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~μ {m} 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~μ {W} , the LED driver is power 29.3~μ {W}. 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~μ {A} 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.