Linearlization of Stochastic Flash A-to-D Converter

Abstract

Reference voltages of a stochastic flash A-to-D converter (SFADC) are defined by comparator offset voltages instead of fixed external reference voltages. Assuming that offset-voltage variation follows Gaussian distribution, its cumulative distribution function becomes non-linear and the linear input signal range is narrow. We propose a way to reduce nonlinearity by dividing the comparators into M groups, and synthesize a single uniform distribution by introducing additional DC reference voltages and weights for each group. This work presents a design guide to determine how many groups we should divide to obtain good linearity.