Functional Verification of Power Gated Designs by Compositional Reasoning

Power gating is a technique for low power design in which whole sections of the chip are powered off when they are not needed, and powered back on when they are. Functional correctness of power gating is usually checked as part of system-level verification, where the most widely used technique is simulation using pseudo-random stimuli. We propose instead to perform a sequential equivalence check between the power gated design and a version of itself in which power gating is disabled. We take a compositional approach that looks for partial equivalence of each unit under a suitable set of assumptions, guaranteed by the neighboring units. We make use of so-called circular reasoning rules to compose the partial equivalences proved on the individual units back into total equivalence on the whole chip.