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) ΔΣ 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 0.5-μm 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