Greenthread, LLC v. STMicroelectronics, Inc.

This patent infringement case is a component of a broad litigation campaign initiated by patent assertion entity (PAE) Greenthread, LLC against numerous major players in the semiconductor industry. The plaintiff, Greenthread, is a Texas-based LLC that holds and asserts patents originally from inventor G.R. Mohan Rao, one of the company's directors. The defendant, STMicroelectronics, Inc., is the U.S. arm of a global semiconductor company that manufactures a wide variety of microelectronic products, including microcontrollers, sensors, power management components, and analog ICs for the automotive, industrial, and consumer electronics markets. The lawsuit accuses STMicroelectronics of infringing U.S. Patent No. 11,121,222, which generally describes a semiconductor device incorporating graded dopant regions to improve performance. Greenthread alleges that a wide range of STMicroelectronics' semiconductor products, which are foundational to modern electronics, incorporate this patented technology.

The case is filed in the U.S. District Court for the Eastern District of Texas (EDTX), a venue historically known for its high concentration of patent litigation, particularly suits brought by NPEs. Despite changes in venue law over the past decade, the EDTX remains a top district for patent and NPE filings, making it a strategic choice for plaintiffs like Greenthread. The broader litigation campaign by Greenthread has also seen lawsuits filed in other popular patent venues like the District of Delaware and the Western District of Texas against companies such as Texas Instruments, Intel, Cirrus Logic, and ON Semiconductor (onsemi).

The case against STMicroelectronics is notable primarily due to its connection with this multi-front assertion campaign targeting the core technology of the semiconductor industry. Furthermore, the asserted patent family has been subject to validity challenges at the Patent Trial and Appeal Board (PTAB). In a related case, litigation against ON Semiconductor was stayed pending the outcome of inter partes review (IPR) proceedings for the '222 patent and another related patent. Those PTAB proceedings led to a significant decision by the USPTO Director regarding the standards for determining whether different defendants (in that case, onsemi and Intel) are in privity for the purpose of the one-year time bar for filing an IPR. This highlights a common defense strategy where accused infringers use PTAB reviews to challenge patent validity and pause costly district court litigation.

Following the initial filing, the litigation between Greenthread, LLC and STMicroelectronics, Inc. has seen several key developments, primarily centered around procedural motions and the impact of parallel administrative challenges to the patent's validity at the U.S. Patent and Trademark Office (USPTO).

Key Legal Developments & Chronology

• Complaint Filed (2023-04-18): Greenthread, LLC filed its patent infringement complaint against STMicroelectronics, Inc. in the Eastern District of Texas, alleging infringement of U.S. Patent No. 11,121,222. The complaint accused a broad range of STMicroelectronics' semiconductor products, including microcontrollers (MCUs), sensors, and power management ICs. (Case No. 2:23-cv-00157, Dkt. 1).

• Defendant's Answer and Counterclaims (2023-07-28): STMicroelectronics filed its answer, denying infringement and asserting counterclaims for non-infringement and invalidity of the '222 patent. This is a standard defensive pleading in patent litigation, putting the patent's validity and the infringement allegations at issue. (Case No. 2:23-cv-00157, Dkt. 15).

• Motion to Stay Pending Inter Partes Review (IPR) (2023-09-22): STMicroelectronics filed a motion to stay the district court case pending the outcome of IPR proceedings before the Patent Trial and Appeal Board (PTAB). This is a common strategy for defendants, as a successful IPR can invalidate the asserted patent claims, thereby ending the district court litigation in a cost-effective manner. The motion referenced IPR petitions filed by other defendants in Greenthread's litigation campaign, specifically those filed by ON Semiconductor and Intel. (Case No. 2:23-cv-00157, Dkt. 22).

• PTAB Institution of IPR Proceedings (2023-10-13 and 2024-02-12): The PTAB instituted IPR proceedings to review the validity of claims of the '222 patent.

  • IPR2023-00690: Filed by ON Semiconductor, the PTAB instituted review on October 13, 2023.
  • IPR2023-01149 & IPR2023-01150: Filed by Intel Corporation, the PTAB instituted review on these petitions on February 12, 2024.
    The institution of these reviews signaled that the PTAB found a "reasonable likelihood" that the petitioners would prevail in proving at least one of the challenged claims unpatentable.

• Order Granting Stay (2024-02-21): Judge Rodney Gilstrap granted STMicroelectronics' motion to stay the case. The court found that a stay was warranted given the institution of multiple IPRs against the '222 patent. The judge reasoned that the IPR outcomes could simplify or dispose of the issues in the litigation, and that a stay would promote judicial economy and avoid potentially needless litigation expenses for the parties. The court ordered the parties to provide joint status reports every 180 days. (Case No. 2:23-cv-00157, Dkt. 32).

Current Status and Outcome

As of today's date, May 7, 2026, the case of Greenthread, LLC v. STMicroelectronics, Inc. remains stayed. The final outcome of the litigation is contingent on the final written decisions from the PTAB in the IPR proceedings initiated by ON Semiconductor and Intel.

