Ultra-Low-Power PPG Analog Signal Processing Circuit for Continuous Blood Pressure Estimation

This paper describes a novel photoplethysmography-based blood pressure estimation circuit developed as a non-invasive and continuous alternative to current clinical blood pressure monitoring devices. The system integrates the function-alities of analogue front-end and analogue-to-digital converter elements in conventional photoplethysmography sensors and extracts features related to blood pressure on chip. The topology operates in analogue domain, current mode and ultra-low-power, thus suppressing digitisation and current-to-voltage conversion errors and reducing overall power consumption. The circuit has been designed in CMOS 65 nm technology. It employs a 1.5 V supply, consumes
${\sim 345\text{nW}}$
(five times less power than state-of-the-art) and generates feature voltages with a 50 mV max. deviation. A linear regressor trained with the extracted features achieves
${0.7\pm 0.9}$
mmHg accuracy (grade A performance). The operation of the topology is described and results depicting its performance are presented
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This work was funded by the Engineering and Physical Research Council under grant EP/T001259/1.