A 62.5 kHz-BW 92 dB-SNDR noise-shaping SAR ADC with NS-CAL method

DAC mismatch is a significant error in NS-SAR ADCs, as it introduces essentially nonlinear behavior and limits the number of bits in the DAC array. In this paper, we propose a novel foreground digital calibration method for NS-SAR ADCs. This method, combined with noise shaping technique, improves calibration accuracy and eliminates the impact of error accumulation on high-bit weights. Thus, it increases the number of bits in the DAC array in NS-SAR ADCs, and decreases the noise floor caused by quantization error. We implemented this design using a 110-nm CMOS process. As a result, post-layout simulation shows 92 dB SNDR and 108 dB SFDR under × 16 OSR and 1.5 V supply. Compared with conventional foreground calibration method, the SNDR increases from 81 dB to 92 dB and the SFDR increases from 84 dB to 108 dB with a power consumption of 40 μW, resulting in a FoMs of 182 dB and a FoMw of 15.3 fJ/conversion-step, respectively.