Post-synthesis leakage power minimization

Abstract

We developed a new post-synthesis algorithm that minimizes leakage power while strictly preserving the delay constraint. A key aspect of the approach is a new threshold voltage (V T ) assignment algorithm that employs a cost function that is globally aware of the entire circuit. Thresholds are first raised as much as possible subject to the delay constraint. To further reduce leakage, the delay constraint is then iteratively increased by Δ time units, each time enabling additional cells to have their threshold voltages increased. For each of the iterations, near-optimal cell size selection is applied so as to reacquire the original delay target. The leakage power iteratively reduces to a minimum, and then increases as substantial cell upsizing is required to re-establish the original delay target. We show results for benchmark and commercial circuits using a 40nm cell library in which four threshold voltage options are available. We show that the application of the new leakage power minimization algorithm appreciably reduces leakage power after multi-V T synthesis by a leading commercial tool, achieving an average post-synthesis leakage reduction of 37% while also reducing total active area and maintaining the original delay target.