An Area-Efficient Interpolator Applied in Audio Σ Δ DAC

An area-efficient 128times interpolation filter (IF) used in audio digital-to-analog converter (DAC) is presented in this paper. The digital interpolation filter consists of cascaded half band filter (HBF) which is followed by a 32timesdigital sample-and-hold (S/H) circuit. Optimization is also performed so that the filter requires no multipliers, with the registers in the filter decreasing by a half. No multiplier requirement and limited storage demand make it an economical alternative to the conventional implementation for audio application. The result shows that the interpolator achieves 66dB stop-band rejection and 0.008dB pass-band ripple when the coefficients are truncated to 16bit. The filter architecture proposed in this paper for the implementation of an area-efficient interpolator has been used in a 24-bit 96-KHz stereo DAC and is fully functional.