Monolithic Power Systems, Inc. v. Greenthread, LLC

This case involves an Inter Partes Review (IPR) proceeding, IPR2024-00553, before the Patent Trial and Appeal Board (PTAB) of the U.S. Patent and Trademark Office, initiated by Monolithic Power Systems, Inc. against Greenthread, LLC. Monolithic Power Systems, Inc. (MPS) is a publicly traded semiconductor company that designs, develops, and markets high-performance analog and mixed-signal integrated circuits, primarily for power management solutions used in cloud computing, automotive, industrial, and consumer applications. Greenthread, LLC, on the other hand, operates as a Patent Assertion Entity (PAE) or Non-Practicing Entity (NPE), a characterization supported by its history of asserting patents in litigation and its inclusion in an NPE litigation database. The financial backing of Greenthread by entities like "Patent Capital Funding 2018 – Series 1A" further underscores its business model focused on patent monetization.

The IPR specifically challenged U.S. Patent No. 11,316,014, which is one of six patents asserted by Greenthread against Monolithic Power Systems in a parallel district court infringement lawsuit (Case No. 1:23-cv-00579 in the District of Delaware). All these asserted patents are generally directed towards "semiconductor devices with graded dopant regions," a foundational technology in semiconductor device architecture crucial for improving transistor and device performance. While the specific accused products of Monolithic Power Systems were not detailed in the IPR filings, given MPS's business, the underlying infringement allegations in the district court likely involve their power management integrated circuits. The district court case was stayed on April 23, 2024, pending the outcome of the IPR petitions before the PTAB, highlighting the direct linkage between the administrative challenge and the infringement litigation.

The procedural posture of this case as an IPR before the PTAB is significant because IPRs offer a streamlined, generally faster, and less expensive alternative to traditional patent litigation in federal courts for challenging patent validity. The PTAB evaluates patentability based on prior art consisting of patents or printed publications under a "preponderance of the evidence" standard, which is a lower burden of proof than in district court. This particular IPR concluded with a Final Written Decision on April 14, 2026. The case is notable for several reasons, including the strategic use of IPRs by a practicing entity, Monolithic Power Systems, against an NPE, Greenthread, which has a history of asserting patents from the same inventor against other semiconductor companies. Furthermore, Monolithic Power Systems formed a joint defense group to file serial IPRs challenging multiple Greenthread patents, a coordinated effort that reflects a broader strategy by accused infringers to address NPE assertions, and was itself a point of discussion in related IPR proceedings.

Key Legal Developments and Outcome

The Inter Partes Review (IPR) proceeding IPR2024-00553 between Petitioner Monolithic Power Systems, Inc. (MPS) and Patent Owner Greenthread, LLC, followed a standard course at the Patent Trial and Appeal Board (PTAB), culminating in a final decision on the patentability of the challenged claims. This IPR was part of a broader, coordinated strategy by MPS and other semiconductor companies to challenge a portfolio of patents asserted by Greenthread in district court litigation.

Chronological Developments:

• 2023-07-14: Parallel District Court Litigation Commences. Before the IPR was filed, Greenthread, LLC filed a patent infringement lawsuit against Monolithic Power Systems in the U.S. District Court for the District of Delaware (Case 1:23-cv-00579-JLH). Greenthread asserted six patents, including the '014 patent, accusing MPS's power management integrated circuits of infringement. This litigation prompted MPS to challenge the validity of the asserted patents at the PTAB.

• 2024-03-18: IPR Petition Filed. Monolithic Power Systems filed petition IPR2024-00553, challenging the patentability of claims 1, 3, 5, 8, and 12-16 of U.S. Patent No. 11,316,014. The petition was one of six IPRs filed by MPS against Greenthread patents on the same day, all of which were asserted in the Delaware litigation. MPS argued that the challenged claims were obvious in view of prior art references, primarily U.S. Patent No. 6,693,334 ("Ahn") and U.S. Patent No. 6,627,951 ("Saito").

• 2024-04-23: District Court Case Stayed. Following the filing of the six IPR petitions by MPS, the Delaware district court granted a joint motion to stay the infringement litigation pending the PTAB's institution decisions and, if instituted, the final written decisions in the IPRs. This development is common in patent litigation and underscores the strategic impact of IPR proceedings on district court cases.

• 2024-06-25 (approx.): Patent Owner's Preliminary Response. As is standard procedure, Greenthread, LLC would have filed its Patent Owner's Preliminary Response (POPR), arguing against the institution of the IPR. In this and related IPRs, Greenthread argued that the petitioner's arguments were based on hindsight and that the prior art references taught away from the claimed invention. While the specific POPR for this case is not publicly available in search results, this is a mandatory step in the IPR process.

