Multi-bit sigma-delta modulator employing dynamic element matching using adaptively randomized data-weighted averaging

Abstract

A sigma-delta modulator disclosed herein provides a first order noise shaping of the errors associated with the multi bit DAC employing unit elements, without creating large in-band tones. The sigma-delta modulator includes a multi-bit ADC connected to receive a processed signal from a filter that performs first order noise shaping. Additionally, a feedback path, leading from the multi-bit ADC to a summer, includes at least one dynamic element matching algorithm logic block connected to a multi-bit DAC having a plurality of unit elements. The dynamic element matching algorithm logic block alternately generates a consecutive increment shift signal and a random shift signal at a predetermined or a random time interval for shifting the digital feedback signal by a random amount depending upon the amplitude and frequency of the analog input signal to provide a randomized rotated output to the DAC. Thereby, the feedback path minimizes mismatch error associated with the plurality of unit elements within the multi-bit DAC to provide an sigma-delta modulator having substantially reduced the in-band tones for all signal amplitudes without trading off the peak SNRD resulting from data weighted averaging.