Monolithic Power Systems, Inc. v. Reed Semiconductor Corp.

This case, IPR2026-00165, involves a patent validity challenge brought before the Patent Trial and Appeal Board (PTAB) of the USPTO by Monolithic Power Systems, Inc. against a patent owned by Reed Semiconductor Corp. Monolithic Power Systems, Inc. (MPS) is an American publicly traded fabless semiconductor company that designs, develops, and markets high-performance power electronics solutions for various applications, including cloud computing, automotive, and consumer electronics. Reed Semiconductor Corp. is an emerging global fabless semiconductor company founded in 2019, specializing in high-performance power management integrated circuits for AI, high-performance computing, automotive, and industrial markets. Both entities are operating companies actively competing in the semiconductor industry.

The patent at issue is U.S. Patent 7,960,955 (the "'955 patent"), titled "Power Supply Device, Electronic Device Using the Same, and Semiconductor Device." This patent describes a power supply apparatus that incorporates a linear regulator to stabilize an input voltage. Specifically, it focuses on an architecture where a linear regulator generates a stable, "clean" voltage from a noisy input, which then powers the control circuit of a switching power supply and its reference voltage source. This design aims to isolate sensitive control circuitry from electrical noise, ensuring stable operation of power converters in various electronic devices. The '955 patent is being asserted by Reed Semiconductor in an underlying patent infringement lawsuit against Monolithic Power Systems in the U.S. District Court for the Western District of Texas (Case No. 6:25-cv-00449), where multiple MPS product families are alleged to infringe.

The procedural posture of this specific case is an Inter Partes Review (IPR) before the Patent Trial and Appeal Board, where Monolithic Power Systems sought to invalidate the '955 patent. On April 14, 2026, the PTAB denied the validity challenge, meaning the Board upheld the patentability of the challenged claims of US Patent 7,960,955. This venue, the PTAB, is significant as it provides an administrative forum for challenging patent validity, often in parallel with district court litigation. The PTAB's decision to deny institution strengthens Reed Semiconductor's position in the ongoing infringement lawsuit in the Western District of Texas, as it maintains the presumed validity of the '955 patent against the prior art arguments raised by MPS. This case is notable as part of broader intellectual property litigation between these two semiconductor companies, highlighting intense competition in the power management solutions market, particularly for technologies crucial to AI and data centers. The legal skirmishes also include Reed Semiconductor's earlier success in invalidating a Monolithic Power Systems patent (U.S. Patent No. 9,041,377 B2) in a separate IPR (IPR2024-01158) in January 2026, indicating a reciprocal pattern of patent challenges.

Key Legal Developments and Outcome in Reed Semiconductor Corp. v. Monolithic Power Systems, Inc. (W.D. Tex. Case No. 6:25-cv-00449)

This analysis outlines the key legal developments, in chronological order, for the patent infringement litigation initiated by Reed Semiconductor Corp. against Monolithic Power Systems, Inc. concerning U.S. Patent 7,960,955. This case is currently pending in the U.S. District Court for the Western District of Texas. Parallel to this, an Inter Partes Review (IPR) was filed by Monolithic Power Systems, Inc. challenging the same patent.

Related Litigation Background

Before Reed Semiconductor filed its suit in Texas, Monolithic Power Systems, Inc. had initiated its own patent infringement lawsuits against Reed Semiconductor Corp. in the U.S. District Court for the District of Delaware. These cases include:

• 2023-10-13: Monolithic Power Systems, Inc. filed a patent infringement lawsuit against Reed Semiconductor Corp. in the District of Delaware, Case No. 1:2023cv01155, asserting its own patents.
• 2023-12-11: Reed Semiconductor Corp. filed an Answer, Jury Demand, and Counterclaims in the Delaware case (1:2023cv01155).
• 2024-02-08: Monolithic Power Systems, Inc. filed another patent infringement lawsuit against Reed Semiconductor Corp. in the District of Delaware, Case No. 1:24-cv-00165.

