An Amplifier-Less Calibration-Free SAR ADC Achieving >100dB SNDR for Multi-Channel ECG Acquisition with 667mVpp Linear Input Range

Abstract

This work presents a time-multiplexing SAR ADC to support up to 5-lead ECG monitoring with >100dB SNDR per readout channel. Its noise and linearity performance are enhanced by a combination of dual-reference architecture and mismatch error shaping (MES) technique without using amplifiers or calibration, resulting in >106dB SFDR and 109.4dB DR within 250Hz bandwidth (FoMS,DR=178.9dB). The ECG analog front-end (AFE), including 3 DC-coupled instrumentation amplifiers (IAs) and 1 ADC, occupies only 0.48mm2 in 55nm CMOS. Each ECG channel achieves 1μVrms (0.5-250Hz) input-referred noise at a low IA gain of 6V/V with a 667mVpp-diff linear input range.