Improved ΔΣ DAC linearity using data weighted averaging

Abstract

A new dynamic element matching (DEM) algorithm, referred to as data weighted averaging (DWA), is presented for improving DAC linearity in multi-bit delta-sigma (/spl Delta//spl Sigma/) data converters. It out-performs all previously described algorithms. By cycling through the elements of the DAC at a rate dependent on the input to the DAC, the elements of the DAC are exercised at the maximum rate possible. With this algorithm, the distortion spectra are shaped by first-order noise shaping which results in 9 dB/octave improvement in the converter dynamic range when DAC errors dominate the performance. Simulating a third-order 3-bit modulator with an oversampling ratio of 128 and 1% DAC element matching, 110 dB signal-to-noise ratio (18 bits) is achieved by employing DWA DEM.