All-Digital Calibration Algorithms to Correct for Static Non-Linearities in ADCs

This paper presents all-digital calibration algorithms for correcting static non-linearities in an ADC. A bit-by-bit (BB) calibration is proposed as an alternative to the existing radix calibration. The proposed calibration algorithm is initially demonstrated using a non-uniform ADC model generated in Matlab. A hybrid radix/bit-by-bit calibration is also developed to reduce the computational complexity of BB calibration. The calibration algorithms are then applied to measurement data from two different ADCs: a 6-bit folding-flash; and a 10-bit dual-split capacitor (DSC)-DAC SAR ADC. In both ADC architectures, the BB and hybrid calibrations outperform radix calibration. The BB calibration improved the SNDR and SFDR of the folding-flash ADC from 29.5 dB to 31.9 dB and 33.3 dB to 43.6 dB, respectively. Likewise, after applying the hybrid calibration on the DSC-DAC SAR ADC, the SNDR and SFDR improved from 31.8 dB to 47 dB and 33.6 dB to 58.9 dB, respectively. The hybrid calibration achieves performance similar to that of BB calibration while demonstrating a significant reduction in computational complexity.