20.5 A 76.6dB-SNDR 50MHz-BW 29.2mW Noise-Coupling-Assisted CT Sturdy MASH ΔΣ Modulator with 1.5b/4b Quantizers in 28nm CMOS

The demands for wider cellular bandwidth (BW) drive the development of continuous time (CT) ΔΣ modulators (DSMs). Oversampling ratio (OSR) is generally restricted due to high signal BW. To obtain an adequate resolution while maintaining good power efficiency, CT DSMs generally need to achieve an aggressive noise shaping and employ a multibit quantizer (QTZ) [1]-[3]. Though multibit operation requires a highly linear feedback (FB) DAC, dictating sophisticated linearization techniques [1]-[3]. Multi-stage noise-shaping (MASH) topologies can be employed to increase the order and they can apply multibit quantization only in the latter stages, where linearity requirements are highly relaxed. However, MASH DSMs suffer from quantization noise (ON) leakage due to the mismatch between analog and digital filters.