Interchannel Mismatch Calibration Techniques for Time-Interleaved SAR ADCs

Interleaving is a powerful technique that boosts the speed of an ADC. The power efficiency of such a technique is mainly affected by the overhead of the circuitry used to mitigate the impact of inter-channel mismatches on the ADC’s performance. This paper reviews some of the most important methods of calibrating such mismatches and presents a frequency-domain analysis of timing skew in a time-interleaved (TI) ADC. A new calibration approach is also proposed that calibrates the timing and offset mismatches between the channels simultaneously. Behavioral modeling simulations of a 15-channel 10-b 2GS/s TI SAR ADC show an improvement of 35 dB in the SFDR after calibration. The impact of circuit nonidealities and noise is also assessed, and mitigation techniques are proposed.