A Fully Integrated, Custom End-to-End PPG Sensing System for Ultra-Low Power Wearables

Photoplethysmography (PPG) is a widely adopted technique for monitoring essential physiological parameters like heart rate and blood oxygen saturation (SpO2). The increasing demand for wearable health monitoring devices necessitates the development of energy-efficient PPG systems. This paper proposes an ultra-low power, end-to-end PPG sensing system with continuous monitoring capabilities. The system consists of three distinct chips: a system-on-chip, an analog-front end chip, and a Bluetooth low-energy transmitter, enabling real-time PPG data transmission to a smartphone. All components are fabricated using the bulk 65 nm low-power CMOS process. This system achieves minimal power consumption of 18.78 µW during idle periods and 148.5 µW during active data transmission when aggressively duty-cycled at 2.4%.