A 400 mV 160 nW/Ch Compact Energy Efficient ∆Σ Modulator for Multichannel Biopotential Signal Acquisition System

Area of Science:

• Electronics
• Biomedical Engineering
• Signal Processing

Background:

• Analog-to-digital converter (ADC) design for biomedical systems faces challenges in high density and low power consumption.
• Passive integrator and loop-filter based delta-sigma modulators (DSMs) offer ultra-low-power solutions for multi-channel biopotential acquisition but require high oversampling ratios (OSR).
• High OSR increases power consumption in both the modulator and subsequent digital filters.

Purpose of the Study:

• To present a low OSR passive integrator-based DSM for energy-efficient multi-channel biopotential recording.
• To enable highly area, power, and energy-efficient DSMs suitable for biomedical applications.

Main Methods:

• Utilized a duty-cycled resistor (DCR) to achieve large time constants in a passive loop-filter.
• Designed and fabricated a second-order, duty-cycled passive integrator-based continuous-time delta-sigma modulator (CTDSM).
• Implemented the design in 65 nm CMOS technology for a 10 kHz biopotential bandwidth.

Main Results:

• Achieved a Signal-to-Noise-and-Distortion Ratio (SNDR)/Dynamic Range (DR) of 56.36/63.1 dB.
• Consumed only 160 nW of power with an OSR of 32.
• Occupied an area of 0.035 mm² with a state-of-the-art energy efficiency of 14.9 fJ/conv.

Conclusions:

• The proposed low OSR DSM with DCR is highly area, power, and energy-efficient.
• This design is suitable for multi-channel biopotential recording systems.
• In-vitro and in-vivo measurements validated the DSM's performance.