Monolithic Power Systems, Inc.

The full register, from 13F filings

The Register tab above is hand research: a dozen holders, each traced to the filing it came from. This asks the same question of the whole market for the quarter ended 31-mar-2026, where 1,104 managers reported a position. Broad where the research is deep, and shallow in the ways a 13F always is.

Built from 13F filings, which report US listed, long, US custodied positions only. A register from this source is a floor rather than a level: a holder's true position can be far larger, as BlackRock's ASML stake shows at 1.28m shares in a 13F against 26.3m in its 13G/A. Holdings held through derivatives, outside US custody, or below a manager's reporting obligation do not appear. Where a holder is marked as a family, its total sums several separate filing entities and describes something no single filing describes; the constituent entities and their share counts are listed so the total can be checked. That roll-up can legitimately exceed the family's own Schedule 13G, because a 13G is filed by one legal entity: Vanguard reports Alphabet through ten advisory entities, and The Vanguard Group Inc itself reported zero after its January 2026 disaggregation.

What a reader needs to know to read these numbers

• Holdings side is empty by design, a sourced finding. The latest 10-Q (period ended 30 Jun 2026, filed 5 Aug 2026) and the latest 10-K (fiscal year ended 31 Dec 2025, filed 27 Feb 2026) were searched for 'non-marketable', 'equity method', 'strategic investment' (2 hits, both generic risk-factor boilerplate about strategic investments and initiatives in general, naming no investee), 'privately held', 'joint venture', 'unconsolidated', 'noncontrolling interest', 'cost method', 'equity investment', 'equity securities' (hits are all about MPWR's own common stock, not an investee), and 'affiliate' (hits are about MPWR's own affiliates for beneficial-ownership purposes, not a holding). All returned zero relevant hits in both filings. The 10-Q's balance sheet fully itemizes 'Other long-term assets' ($217.3 million at 30 Jun 2026) in its own note: deferred compensation plan assets ($115.4 million, itself invested in mutual funds and money-market funds to fund an employee deferred-compensation liability, not a strategic stake), a refundable supplier deposit under a wafer supply agreement, and a small residual; no line names any investee or breaks out an equity-method or non-marketable-securities balance. This is the same shape of finding as Broadcom's case described in the research brief: both filings were searched in full and nothing was found, so it is reported as a finding rather than left as a silent empty array.
• Marketable securities and short-term investments are treasury management, explicitly excluded here. As of 30 Jun 2026 Monolithic Power held $1,005.6 million in cash and cash equivalents plus $408.2 million in short-term investments (total $1,413.8 million, 30.2 percent of total assets), described throughout the 10-Q as liquidity to fund operations, not as strategic stakes in other companies. None of this is treated as a holding in this file.
• Single instrument, no stripping needed. Monolithic Power has only one class of stock (common, CUSIP 609839105) and no preferred stock, convertible notes, depositary shares or dual-class structure: the 10-Q was searched for 'convertible', 'preferred stock', 'Class A', 'Class B' and 'depositary shares' and none were found except an unrelated 'class action lawsuit' hit. Every register row above is CUSIP 609839105 common stock only, confirmed line by line in each filer's own Q2 2026 13F information table; filing.py's derivative filter found no option, warrant or convertible-note lines on any of the checked filers for this issuer. This is unlike Microchip's file, which had to strip preferred depositary shares and convertible-note derivatives from several of the same institutions' MPWR-adjacent rows.
• Share basis: the very high implied per-share price here is real, not a thousands-scaling artifact, except on one row. company.shares_outstanding (49,143,000) is the 10-Q cover page figure 'as of July 29, 2026'. Cross-checking eight independently filed Q2 2026 13F rows (BlackRock, State Street, FMR, Geode, Franklin Resources, Norges Bank and both Vanguard successor sub-totals) gives implied prices per share clustered tightly between $1,377.72 and $1,384.30 as of 30 Jun 2026, and stockanalysis.com shows a live price of $1,316.27 as of 18 Aug 2026 (down 7.04 percent on the day), a plausible decline from the late-June level rather than a data error. The one exception was T. Rowe Price Associates, Inc., whose raw XML value implied $1.38/share: that filer reports VALUES IN THOUSANDS on this CIK, confirmed by rescaling to match the same ~$1,382/share cluster; see that row's method_note. No stock split was found in the 10-Q (searched for 'stock split', 'forward split', 'reverse split', zero hits), so the current 49.1 million share count and the high per-share price are treated as consistent and correct throughout, not as an artifact needing scaling.
