DCT

3:20-cv-04198

Xiaohua Huang v. StarPC Excess LLC

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 4:20-cv-04198, N.D. Cal., 07/28/2020
  • Venue Allegations: Venue is alleged based on Defendant having its main offices in the district and generating revenue from the sale of accused products within the Northern District of California.
  • Core Dispute: Plaintiff alleges that networking equipment refurbished and sold by Defendant, which contains Ternary Content Addressable Memory (TCAM) components, infringes a patent related to high-speed, low-power CAM and TCAM circuit designs.
  • Technical Context: The technology concerns specialized semiconductor memory circuits (TCAMs) that are fundamental components in high-speed network routers and switches, where they are used to perform rapid data lookups for functions like packet forwarding and access control.
  • Key Procedural History: The asserted patent claims priority from a provisional application filed in 2001. The complaint does not mention any other significant procedural events such as prior litigation or post-grant proceedings involving the patent-in-suit.

Case Timeline

Date Event
2001-10-04 ’331 Patent Priority Date
2006-02-14 ’331 Patent Issue Date
2020-07-28 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

  • Patent Identification: U.S. Patent No. 6,999,331, “CAM CELLS AND DIFFERENTIAL SENSE CIRCUITS FOR CONTENT ADDRESSABLE MEMORY (CAM),” issued February 14, 2006 (’331 Patent).
  • The Invention Explained:
    • Problem Addressed: The patent’s background section describes performance limitations in conventional Content Addressable Memory (CAM) designs. These designs can be slow because determining a data mismatch requires a single transistor to discharge the large capacitance of an entire "match line." This process can also be power-intensive, as nearly all match lines in a memory array are discharged during each search operation. (’331 Patent, col. 1:54–col. 2:13).
    • The Patented Solution: The invention proposes a circuit architecture that uses a parallel "dummy line" and associated "dummy" transistors to create a reference signal for each "match line." This enables the use of a differential sense amplifier that can detect a small voltage difference between the match line and the dummy line, rather than waiting for the match line's voltage to swing all the way to a low state. (’331 Patent, Abstract; col. 2:25-39). This differential sensing approach is described as enabling faster, lower-power operation. (’331 Patent, col. 2:35-39; Fig. 1B).
    • Technical Importance: This differential sensing technique addresses speed and power consumption bottlenecks that are critical design constraints for hardware used in high-speed networking applications. (Compl. ¶¶8, 10).
  • Key Claims at a Glance:
    • The complaint asserts infringement of at least independent Claim 1. (Compl. ¶17).
    • The essential elements of Claim 1 include:
      • A ternary content addressable memory (TCAM) comprising an array of TCAM cells.
      • A plurality of match lines, one for each row of TCAM cells.
      • A plurality of dummy lines, one for each row of TCAM cells.
      • A plurality of match data bit lines and their complements for data comparison.
      • A column of dummy TCAM (DTCAM) cells, connected to the match line and the dummy line in each row.
      • A pair of dummy match data bit lines for the column of DTCAM cells.
      • A sense amplifier connected to the match line and the dummy line in each row.
      • Current sources connected to the match line and the dummy line in each row.
    • The complaint alleges infringement "directly, indirectly, literally, on Doctrine of Equivalent [of] one or more of the claims." (Compl. ¶17).

III. The Accused Instrumentality

  • Product Identification: The complaint identifies networking equipment "bought and sold by Star PC Express," including but not limited to the "F5 Networking Local Traffic Manager," "HPE Synergy 867631-B21 12-Port 10G/40G/100G Pass-Thru Module," and "NP-0,NP-1,NP-2,NP-3,NP-4 and SN4000 of Mellanox equipment." (Compl. ¶¶11, 13).
  • Functionality and Market Context: The accused products are networking routers and switches that allegedly contain TCAM components. (Compl. ¶¶13-14). These TCAMs are used to perform high-speed table lookup functions necessary for network operations such as implementing access control lists (ACL), Quality of Service (QoS), VLAN management, and packet forwarding. (Compl. ¶10). The complaint alleges that the TCAMs within these products possess specific features, including a "differential sense amplifier" and a "dummy line to be reference to match line," which form the basis of the infringement claim. (Compl. ¶11). No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint does not include a claim chart and states that the detailed infringement analysis is contained in an expert report, which was not provided as part of the pleading. (Compl. ¶¶11, 17). The following chart summarizes the infringement theory for Claim 1 by mapping its elements to the specific TCAM features alleged in the complaint.

