A Noise-shaping SAR Assisted MASH 2-1 Sigma-Delta Modulator

Abstract

This paper presents a noise-shaping SAR assisted MASH 2-1 sigma-delta modulator (SDM). To implement a SDM with high resolution and high speed, the resolution of the quantizer and the noise-shaping order must rise with a low oversampling ratio (OSR). Based on the proposed MASH structure, the noise-shaping order can be raised, and also the number of OPAMPs and the mismatch effect among different stages can be reduced. Furthermore, two quantizers in the proposed MASH structure are combined into a noise-shaping quantizer for easy implementation. The proof-of-concept prototype was fabricated in TSMC 90-nm CMOS technology. At 1.0V supply, sampling rate of 80-MS/s, bandwidth of 3.333 MHz, the prototype achieves 71.44 dB SNDR. Besides, the slope of it verifies the almost 3rd noise-shaping successfully.