Efficient Computation of Discharge Current Upper Bounds for Clustered Sleep Transistor Sizing

Sleep transistor insertion is a key step in low power design methodologies for nanometer CMOS. In the clustered sleep transistor approach, a single sleep transistor is shared among a number of gates and it must be sized according to the maximum current that can be injected onto the virtual ground by the gates in the cluster. A conservative (upper bound) estimate of the maximum injected current is required in order to avoid excessive speed degradation and possible violations of timing constraints. In this paper the authors propose a scalable algorithm for tightening upper bound computation, with a controlled and tunable computational cost. The algorithm leverages the capabilities of state-of-the-art commercial timing analysis engines, and it is tightly integrated into standard industrial flow for leakage optimization. Benchmark results demonstrate the effectiveness and efficiency of our approach