IP Law Daily Digital click circuit patent asserted against Samsung properly held invalid
Monday, April 6, 2020

Digital click circuit patent asserted against Samsung properly held invalid

By Brian Craig, J.D.

The PTAB correctly construed the "maintaining" limitation in a patent claiming to improve circuits used to synchronize digital clocks.

Concluding that the Patent Trial and Appeal Board properly construed the "maintaining" limitation in a patent to improve circuits in a challenge brought by Samsung Electronics Co., the U.S. Court of Appeals for the Federal Circuit has affirmed the Board’s finding of unpatentability. A divided Federal Circuit panel agreed that the patent owned by ProMOS Technologies, Inc. is unpatentable based on anticipation and obviousness. The Board correctly construed the "maintaining" limitation based on the plain language and prosecution history. Circuit Judge Jimmie Reyna wrote a dissenting opinion arguing that the Board erred in construing the plain and ordinary meaning of claim terms in the context of the patent (ProMOS Technologies, Inc. v. Samsung Electronics Co., Ltd., April 6, 2020, O'Malley, K.).

Samsung Electronics Co. brought two inter partes review proceedings challenging claims of U.S. Patent No. 6,069,507 (the ’507 Patent), which is assigned to ProMOS Technologies, Inc. The ’507 Patent relates to the operation of a delay locked loop (DLL)—a circuit used to synchronize digital clocks by delaying the signal of one clock relative to the signal of another to compensate for the "phase difference" between the signals. The Board found the challenged claims unpatentable as anticipated and obvious. ProMOS appealed: (1) the Board’s construction of the "maintaining" limitation; and (2) the Board’s anticipation and obviousness findings based on its construction of the "maintaining" limitation.

Claim construction. The Federal Circuit held that the Board did not err in its construction of the "maintaining" limitation in the patent. The words of a claim are generally given their ordinary and customary meaning, as the term would have been understood by a person of ordinary skill in the art at the time of the invention. Here, the plain language of the claims and the written description did not support importing a directionality restriction into the "maintaining" limitation. The written description confirms that the patentee understood how to describe the relationship between two clock signals in a manner that makes clear which clock signal leads or lags the other in phase.

The Federal Circuit also found that the prosecution history did not support ProMOS’s narrower proposed construction of the "maintaining" limitation. The court concluded that ProMOS mischaracterized the prosecution history. The patentee did not add the "maintaining" limitation to overcome the prior art. During prosecution, the examiner rejected pending claim 8, which included the "maintaining" limitation, as obvious in view a prior art reference. The facts did not imply that the examiner somehow interpreted the "maintaining" limitation to include a directionality restriction.

Furthermore, the Federal Circuit concluded that the Board’s construction did not render the "maintaining" limitation superfluous. The Supreme Court has stated that each element contained in a patent claim is deemed material to defining the scope of the patented invention. It is generally improper to construe a patent claim so that express claim limitations or elements are rendered superfluous. The plain language of the claims does not require the input clock signal and the feedback clock signal to have the same frequency and period. The Board’s construction did not render the claimed maintaining step superfluous because a pair of clock signals with different frequencies would not satisfy the limitation. Thus, the Board properly construed the patent.

Unpatentability. Both parties agreed that the claim construction dispute over the "maintaining" limitation was dispositive to the Board’s anticipation and obviousness findings. Because the Board correctly construed the "maintaining" limitation, the Federal Circuit concluded that there was no error in the Board’s findings of unpatentability.

Dissenting opinion. Circuit Judge Jimmie Reyna wrote a dissenting opinion arguing that the Board erred in its claim construction analysis in light of the plain and ordinary meaning of claim terms in the context of the patent. When the plain meaning of a claim term does not clarify whether and how a restriction applies, the Federal Circuit has previously held that such ambiguity is to be resolved in the first instance by reviewing the claim language as a whole, the other intrinsic record, and any extrinsic evidence. The unidirectional understanding of "phase difference" is consistent with the usage of the term throughout the claims, Judge Reyna pointed out. Intrinsic evidence also supports the construction of "phase difference" as unidirectional. Nowhere did the majority conduct the principal analysis of determining the plain and ordinary meaning of the claim language, including the words "phase difference," in the context of the patent. There is sometimes a fine line between using the specification to interpret the meaning of a claim and importing limitations from the specification into the claim, Judge Reyna said. He opined that the Board avoided its obligation to engage in the former task by mistaking it for the latter. Accordingly, Judge Reyna would reverse the Board’s analysis.

This case is No. 2019-1343.

Attorneys: Evin Christopher Jones (TechKnowledge Law Group LLP) for ProMOS Technologies, Inc. Naveen Modi (Paul Hastings LLP) for Samsung Electronics Co., Ltd.

Companies: ProMOS Technologies, Inc.; Samsung Electronics Co., Ltd.

MainStory: TopStory Patent GCNNews FedCirNews

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