Isscc 93 / Session 4 / Data Comversion / Paper Wp 4.2 Wp 4.2: a 15b 1mds Digitally Self-calibrated Pipeline Adc'

Unlike analog calibration, digital calibration alone does not correct or create analog decision levels. Therefore, the uncalibrated ADC must provide decision levels spaced no greater than lLSB at the intended resolution. In lb/stage pipeline ADCs with nominal gain of 2, missing decision levels result when the input of any stage exceeds full scale due to capacitor mismatch, capacitor non-linearity, charge injection and comparator offset. Missing decision levels can be eliminated, however, by using gain less than 2 and 2-3 more stages of pipeline giving enough redundancy in the analog decision levels. The missing codes with gain less than 2 are eliminated by digital calibration.