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

2025-09-08

AI Summary

To address the challenges of high sensitivity, ultra-low power consumption, and calibration-free operation in skin electrodermal activity (EDA) sensing for wearable devices, this work proposes a calibration-free analog front-end (AFE) architecture based on a voltage-controlled oscillator (VCO). Instead of conventional resistance or current measurement paradigms requiring subject-specific calibration, the design employs frequency-domain readout to directly map conductance variations. It achieves 40 ps resolution and <0.0025% relative error over a 0–1.5 Hz bandwidth. Through low-noise circuit design and post-layout optimization, the system attains an average power consumption of only 2.3 μW and an input-referred noise of 0.8 μV_rms. The proposed AFE significantly mitigates inter-subject variability, enabling robust, ultra-low-power, on-chip EDA monitoring suitable for continuous, multi-user applications.

Technology Category

• Humans and AI: Brain-Sensing and Analysis
• Machine Learning: Hardware-aware ML
• Cognitive Modeling & Cognitive Systems: Affective Computing

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Data quality aspects of human-annotated datasets

Abstract

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 Voltage-Controlled Oscillator-based Analog Readout tailored for continuous EDA sensing. The results show that our system achieves an exceptional average sensitivity of up to 40 pS within a 0-20 uS 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 uW based on post-layout validations and introduces a low noise contribution, measuring only 0.8 uVrms across the 0-1.5 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.

Problem

• Developing calibration-free analog readout for electrodermal activity sensing
• Addressing high sensitivity and low power requirements for wearables
• Reducing noise and calibration needs in continuous EDA monitoring

Innovation

• Voltage-Controlled Oscillator-based analog readout
• Achieves high sensitivity up to 40 pS
• Consumes only 2.3 uW average power