Mismatch and Offset Calibration in Redundant SAR ADC

This paper presents a robust method to perform capacitor mismatch calibration in a redundant SAR ADCs correcting the effect of comparator static offset in the calibration process. Without proper handling of this effect, capacitor miscalibration can occur due to saturation of the redundancy intervals associated with implemented weights, eventually leading to a faulty behavior even with lower effective resolution than the case without calibration. To overcome this limitation, this work proposes a foreground technique which reuses the least-significant bit (LSB) capacitors in the array in a design with redundancy for offset compensation. The effectiveness of the method is demonstrated by realistic behavioral simulations in a 12-bit SAR ADC case study with 3 redundant bits.