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DAC38J84 and JESD204B latency calculation

Rick Hennegan
Prodigy 10 points

Other Parts Discussed in Thread: DAC38J84

I am trying to calculate the total latency of the DAC38J84 when all the digital signal processing features are bypassed.  Your data sheet has a latency number of 11 DAC clock cycles as the digital latency.  However this is lower than I had imagined and it is not clear to me what the digital latency encompasses.  So I would like to know if the latency of the JESD204B interface is included in this number and if not then how do I determine this additional latency?

Rick

 

 

  • 0
    TI__Genius 17470 points

    Hi Rick,

    Sorry for the long delay, trying to get you the right information here. For 442 mode, the latency numbers are below. This is from the output of the JESD elastic buffer to the output of the DAC. There will be additional latency through the JESD interface. The numbers are in terms of DAC output clock cycles and are assuming all digital functions are bypassed.

    1x interpolation = 162
    2x interpolation = 245
    4x interpolation = 401
    8x interpolation = 740
    16x interpolation = 1423

    The latency through the JESD interface is a bit complex, especially since the transmitter will play a role in the latency, and since you have some control of the latency through the RBD parameter. The app note below discusses the JESD204B latency for an ADC. The concepts are the same. For a rough estimate use 100 ns.

    http://www.ti.com/tool/tida-00153

    Regards,

    Matt Guibord