Switching-activity driven gate sizing and Vth assignment for low power design

Power consumption has gained much saliency in circuit design recently. One design problem is modeled as "under a timing constraint, to minimize power as much as possible". Previous research regarding this problem focused on either minimizing dynamic power by gate sizing, or reducing leakage power by dual threshold voltage assignment on non-critical path. However, given a timing constraint, an optimization algorithm must be able to utilize gate sizing and threshold-voltage assignment interchangeably, in order to minimize total power consumption including dynamic and leakage power in active mode and leakage power in idle mode. We find that switching-activity of a gate plays an important role in making decision as to choosing gate sizing or threshold-voltage assignment for performance improvement. For high switching-activity gates, threshold-voltage assignment should be used while for low switching-activity gates, gate sizing should be utilized. We develop an algorithm to perform gate sizing and threshold-voltage assignment simultaneously taking switching activity into consideration. The results show that under the same timing constraint, our circuits have 16.26%, and 18.53%, improvement of total power as compared to the original circuits for the cases where the percentage of active time are 100%, and 50%, respectively.