Digital Background Calibration Assisted with Noise-Shaping for a 10-b Bridged SAR ADC

Abstract

This paper presents a background calibration method assisted with noise-shaping, for a 10-b bridged SAR ADC. It proposes calibrating the mismatches from the MSB capacitors using the LSBs. First-order noise-shaping has been employed to facilitate the calibration as well as the analog-to-digital conversion. Since noise-shaping is able to shape both the comparator input and quantization noise, it is expected to improve the calibration effects as well as the SNR, for the SAR ADC. Measurement results show, upon the proposed calibration, the SAR’s INL and SNR are improved by 3[Formula: see text]LSB and 9[Formula: see text]dB, respectively, compared to when the noise shaping is off. Fabricated using a 55[Formula: see text]nm CMOS MOMCAP technology and tested with a −2.5[Formula: see text]dB sinewave input, the bridged SAR ADC achieves an SNR of 62.2[Formula: see text]dB and an INL better than 1[Formula: see text]LSB, when consuming a power of [Formula: see text], at a supply voltage of 1.2[Formula: see text]V and sampling frequency of 50[Formula: see text]kHz. The ADC’s active area is [Formula: see text].