Adaptive calibration of multiple quantization oversampled A/D converters

Multiple quantization delta-sigma modulators for oversampled A/D conversion are known to suffer from performance degradation in the presence of analog imperfections in the implementation, such as finite gain of the amplifiers and capacitor ratio mismatches. We present algorithms and architectures for on-line and off-line digital correction of such analog imperfections. The digital correction compensates for incomplete cancellation of quantization noise from individual delta-sigma stages, and for gain and spectral distortion of the signal transfer function. Simulation results demonstrate that a simple off-line calibration method is effective to achieve neat-perfect digital correction of analog sources of error and spectral distortion. We discuss on-line extensions of the calibration procedure in a multiplexed or multi-rate arrangement with multiple oversampled converters operating in parallel