Compensation of Transfer Function Mismatch in a Two-stage MASH ADC with a Single SAR Quantizer

Abstract

Recently, a two-stage MASH type delta-sigma ADC structure, in which a single SAR ADC functions as the quantizer for both the first and the second stages, was proposed. A challenge in the design of the MASH ADC is exact matching between the noise transfer function of the first stage and the transfer function of the digital filters which process the digital outputs. In this work, we show that the mismatch between the filter functions due to the finite gains of op-amps used in the loop filter of the delta-sigma ADC can be greatly reduced by employing correlated double sampling along with the adjustments of the loop gain.