A Lean Noise-Cancelling Sturdy MASH Delta-Sigma ADC with a Noise-Shaping SAR Stage

Abstract

This paper introduces a lean noise-cancelling sturdy-MASH delta-sigma ADC, achieved through the implementation of a noise-shaping SAR second stage, the use of which instead of the usual delta-sigma stage, eliminates, by virtue of its inherent feedforward mechanism, the quantization noise of the first stage. Moreover, any mismatch-induced error of the noise-shaping SAR gets shaped by the first stage, circumventing the need for strict capacitor matching or calibration. The elimination of noisecancelling and/or calibration circuitry, as well as the inclusion of the area-efficient noise-shaping SAR qualify this topology as lean. Simulations demonstrate a proof-of-concept design achieving 107.7 dB SQNR for an OSR of 14 over a 1 MHz bandwidth.