A 174.3-dB FoM VCO-Based CT $\Delta \Sigma $ Modulator With a Fully-Digital Phase Extended Quantizer and Tri-Level Resistor DAC in 130-nm CMOS

This paper presents a high dynamic range (DR) power-efficient voltage-controlled oscillator (VCO)-based continuous-time $\Delta \Sigma $ modulator. It introduces a robust and low-power fully-digital phase extended quantizer that doubles the VCO quantizer resolution compared to a conventional XOR-based phase detector. A tri-level resistor digital-to-analog converter is also introduced as complementary to the new quantizer, enabling high DR while creating a dynamic power saving mechanism for the proposed design. Fabricated in 130-nm CMOS, the analog-to-digital converter achieved peak Schreier Figure-of-Merit (FoM) of 174.3 dB with a high DR of 89 dB over 0.4-MHz BW, consuming only 1 mW under 1.2-V power supply. It also reaches a peak Walden FoM of 59 fJ/conv with 74.7-dB signal-to-noise-and-distortion ratio over 2-MHz BW.