The IObundle 24-bit/-130dB THD+N Multi-Channel Audio Asynchronous Sample Rate Converter resamples the input audio digital signal, sampled at frequency Fin, and produces an output signal, sampled at frequency Fout . It uses a variable-coefficient FIR filter, a ratio estimator module to compute the conversion ratio ρ = F out /F in and its inverse 1/ρ, a
ROM&Interpolation module to compute the filter coefficients, a circular RAM block to store the input samples and an output FIFO to store the output samples. The FIR filter has order 32 for up conversions and 32/ρ for down conversions. Conversions between any two frequencies in the [8, 192] kHz range have been exhaustively tested. The design uses three clock domains. The input and output word clocks are asynchronously sampled to compute their periods and
therefore ρ and 1/ρ. All computation is performed in the system clock domain. The core can process tens to hundreds of Time-Division Multiplexed (TDM) audio channels, depending on the system clock frequency. The output group delay variation upon reset is less than one output sample period. The Total Harmonic Distortion plus Noise (THD+N) has an average of -140dB and is never higher than -130dB. TheseTHD+N values are achieved after a fixed sync time of 20 ms.