A Two-Electrode 2.88nJ/Conversion Biopotential Acquisition System for Portable Healthcare Device

Abstract

A 2.88nJ/Conversion low energy biopotential acquisition system is designed for portable healthcare device. Two dry copper contact electrodes with 1.2-cm diameter are used to easily interface between skin and healthcare device. Chopping technique is adopted at readout front end to obtain thermal noise floor of 1.3uVrms over 0.5 similar to 200Hz and CMRR over 100dB to mitigate common-mode body potential induced from AC power line. A 4-stage gain control and band selection blocks are integrated to digitally calibrate for different types of biomedical signal and an 8-bit synchronous successive approximation register (SAR) A/D is used to digitize sensed biopotentials. A test chip is implemented in 0.18um, 1.8V supply CMOS technology and successively verified by readout ECG signal with two electrodes contact at chest of body with separating 6cm.