A digital foreground calibration method for SAR ADCs with redundancy

Abstract

This paper presents a digital foreground calibration method intended for Successive Approximation (SAR) Analog-to-Digital Converters (ADCs). It begins by investigating the Integral Non-linearity (INL) and Signal to Noise Ratio (SNR) degradation with 1% capacitor mismatches. Later, it compares the INL and SNR for the ADC with and without using the proposed calibration method, and with various levels of capacitor redundancy and mismatches. The MATLAB simulation results show the proposed method can improve the ADCs’ INL and SNR by 0.8 LSB and 5.8dB, on average for 100 runs, respectively, when 1% capacitor mismatches are present. Measurement results of the 15 column SAR ADCs indicate that the INL and the SNR can be improved by 1 LSB and 2dB, respectively, using the proposed calibration method.