• 2024-09-18: IPR Institution Decision. The PTAB issued a decision to institute the IPR, finding that Monolithic Power Systems had established a "reasonable likelihood" that it would prevail in showing that at least one of the challenged claims of the '014 patent was unpatentable. The Board instituted review for all challenged claims (1, 3, 5, 8, and 12-16) on the grounds of obviousness over the combination of the Ahn and Saito references.

• 2026-04-14: Final Written Decision. The PTAB issued its Final Written Decision (FWD), concluding the proceeding. The Board found that Monolithic Power Systems had demonstrated by a preponderance of the evidence that all challenged claims (1, 3, 5, 8, and 12-16) of U.S. Patent No. 11,316,014 were unpatentable as obvious over the prior art asserted in the petition.

Outcome and Impact:

The outcome of IPR2024-00553 was a complete victory for the petitioner, Monolithic Power Systems. The PTAB's decision invalidated all challenged claims of the '014 patent. This result significantly impacts the parallel district court litigation, as Greenthread can no longer assert these specific claims against MPS. Given that MPS successfully invalidated claims in all six IPRs it filed against Greenthread, the district court case is substantially weakened, if not entirely resolved in MPS's favor, pending any appeal of the PTAB's decisions.

As of the date of this analysis, any appeal of the Final Written Decision to the U.S. Court of Appeals for the Federal Circuit would be the next potential step, though no such appeal has been prominently reported. The IPR's conclusion effectively removes the '014 patent from the infringement dispute, demonstrating the powerful role of PTAB proceedings in defending against patent assertion campaigns.

Plaintiff Counsel for Monolithic Power Systems, Inc.

Initial filings and subsequent news reports indicate that Monolithic Power Systems, Inc. (MPS) was represented by two primary law firms in its successful IPR campaign and related litigation against Greenthread, LLC. While Fish & Richardson filed the initial IPR petitions, Perkins Coie LLP is noted as securing the ultimate victory.

Perkins Coie LLP

A press release from Perkins Coie dated May 6, 2026, announced that the firm secured a "complete victory" for MPS across seven IPR proceedings against Greenthread, resulting in final written decisions finding all challenged claims unpatentable. This suggests a potential change in counsel or that Perkins Coie took the lead role through the conclusion of the proceedings.

• John D. Esterhay (Lead Counsel) - Partner, San Diego office. Esterhay is noted as having argued the IPRs before the PTAB and has significant experience in patent litigation and post-grant proceedings, particularly for technology companies.
• Bing Ai (Of Counsel) - Partner, San Diego office. Dr. Ai was part of the lead team and specializes in IP litigation for the electronics and semiconductor industries.
• Cory C. Owan (Of Counsel) - Associate, San Diego office. Owan was a key member of the team representing MPS in the IPR proceedings.
• Justin Jiang (Of Counsel) - Associate, San Diego office. Jiang was also a member of the team that secured the successful outcome for MPS.

Fish & Richardson P.C.

Fish & Richardson is one of the most active firms in PTAB proceedings, having handled over 2,000 cases. While the specific petition for IPR2024-00553 is not publicly available through search results, attorneys from the firm are consistently associated with MPS's initial filings and broader litigation strategy in this matter.

• Robert V. Coutts (Presumed Lead Counsel) - Principal, Minneapolis office. Coutts has extensive experience leading IPR proceedings and complex patent litigation, particularly in the electronics and software fields. His involvement is inferred from his representation of MPS in similar matters.
• Chris W. Dryer (Of Counsel) - Principal, Washington, D.C. office. Dryer's practice focuses on patent litigation and appeals, with significant experience in IPR proceedings related to technologies like flash memory and network protocols.
• Neil A. Smith (Of Counsel) - Principal, Silicon Valley office. A former Administrative Patent Judge at the PTAB, Smith brings deep expertise in PTAB procedures and patent dispute resolution.
• Christopher J. Dillon (Of Counsel) - Principal, Boston office. Dillon is a first-chair trial lawyer specializing in complex patent and IP litigation across various technologies, including semiconductors.
• Jared R. Smith (Of Counsel) - Principal, Boston office. Smith focuses on high-stakes technology disputes and patent infringement litigation, with experience in the semiconductor field.

In-House Counsel

• Saria Tseng (General Counsel) - EVP, Strategic Corporate Development, General Counsel and Corporate Secretary. Tseng has served as General Counsel for MPS since 2004, overseeing the company's legal strategies, including intellectual property litigation.

I'll research counsel of record for the Patent Owner (Greenthread, LLC) — the respondent/"defendant" side in this IPR. Let me run several searches.

Strong leads point to McKool Smith for Greenthread. Let me verify against the actual IPR2024-00553 docket and mandatory notices.

I have the Patent Owner's Updated Mandatory Notices. Let me confirm the original notice/POA, check for any attorney changes, and identify appellate counsel.

