Monolithic Power Systems, Inc.
MX ˙ BMV ˙ US6098391054
SecurityMX:MPWR / Monolithic Power Systems, Inc.
InstitutionRobeco Schweiz AG
Latest Disclosed Ownership94,993 shares
Latest Disclosed Value $ 103,860,596
Robeco Schweiz AG reports 0.03% decrease in ownership of MPWR / Monolithic Power Systems, Inc.

On May 7, 2026 - Robeco Schweiz AG filed a 13F-HR form disclosing ownership of 94,993 shares of Monolithic Power Systems, Inc. (MX:MPWR) valued at $103,860,596 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 3, 2026 disclosing 95,018 shares of Monolithic Power Systems, Inc.. This represents a change in shares of -0.03% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-07 2026-03-31 13F MONOLITHIC PWR SYS COM 609839105 94,993 -25 -0.03 103,861 20.60 2.1965
2026-02-03 2025-12-31 13F MONOLITHIC PWR SYS COM 609839105 95,018 -8,219 -7.96 86,121 -9.39 1.9296
2025-10-27 2025-09-30 13F MONOLITHIC PWR SYS COM 609839105 103,237 -3,506 -3.28 95,044 21.74 2.1367
2025-08-07 2025-06-30 13F MONOLITHIC PWR SYS COM 609839105 106,743 -9,303 -8.02 78,070 15.99 1.8017
2025-04-30 2025-03-31 13F MONOLITHIC PWR SYS COM 609839105 116,046 5,819 5.28 67,304 3.19 1.6558
2025-02-05 2024-12-31 13F MONOLITHIC PWR SYS COM 609839105 110,227 -29,590 -21.16 65,221 -49.54 1.3936
2024-11-04 2024-09-30 13F MONOLITHIC PWR SYS COM 609839105 139,817 -2,430 -1.71 129,261 10.59 2.4218
2024-08-08 2024-06-30 13F MONOLITHIC PWR SYS COM 609839105 142,247 -83,670 -37.04 116,882 -23.63 2.2446
2024-04-25 2024-03-31 13F MONOLITHIC PWR SYS COM 609839105 225,917 -24,455 -9.77 153,041 -3.10 2.6707
2024-02-14 2023-12-31 13F MONOLITHIC PWR SYS COM 609839105 250,372 6,162 2.52 157,930 39.98 2.6531
2023-11-08 2023-09-30 13F MONOLITHIC PWR SYS COM 609839105 244,210 -4,600 -1.85 112,825 -16.06 1.9073
2023-08-14 2023-06-30 13F MONOLITHIC PWR SYS COM 609839105 248,810 10,160 4.26 134,415 12.52 2.0022
2023-05-08 2023-03-31 13F MONOLITHIC PWR SYS COM 609839105 238,650 -2,730 -1.13 119,454 39.95 1.9302
2023-02-07 2022-12-31 13F MONOLITHIC PWR SYS COM 609839105 241,380 -100 -0.04 85,354 -2.73 1.5591
2022-11-10 2022-09-30 13F MONOLITHIC PWR SYS COM 609839105 241,480 6,055 2.57 87,754 -2.94 1.7064
2022-08-03 2022-06-30 13F MONOLITHIC PWR SYS COM 609839105 235,425 0 0.00 90,413 -20.93 1.6123
2022-05-13 2022-03-31 13F MONOLITHIC PWR SYS COM 609839105 235,425 82,725 54.17 114,341 51.78 1.6111
2022-02-08 2021-12-31 13F MONOLITHIC PWR SYS COM 609839105 152,700 -8,206 -5.10 75,331 -3.41 0.9764
2021-10-13 2021-09-30 13F MONOLITHIC PWR SYS COM 609839105 160,906 -105,071 -39.50 77,988 -21.49 0.9096
2021-07-15 2021-06-30 13F MONOLITHIC PWR SYS COM 609839105 265,977 -25,562 -8.77 99,329 -3.54 1.3837
2021-05-04 2021-03-31 13F MONOLITHIC PWR SYS COM 609839105 291,539 90,539 45.04 102,974 39.89 1.5732
2021-02-16 2020-12-31 13F MONOLITHIC PWR SYS COM 609839105 201,000 -500 -0.25 73,612 30.65 1.5775
2020-10-13 2020-09-30 13F MONOLITHIC PWR SYS COM 609839105 201,500 -109,500 -35.21 56,341 -23.56 1.6690
