Blind On-line Digital Calibration of Multi-stage Nyquist-rate and Oversampled A/d Converters

A linear calibration technique for on-line digital correction of analog imprecisions in the implementation of multi-stage analog-todigital converters, is presented. The calibration is ‘blind’, in that it uses no reference and operates directly on the digital output during conversion. The only assumption made on the input signal is that its spectrum is bandlimited. The excess sampling over Nyquist bandwidth is used for least-squares auto-zeroing calibration. The technique extends directly to digital correction of multi-stage oversampled A/D converters where a multi-bit quantizer is implemented using a pipelined algorithmic A/D converter. Behavioral simulations on pipelined algorithmic and dual-quantization oversampled A/D converters demonstrate significant improvements in signal-toquantization-noise performance over the uncalibrated case.