An Ultra-Low Power Fixed-Window Level Crossing ADC for ECG Recording

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Signal Processing

Background:

• Electrocardiogram (ECG) monitoring requires efficient analog-to-digital converters (ADCs) for accurate signal acquisition.
• Conventional ADCs can be complex and power-hungry, limiting their use in portable or implantable devices.
• Level-crossing ADCs offer an alternative sampling strategy that can reduce data rates and power consumption.

Purpose of the Study:

• To propose and evaluate a novel fixed-window level-crossing analog-to-digital converter (LCADC) specifically designed for ECG monitoring applications.
• To reduce the complexity, silicon area, and power consumption of the ADC compared to conventional designs.
• To demonstrate the effectiveness of the proposed LCADC for R-peak detection in ECG signals.

Main Methods:

• Design and simulation of a fixed-window level-crossing analog-to-digital converter (LCADC).
• Implementation of the circuit using 0.18 µm CMOS technology with a 0.9 V supply voltage.
• Evaluation of performance using standard ECG signals and a level-crossing-based R-peak detection algorithm.

Main Results:

• The proposed LCADC utilizes fewer comparators and reference levels, reducing circuit complexity and silicon area (0.05846 mm²).
• Achieved a significant 5-fold reduction in comparator activity with standard ECG signals.
• Demonstrated a low power consumption of 5.9 nW and a resolution of 7.4 bits.
• Successful application of an R-peak detection algorithm to the LCADC output samples.

Conclusions:

• The novel fixed-window LCADC is a highly efficient solution for ECG monitoring, offering reduced power consumption and complexity.
• The design proves effective for capturing ECG signals and enabling critical diagnostic algorithms like R-peak detection.
• This work contributes to the development of more compact and power-efficient wearable or implantable ECG monitoring systems.