SAR-assisted continuous-time 1-0 MASH delta-sigma modulator utilizing digital noise coupling

Abstract

Recently, the demand of the low power high resolution ADC (Analog Digital Converter) for sensor or audio application has been increasing. These days, for such low power and high-resolution ADC, DSM (Delta Sigma Modulator) has become popular architecture and various technique to improve the performance for DSM has been introduced. In this research, by using that techniques, SAR-Assisted continuous-time 1-0 multi stage noise shaping (MASH) DSM utilizing digital noise coupling (DNC) is proposed. M-0 MASH which is also called as Leslie-Singh structure can increase effective resolution due to its structure advantage without increasing actual DSM loop resolution and it leads to the reduction of the quantization noise. Unlike the normal MASH structure, M-0 MASH cannot obtain additional noise shaping order. However, if DNC is employed to DSM, additional noise shaping order can be obtained without increasing DSM loop filter order. Therefore, in this research, the proposed architecture is designed to achieve high signal-to-distortion and noise ratio (SNDR) while minimizing power consumption by utilizing M-0 MASH and DNC structure. This work was implemented in a 28nm CMOS technology and its core layout occupies 0.24mm2. In 25kHz bandwidth with an oversampling ratio (OSR) of 256, this work could achieve 98.8dB SNDR with 202.8μW power consumption and it leads to 179.7dB Schreier figure of merit (FoM) which is competitive compared with other similar bandwidth works.