BACKGROUND DIGITAL CALIBRATION TECHNIQUES FOR PIPELINED ADCS

A skip and fill algorithm is developed to digitally self-calibrate pip elined analog-to-digital converters (ADC's) in real time, The proposed digital calibration technique is applicable to capacitor-ratioed mult iplying digital-to-analog converters (MDAC's) commonly used in multist ep or pipelined ADC's, This background calibration process can replace , in effect, a trimming procedure usually done in the factory with a h idden electronic calibration, Unlike other self-calibration techniques working in the foreground, the proposed technique is based on the con cept of skipping conversion cycles randomly but filling in data later by nonlinear interpolation, This opens up the feasibility of digitally implementing calibration hardware and simplifying the task of self-ca librating multistep or pipelined ADC's, The proposed method improves t he performance of the inherently fast ADC's by maintaining simple syst em architectures, To measure errors resulting from capacitor mismatch, op amp de gain, offset, and switch feedthrough in real time, the cali bration test signal is injected in place of the input signal using a s plit-reference injection technique. Ultimately, the missing signal wit hin two-thirds of the Nyquist bandwidth is recovered with 16-b accurac y using a forty-fourth order polynomial interpolation, behaving essent ially as an FIR filter.