Monolithic Power CEO sells 30,000 shares under plan

What happened

Monolithic Power Systems, Inc. (NASDAQ: MPWR) CEO and director Michael Hsing sold 30,000 shares on 2026-09-28, according to a Form 4 filing. The shares sold at prices from $1,323.31 to $1,356.94 each, for about $40.35 million. After the sale, he held 818,264 shares directly. The filing also lists 133,040 shares held indirectly by M Hsing 04 Trust and 12,825 shares held indirectly by ZH Family 2020 Trust. The filing was reported on 2026-09-30.

Key numbers

Metric	Latest	Change	Source
Shares sold	30,000 shares		SEC Form 4
Sale price range	$1,323.31 to $1,356.94 per share		SEC Form 4
Total value	about $40.35 million		SEC Form 4
Shares held after sale	818,264 shares		SEC Form 4

Read more: Monolithic Power Systems (MPWR) stock analysis and investment case

Why it matters

OptimistFi's case is that MPWR can compound value if its differentiated, fabless power-electronics platform keeps winning high-value design sockets while preserving premium gross margins and cash conversion. This filing is mixed for that view. It shows the CEO and director cut his direct stake, but he still held a large position after the trade. OptimistFi calculates that the 30,000 shares were about 3.5% of Hsing's 848,264-share pre-trade holding.

The sale was large in dollar terms at about $40.35 million. Even so, the filing still shows a material direct stake for investors who track insider ownership. It also shows indirect holdings of 133,040 shares in M Hsing 04 Trust and 12,825 shares in ZH Family 2020 Trust.

The Form 4 lists eight sale lines on 2026-09-28. It shows 596 shares at $1,323.31, 2,121 at $1,328.54, 1,111 at $1,333.34, 2,949 at $1,338.66, 5,783 at $1,343.76, 6,343 at $1,347.15, 10,967 at $1,351.43 and 130 at $1,356.94. The note says those were weighted average sale prices, with actual ranges from $1,320.64 to $1,325.61 on the first line and from $1,356.78 to $1,357.00 on the last line.

The filing says the trades were made under a Rule 10b5-1 trading plan adopted on 05/29/2026. That makes the timing less useful as a fresh signal on his view of the business.

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What's next

The next check is any later Form 4 under the same plan. More sales would show the planned trim continuing. No further sales would leave this as a prearranged reduction in Hsing's direct stake.

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