(A) ∆-∆Σ-based bio-impedance readout IC with baseline cancellation

Abstract

The measurement of bio-impedance (BioZ) is a common technique that monitors health status and detects abnormal physiological features. This paper presents a BioZ readout IC with baseline cancellation. The baseline cancellation based on ∆-modulation is implemented to achieve a wide input dynamic range by rejecting the large static baseline impedance. In addition, techniques such as chopping and dynamic element matching (DEM) are used to mitigate the noise, which is a dominant source in the signal bandwidth. The current generator(CG) generates the square wave for the stimulus current, and its current magnitude is from 5µApk to 100µApk, which can measure the frequency range from 1kHz to 1MHz. The signal generated by BioZ is measured through a readout front-end (RFE) based on ∆-∆Σ modulator. The full channel signal-to-noise ratio (SNR) is 72.8dB for 20Ω input impedance and 94.2dB for 30kΩ input impedance. The RFE consumes only 14.2µW, while the total power consumption of each channel is 173.1µW.