Robust multi-stage noise shaping (R-MASH) architecture assisted by subrange SAR ADC

Abstract

In touch integrated circuit (IC) application, analog-to-digital converter (ADC) plays an important role as a readout stage. Noise shaping (NS) successive approximation register (SAR) ADC is one of the most fitting choices in this application, thanks to its sensor-friendly properties. To enhance the resolution of the NS SAR, multi-stage noise shaping (MASH) architecture is implemented. However, MASH architecture suffers from quantization noise leakage due to mismatches, which are unavoidable in practice. In this article, Robust MASH (R-MASH) architecture is proposed to alleviate the quantization noise leakage. Unlike conventional MASH, the proposed R-MASH architecture shapes the inter-stage quantization noise. As a result, R-MASH attains stability in terms of resolution. The proposed architecture operates with a sampling rate of 16MS/s with an OSR of 16. Ideal performance is simulated in both DSM mode and incremental mode. In DSM mode, the result shows an effective number of bits (ENOB) of 16.35 bits, signal-to-noise-and-distortion-ratio (SNDR) of 100.22dB, and spurious-free dynamic range (SFDR) of 106.26dB. In incremental mode, which is for the ADC in sensor application, the simulation result shows ENOB of 15.25 bits, SNDR of 93.56dB, and SFDR of 102.36dB.