Low Power IC Design for Health Sensing

Abstract

This work proposes a new time-domain integration method to realize Electrochemical Impedance Spectroscopy (EIS). Unlike traditional EIS systems using Fast Fourier Transform (FFT) or Frequency Response Analyzer (FRA) based on a clean quadrature sinusoid stimulus, A single low-frequency, low-amplitude sinusoid stimulus is proposed by using a sinusoid DAC which fully eliminates the analog filter. The response current is integrated by a switched capacitor circuit which is synchronized by the proposed sinusoid DAC. The integration output is sampled and digitized by an 8-bit SAR ADC. The phase and amplitude information of target impedance can be extracted from the time-domain data. The error caused by harmonic generation in the sinusoid DAC can be suppressed by the time-domain integration. The (1×1.1) mm^2 prototype is fabricated in a 130nm CMOS process. It consumes 10µA from a 1.2V supply. Compared with the existing EIS systems, the test results show that the system can obtain a reasonable error with much smaller area and much lower power consumption.