighted average prices for trades executed within narrow price ranges on May 6, 2026.

Did Deming Xiao exercise any stock options in connection with these MPWR trades?

No, the Form 4 does not report any option exercises or derivative security transactions. All listed activities are non-derivative common stock sales, indicating Xiao reduced an existing share position rather than converting options or other derivatives into stock.

What indirect MPWR shareholdings are disclosed for Deming Xiao in this filing?

The filing discloses 4,336 shares of Monolithic Power Systems common stock held indirectly through the Christopher Chao Xiao Trust and 20,455 shares held by his spouse. These positions are reported as indirect ownership interests separate from his direct holdings.

Does this MPWR Form 4 mention shares acquired through an employee stock plan?

Yes. A footnote explains that the ending balance includes 27 shares acquired on February 17, 2026 through Monolithic Power Systems’ qualified employee stock purchase plan. This indicates part of Xiao’s holdings comes from ongoing employee participation in the ESPP.