Optimum measurement of ADC code transitions using a feedback loop

Code transitions on high speed analog to digital converters have been measured for many years using a feedback loop. The dynamics of the settling of the feedback loop are strongly dependent on the noise of the converter, and the step size of the feedback loop. An analysis of the response of the feedback loop is described and the optimum parameters of the loop are developed. The speed of measurement of the different methods for measuring code transitions are calculated and compared. Examples are given of the test times required for testing commercial converters. Bandwidth reduction of the feedback loop in the presence of noise is demonstrated.