Key Legal Developments for U.S. Patent 7,960,955

The primary litigation concerning U.S. Patent 7,960,955 is as follows:

• 2025-09-30: Reed Semiconductor Corp. filed a patent infringement lawsuit against Monolithic Power Systems, Inc. in the U.S. District Court for the Western District of Texas, Waco Division, Case No. 6:25-cv-00449. The lawsuit alleges infringement of U.S. Patent No. 7,960,955, which covers power semiconductor devices incorporating a linear regulator for stabilizing input voltage. The complaint also included allegations of bad-faith interference with business relationships and contractual agreements by Monolithic Power Systems. Reed Semiconductor is represented by Morgan Lewis LLP.
• 2025-10-06: Public announcements by Reed Semiconductor Corp. confirmed the filing of the Western District of Texas lawsuit.
• 2025-12-01: Monolithic Power Systems, Inc. initiated an Inter Partes Review (IPR2026-00165) at the Patent Trial and Appeal Board (PTAB) of the USPTO, challenging the validity of U.S. Patent 7,960,955.
• 2025-12-08: In the WDTX litigation (6:25-cv-00449), Reed Semiconductor served its preliminary infringement contentions, specifically asserting claims 1, 2, 7, 8, and 9 of the '955 patent.
• 2025-12-15: A Case Management Conference was deemed to have occurred in the WDTX case for scheduling purposes.
• 2025-12-29: The parties were scheduled to file a motion for an agreed Scheduling Order in the WDTX case.
• 22026-02-05: Monolithic Power Systems, Inc. served its preliminary invalidity contentions for the '955 patent in the WDTX case. These contentions included allegations of lack of written description and enablement under 35 U.S.C. § 112 ¶ 1.
• 2026-02-26: The parties in the WDTX case exchanged lists of claim terms for construction.
• 2026-03-03: Reed Semiconductor's response to a motion to dismiss filed by Monolithic Power Systems (alleging improper venue, lack of personal jurisdiction, and lack of subject-matter jurisdiction) was due in the WDTX case.
• 2026-03-11: A Daubert Hearing took place in the related Delaware cases (1:23-cv-01155, 1:24-cv-00165) before Judge John F. Murphy.
• 2026-03-12: The parties in the WDTX case exchanged proposed claim constructions.
• 2026-03-19: The parties in the WDTX case disclosed extrinsic evidence relevant to claim construction.
• 2026-03-26: The deadline for the parties to meet and confer to narrow disputed claim terms and exchange revised lists of terms and constructions.
• 2026-04-02: Monolithic Power Systems, Inc. was scheduled to file its opening claim construction brief in the WDTX case.
• 2026-04-14: The PTAB denied Monolithic Power Systems, Inc.'s validity challenge in IPR2026-00165, upholding the validity of U.S. Patent 7,960,955.
• 2026-04-17: Reed Semiconductor Corp. announced the PTAB's decision to uphold the '955 patent.
• 2026-04-23: Reed Semiconductor was scheduled to file its responsive claim construction brief in the WDTX case.
• 2026-05-07: Monolithic Power Systems, Inc. was scheduled to file its reply claim construction brief in the WDTX case. On this date, the parties were also to contact law clerks to confirm the Markman date and the status of any unresolved venue or jurisdictional motions.
• 2026-05-21: Reed Semiconductor was scheduled to file its sur-reply claim construction brief in the WDTX case.

Current Posture and Upcoming Milestones

As of the current date (2026-05-29), the Western District of Texas litigation (6:25-cv-00449) is in the claim construction phase.

• 2026-06-11: A Markman hearing (claim construction hearing) is tentatively scheduled for 9:00 a.m. in the WDTX case, though this date may be adjusted.
• 2026-06-12: Fact discovery is set to open in the WDTX case, with the deadline to serve Initial Disclosures under Rule 26(a).
• 2026-08-06: The deadline for the parties to serve final infringement and invalidity contentions in the WDTX case.

