<p>This study presents a new low power reflectance type optical Photoplethysmography (PPG) Acquisition system for the Mental Distress estimation. The design system incorporates a new trans-impedance amplifier with DC drift compensation (TIA), a high pass filter (HPF), a current steering low pass filter (LPF), an oscillator (OSC), an adaptive reference generator and a comparator (COMP). TIA convert the photocurrent to voltage. HPF and LPF are used herein to remove the 0.1HZ-10Hz noise whereas the clocked comparator is used herein to converter the receive PPG signal in a pulse. OSC is used herein to generate the clock for the comparator as well as the LED driver circuit. Heartbeat locked has been used to control the LED intensity to achieve ultra-low power consumption. The front-end circuit is implemented in the integrated chip with chip area of 1200μm × 1200μm and fabricated via TSMC T18 process. The sensing range of the readout circuit is 20nA to 11µA, with 1.8 V supply and the total power consumption of the readout system is 52.2µW. The readout system bandwidth is 0.1Hz-10Hz. The power consumption of the voltage control oscillator (@1MHZ) and 4096 dividers is 48.6 µW. Thence the total power consumption of the design chip is 100.2µW. The designed acquisition system is applied to the wrist artery of the five healthy patients when calculating the pictorial puzzles. The blood volume information and pulse interval are used to find the number of temporals, morphological and frequency features. The obtained has been used to characterize the pulse rate variability (PRV). The statistical deviation of the PRV has been analyzed on the basis of obtained features. The standard deviation of NN interval, the dynamic range of the NN interval, and the standard deviation of PRV derivative show increasing value when subjects are in the stress. &nbsp;</p>

A New Low Power Photoplethysmography Signal Acquisition System For Mental Stress Estimation

Paper Proceedings: https://asmedigitalcollection.asme.org/ISPS/ISPS2021/volume/84799

ASME 2021 Information Storage and Processing Systems (ISPS2021)

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