Ultra-Low OSR Calibration Free MASH Noise Shaping SAR ADC.

This paper demonstrates a proposed architecture of multi-stage noise-shaping (MASH) structure with noise shaping successive-approximation (NSSAR) ADC. The proposed intrinsic stable 4th order MASH NSSAR ADC can not only take advantage of sharp noise shaping effect but also gain benefits from hardware reuse. With ultra-low oversampling ratio (OSR) the MASH NSSAR is realized in Intel 22nm FinFET process with 0.9V supply. The noise leakage introduced by the analog and digital filter mismatch will be analyzed and indicates no calibration needed in the proposed MASH under reasonable mismatch range. A PVT stable ring amplifier that can achieve high-speed settling is also proposed in this article. With 100MHz bandwidth (OSR=3) and 50MHz (OSR=6), the topology can achieve 78dB and 85dB SNDR respectively.