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Sample Rate Converter SRC4392 Conversion Rate

shadders
Expert 1065 points
Other Parts Discussed in Thread: SRC4392, PCM1792A

Hi,

I have examined the product data sheet for the SRC4392 Sample Rate Converter used for audio purposes. The literature states that the SRC4392 uses automatic sample rate conversion, but does not detail what the criteria are for this conversion.

As such, i propose to clock the IC at 24.576MHz which is a multiple of 192KHz sampling frequency (128 x fs).

How can the sample rate conversion be set to output 192kHz sampling frequency ?.

If the sample rate conversion (input to output) is automatically determined, can the SRC4392 be configured only to output at 192kHz ?.

I propose to feed the output of the SRC4392 into the TI PCM1792A DAC.

Thanks and Regards,

Richard.

  • 0
    Expert 1065 points

    OK - worked it out - by setting the PortA or B to a specified Master Clock division - this sets the sampling frequency for that port. Can anyone confirm that i have this correct ?

    If the Master Clock Frequency 24.576MHz and the PORTA division is 128, this sets the PORTA output sampling frequency to 192kHz.

    I was getting stuck on the 4th sentence, third paragraph on page 22 of the SRC4392 datasheet. It states that the input-output sampling ratio is determined automatically by the rate estimation circuitry.

    If it had stated that the input-output ratio is determined by the settings of the output port Master Clock divider and the input sampling frequency - would add more clarification.

    Although this seems to be the case - it is still not stated explicitly enough.

    Hopefully what i have stated above is correct.

    Regards,

    Richard.

  • 0 in reply to shadders
    TI__Intellectual 2810 points

    Hello Richard,

    If Port A or Port B is configured for Master mode operation, then the corresponding LRCK rate is determined by a combination of the master clock source frequency and the master clock dividers for the port.. If the port is configured for Slave mode operation, then the external LRCKA or LRCKB clock sets the sampling rate for the corresponding port.

    The input and output of the SRC block within the SRC4392 are slaved to other functions inside the device. For example, the SRC input is slaved to etiher Port A, Port B, or the DIR. Likewise, the SRC output may be slaved to Port A, Port B, or the DIT. The port or receiver or transmitter LRCK or frame rate dictates the input and output sampling rates for the SRC. However, the rate estimator block within the SRC automatically determines the input-to-output sampling ratio, which is then used to program the re-sampler coefficients and pointers on the fly. As the input or output sample rates change, the rate estimator determines the new ratio and updates the re-sampler accordingly.

    I hope that this information provides further clarification.

     

    Regards,

    Bob Martin, Systems Engineering - TI Audio Converters

     

  • 0 in reply to Bob Martin
    Expert 1065 points

    Hi Bob,

    Many thanks for the reply and confirming my expectations on how the device worked.

    I will be using Port B as the input for the USB Audio DAC output to obtain a USB connection to the DAC project. Thanks again for your help, much appreciated.

    Regards,

    Richard.