A 0.6-V 94-nW 10-Bit 200-kS/s Single-Ended SAR ADC for Implantable Biosensor Applications

This work presents an ultralow-power 10-bit 200-kS/s single-ended successive approximation register (SAR) analog-to-digital converter (ADC) for implantable biosensor applications. A high energy- and area-efficient switching scheme is proposed, which realizes 95.4% energy saving in a digital-to-analog converter (DAC) switching and two times DAC area reduction compared to the conventional single-ended SAR ADC. The common-mode variation in the proposed scheme is input-independent, resulting in a reduced dynamic offset and harmonic distortion. Besides, a low offset and low kickback noise dynamic comparator with P-type input pair is realized. The prototype is fabricated in 65-nm CMOS technology, consuming 94 nW at 0.6-V supply and occupying a 0.02-mm
²
active area. With the Nyquist input frequency, it achieves the signal to noise and distortion ratio (SNDR) of 56.42 dB, leading to a Walden figure of merit (FoM) of 0.87 fJ/conv.-step.