A TDM-Based 16-Channel AFE ASIC With Enhanced System-Level CMRR for Wearable EEG Recording With Dry Electrodes.

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Wearable Technology

Background:

• Wearable electroencephalography (EEG) recording demands compact, low-power analog front-end (AFE) integrated circuits (ICs).
• Existing AFEs often struggle with input-referred noise and common-mode rejection ratio (CMRR) in multi-channel systems.
• Reducing chip size and power consumption are critical for wearable applications.

Purpose of the Study:

• To develop a multi-channel AFE ASIC for wearable EEG applications.
• To improve input-referred noise and system-level CMRR using a unified TDM/CS approach.
• To reduce chip size and power consumption through shared second-stage amplification.

Main Methods:

• A multi-channel AFE ASIC was designed integrating chopping stabilization (CS) and time-division-multiplexing (TDM).
• Dual feedback loops were incorporated for input impedance boosting and electrode offset cancellation.
• The AFE was implemented using a 0.18-μm CMOS process.

Main Results:

• The AFE achieved an input-referred noise of 0.63 μVrms (0.5 Hz-100 Hz).
• Input impedance was boosted to 560 MΩ at 50 Hz.
• Measured amplifier intrinsic CMRR was 89 dB, and system-level AFE CMRR was 82 dB.
• The AFE demonstrated low power consumption of 24 μW at a 1 V supply.

Conclusions:

• The proposed TDM/CS structure effectively enhances noise performance and CMRR for multi-channel wearable EEG AFEs.
• The integrated design significantly reduces chip size and power consumption, making it suitable for wearable devices.
• The developed AFE meets key performance metrics for advanced EEG monitoring applications.