A Motion-Artifact-Tolerant Biopotential-Recording IC With a Digital-Assisted Loop

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Signal Processing

Background:

• Motion artifacts are a significant challenge in multi-channel biopotential recording, often leading to signal loss and reduced data quality.
• Existing systems struggle to accurately track and compensate for large amplitude motion artifacts across varying bandwidths.
• Electrode DC offsets and 1/f noise further degrade the quality of recorded biopotential signals.

Purpose of the Study:

• To propose and characterize a novel motion-artifact-tolerant multi-channel biopotential-recording integrated circuit (IC).
• To demonstrate the effectiveness of a digital-assisted loop (DAL) in tracking and mitigating motion artifacts.
• To achieve low noise levels and high signal-to-noise-and-distortion ratio (SNDR) for reliable biopotential signal acquisition.

Main Methods:

• Implementation of a novel counter-based digital-assisted loop (DAL) for motion artifact tracking.
• Integration of four analog front-end (AFE) channels sharing a programmable gain amplifier (PGA) and analog-to-digital converter (ADC) via time-multiplexing.
• Inclusion of a chopper with an analog DC-servo loop (DSL) for electrode DC offset (EDO) cancellation and 1/f noise reduction.

Main Results:

• The DAL effectively tracks motion artifacts up to 120 mV with a 10 Hz bandwidth and up to 240 mV with a 5 Hz bandwidth without signal loss.
• The fabricated IC achieves a low input-referred noise (IRN) of 0.71 µV over a 0.5–500 Hz bandwidth and an SNDR of 63.34 dB.
• The IC demonstrates efficient power consumption (5.74 µW) and a compact area (0.40 mm²/channel) in a 0.18-µm CMOS process.

Conclusions:

• The proposed IC offers robust performance in the presence of significant motion artifacts, making it suitable for various biopotential recording applications.
• The combination of DAL, shared PGA/ADC, and DSL effectively addresses key challenges in biopotential signal acquisition, including motion artifacts, DC offsets, and noise.
• This artifact-tolerant, low-noise IC represents a significant advancement for wearable and implantable biopotential monitoring systems.