An Audio ADC Delta–Sigma Modulator with 100-dB Peak SINAD and 102-dB DR Using a Second-Order Mismatch-Shaping DAC

A second-order audio analog-to-digital converter (ADC) modulator using a second-order 33-level tree-structured mismatch-shaping digital-to-analog converter (DAC) is presented. Key logic simplifications in the design of the mismatch-shaping DAC encoder are shown which yield the lowest complexity second-order mismatch-shaping DAC known to the authors. The phenomenon of signal-dependent DAC noise modulation in mismatch-shaping DACs is illustrated, and a modified second-order input-layer switching block is presented which reduces inband DAC noise modulation by 6 dB. Implementation details and measured performance of the 3.3-V 0.5m single-poly CMOS prototype are presented. All 12 prototype devices achieve better than 100-dB signal-to-noise-and-distortion and 102-dB dynamic range over a 10–20 kHz measurement bandwidth.