A 1.1 V 82.3dB audio ΔΣ ADC using asynchronous SAR type quantizer

A switched-capacitor second-order audio ΔΣ analog-to-digital converter (ADC) is presented. The proposed ΔΣ ADC employs low-distortion input feed-forward architecture to relax the linearity requirement of the integrators. A 4-bit asynchronous successive approximation register (SAR) type internal quantizer is used for power efficient design by incorporating the analog adder with the quantizer. A tree-structured dynamic element matching (DEM) technique is employed to reduce the distortion resulted from the capacitor mismatch in the feedback digital-to-analog converter (DAC). The prototype ΔΣ ADC implemented in a 45nm CMOS process achieves 85.4 dB peak signal-to-noise ratio (SNR), 82.3 dB peak signal-to-noise and distortion ratio (SNDR) and 98.1 dB dynamic range (DR) for a signal bandwidth of 24 kHz while consuming 517.4 µW at 1.1 V supply voltage.