A stereo audio sigma-delta A/D-converter

A stereo sigma delta A/D-converter for audio applications is presented. In this converter, two identical cascaded fourth-order sigma-delta modulators and a sophisticated multistage linear-phase FIR decimation filter with oversampling ratio of 64 are implemented on the same die. The analog part is designed to operate at a low voltage with a low power consumption. Techniques to achieve simultaneously a high performance and a low power consumption are discussed in details. The minimum stopband attenuation of the decimator is more than 120 dB and the passband ripple of the overall converter is less than 0.0003 dB. The first decimation stage is a special tapped comb filter, whereas the remaining stages are realized without general multipliers by simultaneously implementing all the filter coefficients by using special bit-serial networks. For the integrated overall stereo converter, the power consumption and the signal-to-noise ratio are 180 mW and 97 dB (85 mW and 95 dB) for a 5 V (3 V) power supply. The circuit die area is only 4.7 mm×5.5 mm using a 1.2 μm double-poly BiCMOS process