Westpac Banking Corp reports 10.68% increase in ownership of MPWR / Monolithic Power Systems, Inc.

Monolithic Power Systems, Inc.

MX ˙ BMV ˙ US6098391054

Security	MX:MPWR / Monolithic Power Systems, Inc.
Institution	Westpac Banking Corp
Latest Disclosed Ownership	1,316 shares
Latest Disclosed Value	$ 1,438,848

On May 11, 2026 - Westpac Banking Corp filed a 13F-HR form disclosing ownership of 1,316 shares of Monolithic Power Systems, Inc. (MX:MPWR) valued at $1,438,848 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 10, 2026 disclosing 1,189 shares of Monolithic Power Systems, Inc.. This represents a change in shares of 10.68% 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	Reported Shares	ΔShares	ΔShares (%)	Reported Value (x1000)	ΔValue (%)	Alloc (%)
2026-05-11	2026-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	1,316	127	10.68	1,439	33.52	0.0501
2026-02-10	2025-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	1,189	740	164.81	1,078	160.77	0.0681
2025-11-14	2025-09-30	13F/A-1	MONOLITHIC POWER SYSTEMS INC USD 0.001	COM	609839105	449	0	0.00	413	25.91	0.0256
2025-11-12	2025-09-30	13F	MONOLITHIC POWER SYSTEMS INC USD 0.001	COM	609839105	449	0		413		0.0104
2025-08-11	2025-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	449	0	0.00	328	26.15	0.0220
2025-05-13	2025-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	449	0	0.00	260	-1.89	0.0192
2025-02-12	2024-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	449	449		266		0.0176
2023-08-10	2023-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	0	-3,474	-100.00	0	-100.00
2023-05-04	2023-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	3,474	0	0.00	1,739	41.53	0.0234
2023-02-06	2022-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	3,474	0	0.00	1,228	-2.69	0.0182
2022-11-08	2022-09-30	13F	MONOLITHIC PWR SYS	COM	609839105	3,474	0	0.00	1,262	-5.40	0.0192
2022-08-10	2022-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	3,474	0	0.00	1,334	-20.92	0.0174
2022-05-11	2022-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	3,474	-12,286	-77.96	1,687	-78.30	0.0194
2022-02-08	2021-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	15,760	-5,700	-26.56	7,775	-25.26	0.0805
2021-10-27	2021-09-30	13F	MONOLITHIC PWR SYS	COM	609839105	21,460	-1,612	-6.99	10,401	20.72	0.1112
2021-08-11	2021-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	23,072	1,328	6.11	8,616	12.19	0.0865
2021-05-13	2021-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	21,744	18,270	525.91	7,680	503.77	0.0847
2021-02-11	2020-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	3,474	3,474		1,272		0.0144
2020-05-14	2020-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	0	-49,556	-100.00	0	-100.00
2020-02-11	2019-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	49,556	6,200	14.30	8,822	30.74	0.1136
2019-11-13	2019-09-30	13F	MONOLITHIC PWR SYS	COM	609839105	43,356	-7,400	-14.58	6,747	-2.09	0.0938
2019-08-01	2019-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	50,756	8,800	20.97	6,892	21.24	0.1052
2019-05-14	2019-03-31	13F	MONOLITHIC PWR SYS	COM	609839105	41,956	-3,400	-7.50	5,685	7.81	0.0938
2019-02-07	2018-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	45,356	0	0.00	5,273	-7.40	0.0899
2018-11-13	2018-09-30	13F	MONOLITHIC PWR SYS	COM	609839105	45,356	3,200	7.59	5,694	1.05	0.0976
2018-07-18	2018-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	42,156	42,156		5,635		0.1083
2018-01-18	2017-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	0	-58,000	-100.00	0	-100.00
2017-10-30	2017-09-30	13F	MONOLITHIC PWR SYS	COM	609839105	58,000	-1,000	-1.69	6,180	8.65	0.1361
2017-08-09	2017-06-30	13F	MONOLITHIC PWR SYS	COM	609839105	59,000	-15,000	-20.27	5,688	-16.55	0.1252
2017-05-18	2017-03-31	13F/A-1	MONOLITHIC PWR SYS	COM	609839105	74,000	-2,500	-3.27	6,815	0.86	0.0546
2017-02-09	2016-12-31	13F	MONOLITHIC PWR SYS	COM	609839105	76,500	-10,600	-12.17	6,757	-3.62	0.0637
2016-11-10	2016-09-30	13F	MONOLITHIC PWR SYS	COM	609839105	87,100	87,100		7,012		0.0757

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.