A semiempirical model for wakeup time estimation in power-gated logic clusters

Wakeup time is an important overhead that must be determined for effective power gating, particularly in logic clusters that undergo frequent mode transitions for run-time leakage power reduction. In this paper, a semiempirical model for virtual supply voltage in terms of basic parameters of the power-gated circuit is presented. Hence a closed-form expression for estimation of wakeup time of a power-gated logic cluster is derived. Experimental results of application of the model to ISCAS85 benchmark circuits show that wakeup time may be estimated within an average error of 16.3% across 22× variation in sleep transistor sizes and 13× variation in circuit sizes with significant speedup in computation time compared to SPICE level circuit simulations.