VCO-CARE: VCO-based Calibration-free Analog Readout for Electrodermal activity sensing

Continuous monitoring of electrodermal activity (EDA) through wearable devices has attracted much attention in recent times. However, the persistent challenge demands analog front-end (AFE) systems with high sensitivity, low power consumption, and minimal calibration requirements to ensure practical usability in wearable technologies. In response to this challenge, this research introduces VCO-CARE, a VoltageControlled Oscillator-based Analog Readout tailored for continuous EDA sensing. The results show that our system achieves an exceptional average sensitivity of up to $\mathbf{4 0 ~ p S}$ within a $\mathbf{0 - 2 0} \mu \mathrm{S}$ range and a negligible relative error of less than 0.0025% for fixed-resistance. Furthermore, the proposed system consumes only an average of $2.3 \mu \mathrm{~W}$ based on post-layout validations and introduces a low noise contribution, measuring only $0.8 \mu \mathrm{~V}_{\text {rms }}$ across the $0-1.5 \mathrm{~Hz}$ EDA signal band. This research aims to drive the evolution of wearable sensors characterized by seamless adaptability to diverse users, minimal power consumption, and outstanding noise resilience.