A hybrid Sigma-Delta modulator with reusable SAR quantizer

Abstract

A novel energy-efficient hybrid multi-bit Sigma-Delta modulator with a reusable successive approximation register (SAR) quantizer is proposed. By reusing the SAR quantizer, sampling capacitors in the first integrator of the modulator could be eliminated and almost rail to rail input signal range could be achieved by the modulator without the requirement of a high-swing analog adder in front of the quantizer, which is usually power hungry in multi-bit modulators. In this way, small capacitors could be used to meet the thermal noise requirements, thus reducing the power and area consumption. With an improved switching procedure, only a half number of the unit capacitors are needed in the SAR quantizer, which further reduce the area consumption.