An Ultra-Low Power Charge Redistribution Successive Approximation Register A/D Converter for Biomedical Applications

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Microelectronics

Background:

• Power consumption is critical for implantable biomedical devices, necessitating efficient components.
• Analog-to-Digital Converters (ADCs) are essential interfaces in these devices, impacting overall system power draw.

Purpose of the Study:

• To design and characterize an ultra-low-power 8-bit Charge Redistribution Successive Approximation Register (CR-SAR) analog-to-digital converter.
• To meet the stringent power constraints of battery-operated biomedical devices, specifically targeting applications like pacemakers.

Main Methods:

• Implementation of an 8-bit CR-SAR ADC architecture.
• Utilizing standard TSMC 0.18μm CMOS technology for fabrication.
• Optimization of the ADC design for minimal power consumption and specific data rates.

Main Results:

• Achieved ultra-low power consumption below 250nW at a 1KB/s conversion rate.
• Demonstrated high accuracy with Integral Nonlinearity (INL) < 0.22 LSB and Differential Nonlinearity (DNL) < 0.04 LSB.
• Operated at a 1V supply voltage, converting input signals from 0V to 250mV.

Conclusions:

• The designed 8-bit CR-SAR ADC is suitable for low-power, low-data-rate biomedical applications.
• The ADC's performance metrics significantly exceed standard requirements for INL and DNL.
• This design offers a viable solution for extending the operational lifetime of pacemakers and similar devices.