Analysis and Design of RC -Variation-Robust Continuous-Time Delta-Sigma Modulator With Boosted MSA

Continuous-time delta-sigma modulators (CT DSMs) have been widely adopted in IoT and sensor applications. Despite the merits of the inherent anti-alias property and easy-driving resistive input, CT DSMs always suffer from theRCvariation issue. While a higher maximum stable amplitude (MSA) can result in a higher dynamic range (DR) with better efficiency, it is often limited to -1 dBFS. To address the above issues, this article presents a hybrid 1-2 sturdy multi-stage noise-shaping (MASH) architecture that exhibits high robustness againstRCvariations. The proposed modulator integrates a first-orderRC-variation-insensitive CT loop filter with a second-order noise-shaping (NS) successive approximation register (SAR) quantizer. By leveraging the inherent unity signal transfer function (STF) of the NS-SAR quantizer, the quantization noise of the first stage is effectively canceled without requiring analog-digital matching. This enables the modulator to achieve a beyond-the-rail MSA while performing aggressive third-order NS. Fabricated in a 55-nm CMOS process, the prototype achieves a measured signal-to-noise-and-distortion ratio (SNDR) of 89.1 dB and a DR of 95.3 dB over a signal bandwidth of 100 kHz, while consuming 459 μW from a single 1.2-V supply. These results yield a state-of-the-art Schreier figure of merit of 178.7 dB among prior art with similar bandwidth. Additionally, the prototype demonstrates robust performance across a wide range of temperatures.