Specific Specifications: Takeaways From Inphi Patent Case

The patent attorney often faces the problem that broad claims for a class can be rejected when prior art surfaces for one of the members of the class. One strategy is to exclude those members of the class found in the prior art, and to claim the rest of the class.

When may a patent claim exclude a member of the class in the claim? This question was answered in a recent Federal Circuit case, Inphi Corp v. Netlist Inc.,¹ an appeal from the Patent Trial and Appeal Board’s final written decision in an inter partes re-examination. The petitioner challenging validity argued that the specification did not provide enablement under Section 112, first paragraph, to justify the exclusion of the elements, so the exclusion was new matter.

The patent of Netlist, U.S. Patent No. 7,532,537 (“the ‘537 patent”), titled, “Memory Module with a Circuit Providing Load Isolation and Memory Domain Translation,” concerned short-term storage of data. The memory module comprised a printed circuit board on which were mounted different kinds of memory devices including “random-access memory, dynamic random-access memory (DRAM), synchronous DRAM, and double-data-rate DRAM (e.g., SDR, DDR-1, DDR-2, DDR-3).” ‘537 patent, at col. 5, ll. 41–44. Additional language in the specification identified a subgroup of DDR memory devices known as CAS, RAS, and bank address signals.

Claim 1 was representative, and it provided:

1. A memory module comprising:

a plurality of memory devices, each memory device having a corresponding load; and

a circuit electrically coupled to the plurality of memory devices and configured to be electrically coupled to a memory controller of a computer system, the circuit selectively isolating one or more of the loads of the memory devices from the computer system, the circuit comprising logic which translates between a system memory domain of the computer system and a physical memory domain of the memory module, wherein the system memory domain is compatible with a first number of chip selects, and the physical memory domain is compatible with a second number of chip selects equal to twice the first number of chip selects, wherein the plurality of memory devices comprises double-data rate (DDR) dynamic random-access memory (DRAM) devices and the chip selects of the first and second number of chip selects are DDR chip selects that are not CAS, RAS, or bank address signals.

The underlined language at the end of claim 1 was the negative claim limitation added by the patent owner in the re-examination to avoid an obviousness rejection.

Previous law, Santarus Inc. v. Par Pharm. Inc., had been clear that a claim can contain a negative list excluding elements in a class if the specification provides differences between those excluded and those retained: “[n]egative claim limitations are adequately supported when the specification describes a reason to exclude the relevant limitation.”²

The ‘537 patent’s specification had included groupings of the excluded elements without stating the express advantages and disadvantages of each. The specification was not explicit about the reasons to include or exclude the excluded elements: CAS, RAS or bank address signals. Petitioner argued that “the phrase ‘reason to exclude’ requires something more than properly describing alternate features of the patented invention.”³ The petitioner claimed that the “reason to exclude” must be explained in so many words in the specification, i.e., “that Santarus requires ‘that the patentee describes a preference for the included signal(s) over the excluded signals (or alternatively a disadvantage of the excluded signals).’”⁴

The question before the Federal Circuit was “whether properly describing alternative features — without articulating advantages or disadvantages of each feature — can constitute a ‘reason to exclude’ under the standard articulated in Santarus.”⁵ The court held that a “reason to exclude” was provided by properly describing alternate features of the patented invention.

The Federal Circuit declined to extend the law as far as petitioner alleged, holding that Santarus “did not create a heightened written description standard for negative claim limitations and that properly described, alternative features are sufficient to satisfy the written description standard of § 112, paragraph 1, for negative claim limitations.” The Federal Circuit held that the “reason to exclude” need not be expressly set out but could be implicit in the groupings of the elements.

Section 112, first paragraph (now 112(a)), can be satisfied if groupings of possible elements are differentiated by implication, but it is much safer to state the differences in detail. Specifications, as in Inphi, sometimes include only inherent differences about the various options in composing the invention. Factual determinations by the PTAB are upheld by the Federal Circuit if there is substantial evidence to support the PTAB’s findings, so greater specificity in the specification will lead to better and faster outcomes in prosecution or on appeal. The patent owner here was fortunate the examiner and the PTAB made factual findings in favor of validity.

Takeaways for Prosecution

1. Provide detailed specifications.

If an applied-for invention contains many elements in a larger class, the specification should group the elements into subclasses and explain why the elements may be grouped separately. If there are inherent differences in elements, the specification should set forth those differences in detail. Spelling out the advantages and disadvantages of each element, or group of elements, could provide the basis for a claim which includes many — if not all — of the members of a class. For example, if data is presented on different elements, the specification should include a description of why the data is different. It is impossible to know exactly which references might surface during prosecution, and grouping elements of a class into clearly described subclasses will at least provide opportunity to obtain claims for a subclass.

2. Be careful of Markush groups in claims.

Prior art for any member of a Markush group can be used in a § 103 rejection for obviousness. Although this issue was not presented in Inphi, if a Markush-type claim had been made, it would have been rejected under § 103. Separate claims for each member of a class can add to the cost, but the added costs for extra claims can be small compared to the extra costs of attorney’s fees and longer prosecution times. 


1 United States Court of Appeals for the Federal Circuit, Appeal No. 2015-1179 (Nov. 13, 2015) 
2 Santarus, Inc. v. Par Pharm., Inc., 694 F.3d 1344, 1351 (Fed. Cir. 2012). 
3 Inphi, slip op. at 12. 
4 Inphi, slip op. at 10. 
5 Inphi, slip op. at 10.

Republished with permission. This article first appeared in Law360 on February 17, 2016.