Vanguard Capital Management (MPWR) discloses 3.56M-share, 7.25% stake

Rhea-AI Filing Summary

Vanguard Capital Management reported beneficial ownership of 3,561,866 shares of Monolithic Power Systems Inc. The filing, covering holdings as of 03/31/2026, shows a 7.25% stake in the common stock. Vanguard reports sole dispositive power over 3,561,866 shares and sole voting power for 478,417 shares. The statement discloses that the position reflects holdings across Vanguard Capital Management LLC and affiliated business divisions and funds. The filing is signed by the Head of Global Fund Administration on 04/30/2026.

Insights

Institutional Ownership Analyst

Passive disclosure of a sizable institutional stake by Vanguard.

Vanguard Capital Management reports owning 3,561,866 shares (7.25%) as of 03/31/2026, indicating a material passive holding that must be reported under Schedule 13G. The filing attributes voting and dispositive powers across Vanguard affiliates and pooled vehicles.

Implications hinge on Vanguard's investment mandate; the filing itself does not indicate any change in strategy or planned transactions. Subsequent Form 13D or Form 13G amendments would show activist intent or changes in ownership.

Corporate Governance Specialist

Voting and dispositive power split is typical for asset managers with fund overlays.

The report shows 478,417 shares subject to sole voting power and 3,561,866 shares subject to sole dispositive power, reflecting custody/management arrangements across Vanguard funds and accounts. The filing cites SEC Release No. 34-39538 disclosure conventions for affiliate aggregation.

Monitor future filings for changes to voting power or reclassification; voting concentrations can matter for proxy seasons and shareholder votes.

Key Figures

Beneficial ownership: 3,561,866 shares Percent of class: 7.25% Sole voting power: 478,417 shares +3 more

6 metrics

Beneficial ownership 3,561,866 shares Amount beneficially owned as of 03/31/2026

Percent of class 7.25% Percentage of common stock outstanding as reported

Sole voting power 478,417 shares Shares with sole power to vote reported in Item 4

Sole dispositive power 3,561,866 shares Shares with sole power to dispose reported in Item 4

Filing type Schedule 13G Passive investor beneficial ownership disclosure

Signature date 04/30/2026 Filing signed by Head of Global Fund Administration

Key Terms

Beneficially owned, Sole dispositive power, Schedule 13G, Investment Company Act

4 terms

Beneficially owned regulatory

"This reflects the securities beneficially owned, or deemed to be beneficially owned"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 3561866"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Schedule 13G regulatory

"form_type: SCHEDULE 13G"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

Investment Company Act regulatory

"investment company registered under the Investment Company Act of 1940"

The Investment Company Act is a law that sets rules for businesses whose main activity is managing and selling pooled money, such as mutual funds and other investment funds. It matters to investors because it requires clear reporting, limits managers from putting their own interests ahead of clients, and mandates safekeeping and oversight of assets—similar to safety inspections and traffic rules that help keep shared vehicles reliable and trustworthy.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Monolithic Power Systems Inc

(Name of Issuer)

Common Stock

(Title of Class of Securities)

609839105

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 609839105

1

Names of Reporting Persons

Vanguard Capital Management

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 478,417.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 3,561,866.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,561,866.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

7.25 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Vanguard Capital Management LLC and the following affiliates of Vanguard Capital Management LLC or business divisions of such affiliates: Vanguard Asset Management Limited, Vanguard Fiduciary Trust Company, Vanguard Global Advisers, LLC and Vanguard Investments Australia Ltd. This Schedule 13G includes securities held by Vanguard funds, or sleeves thereof, over which Vanguard Capital Management LLC exercises dispositive power, in addition to securities held by clients over which the affiliates or business divisions of such affiliates indicated above exercise dispositive and/or voting power. This Schedule 13G does not include securities, if any, beneficially owned by other subsidiaries or affiliates of Vanguard Capital Management LLC, or business divisions of such subsidiaries, whose ownership of securities is disaggregated from that of the reporting business unit in accordance with such release.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Monolithic Power Systems Inc
(b)	Address of issuer's principal executive offices: 5808 Lake Washington Blvd Nort, Kirkland, WA, 98033
Item 2.
(a)	Name of person filing: Vanguard Capital Management
(b)	Address or principal business office or, if none, residence: 100 Vanguard Blvd,, Malvern, PA, 19355
(c)	Citizenship: PA
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 609839105
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 3561866
(b)	Percent of class: 7.25 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 478417
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 3561866
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Vanguard Capital Management, including investment companies registered under the Investment Company Act of 1940 and other managed accounts, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities reported herein.No one other person's interest in the securities reported herein is more than 5%.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Vanguard Capital Management

Signature:	Ashley Grim
Name/Title:	Head of Global Fund Administration
Date:	04/30/2026

FAQ

What stake does Vanguard Capital Management report in MPWR?

Vanguard reports owning 3,561,866 shares, representing 7.25% of Monolithic Power Systems common stock as of 03/31/2026. The amount aggregates holdings across Vanguard affiliates and managed funds.

Does Vanguard have voting control over the MPWR shares it reports?

Vanguard reports sole voting power for 478,417 shares and sole dispositive power for 3,561,866 shares, indicating they control dispositions while voting authority is held for a subset.

What type of SEC filing is this for MPWR?

This is a Schedule 13G filing, a passive investor disclosure form reporting beneficial ownership when an investor is not seeking active control and meets SEC thresholds.

What date does the ownership information cover in the MPWR filing?

The reported ownership is stated as of 03/31/2026, and the filing is signed on 04/30/2026 by Vanguard's Head of Global Fund Administration.

Why does the filing reference Vanguard affiliates and funds?

Vanguard aggregates holdings across certain affiliates and funds under SEC Release No. 34-39538, so the reported 3,561,866 shares reflect securities managed or held across those related entities.