A 0.62 $\mu$W/sensor 82 fps Time-to-Digital Impedance Measurement IC with Unified Excitation/Readout Front-end for Large-Scale Piezo-Resistive Sensor Array

This paper presents a fast impedance measurement IC for large-scale piezo-resistive sensor array. It features a unified differential time-to-digital demodulation architecture that readout impedance directly through the excitation circuit. The proposed pre-saturation adaptive bias technique further improves power efficiency. The chip scans 253 sensors in 12.2 ms (82 fps) at 125 kHz, consuming 158 $\mu$W (7.5 nJ/sensor). With loads from 20 $\mathrm{\Omega }$ to 500 k$\mathrm{\Omega }$, it achieves 0.5% error and up to 71.1 dB SNR.