The denial of the IPR by the PTAB (IPR2026-00165) means that Monolithic Power Systems' challenge to the validity of U.S. Patent 7,960,955 was unsuccessful, strengthening Reed Semiconductor's position regarding the patent's enforceability in the district court litigation. The status of Monolithic Power Systems' motion to dismiss for venue and jurisdiction in the WDTX case is not yet publicly disclosed as resolved.

Separately, the Delaware cases (1:23-cv-01155, 1:24-cv-00165) have a Case Management Conference scheduled for 2026-10-21 and a Jury Trial scheduled for 2026-11-02.

Monolithic Power Systems, Inc. was represented by counsel from several law firms in IPR2026-00165. The available public records, particularly those referencing related district court cases and the IPR petition itself, indicate the involvement of the following attorneys:

• J. Day, Esq.

  • Role: Likely lead counsel or significant counsel.
  • Firm: Not explicitly stated for the IPR, but mentioned as plaintiff's counsel for Monolithic Power Systems in related District of Delaware case 1:24-cv-00165.
  • Relevant Experience: Patent litigation, as evidenced by appearance in related patent infringement proceedings.

• John P. Schnurer, Esq.

  • Role: Likely lead counsel or significant counsel.
  • Firm: Not explicitly stated for the IPR, but an attorney for Monolithic Power Systems, Inc. in related District of Delaware cases (e.g., pro hac vice admission in 1:2025cv00536 on October 17, 2025).
  • Relevant Experience: Patent litigation.

• M. Manookin, Esq.

  • Role: Counsel.
  • Firm: Not explicitly stated for the IPR, but mentioned as plaintiff's counsel for Monolithic Power Systems in related District of Delaware case 1:24-cv-00165.
  • Relevant Experience: Patent litigation.

• M. Bomback, Esq.

  • Role: Counsel.
  • Firm: Not explicitly stated for the IPR, but mentioned as plaintiff's counsel for Monolithic Power Systems in related District of Delaware case 1:24-cv-00165.
  • Relevant Experience: Patent litigation.

• K. Patariu, Esq.

  • Role: Counsel.
  • Firm: Not explicitly stated for the IPR, but mentioned as plaintiff's counsel for Monolithic Power Systems in related District of Delaware case 1:24-cv-00165.
  • Relevant Experience: Patent litigation.

While these attorneys are identified in related district court patent litigation involving Monolithic Power Systems and Reed Semiconductor, direct PTAB docket entries for IPR2026-00165 explicitly naming all counsel of record for Monolithic Power Systems were not readily available without a specialized subscription service for PTAB dockets. However, it is common for attorneys representing a party in related district court infringement actions to also represent that party in parallel IPR proceedings. Monolithic Power Systems initiated IPR2026-00165 as the Petitioner to challenge the validity of Reed Semiconductor's US Patent 7960955. The PTAB denied the validity challenge on April 14, 2026.

Reed Semiconductor Corp. was represented by counsel from Morgan, Lewis & Bockius LLP. Based on the available information, the primary identified attorney is:

Rick L. Rambo

• Role: Partner (Lead Counsel is a reasonable inference given his experience and the email for service, though not explicitly stated as "lead counsel" in search results for this specific IPR).
• Firm: Morgan, Lewis & Bockius LLP, Houston, Texas.
• Relevant Patent Litigation Experience: Rick L. Rambo regularly represents clients in complex patent infringement disputes and other intellectual property disputes for technology, energy, and e-commerce sector clients, litigating in US federal and state courts, the International Trade Commission, and before international arbitration panels.

While Morgan, Lewis & Bockius LLP is known for its extensive intellectual property practice and involvement in numerous PTAB proceedings, specific additional attorneys directly named as counsel of record for Reed Semiconductor Corp. in IPR2026-00165 beyond Rick L. Rambo were not explicitly identified in the available search results. The firm's general representation in PTAB matters for Reed Semiconductor Corp. has been noted.