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

• Published in: IEEE sensors journal Vol. 21; no. 14; pp. 16141 - 16151
• Main Authors: Lin, Binghui, Ma, Zhouchen, Atef, Mohamed, Ying, Liang, Wang, Guoxing
• Format: Journal Article
• Language: English
• Published: New York IEEE 15.07.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: analog front end; Automatic control; Biomedical electronics; Blood; Blood pressure; CMOS; duty cycling; Heart rate; LED driver; Light emitting diodes; low-power; Optical receivers; Optical sensors; Optical transmitters; Photoelectric effect; Photoelectric emission; Photoplethysmography; Power consumption; Resistors; Signal processing; Telemedicine; wearable sensors
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2021.3062189

This article presents a Photoplethysmography (PPG) sensory system for continuous health monitoring. The PPG chip is fabricated using <inline-formula> <tex-math notation="LaTeX">0.35~\mu \text{m} </tex-math></inline-formula> standard CMOS technology and occupies 2.3 mm <inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> 1.7 mm. The average power consumption of the receiver analog front-end (AFE) is <inline-formula> <tex-math notation="LaTeX">50.75~\mu \text{W} </tex-math></inline-formula>, the LED driver is power <inline-formula> <tex-math notation="LaTeX">29.3~\mu \text{W} </tex-math></inline-formula>. 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 <inline-formula> <tex-math notation="LaTeX">24~\mu \text{A} </tex-math></inline-formula> 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.