A 25-kHz-BW 97.4-dB-SNDR SAR-Assisted Continuous-Time 1-0 MASH Delta-Sigma Modulator With Digital Noise Coupling

• Published in: IEEE journal of solid-state circuits 2024-10, Vol.59 (10), p.3232-3241
• Main Authors: Lee, Dong-Hun, Lozada, Kent Edrian, Kim, Ye-Dam, Kim, Ho-Jin, Cho, Youngjae, Choi, Michael, Ryu, Seung-Tak
• Format: Article
• Language: English
• Subjects: Analog-to-digital converter (ADC); continuoustime delta–sigma modulator (CT DSM); Coupling; digital noise coupling (DNC); Figure of merit; Finite impulse response filters; Low-pass filters; Matched filters; Modulation; Modulators; Multi-stage noise shaping; multi-stage noise shaping (MASH); Noise; noise coupling (NC); Quantization (signal); Signal to noise ratio; successive approximation register (SAR); Transfer functions
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2024.3391902

This article introduces a high-resolution continuous-time delta-sigma modulator (CT DSM) architecture that incorporates a successive approximation register (SAR)-assisted digital noise coupling (DNC) technique and a multi-stage noise-shaping (MASH) structure. The limited maximum stable amplitude (MSA) problem due to the high-order-shaped large quantization error ( E {_{\mathrm{ 1}}} ) in the previous single-loop DNC DSM is alleviated by adopting an M-0 MASH architecture, where E {_{\mathrm{ 1}}} is low-order shaped within the first stage. With a zeroth-order second stage and digital cancellation filter, only the second-stage quantization error ( E {_{\mathrm{ 2}}} ) is present in the final output, where it is shaped aggressively by the conjunction of the first-stage noise-transfer function (NTF) and DNC. Fabricated in 28-nm CMOS, the prototype demonstrates that a high-order CT DSM can be realized with low-order analog loop filters through the combination of MASH and DNC architecture, achieving peak values of signal-to-noise and distortion ratio (SNDR), signal-to-noise ratio (SNR), and dynamic range (DR) of 97.4, 98.4, and 100.2 dB, respectively, in a 25-kHz bandwidth while consuming only 260 ~\mu \text{W} from a 1.1-V supply. The SNDR-based Schreier figure-of-merit (FoM) is 177.2 dB.