A 105 dB SNR multibit ΣΔ ADC for digital audio applications

A four-channel multibit ΣΔ analog-to-digital converter (ADC) for consumer audio applications is described. The converter uses a second order switched-capacitor modulator with a 4-bit quantizer and a noise-shaped scrambler for dynamic element matching. To achieve the target settling time with reduced power consumption, the opamps are dynamically compensated. A multi-stage decimation filter with adjustable front-end sine filter is used to produce the PCM output at a selectable sample rate of 48/96 kHz. The converter achieves an SNR and D-range of 105 dB (A-weighted), THD+N of -98 dB at 48 kHz sample rate. The circuit is implemented in 0.5 μm DPTM CMOS, dissipating 90 mW per channels. The core die size is 1.6 mm² per channel