Monolithic Power CEO Hsing Sells $59M as MPWR Tops $1,500

Few semiconductor stocks have ridden the AI power buildout harder than Monolithic Power Systems, and on May 18, 2026, its founder and chief executive trimmed into the run. Michael Hsing sold 40,000 shares of MPWR for roughly $59.3 million, executing across 13 open-market lots priced between about $1,462 and $1,521 — within a few percent of the stock's all-time high. The sale landed just after a quarter in which Monolithic's enterprise-data revenue, the segment most exposed to AI server power, grew nearly 98% year over year.

The headline number is large, but the position behind it is larger. After the May 18 sale, Hsing still held roughly 848,000 MPWR shares — a stake worth more than $1.3 billion at the prevailing price. This is a founder taking a sliver off the top of a position that has compounded for two decades, not a leader heading for the exits. Reading the Hsing trading history alongside Monolithic's results is the only way to size the signal correctly.

What the May 18 Form 4 shows

The filing records 13 separate sale lots (transaction code S) executed on May 18, 2026, totaling 40,000 shares and approximately $59.3 million in proceeds. The lots walk down in price from $1,521.43 to $1,462.61, the signature of a single large order worked through the market over a session rather than a panic dump at the open. The transactions appear under accession 0001214659-26-006625 and can be inspected directly on SEC EDGAR. Hsing is classified as an officer and director but not a greater-than-10% owner, and the remaining ~848,000 shares confirm the sale was a partial trim, not a reduction to zero.

It is also worth separating this open-market sale from the routine compensation mechanics elsewhere in Hsing's recent record — an award (code A) in February 2026 and a gift (code G) in December 2025. Those are grant and transfer events, not sentiment signals. The May 18 block is the discretionary action, and it is the one that carries information.

Selling into an AI-fueled surge

The timing tracks the stock, not a stumble. Monolithic reported first-quarter 2026 revenue of $804 million, up 26% year over year and ahead of estimates, with non-GAAP earnings of $5.10 per share. The standout was the enterprise-data segment — power-management chips and modules for AI servers and optical modules — which grew about 97.7% year over year, with management raising its full-year growth floor for the segment to roughly 85%. Second-quarter guidance of $890 million to $910 million came in above consensus, and MPWR has climbed more than 70% year to date in 2026, trading above $1,550 by May 20.

The strategic question hovering over the stock is whether Monolithic's integrated power modules remain the default choice for Nvidia's Blackwell and next-generation Vera Rubin GPU platforms, where power delivery has become a gating constraint on rack density. As long as that design-win position holds, the enterprise-data growth has a long runway — and a founder selling $59 million against a $1.3 billion-plus retained stake reads as diversification near a high, not a verdict on the franchise. There is no earnings miss or guidance cut in the record to support a bearish interpretation of the timing.

Who owns the other side

Monolithic's register is dominated by the large index complexes and diversified managers. BlackRock leads the 13F holder list, followed by FMR (Fidelity), Vanguard Capital Management, Vanguard Portfolio Management, State Street, and Invesco. Most of that ownership is mechanical index exposure that scales with MPWR's weight in semiconductor and growth benchmarks rather than an active call on the AI-power thesis. The full institutional breakdown lives on the MPWR holder page, and Hsing's own filings sit on his insider profile.

What to watch next

The next hard checkpoint is Monolithic's second-quarter 2026 earnings report, due in late July or early August, which will test the $890-$910 million guide and show whether enterprise-data growth is holding near the raised 85% floor. A second marker is design-win commentary tied to Nvidia's Vera Rubin ramp — the clearest read on whether Monolithic keeps its power-module position. And on the insider side, watch whether the May 18 block was a one-off trim or the start of a faster cadence: a single $59 million sale against a multi-billion-dollar stake is routine, but a repeat near the same levels would shift the read. The authoritative source remains the Form 4 record itself.

FAQ

How much Monolithic Power stock did Michael Hsing sell in May 2026?
Hsing sold 40,000 MPWR shares for roughly $59.3 million on May 18, 2026, across 13 open-market lots priced between about $1,462 and $1,521 per share.

Does Michael Hsing still own Monolithic Power shares?
Yes. After the May 18 sale, Hsing retained roughly 848,000 MPWR shares, a stake worth more than $1.3 billion at the prevailing price. The sale was a partial trim, not an exit.

Why is Monolithic Power's CEO selling near record highs?
MPWR has risen more than 70% in 2026 on AI data-center power demand, with enterprise-data revenue up about 97.7% year over year. A founder selling $59 million against a $1.3 billion-plus stake reads as diversification near a high rather than a change in conviction; no earnings miss or guidance cut accompanied the sale.

What did Monolithic Power report for Q1 2026?
Revenue of $804 million, up 26% year over year, with non-GAAP EPS of $5.10 and Q2 guidance of $890-$910 million, above consensus.