Continuous Time Level Crossing Sampling ADC for Bio-Potential Recording Systems.

Area of Science:

• Biomedical Engineering
• Analog Circuit Design
• Sensor Technology

Background:

• Wireless neurophysiological sensor systems require efficient analog-to-digital converters (ADCs) for bio-potential recording.
• Existing ADCs often face challenges with data size, power consumption, and silicon area.
• The development of low-power, compact ADCs is crucial for advanced bio-signal monitoring.

Purpose of the Study:

• To present the first fixed window level crossing sampling analog-to-digital converter (ADC) without local DACs and clocks.
• To design a circuit that minimizes data size, power consumption, and silicon area for wireless neurophysiological sensors.
• To evaluate the performance of the developed ADC for bio-potential signal recording.

Main Methods:

• Developed a novel fixed window level crossing sampling ADC architecture.
• Integrated a bio-potential amplifier with 53 dB gain and 200 Hz-20 kHz bandwidth.
• Fabricated the system using AMI 0.5 µm CMOS process on a 1.5 mm by 1.5 mm chip.

Main Results:

• Achieved an input-referred RMS noise of 2.8 µV for the bio-potential amplifier.
• Demonstrated a minimum delta resolution of 4 mV and an input signal frequency up to 5 kHz for the ADC.
• Reported a 4-channel system power consumption of 118.8 µW (static) and 501.6 µW (240 kS/s sampling rate).
• Attained a conversion efficiency of 1.6 nJ/conversion.

Conclusions:

• The proposed fixed window level crossing ADC is a viable solution for low-power, compact bio-potential recording.
• The circuit effectively reduces data size and power consumption, suitable for future wireless neurophysiological applications.
• The fabricated system demonstrates promising performance metrics for bio-signal acquisition.