2020-07-07 2020-06-30 13F MONOLITHIC PWR SYS COM 609839105 311,000 16,000 5.42 73,707 51.25 2.6467
2020-04-10 2020-03-31 13F MONOLITHIC PWR SYS COM 609839105 295,000 74,000 33.48 48,731 23.61 2.0872
2020-02-19 2019-12-31 13F/A-1 MONOLITHIC PWR SYS COM 609839105 221,000 89,000 67.42 39,424 90.69 1.4698
2020-02-13 2019-12-31 13F MONOLITHIC PWR SYS COM 609839105 221,000 89,000 178 1,022,342.1975
2019-10-18 2019-09-30 13F MONOLITHIC PWR SYS COM 609839105 132,000 -31,000 -19.02 20,674 -4.51 0.8878
2019-07-31 2019-06-30 13F MONOLITHIC PWR SYS COM 609839105 163,000 -131,000 -44.56 21,650 -45.65 0.9180
2019-05-14 2019-03-31 13F MONOLITHIC PWR SYS COM 609839105 294,000 -373,000 -55.92 39,834 -48.07 1.6476
2019-02-01 2018-12-31 13F MONOLITHIC PWR SYS COM 609839105 667,000 18,000 2.77 76,705 -6.43 3.5475
2018-10-30 2018-09-30 13F MONOLITHIC PWR SYS COM 609839105 649,000 49,000 8.17 81,975 1.53 3.1985
2018-08-09 2018-06-30 13F MONOLITHIC PWR SYS COM 609839105 600,000 40,000 7.14 80,742 24.54 3.4422
2018-05-16 2018-03-31 13F MONOLITHIC PWR SYS COM 609839105 560,000 460,000 460.00 64,831 472.16 3.0033
2018-02-14 2017-12-31 13F MONOLITHIC PWR SYS COM 609839105 100,000 0 0.00 11,331 6.46 0.7481
2017-11-09 2017-09-30 13F MONOLITHIC PWR SYS COM 609839105 100,000 10,000 11.11 10,643 21.76 0.8206
2017-08-15 2017-06-30 13F MONOLITHIC PWR SYS COM 609839105 90,000 -35,000 -28.00 8,741 -23.93 0.7331
2017-05-10 2017-03-31 13F MONOLITHIC PWR SYS COM 609839105 125,000 50,000 66.67 11,491 84.09 0.9798
2017-01-10 2016-12-31 13F/A-1 MONOLITHIC PWR SYS COM 609839105 75,000 -37,500 -33.33 6,242 -29.72 0.5742
2017-01-09 2016-12-31 13F MONOLITHIC PWR SYS COM 609839105 75,000 6,242
2016-11-15 2016-09-30 13F MONOLITHIC PWR SYS COM 609839105 112,500 -7,500 -6.25 8,882 10.61 0.7704
2016-08-12 2016-06-30 13F MONOLITHIC PWR SYS COM 609839105 120,000 28,000 30.43 8,030 39.53 0.7360
2016-05-18 2016-03-31 13F MONOLITHIC PWR SYS COM 609839105 92,000 -111,500 -54.79 5,755 -56.35 0.5525
2016-02-16 2015-12-31 13F MONOLITHIC PWR SYS COM 609839105 203,500 -60,500 -22.92 13,183 0.80 1.1293
2015-10-27 2015-09-30 13F MONOLITHIC PWR SYS COM 609839105 264,000 83,200 46.02 13,079 42.40 1.2203
2015-08-24 2015-06-30 13F MONOLITHIC PWR SYS COM 609839105 180,800 85,800 90.32 9,185 81.27 0.7618
2015-04-20 2015-03-31 13F MONOLITHIC PWR SYS COM 609839105 95,000 95,000 0.00 5,067 0.3978
2015-01-26 2014-12-31 13F MONOLITHIC PWR SYS COM 609839105 0 -108,000 -100.00 0 -100.00
2014-10-22 2014-09-30 13F MONOLITHIC PWR SYS COM 609839105 108,000 -64,000 -37.21 4,818 -33.51 0.3849
2014-08-08 2014-06-30 13F MONOLITHIC PWR SYS COM 609839105 172,000 71,500 71.14 7,246 94.21 0.5905
2014-05-05 2014-03-31 13F MONOLITHIC PWR SYS COM 609839105 100,500 -10,500 -9.46 3,731 -1.58 0.3236
2014-01-22 2013-12-31 13F MONOLITHIC PWR SYS COM 609839105 111,000 111,000 3,791 0.3352
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.