A 101-dB DR 2.2GΩ-Input-Impedance Direct Digitization ExG Front-End With Δ-Modulation

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Signal Processing

Background:

• Continuous health monitoring requires analog front-end (AFE) circuits with high dynamic range (DR), low noise, high input impedance, and low power consumption.
• Conventional G m -C ΔΣ ADCs face challenges in meeting these stringent demands for long-term bio-signal acquisition.

Purpose of the Study:

• To introduce a DR-enhanced direct-digitization AFE for improved bio-signal recording.
• To relax dynamic range constraints in ΔΣ ADCs through a novel architecture.

Main Methods:

• Developed a DR-enhanced direct-digitization AFE utilizing a Δ-modulated transconductor (TC) stage and a second-order ΔΣ ADC.
• Implemented a current-balancing transconductor and a flipped-voltage-follower (FVF) loop for high input impedance and linearity.
• Fabricated the AFE using a standard 180nm CMOS process.

Main Results:

• Achieved a Signal-to-Noise and Distortion Ratio (SNDR) of 91 dB and a dynamic range (DR) of 101 dB.
• Measured input-referred noise of 58 nV/√Hz and power consumption of 63 μW.
• Demonstrated high Figure of Merit (FoM) values: FoMSNDR of 160.1 dB and FoMDR of 170 dB.

Conclusions:

• The proposed Δ-ΔΣ AFE effectively enhances DR and reduces noise for bio-signal acquisition.
• Validated through scalp EEG, leg EMG, and chest ECG recordings, proving motion-artifact tolerance.
• Suitable for long-term, continuous health monitoring applications requiring robust bio-signal front ends.