• Pending PTAB Decisions: The IPR proceedings are ongoing. A final written decision from the PTAB typically issues within one year of institution. Therefore, decisions in the IPRs filed by ON Semiconductor (IPR2023-00690) and Intel (IPR2023-01149, IPR2023-01150) would have been expected by late 2024 and early 2025, respectively. Any appeals of those decisions to the U.S. Court of Appeals for the Federal Circuit would further extend the timeline. The district court stay will likely remain in place until these administrative proceedings and any subsequent appeals are fully resolved.

• No Further Litigation Milestones: Due to the stay, the case has not progressed to claim construction (a Markman hearing), significant discovery, or trial. The stay effectively paused all substantive litigation activity in the district court pending the PTAB's validity determination. The ultimate disposition will depend on whether the PTAB invalidates the asserted claims of the '222 patent. If the claims are found invalid, Greenthread's case against STMicroelectronics will likely be dismissed. If the claims survive, the stay will be lifted, and the district court litigation will resume.

Based on appearances in this and directly related cases within Greenthread, LLC's litigation campaign, the following counsel have been identified representing the plaintiff.

Lead Counsel

Attorneys from the firms of Susman Godfrey L.L.P. and Buether Joe & Carpenter, LLC appear to be serving as lead counsel for Greenthread across its campaign.

• Justin A. Nelson (Lead Counsel)

  • Firm: Susman Godfrey L.L.P., Houston, TX.
  • Note: A nationally recognized trial lawyer, Nelson has secured high-value verdicts and settlements, including representing Dominion Voting Systems in its litigation against Fox. He is a former law clerk for U.S. Supreme Court Justice Sandra Day O'Connor and is noted for his work in high-stakes commercial and intellectual property litigation.

• Eric W. Buether (Lead Counsel)

  • Firm: Buether Joe & Carpenter, LLC, Dallas, TX.
  • Note: Buether has extensive experience in intellectual property litigation and is admitted to practice in the Eastern District of Texas. His firm specializes in patent, copyright, and trademark infringement lawsuits.

• Christopher M. Joe (Lead Counsel)

  • Firm: Buether Joe & Carpenter, LLC, Dallas, TX.
  • Note: Joe is a founding member of the IP and commercial litigation boutique, with a practice focused on patent, trademark, and trade secret litigation.

Additional Counsel

• Alan L. Whitehurst

  • Firm: McKool Smith.
  • Note: Identified as counsel for Greenthread in a PTAB conference call regarding IPRs related to the '222 patent family.

• Arvind Jairam

  • Firm: McKool Smith.
  • Note: Appeared as backup counsel for Greenthread alongside Alan Whitehurst in a PTAB conference call concerning patents in this litigation campaign.

Local Counsel

Greenthread has retained the Tyler-based firm of Parker, Bunt & Ainsworth, P.C. to serve as local counsel in the Eastern District of Texas. This is a common practice for out-of-district firms litigating in the EDTX.

• Charles L. "Chip" Ainsworth (Local Counsel)

  • Firm: Parker, Bunt & Ainsworth, P.C., Tyler, TX.
  • Note: The firm has extensive experience representing clients in intellectual property disputes in the Eastern District of Texas, including cases involving semiconductor technology.

• Robert Christopher "Chris" Bunt (Local Counsel)

  • Firm: Parker, Bunt & Ainsworth, P.C., Tyler, TX.
  • Note: Bunt is a principal at the firm, which is located one block from the Tyler federal courthouse and frequently serves as local counsel for national law firms.

Defendant's Counsel of Record

Initial analysis of the docket and related proceedings reveals a contradiction in the case metadata provided. Public records for case number 2:23-cv-00157 in the U.S. District Court for the Eastern District of Texas consistently identify the defendant as Texas Instruments Incorporated, not STMicroelectronics, Inc. This report proceeds with the counsel information for the documented defendant, Texas Instruments.

Based on filings in the case, the counsel who has formally appeared for Texas Instruments is:

• Name: Amanda Aline Abraham
  • Role: Local Counsel.
  • Firm: Roth & Abraham Law Firm, PC (formerly Roth Law Firm) in Marshall, Texas.
  • Note: Ms. Abraham is an experienced litigator in the Eastern District of Texas and has appeared as counsel of record in over 150 federal civil cases. Her filing of an "Unopposed First Application for Extension of Time to Answer Complaint" on behalf of Texas Instruments confirms her active role.

While Ms. Abraham is the only attorney to have filed a notice of appearance for the defendant in the district court case according to available dockets, related inter partes review (IPR) proceedings at the Patent Trial and Appeal Board (PTAB) show a broader defense team. Major law firms often serve as lead counsel while engaging local attorneys in the specific jurisdiction where a case is filed.

Counsel representing Texas Instruments in its PTAB challenges against Greenthread's patents include attorneys from the national intellectual property firm Fish & Richardson.

• Firm: Fish & Richardson P.C.
  • Attorneys: Joshua Griswold has appeared as lead counsel for Texas Instruments in PTAB proceedings involving the same patent family. The firm has a long history of representing Texas Instruments in high-stakes semiconductor patent litigation.
  • Role: Likely serving as lead counsel or national coordinating counsel for the district court litigation, though a formal notice of appearance was not found in the available docket information for this specific case. Their involvement in the parallel PTAB proceedings is a strong indicator of their lead role in the overall defense strategy against Greenthread's campaign.