A 7b 2 GS/s Time-Interleaved SAR ADC with Time Skew Calibration Based on Current Integrating Sampler

This paper presents a time-interleaved (TI) SAR ADC that utilizes the characteristic of the current integrating (CI) sampler for sampling time skew background calibration, while it also provides buffering and anti-aliasing filtering functions, simultaneously. The inter-sample interaction in the CI sampler enables the mapping of the time domain information to the amplitude domain. Time skew errors can therefore be extracted by comparing the output-code variance among channels without requiring a reference path. A 2-channel 2 GS/s 7b TI-SAR prototype realized in 28-nm CMOS achieves a 36.4 dB SNDR at Nyquist with >2.6 GHz ERBW after calibration. The ADC with CI sampler consumes 7.62 mW, leading to a Walden FoM of 70.8 fJ/conversion-step.

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