Federal Circuit Upholds PTAB Obviousness Finding Against Memory Module Patent

The U.S. Court of Appeals for the Federal Circuit (CAFC) issued a precedential decision today in Netlist, Inc. v. Micron Technology, Inc., affirming a Patent Trial and Appeal Board (PTAB) final written decision that found all challenged claims of a Netlist computer memory patent unpatentable as obvious. The court rejected Netlist’s arguments that the Board’s findings lacked substantial evidentiary support and that the Board violated the Administrative Procedure Act (APA) in reaching its conclusions.

Netlist, Inc. owns U.S. Patent No. 10,949,339, which is a computer memory system designed to improve the performance and capacity of memory boards containing dual in-line memory modules. The specification describes adding buffers between a memory controller and dynamic random access memory (DRAM) devices. These buffers include data paths that remain disabled by default, isolating the DRAM devices from the memory controller, and are selectively enabled during read or write operations to drive data signals between the two components.

Samsung Electronics Co., Ltd. filed a petition for inter partes review (IPR) challenging claims 1 through 35 of the ‘339 patent as obvious over U.S. Patent Application Publication No. 2006/0277355 (Ellsberry) with U.S. Patent No. 7,024,518 (Halbert). Micron Technology, Inc., along with two affiliated entities, filed a separate IPR petition raising the same challenge and was joined by Samsung. Samsung later settled with Netlist and withdrew from the appeal, and Micron continued as the sole appellee. The Board instituted review and found all challenged claims unpatentable, and treated independent claim 1 as representative.

Two limitations of claim 1 were at issue on appeal. Limitations 1e and 1f require that a data path through the buffer be enabled so that the memory controller can drive write data to the DRAM device. Limitation 1e further requires that the data path be enabled at a specific time, described as occurring “in accordance with a latency parameter.”

Netlist first argued that the Board’s finding that Ellsberry teaches a latency-controlled data path was based on what it characterized as “unsubstantiated speculation about Ellsberry’s operation.” Netlist contended that Ellsberry’s switch ASICs merely pass a timing signal through to the DRAM devices. According to Netlist, the switch ASICs do not use the timing signal to control the buffer. The Federal Circuit disagreed, holding that the Board’s finding was supported by substantial evidence, which it described using the standard articulated in Incept LLC v. Palette Life Sciences, Inc. as “such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.” The Board had relied on expert testimony establishing that Ellsberry stores a timing parameter in its memory bank switch during initialization, and on Joint Electron Device Engineering Council standards showing that read and write latencies depend on the same type of parameter.

Netlist separately argued the Board improperly relied on Netlist’s own U.S. Patent No. 7,532,537 to fill a gap in the challenge, since that patent was not asserted as prior art in Samsung’s petition. The Federal Circuit found any such error harmless, since the Board had made an alternative finding, independent of the ‘537 patent, that Ellsberry alone teaches accounting for propagation delay through its buffer components. Since that alternative finding was supported by substantial evidence and matched the ground presented in the petition, the court determined it did not need to reach the question of whether reliance on the ‘537 patent was improper.

Furthermore, Netlist was concerned about whether Ellsberry teaches enabling a data path at all, rather than merely selecting a memory bank located outside the buffer. Netlist contended that the components Ellsberry describes as Ports A and B sit outside the switch ASIC that the Board equated with the claimed buffer. The Board had called this argument “manifestly incorrect,” finding that Ellsberry’s own disclosure places the ports within the switch ASIC rather than within the physical memory banks. The Federal Circuit agreed, and further upheld the Board’s finding that Ellsberry’s bidirectional drivers enable and disable those data paths. The court also noted the Board’s alternative determination that Ellsberry combined with Halbert, whose bidirectional buffers and data registers were identified as tristate buffers in Halbert’s own figures.

Netlist raised additional APA challenges, arguing the Board failed to adequately explain its reasoning across most of claim 1’s limitations. The court found this argument undeveloped, since Netlist did not identify which limitations it was challenging, citing Monsanto Co. v. Scruggs for the principle that an issue must be adequately developed for appellate review. Netlist also argued the Board failed to address its arguments concerning dependent claims 7, 16, and 21, which require that module control signals control timing in accordance with the latency parameter. The CAFC found the Board had directly addressed both arguments in its final written decision, and  “concludes this is substantial evidence that Ellsberry discloses enabling data paths.

The Federal Circuit affirmed the Board’s final written decision holding all challenged claims of the ‘339 patent unpatentable as obvious over Ellsberry and Halbert. Today, the Federal Circuit also issued a decision in a related dispute, Netlist, Inc. v. Micron Technology, Inc., affirming two consolidated PTAB final written decisions that found all challenged claims of Netlist’s U.S. Patent Nos. 11,016,918 and 11,232,054 unpatentable as obvious. The Board found the claims obvious based on combinations of a prior art patent publication and the Joint Electron Device Engineering Council’s Fully Buffered DIMM standards, along with additional prior art addressing voltage monitoring and backup power. The Federal Circuit rejected Netlist’s arguments that the Board exceeded the scope of the petitions, found the obviousness determinations supported by substantial evidence, and found no violation of the APA in the Board’s treatment of the dependent claims.

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Author: billperry