Low-Power High-Sensitivity Photoplethysmography Sensor for Wearable Health Monitoring System

This article presents a Photoplethysmography (PPG) sensory system for continuous health monitoring. The PPG chip is fabricated using 0.35 μm standard CMOS technology and occupies 2.3 mm × 1.7 mm. The average power consumption of the receiver analog front-end (AFE) is 50.75 μW, the LED driver is power 29.3 μW. The consumed power is dramatically reduced due to the using of both low duty cycle for LED lighting and automatic light control (ALC). The PPG sensor has a low input noise current of 41.3 pA and can reject a DC photocurrent up to 24 μA because of the integrated background light cancelation (BLC) loop. 12-b SAR-ADC and Serial Peripheral Interface (SPI) are integrated for communication with MCU used for signal processing and results display. Readings of 9 subjects show mean absolute error (MAE) and standard deviation (SD) of 1.95±2.13 beats per minute (BPM), 6.00±4.18mmHg, and 6.13±3.93mmHg, for heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP), respectively.