A calibration system for an analog-to-digital converter (ADC) an internal ADC that receives an analog input and converts the analog input to digital multi-bit data. The calibration system also includes a reference shuffling circuit that shuffles reference values of comparators of the internal ADC. Further, the calibration system includes a calibration circuit that calibrates the comparators of the internal ADC. The calibration system includes a digital block that measures an amplitude based on the digital multi-bit data. Additionally, the calibration system includes calibration logic that controls the calibration circuit based on an output of the digital block.