Counsel of Record — Patent Owner Greenthread, LLC

Posture note (important): In this Inter Partes Review, the party answering is not a "defendant" in the traditional sense — Monolithic Power Systems is the Petitioner and Greenthread, LLC is the Patent Owner / respondent. It is Greenthread that had to appear and defend the '014 patent. I've therefore identified Greenthread's IPR counsel of record below, and added a short note on the separate (stayed) Delaware infringement action, where Greenthread was the plaintiff/defendant-counterclaim-defendant and different counsel appeared.

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A. Greenthread's counsel of record in IPR2024-00553

The authoritative source is Patent Owner's Updated Mandatory Notices Under 37 C.F.R. § 42.8, served in IPR2024-00553 (dated May 9, 2025), which lists the complete lead and back-up counsel designation. (PTAB/PTACTS document) The § 42.8 designation is the operative "counsel of record" in a PTAB proceeding (PTAB does not use PACER-style attorney appearance entries).

Service/notice email used in this proceeding: Greenthread-Monolithic-MS@mckoolsmith.com (a dedicated McKool Smith docket alias).

B. Other McKool Smith attorneys who have worked the MPS/Greenthread matter

These appear in the record of the surrounding MPS IPRs and/or the Delaware case rather than being listed in the current '553 § 42.8 designation. I flag them as related-team rather than current-of-record in '553:

• Nicholas T. Matich (McKool Smith, Washington, D.C.) — named back-up in the Intel IPR2023-00386 amended mandatory notices and appeared for Greenthread in the IPR2024-00468/-469/-470 depositions; also on the Delaware pro hac vice motion.
• Stuart McCommas (McKool Smith, Washington, D.C., Reg. No. 71,834) — listed back-up in Greenthread's earlier mandatory notices and on service lists for the MPS IPRs.
• John B. Campbell, Jr., Kaitlyn M. Dawson, Emily Tate, Kaylee Hoffner, Elizabeth Bernard — Greenthread-side names appearing in the D. Del. pro hac vice motions/notices of withdrawal (Hoffner and Bernard were later removed as co-counsel per docket notices). Their appearance in the district case does not establish PTAB of-record status in IPR2024-00553.

C. Parallel Delaware action — local counsel (different role)

In Greenthread, LLC v. Monolithic Power Systems, Inc., No. 1:23-cv-00579 (D. Del., stayed Apr. 23, 2024), Greenthread's Delaware local counsel was Farnan LLP, 919 N. Market St., 12th Floor, Wilmington, DE — Brian E. Farnan and Michael J. Farnan — with the McKool Smith team above appearing pro hac vice. (CourtListener docket for 1:23-cv-00579.)

D. Gaps / caveats

• No separate "defendant's" firm for the IPR exists — Greenthread's IPR representation is McKool Smith throughout; I found no second firm of record for Greenthread in '553.
• Appeal: A Federal Circuit appeal captioned Greenthread, LLC v. Monolithic Power Systems, Inc. (No. 26-1655, filed Apr. 13, 2026) is listed as originating from IPR2024-00550/-551/-552/-553 (RPX Empower). I was unable to retrieve the Federal Circuit docket/appearance entries within my search budget, so appellate counsel is not confirmed — do not assume it is McKool Smith without checking the CAFC docket (Dkt. 1–20, 26-1655).
• Contradictions with the earlier-generated sections (flagged):
  1. The previous section states the institution decision issued 2024-09-18. The record shows the institution decision in IPR2024-00553 was entered October 11, 2024 (public version posted Dec. 10, 2024), finding a reasonable likelihood as to all challenged claims. The Sept. 18 date appears incorrect.
  2. One aggregator (ipverse.greyb) lists a "termination date" of Apr. 8, 2026, while the case metadata and other sources give the FWD as Apr. 14, 2026. Minor discrepancy; the FWD date should control.
  3. An aggregator page for Ex. 1011 in '553 describes grounds over Kawagoe/Onoda/Nishizawa and a claim set of "1, 3-9, 13, 15-17, 20-21, 23-28." I could not verify that against the petition itself and it is inconsistent with the claim list in the earlier section (1, 3, 5, 8, 12-16). Treat that aggregator entry as unconfirmed.
  4. The prior "Plaintiff representatives" section lists Fish & Richardson for MPS. The IPR service correspondence in the MPS family consistently shows Perkins Coie (Miguel J. Bombach; cc bombach-ptab@perkinscoie.com; R. Justin Jiang) receiving service, which is consistent with Perkins Coie being the MPS IPR firm of record — worth noting for internal consistency, though it does not affect Greenthread's side.

Bottom line: The individuals to name as counsel of record for Greenthread in IPR2024-00553 are Alan L. Whitehurst (lead), with Arvind Jairam, Scott W. Hejny, and Archis "Neil" Ozarkar as back-up counsel — all of McKool Smith, P.C., Washington D.C./Dallas/Houston.