A New 12-bit Fully Differential SAR ADC for Wireless Implantable Neural Recording System

Low power, small volume and high acquisition precision are always important in the internal module of wireless implantable neural recording system. This paper describes the design and implementation of a new successive approximation (SAR) ADC to meet the unique requirements of wireless implantable neural recording system. In the designed new ADC, a fully differential structure is used to avoid the crosstalk from the digital circuit to the converter. Instead of using all capacitive DAC traditionally, a resistor array Sub-DAC is interpolated to increase the resolution and to avoid a large capacitor array. Moreover, after every conversion period, the sleep mode is introduced to reduce power consumption. Designed in a 0.35-mu m CMOS process with a 3.3-V supply, the entire ADC, working at 20kS/s, consumes 38 mu W power and occupies an area of 0.17mm(2).