• Founder holding: Michael Hsing founded the company in August 1997 and remains Chairman of the Board, President and CEO. His full beneficial ownership (1,034,099 shares, 2.1%, per the 2026 proxy) is held directly and through two trusts of which he himself is trustee (the Michael Hsing 2004 Trust and the ZH Family Trust); there is no separate founder or family vehicle held by someone outside the officers-and-directors group, unlike the Walmart Walton or Marriott JWM Family Enterprises cases the brief warns about. His row is therefore marked as rolling up fully into the officers-and-directors group.
• Vanguard: parent CIK 0000102909 filed Form 13F-NT (no holdings) for Q2 2026, confirmed against its EDGAR submissions feed. Per the brief's rule, the position is reported entirely by successor entities, summed rather than substituted. Seven successor entities were identified from this project's own data/registers/MPWR.json register (built from an earlier, 31-Mar-2026 snapshot) and every one was individually re-verified against its own fresh Q2 2026 13F-HR: Vanguard Capital Management LLC (0002100119), Vanguard Portfolio Management LLC (0002100121), Vanguard Fiduciary Trust Co (0000933478), Vanguard Global Advisers, LLC (0001811242), Vanguard Asset Management, Ltd (0001680208), Vanguard Investments Australia, Ltd. (0001550100), and Vanguard Personalized Indexing Management, LLC (0001767306), summing to 6,144,593 shares, $8,494,039,579.
• T. Rowe Price Investment Management, Inc. (CIK 0001897612), the second mandated T. Rowe CIK, held 721,622 MPWR shares as of 31 Mar 2026 per this project's baseline register but reported ZERO MPWR holdings in its fresh Q2 2026 13F-HR (filed 14 Aug 2026, 738 info table rows, no match on 'MONOLITHIC' or 'PWR'). This is treated as a genuine exit or a drop below reporting threshold between quarters rather than an omission, since the fragment 'PWR' was confirmed to correctly match other companies elsewhere and the filing was read directly.
• Capital Group family (mandated check): all three CIKs, Capital World Investors (0001422849), Capital International Investors (0001562230) and Capital Research Global Investors (0001422848), were checked against their own fresh Q2 2026 13F-HR filings and NONE holds any Monolithic Power position (no match on 'MONOLITHIC' or 'PWR' in any of the three info tables; 'PWR' was confirmed live elsewhere in two of the three, matching American Electric Power, so the fragment works and the absence is real). No Capital Group row is included in this register.
• Self-gate, computed with the chart's own arithmetic on this final file: 10 register rows (8 institutional 13F rows plus 2 proxy insider rows). Michael Hsing counted at full value (1,034,099 shares) and the officers-and-directors group reduced to its residual (1,786,772 minus 1,034,099 = 752,673 shares) because his row rolls up into it. Sum: 6,144,593 + 5,589,925 + 5,177,258 + 2,282,186 + 1,195,281 + 976,798 + 811,974 + 751,399 + 1,034,099 + 752,673 = 24,716,186 shares against 49,143,000 shares outstanding, or 50.29 percent. This is above the brief's typical 25-to-45-percent band but below its 55-percent hard-alarm threshold. It is attributed to genuinely concentrated ownership in a small-float, high-price stock (only 49.1 million shares outstanding total) rather than to a double-counted holder or a mixed instrument basis: every row above is confirmed single-CUSIP common stock, the implied per-share price is consistent to within half a percent across eight independently filed Q2 2026 13Fs, and the Vanguard family sum was cross-checked entity by entity against the parent's 13F-NT rather than assumed.
• Market cap ($64,685,456,610, i.e. about $64.69 billion) and share price ($1,316.27) are from stockanalysis.com as of 18 Aug 2026, 1:26pm EDT intraday, which also reports 49.14 million shares outstanding, consistent with the 10-Q cover page figure of 49,143,000 used throughout this file. stockanalysis.com reported the stock down about 7.04 percent on the day.