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PCM5141: Clocking options

fpatz
Prodigy 90 points
Part Number: PCM5141

Hi,

I have two questions according to the clocking options/recommendations for the PCM5141

1.)

Under 8.3.6.1, the datasheets it says:

"In situations where the highest audio performance is required, it is suggested that the SCK is brought to the device, along with BCK and LRCK".

Can someone explains, why SCK AND BCK/LRCK should be provided externally? As far as I understand the jitter that has impact on the audio signal is the jitter present in the SCK signal (and only the SCK signal?), because the output DACS operate on this frequency. Does the internal derivation of BCK and LRCK from the externally provided SCK really have an inpact on audio performance?

2.)

Related to 1.): Assume that I can NOT follow the recommendations in 1.) by providing ALL of the three signals (SCK, BCK and LRCK) externally, what is the next best option to go concerning audio quality? I would assume it is the variant described in 8.3.6.6 Clock Master Mode from Audio Rate Master Clock. I would think so because of my thoughts in 1.). Can you tell me whether this is correct?

Thanks a lot

  • 0
    TI__Guru 53333 points

    Hi,

    If SCK is not supplied externally, the device must use the internal PLL to generate a high-frequency clock internally to drive the delta-sigma modulator and the DSP.  The is PLL must be sourced from the BCK or another external clock input (GPIO pin).  The PLL is okay, but will likely have more jitter than most external oscillators.  

    For this reason, we recommend in order of audio performance:

    1. Quality SCK signal, of which BCK and LRCK are derived externally or internally by the DAC.

    2. Quality BCK signal, where the SCK is generated internally using the internal PLL.

    3. Some other quality clock provided to a GPIO pin, with the device configured to generate the SCK from that.

    It does not really matter if the device is in master mode, as long as there is some kind of quality master clock to derive the other clocks from.

    Thanks,

    Paul