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PCM1840: PCM1840 TDM format 8ch?

brett kelly
Prodigy 90 points
Part Number: PCM1840

Hi

I need to cascade 2x PCM1840 TDM   into a single TDM 8ch Buss to have 8 ADC channels to the DSP

Is the PCM1840capable of this. The datasheet is unclear. as it talks about 4ch  and the ability to have 8 Digital Mics,

Thanks

Brett

  • 0
    TI__Mastermind 23050 points

    Hi Brett,

    The PCM1840 unfortunately does not provide a direct way to offset the data in the TDM stream to allow multiple PCM1840s to share the same TDM bus. In order to do this though you could use a 50% duty cycle FSYNC and invert the clock sent to one of the devices so that one outputs data on the rising edge of FSYNC and the other on the falling edge.

    Best,

    Zak

  • +1 in reply to Zak Kaye
    Prodigy 90 points

    Hi Zak

     In order for this to work The PCM1840 SData out would need to Hiz when its LrClk is not the Active Side. And the IC has to be capable of 2 x BCLK rate

    Or do we need a data Mux IC?

    Thanks

  • 0 in reply to brett kelly
    TI__Mastermind 23050 points

    Hey Brett,

    No data mux would be needed, but that could be another option. The PCM1840 will set the DOUT to HiZ for the BCLK cycles/slots it doesn't use and can support high enough BCLK that this shouldn't be an issue. The device fully supports TDM, it just doesn't have a way to daisy chain data lines.

    Best,

    Zak