Capacitor mismatch calibration for SAR ADCs based on comparator metastability detection

A novel digital calibration technique is proposed to calibrate the capacitor mismatch in SAR ADCs. The capacitor mismatches are extracted based on the comparator metastability and intrinsic noise. The proposed technique does not require additional external control sequences or any modification of the main DAC. The simulation results of a 12-bit SAR ADC with 10% capacitor mismatch show that the SNDR and SFDR are improved by 13.9dB and 34.9dB respectively with the proposed calibration technique. The calibration technique is effective under process variation based on a Monte-Carlo simulation.