Double-index averaging: a novel technique for dynamic element matching in Σ-Δ A/D converters

We report the study of a second-order Σ-Δ modulator for audio applications with a nine-levels quantizer. The feedback digital-to-analog has been implemented with four capacitors and two voltage references, taking the structure typical of fully differential system. We first discuss the performance achievable with the most popular dynamic element-matching techniques, namely the data-weighted averaging and individual-level averaging. We then introduce a new algorithm, the double-index averaging, that performs better than the other algorithms by 10-15 dB over the entire dynamic range of the modulator, and 6 dB at the peak of signal/(quantization noise+total harmonic distortion)