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ADS52J90EVM: Can I use FMC TO FMC cable to connect FPGA board with ADC board?

Hyunok Kim
Prodigy 40 points
Part Number: ADS52J90EVM
Other Parts Discussed in Thread: ADS52J90

Hi

I would like to connect ALINX board (https://www.alinx.com/en/detail/262) with ADS52J90EVM

Because ALINX's FMC connector doesn't locate on it's edge side, I should use fmc to fmc cable(https://hitechglobal.us/index.php?route=product/product&path=25&product_id=171)

But I'm worried about whether the length is too long or not.

The Line Late for JESD205B is 6.4 Gbps

Can I use FMC TO FMC cable to connect FPGA board with ADC board?

Thanks in advance

  • +1
    TI__Expert 6580 points

    Hi Hyunok,

    We typically test the JESD performance at various lengths. 

    From the datasheet of the device, Figure 40 will show you the Total Jitter vs Trace length (in inches) across various speeds.

    In your case, while adding additional 9 inches between the ADC and the FPGA, you will definitely see some jitter degradation. For example, as a datapoint you see that with 13 inch trace length of the CML lanes, at 6.4 Gbps, the TJ is 50% of the Unit Interval.

    If that is acceptable in your case, you may go ahead and use the FMC to FMC extender.

    Thanks & regards,

    Abhishek

  • 0 in reply to Abhishek Vishwa1
    Prodigy 40 points

    Thank you for your quick response.

    Because we will make our custom board, some jitter degration is no problem in evaluation.

    But, to be honest, I don't know what is the proper tolerance value

    Could you tell me the value for our board?

  • 0 in reply to Hyunok Kim
    TI__Expert 6580 points

    Hi Hyunok,

    The JESD recommendation is 30% Total Jitter (TJ) with respect to Unit Interval (UI) at the Transmitter end i.e. ADS52J90 in your case.

    And at the Receiver end i.e. the FPGA, the jitter degradation tolerance is at 70%. Hence there is a margin of about 40 % for accounting the jitter degradation due to the routing length between the Transmitter and the Receiver.

    I hope this answers your question.

    Thanks & regards,

    Abhishek