A 10.5-b ENOB 645 nW 100kS/s SAR ADC with statistical estimation based noise reduction

This paper presents a power-efficient SNR enhancement technique for SAR ADCs. By accurately estimating the conversion residue, it can suppress both comparator noise and quantization error. Thus, it allows the use of a noisy low-power comparator and a relatively low resolution DAC to achieve high resolution. The proposed technique has low hardware complexity, requiring no change to the standard ADC operation except for repeating the LSB comparisons. A prototype ADC is designed in 65nm CMOS. Its SNR is improved by 7dB with the proposed technique. Overall, it achieves 10.5-b ENOB while operating at 100kS/s and consuming 645nW from a 0.7V power supply.