=== SEC Form 4 — Statement of Changes in Beneficial Ownership ===
Document Type: 4
Period of Report: 2026-07-15
10b5-1 Pre-arranged Plan: Yes
--- Issuer ---
Name: MONOLITHIC POWER SYSTEMS, INC. (MPWR)
CIK: 0001280452
--- Reporting Owner ---
Name: Sciammas Maurice
CIK: 0001360833
Role: Officer (EVP, WW Sales & Marketing)
--- Non-Derivative Transactions ---
[Transaction #1]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -527 | Price: $1,314.03
Total Value: $692,493.81
Shares Owned After: 166,117 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F2] 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 $1,311.45 to $1,316.40 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.
[Transaction #2]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -274 | Price: $1,318.42
Total Value: $361,247.08
Shares Owned After: 165,843 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F3] 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 $1,316.56 to $1,321.56. 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.
[Transaction #3]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -409 | Price: $1,323.93
Total Value: $541,487.37
Shares Owned After: 165,434 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F4] 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 $1,321.72 to $1,326.11. 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.
[Transaction #4]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -464 | Price: $1,329.30
Total Value: $616,795.20
Shares Owned After: 164,970 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F5] 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 $1,326.94 to $1,331.90. 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.
[Transaction #5]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -776 | Price: $1,334.59
Total Value: $1,035,641.84
Shares Owned After: 164,194 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F6] 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 $1,331.95 to $1,336.95. 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.
[Transaction #6]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -1,460 | Price: $1,339.59
Total Value: $1,955,801.40
Shares Owned After: 162,734 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F7] 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 $1,336.97 to $1,341.96. 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.
[Transaction #7]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -1,864 | Price: $1,344.16
Total Value: $2,505,514.24
Shares Owned After: 160,870 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F8] 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 $1,341.99 to $1,346.96. 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.
[Transaction #8]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -1,506 | Price: $1,348.91
Total Value: $2,031,458.46
Shares Owned After: 159,364 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F9] 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 $1,347.09 to $1,352.00. 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.
[Transaction #9]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -5,640 | Price: $1,352.95
Total Value: $7,630,638.00
Shares Owned After: 153,724 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F10] 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 $1,352.13 to $1,357.03. 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.
[Transaction #10]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -50 | Price: $1,359.36
Total Value: $67,968.00
Shares Owned After: 153,674 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F11] 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 $1,357.88 to $1,362.57. 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.
[Transaction #11]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -240 | Price: $1,369.18
Total Value: $328,603.20
Shares Owned After: 153,434 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F12] 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 $1,366.15 to $1,371.04. 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.
[Transaction #12]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -472 | Price: $1,375.47
Total Value: $649,221.84
Shares Owned After: 152,962 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F13] 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 $1,371.23 to $1,376.20. 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.
[Transaction #13]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -418 | Price: $1,378.73
Total Value: $576,309.14
Shares Owned After: 152,544 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F14] 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 $1,376.51 to $1,381.11. 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.
[Transaction #14]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -410 | Price: $1,384.11
Total Value: $567,485.10
Shares Owned After: 152,134 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F15] 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 $1,381.79 to $1,386.22. 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.
[Transaction #15]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -50 | Price: $1,388.19
Total Value: $69,409.50
Shares Owned After: 152,084 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F16] 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 $1,388.18 to $1,388.22. 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.
[Transaction #16]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -213 | Price: $1,396.16
Total Value: $297,382.08
Shares Owned After: 151,871 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F17] 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 $1,393.94 to $1,398.92. 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.
[Transaction #17]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -117 | Price: $1,400.45
Total Value: $163,852.65
Shares Owned After: 151,754 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F18] 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 $1,398.97 to $1,400.85. 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.
[Transaction #18]
Security: Common Stock
Date: 2026-07-15 | Code: S (Open market sale)
Shares: -110 | Price: $1,405.71
Total Value: $154,628.10
Shares Owned After: 151,644 | Ownership: D (Direct)
Footnotes:
[F1] This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
[F19] 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 $1,404.25 to $1,406.04. 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.
--- Holdings ---
[Holding #1]
Security: Common Stock
Ownership: I (Indirect)
[Holding #2]
Security: Common Stock
Ownership: I (Indirect)
[Holding #3]
Security: Common Stock
Ownership: I (Indirect)
[Holding #4]
Security: Common Stock
Ownership: I (Indirect)
[Holding #5]
Security: Common Stock
Ownership: I (Indirect)
[Holding #6]
Security: Common Stock
Ownership: I (Indirect)
[Holding #7]
Security: Common Stock
Ownership: I (Indirect)
[Holding #8]
Security: Common Stock
Ownership: I (Indirect)
[Holding #9]
Security: Common Stock
Ownership: I (Indirect)
[Holding #10]
Security: Common Stock
Ownership: I (Indirect)
[Holding #11]
Security: Common Stock
Ownership: I (Indirect)
--- Footnotes (Complete Index) ---
F1: This transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 11/24/2025.
F10: 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 $1,352.13 to $1,357.03. 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.
F11: 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 $1,357.88 to $1,362.57. 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.
F12: 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 $1,366.15 to $1,371.04. 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.
F13: 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 $1,371.23 to $1,376.20. 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.
F14: 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 $1,376.51 to $1,381.11. 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.
F15: 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 $1,381.79 to $1,386.22. 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.
F16: 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 $1,388.18 to $1,388.22. 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.
F17: 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 $1,393.94 to $1,398.92. 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.
F18: 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 $1,398.97 to $1,400.85. 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.
F19: 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 $1,404.25 to $1,406.04. 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.
F2: 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 $1,311.45 to $1,316.40 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.
F3: 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 $1,316.56 to $1,321.56. 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.
F4: 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 $1,321.72 to $1,326.11. 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.
F5: 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 $1,326.94 to $1,331.90. 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.
F6: 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 $1,331.95 to $1,336.95. 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.
F7: 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 $1,336.97 to $1,341.96. 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.
F8: 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 $1,341.99 to $1,346.96. 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.
F9: 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 $1,347.09 to $1,352.00. 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.
--- Signature ---
/s/ /s/ Saria Tseng, attorney-in-fact for Mr. Maurice Sciammas (2026-07-17)
