Towards a Self-Powered ECG and PPG Sensing Wearable Device.

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Wearable Technology

Background:

• Wearable biosensing devices require integrated, low-power solutions for continuous health monitoring.
• Existing systems often face challenges with power management and signal acquisition accuracy.
• Development of self-powered systems is crucial for user convenience and prolonged operation.

Purpose of the Study:

• To present a multifunctional sensor interface system-on-chip (SoC) for self-powered Electrocardiography (ECG) and Photoplethysmography (PPG) wearable devices.
• To demonstrate the integration of PPG and ECG sensing AFEs with a power management unit for energy harvesting.
• To verify the functionality and performance of the proposed SoC through post-layout simulations.

Main Methods:

• Design and simulation of a 2x2.5 mm² SoC in 0.18μm CMOS technology.
• Implementation of a switch-capacitor-based LED driver and analog front-end (AFE) for PPG sensing.
• Development of an ECG sensing AFE and a power management unit for Thermoelectric Generator (TEG) energy harvesting.

Main Results:

• The LED driver achieves instantaneous current up to 40 mA.
• PPG AFE offers adjustable gain (114-120 dBΩ) and low input-referred noise (119 pA_RMS).
• ECG AFE provides adjustable gain (47-63 dB) and low input-referred noise (7.83 µV_RMS), with efficient TEG energy harvesting from 350 mV.

Conclusions:

• The developed SoC is a promising integrated solution for self-powered wearable ECG and PPG devices.
• The system demonstrates effective energy harvesting and high-performance biosignal acquisition.
• This technology facilitates the advancement of unobtrusive and continuous health monitoring systems.