’331 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a sense amplifier connected to the match line and the dummy line in each row The TCAMs allegedly contain "a differential sense amplifier to sense match line signal." ¶11 col. 2:40-44
a plurality of dummy lines, one dummy line for each row of TCAM cells... The TCAMs allegedly use a "dummy line to be reference to match line." ¶11 col. 2:30-32
a column of dummy TCAM (DTCAM) cells, each connected to the match line and the dummy line in each row The TCAMs allegedly contain a "dummy TCAM cell." ¶11 col. 3:32-34
  • Identified Points of Contention:
    • Evidentiary Questions: The complaint's infringement theory is premised entirely on an unprovided expert report. A central question for the case will be what evidence, if any, the Plaintiff can produce through discovery to substantiate the allegation that the accused products' internal circuitry practices each limitation of the asserted claims.
    • Scope Questions: The analysis will likely focus on whether the reference-generating circuitry within the accused TCAMs meets the specific structural requirements of Claim 1. For instance, does the accused "dummy TCAM cell" and "dummy line" correspond to the structures defined by the claim, particularly the requirement for "a column of dummy TCAM (DTCAM) cells"?
    • Technical Questions: What is the precise architecture and method of operation of the accused TCAMs' sensing circuits? Does the alleged "differential sense amplifier" function by comparing a match line signal to a reference signal generated by a dedicated "dummy line" and a "column of dummy TCAM cells" as required by the claim, or does it operate in a technically distinct manner?

V. Key Claim Terms for Construction

  • The Term: "dummy TCAM (DTCAM) cells"
  • Context and Importance: This term appears to be a central inventive concept of the patent. The definition of what constitutes a "dummy TCAM cell" will be critical for determining the scope of the claim and whether the reference-signal-generating circuits in the accused products infringe. Practitioners may focus on whether this term requires a specific circuit structure or can be read more broadly to cover a function.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The Summary of the Invention describes the function of the "dummy transistor" more generally as being "used to achieve low voltage swing (small signal) sensing and provides for low power and high-speed operation," which could support an interpretation based on function rather than specific structure. (’331 Patent, col. 2:35-39).
    • Evidence for a Narrower Interpretation: Claim 1 requires "a column of" these cells, implying a specific physical array structure, not just a single reference circuit. Furthermore, the detailed description provides specific circuit diagrams for "dummy CAM cell 124x," showing a particular arrangement of transistors. (’331 Patent, col. 6:1-12; Fig. 2E). A defendant may argue the term should be limited to these disclosed embodiments.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges inducement and contributory infringement in general terms. It asserts inducement based on customers "accessing and using the TCAM function of the equipment," and contributory infringement based on Defendant "selling its networking equipment to build the access of the Internet system." (Compl. ¶¶12, 14, 18-19). The complaint does not allege specific facts regarding intent, such as referencing user manuals or advertising materials that instruct on infringing use.
  • Willful Infringement: The complaint does not explicitly allege willful infringement or plead facts suggesting Defendant had pre-suit knowledge of the ’331 Patent.

VII. Analyst’s Conclusion: Key Questions for the Case

  • Evidentiary Sufficiency: A primary challenge will be evidentiary. Can the plaintiff substantiate the highly technical infringement allegations, which the complaint defers entirely to an unprovided expert report, by developing sufficient evidence through fact and expert discovery to show that the complex circuitry inside the accused products meets every limitation of the asserted claim?
  • Structural Congruence: A key technical question will be one of structural and functional equivalence. Does the architecture of the industry-standard TCAMs in the accused networking equipment map onto the specific combination of elements required by Claim 1—including a "sense amplifier," a "match line," a "dummy line," and a dedicated "column of dummy TCAM cells"—or is there a fundamental mismatch in their circuit-level structure and operation?
  • Definitional Scope: The case may turn on a core issue of claim construction: can the term "dummy TCAM (DTCAM) cells," as used in the context of the patent, be construed to cover the reference-generating circuits allegedly present in the accused products, or is the term limited by the specification to the specific circuit layouts and array structures disclosed in the patent's embodiments?