A 10-Bit 300 kS/s Reference-Voltage Regulator Free SAR ADC for Wireless-Powered Implantable Medical Devices

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Integrated Circuit Design

Background:

• Implantable medical devices require low-power, miniaturized electronic components.
• Traditional analog-to-digital converters (ADCs) often rely on power-hungry voltage regulators and bulky decoupling capacitors.
• Supply voltage fluctuations can degrade ADC performance, a critical issue in wireless-powered systems.

Purpose of the Study:

• To develop a reference-voltage regulator-free SAR ADC for wireless-powered implantable medical devices.
• To enhance power efficiency and reduce the form factor of implantable ADCs.
• To maintain high performance despite supply voltage variations.

Main Methods:

• Implementation of a self-timed pre-charging technique within the SAR ADC architecture.
• Fabrication using 0.18-µm complementary metal-oxide-semiconductor (CMOS) technology.
• Characterization of the ADC's performance, including SNDR, power consumption, and FOM.

Main Results:

• Achieved a Signal To Noise And Distortion Ratio (SNDR) of 53.32 dB at 0.8 V.
• Demonstrated insensitivity to a 50 mVpp supply voltage fluctuation.
• Consumed only 2.72 µW at a 300 kS/s sampling rate.
• Attained a figure-of-merit (FOM) of 23.9 fJ/conversion-step.

Conclusions:

• The proposed self-timed pre-charging SAR ADC effectively eliminates the need for a reference voltage regulator and decoupling capacitor.
• This design offers a significant reduction in power consumption and area, suitable for wireless-powered implantable medical devices.
• The ADC maintains robust performance under supply voltage fluctuations, ensuring reliability in its target application.