A 600mVPP-Input-Range 94.5dB-SNDR NS-SAR-Nested DSM with 4th-Order Truncation-Error Shaping and Input-Impedance Boosting for Biosignal Acquisition

Abstract

We present a 600mVPP-linear-input-range 94.5dB-SNDR NS-SAR-based DSM with input-impedance (ZIN) boosting for biopotential recording. The proposed direct-conversion ADC utilizes a 1st-order DSM to widen the input range and a 2nd-order noise-shaping SAR (NS-SAR) ADC for high resolution and power efficiency. Also, by feeding the truncation (TRNC) error back to the NS-SAR ADC, the error is shaped in the 4th order, further lowering the noise. Fabricated in 65nm CMOS, the NS-SAR-nested DSM achieves 208MO ZIN at DC, 174.3dB FOMSNDR, and 175.6dB FOMDR, consuming 5.2W.