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

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 LSB and 9 dB, respectively, compared to when the noise shaping is off. Fabricated using a 55 nm CMOS MOMCAP technology and tested with a −2.5 dB sinewave input, the bridged SAR ADC achieves an SNR of 62.2 dB and an INL better than 1 LSB, when consuming a power of 7 2 μ W , at a supply voltage of 1.2 V and sampling frequency of 50 kHz. The ADC's active area is 3 0 0 × 3 8 0 μ m 2 . [ABSTRACT FROM AUTHOR]