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DS280DF810: PRBS generator issues

Kannan Sockalingam
Intellectual 1775 points
Part Number: DS280DF810

Hi, working with a customer and this is an urgent request. Trying to run a PRBS using an external loopback using SigCon without success.

The setup: PRBS generator on the retimer TX doesn’t have anything connected to its inputs and the retimer configured for PRBS checker isn’t detecting an signal.

Does the retimer used for PRBS generation need to have something driving it’s inputs to work?

Do you have any app notes that describe PRBS loopback testing using SigCon?

  • 0
    TI__Mastermind 24432 points

    Hi Kannan,

    The customer's observations make sense in this setup.  The retimer requires CDR lock in order to use the PRBS generator as the retimer uses a reference-less clocking architecture (clock is recovered from the data the retimer receives).

    The customer can either provide data to the retimer input, or provide a sub-rate clock input in order to get CDR lock.  Regarding the sub-rate clock input, we often use a div 16 clock in lab.  For example, for 25.78125 Gbps, I use a 1.611328125 GHz clock input to the retimer to get CDR lock.  I expect div 4, 8, and 32 to work as well.

    We don't have any application notes on this, although the basic setup in sigcon architect is generally pretty straightforward.  Once the retimer has CDR lock, enable the PRBS generator on the transmitting channel of the loopback.  Then once the receiving channel has CDR lock, enable the PRBS checker on the receiving channel.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    TI__Intellectual 1775 points

    Drew, still working with the customer on this. 

    We are not able to drive the RX inputs using a clock without damaging the pads on our CCA.

    Is there a way to use the CAL_CLK_IN for CDR lock?

  • 0 in reply to Kannan Sockalingam
    TI__Mastermind 24432 points

    Hi Kannan,

    There is not a way to use CAL_CLK_IN for CDR lock.

    Thanks,

    Drew