A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter

Son, Chanyoung; Koh, Seok-Tae; Jeon, Hyuntak

doi:10.3390/mi16040398

Open AccessArticle

A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter

by

Chanyoung Son

¹,

Seok-Tae Koh

^2,* and

Hyuntak Jeon

^1,*

¹

School of Semiconductor Engineering, Chungbuk National University (CBNU), Cheongju 28644, Republic of Korea

²

School of Electrical Engineering, Chungbuk National University (CBNU), Cheongju 28644, Republic of Korea

^*

Authors to whom correspondence should be addressed.

Micromachines 2025, 16(4), 398; https://doi.org/10.3390/mi16040398

Submission received: 20 February 2025 / Revised: 25 March 2025 / Accepted: 26 March 2025 / Published: 29 March 2025

(This article belongs to the Special Issue Micro/Nano Sensors: Fabrication and Applications)

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Abstract

This paper presents a low-power photoplethysmography (PPG) readout system designed for wearable health monitoring. The system employs a differential current mirror (DCM) to convert single-ended PPG currents into differential voltages, inherently suppressing DC components. A wide common-mode input range (WCMIR) SAR ADC processes the differential signals, ensuring accurate analog-to-digital conversion. The DCM eliminates the need for DC cancelation loops, simplifying the design and reducing power consumption. Implemented in a 0.18 µm CMOS process, the system occupies only 0.30 mm², making it suitable for multi-channel applications. The system achieves over 60 dB DC dynamic range and consumes only 9.6 µW, demonstrating its efficiency for portable devices. The simulation results validate its ability to process PPG signals across various conditions, offering a scalable solution for advanced biomedical sensing platforms.

Keywords: PPG (photoplethysmography); readout ICs (ROICs); differential current mirror (DCM); successive approximation register (SAR); analog-to-digital converter (ADC)

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MDPI and ACS Style

Son, C.; Koh, S.-T.; Jeon, H. A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter. Micromachines 2025, 16, 398. https://doi.org/10.3390/mi16040398

AMA Style

Son C, Koh S-T, Jeon H. A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter. Micromachines. 2025; 16(4):398. https://doi.org/10.3390/mi16040398

Chicago/Turabian Style

Son, Chanyoung, Seok-Tae Koh, and Hyuntak Jeon. 2025. "A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter" Micromachines 16, no. 4: 398. https://doi.org/10.3390/mi16040398

APA Style

Son, C., Koh, S.-T., & Jeon, H. (2025). A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter. Micromachines, 16(4), 398. https://doi.org/10.3390/mi16040398

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

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A Low-Power, Auto-DC-Suppressed Photoplethysmography Readout System with Differential Current Mirrors and Wide Common-Mode Input Range Successive Approximation Register Analog-to-Digital Converter

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