Dynamic Element Matching to Prevent Nonlinear Distortion From Pulse-Shape Mismatches in High-Resolution DACs

This paper shows analytically and experimentally that properly-designed dynamic element matching (DEM) eliminates pulse shape, timing, and amplitude errors arising from component mismatches as sources of nonlinear distortion in high-resolution DACs. A set of sufficient conditions on the DEM encoder that ensure this effect, and a specific segmented DEM encoder that satisfies the sufficient conditions are presented. Unlike most previously published DEM encoders, the new DEM encoder´s complexity does not grow exponentially with the number of bits of DAC resolution, so it is practical for high-resolution Nyquist-rate DACs. These analytical results are demonstrated experimentally with a 0.18 mum CMOS 14-bit DAC IC that has a sample rate of 100 MHz and worst case, single and two-tone spurious-free dynamic ranges of 83 dB and 84 dB, respectively, across the Nyquist band.