Decreasing low-voltage manufacturing-induced delay variations with adaptive mixed-voltage-swing circuits

One of the major problems faced by the designer when operating CMOS static logic circuits at low power supply voltages (normalized to V/sub T/) is that the delay spread introduced by today´s IC manufacturing variations can increase dramatically. In this paper we describe an approach for decreasing the delay spread and power spread in ICs based on adaptively servoing the circuits between static CMOS operation and QuadRail operation. An on-chip series-regulator employing a dummy delay path is used to generate the adaptive low swing power supply rails making this approach fully compatible with a standard CMOS IC design methodology. Simulation results are presented demonstrating that for a 16*16+36-bit multiplier-accumulator designed in 0.5 /spl mu/m CMOS process the proposed approach decreases the delay spread from 3.9/spl times/ to 2.3/spl times/ and the power spread from 3.6/spl times/ to 1.8/spl times/.