Various calibration algorithms for self-calibration A/D converters

Error cancellation of capacitor arrays in self-calibrating, successive approximation A/D converters is discussed. The two known methods are based on iterative sequential computation of the correction voltages used during A/D conversion. The original method employs one calibration capacitor, whereas the modified method requires N calibration capacitors for the N-bit converter. An algorithm is presented for determining the correction voltages, based on two source voltages generated by precision D/A converters. This allows direct measurement with no need for long sequential computations