A 174.3dB FoM VCO-based CT ΔΣ modulator with a fully digital phase extended quantizer and tri-level resistor DAC in 130nm CMOS

This paper presents a high dynamic range (DR), power efficient VCO-based continuous time ΔΣ modulator (CTDSM). It introduces a simple, robust and low power fully digital phase extended quantizer (PEQ) that doubles the VCO quantizer resolution compared to conventional XOR-based phase detector with minimum overhead. A tri-level resistor DAC 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 130nm CMOS, the ADC achieved peak Schreier FoM of 174.3dB with a high DR of 89dB over 0.4MHz BW, consuming only 1mW under 1.2 V power supply. It also reaches a peak Walden FoM of 59fJ/conv with 74.7dB SNDR over 2MHz BW.