Inphi Corp. v. Netlist, Inc.

Do negative claim limitations need to adhere to a heightened written description standard? That was the question the U.S. Court of Appeals for the Federal Circuit addressed in an appeal from a inter partes reexamination, rejecting a heightened standard, the Court concluded that “properly described, alternative features are sufficient to satisfy the written description standard of 35 U.S.C. § 112, ¶ 1.”Inphi Corp. v. Netlist, Inc., Case No. 15-1179 (Fed. Cir., Nov. 13, 2015) (O’Malley, J.).

Inphi petitioned for inter partes reexamination of a Netlist patent directed to a memory module. After the examiner rejected more than 30 claims as obvious, the patent owner, Netlist, amended the claims to include a negative limitation, after which the examiner withdrew his objections.

As background, the patent relates to computer memory modules that comprise a printed circuit with upwards of a dozen “random access memory” (RAM) chips (sometime on both sides of the circuit board) for short-term storage. When plugged into a computer’s memory slot, a memory module receives multiple command and control signals that are defined by the Joint Electron Device Engineering Council (JEDEC)—a standards body much like the IEEE, but with a focus on computer memory. While memory modules are typically required to send and receive standard signals to be compatible with computer memory systems, memory module makers are free to adjust on-module signaling to improve, for example, capacity and/or performance. The Netlist patent claims methods and apparatus for such improvements.

To save the claims, Netlist added a limitation excluding the use of three standard signals —CAS, RAS, and bank-address signals—as “chip select” signals, but allowing the use of other standard signals as “chip select” signal.

After the examiner withdrew his objection, the requestor, Inphi appealed the amended claims to the Patent Trial and Appeal Board (Board), arguing Netlist introduced a negative claim limitation lacking support from the specification and, as a result, failing to satisfy the written description requirement (§ 112, ¶ 1). The Board affirmed the examiner’s allowance of the amended claims and denied Inphi’s request for a rehearing. Inphi appealed.

Relying on Santarus v. Par Pharm., (IP Update, Vol. 15, No. 10), Inphi argued that the Court’s precedent demanded a heightened written description standard for negative claim limitations requiring that the specification “describe[e] a reason to exclude the relevant limitation.” Inphi further asserted that the “reason to exclude” necessitates something more that describing alternative features—such as describing the advantages of excluding the feature, or the disadvantages of including it—and that Netlist’s patent failed to expressly articulate a reason to exclude the RAS, CAS and bank address signals. The Federal Circuit took issue with Inphi’s recitation of the standard.

Reconciling its decision in Santarus with its existing jurisprudence on written description, the Court clarified that Santarus describes one way of satisfying a negative limitation, not the only way. Listing advantages and/or disadvantages of the claim exclusion is therefore unnecessary when the specification “properly describes alternative feature of the patented invention.”

Applying the deferential substantial evidence standard, the Court concluded that the patent specification and JEDEC documents incorporated by reference supported the Board’s finding that Netlist had adequately described the added negative limitation.

Practice Note: For future guidance, the Federal Circuit noted that if the specification foreclosed on the negative limitation, then the amendment would be improper and the patent invalid—as was the case with In re Bimeda Research & Dev. Ltd., (IP Update, Vol. 16, No. 8).