A 7.6-nW 1-kS/s 10-Bit SAR ADC for Biomedical Applications

Area of Science:

• * Electrical Engineering
• * Biomedical Engineering
• * Integrated Circuit Design

Background:

• * Conventional successive approximation register (SAR) analog-to-digital converters (ADCs) face challenges in power consumption and complexity for biomedical applications.
• * Existing capacitor digital-to-analog converter (CDAC) switching schemes can be energy-intensive and sensitive to voltage variations.
• * Power management in high-resolution ADCs for portable biomedical devices is critical.

Purpose of the Study:

• * To develop an energy-efficient 10-bit SAR ADC with a low-complexity switching scheme.
• * To integrate automatic ON/OFF functionalities for the comparator and SAR logic to minimize power draw.
• * To optimize the ADC design for reduced dependency on voltage accuracy and DAC control complexity for biomedical applications.

Main Methods:

• * Implementation of an energy-efficient capacitor switching scheme for the CDAC.
• * Integration of automatic ON/OFF comparator and SAR logic using dynamic circuits.
• * Design and fabrication of a prototype 10-bit SAR ADC in a 180 nm CMOS process.

Main Results:

• * Achieved an average digital-to-analog converter switching energy of 63.56 CVref^2, a 95.34% reduction from conventional schemes.
• * Demonstrated a power consumption of 7.6 nW at 1 kS/s sampling rate with a 1.8-V supply.
• * Obtained a signal-to-noise-and distortion ratio (SNDR) of 45.90 dB and a figure of merit (FoM) of 51.7 fJ/conv.-step.

Conclusions:

• * The proposed energy-efficient switching scheme and automatic ON/OFF techniques significantly reduce power consumption in SAR ADCs.
• * The developed ADC is suitable for low-power biomedical applications due to its low energy footprint and reduced complexity.
• * The design demonstrates a promising trade-off between performance metrics (SNDR, FoM) and power efficiency.