A background time-skew calibration technique in flash-assisted time-interleaved SAR ADCs

This paper introduces a background time-skew calibration technique in a flash-assisted time-interleaved SAR ADC structure. This technique processes the digital output data to synchronize the sampling clocks of the flash ADC and sub-SAR ADCs. A time-skew detection algorithm is proposed based on a linear model that analyzes the correlativity between flash ADC and sub-SAR ADCs. An adaptive calibration algorithm is applied to compensate the time-skew and solves the nonlinearity of the model in high input frequency. An additional calibration round is added to reduce the correlation between extracted time-skew information and the input signal and to speed up the calibration. By applying this technique into a 10bit 2GS/s FATI ADC model, this calibration keeps effective as the input frequency distributes from dc to 3rd Nyquist band and the spurious signals introduced by time-skew are suppressed below −70dB.

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