Petitioner Maxlinear filed two co-pending IPR proceedings against the '585 patent, each asserting different prior art.  In one IPR proceeding, the PTAB invalidated the independent claims, which the Federal Circuit affirmed in CF Crespe LLC v. Silicon Labs. Inc., No. 2017-1072, 2017 WL 6044690 (Fed. Cir. Dec. 7, 2017). But because the IPR did not involve dependent claims 4, 6-9, and 21, those claims remained patentable and available for assertion against Petitioner Maxlinear. 

In the other proceeding, the PTAB upheld the instituted claims, but based its decision on the patentability of the independent claims over the asserted prior art, and did not separately discuss or analyze the dependent claims.  On appeal, the Federal Circuit concluded that collateral estoppel applied as to the independent claims based on the invalidity holding from the earlier appeal in the co-pending IPR.  This estoppel, as the Federal Circuit stated, abrogated the basis of the PTAB's decision on the dependent claims in the second IPR, because the dependent claims were upheld solely based on the patentability of the now-invalid independent claims.  Thus, the court vacated and remanded for the PTAB to re-analyze dependent claims 4, 6-9, and 21.

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