Comparative study and optimization of synchronous and asynchronous comparators at near-threshold voltages

Abstract

We optimize and compare the performance of synchronous and asynchronous comparators across near-threshold and nominal supply voltage (0.5∼1V). Comparators are the key components that determine the fundamental performance of analog-to-digital conversion in control and digital-signal processing (DSP) systems. While the asynchronous comparator has been considered inferior, operation of transistors in the near-threshold regime grants asynchronous comparators opportunities to improve power efficiency due to the more reduction in crowbar current than saturation drain current. We propose an enhanced asynchronous CSDA based comparator capable of achieving a superior latency vs. quiescent power dissipation trade-off to the synchronous clocked comparator in the near-threshold regime, a metric that is beneficial particularly to event-driven control systems. In-depth optimization and comparison results are presented.