A skip and fill algorithm is developed to digitally self-calibratenpipelined analog-to-digital converters (ADC's) in real time. Thenproposed digital calibration technique is applicable toncapacitor-ratioed multiplying digital-to-analog converters (MDACs)ncommonly used in multistep or pipelined ADCs. This backgroundncalibration process can replace, in effect, a trimming procedure usuallyndone in the factory with a hidden electronic calibration. Unlike othernself-calibration techniques working in the foreground, the proposedntechnique is based on the concept of skipping conversion cycles randomlynbut filling in data later by nonlinear interpolation. This opens up thenfeasibility of digitally implementing calibration hardware andnsimplifying the task of self-calibrating multistep or pipelined ADCs.nThe proposed method improves the performance of the inherently fast ADCsnby maintaining simple system architectures. To measure errors resultingnfrom capacitor mismatch, of amp DC gain, offset, and switch feedthroughnin real time, the calibration test signal is injected in place of theninput signal using a split-reference injection technique. Ultimately,nthe missing signal within two-thirds of the Nyquist bandwidth isnrecovered with 16-b accuracy using a forty-fourth order polynomialninterpolation, behaving essentially as an FIR filter,
展开▼
