Negative Claim Limitations Do Not Have a Higher Written Description Standard

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Federal Circuit Review No. 77-1.
Negative Claim Limitations Do Not Have a Higher Written Description Standard; Optional Features Can Be Excluded From Claims

Inphi Corp. v. Netlist Inc., No. 2015-1179 U.S. App. LEXIS 19746 (Fed. Cir. Nov. 13, 2015) (Before O’Malley, Reyna, and Chen, J.) (Opinion for the court, O’Malley, J.). Click Here for a copy of the opinion.

Inphi filed a request for inter partes reexamination of Netlist’s patent on random access memory chips. The examiner rejected several claims as obvious in the first Office Action.  Netlist amended its claims by adding a negative claim limitation, requiring that certain signals used by the chip are “not CAS, RAS, or bank address signals.”  The examiner withdrew his rejections and allowed the claims.  Inphi appealed to the Patent Trial and Appeal Board (PTAB), alleging that Netlist’s amendments did not comply with the written description requirement.  The PTAB rejected Inphi’s argument and affirmed the examiner.  Inphi appealed to the Federal Circuit.

The written description requirement is met where the specification shows to a person of ordinary skill in the art that the inventor was in possession of the claimed invention.  In Santarus, Inc. v. Par Pharm., Inc., the Court previously held that negative claim limitations were supported by the written description “when the specification describes a reason to exclude the relevant limitation.”  In that case, the court found that claims reciting a particular composition having “no sucralfate” were supported by the specification.

cafc-federal-circuit-statue-335b copyHere, the parties disputed the meaning of the phrase “reason to exclude” in Santarus.  Inphi argued that this language meant that there must be a specific reason for the negative limitations, such as an explanation of the disadvantages of including it.  In Santarus, for example, the specification discussed that using sucralfate led to several disadvantages that were cured by its exclusion.  Netlist argued that the written description requirement was satisfied when the limitations that are excluded are merely described as alternative or optional, and that there should be no extra reasoning requirement for negative limitations.

The court rejected Inphi’s argument, and held that the written description requirement is met for negative claim limitations where the specification simply describes alternatives.  In other words, the “reason to exclude” required by Santarus can be met without discussion of advantages of exclusion or disadvantages of inclusion.  Further, alternative elements need not be explicitly described as alternatives, so long as the specification conveys to a person of skill in the art that those elements are, in fact, alternative or optional.  Negative limitations are only unsupported where the specification provides no examples or suggestions that such limitations are alternative or optional.

Here, the negative limitation was supported by three parts of the specification.  First, the specification incorporated by reference an electronic standards publication for memory devices of a particular kind.  This standard included a table that described each of the excluded signals as distinct from each other.  Second, the specification included a table which provided separate sections for each of the CS, RAS, and CAS signals.  Third, the specification described that “chip select[ signals] are distinct from CAS, RAS, and bank address signals.”

The court thus affirmed PTAB’s decision, holding that these portions of the specification provided substantial evidence to show that the patentee was in possession of the negative limitation as of the filing date of the patent.


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