A 0.6V 785-nW Multimodal Sensor Interface IC for Ozone Pollutant Sensing and Correlated Cardiovascular Disease Monitoring
Rishika Agarwala, Peng Wang, Henry L. Bishop, Anjana Dissanayake, Benton H. Calhoun
Abstract
In this article, we present the design and analysis of a 785-nW multimodal sensor interface IC for ozone pollutant sensing and correlated cardiovascular disease monitoring based on electrocardiography (ECG) and photoplethysmography (PPG). The proposed hybrid dc offset current cancellation (DCOC) along with a 4- MΩ gain-regulated cascode transimpedance amplifier (RGC-TIA) enable PPG readout power reduction by 37×, compared with the state-of-the-art PPG sensor interfaces. The ozone sensing channel proposes an adaptive architecture to enable low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> operation, achieving a 300× power reduction, compared with the state-of-the-art gas sensing readouts. The ozone sensing channel's performance was also verified using custom resistive metal-oxide sensors for concentrations from 50 to 900 ppb. The sensor interface IC is fabricated in a 65-nm CMOS, integrating a 165-nW voltage-mode ECG channel, a 532-nW current-mode PPG channel, 76-nW resistive-mode ozone channel, and 12.6-nW peripheral circuits, all at 0.6 V. The total system power consumption including the LED and a custom digital readout IC is 10.98- 15.51 μW, which is 41×- 57× less than prior ozone/CVD joint monitoring sensor interface systems.