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LMH1983: LMH1983 CLKOUT protection circuit

Kawai
Guru 19785 points
Part Number: LMH1983
Other Parts Discussed in Thread: LMK03328, LMK03000

Hi Team,

Does LMH1983 CLKOUTx outputs have protection circuit to disable output ?

When DC coupling with LMK03328, customer design of LMK03328 input interface was miss programmed that it was set as AC-LVDS.

In this case, there is DC bias at the LMK03328 input that this may be affecting the LMH1983 CLKTOUT driver circuit that LMK03328 cannot get locked.

Best Regards,

Kawai

  • 0
    TI__Guru** 107830 points
    Hi Kawai-san,

    Is there output clock from LMH1983?
    If there is a valid clock from LMH1983, then did you configure LMK03328 properly?
    When LMK03328 input is setup as AC couple with internal bias, the pull-up is weak, that means the pull-up resistors are big. In other words, if there is current flowing through the pull-up, the current will be small and therefore would not causing damage.
  • 0 in reply to Noel Fung
    Guru 19785 points
    Hi Noel-san,

    In the past I faced a problem that LMK03000 had internal short protection at the clock output that when the device output detected short, not only hard short, LMK03000 had stopped clocking.

    I just wanted to make sure that LMH1983 would have similar protection circuit or not to fully understand all the possibilities.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru** 107830 points
    Hi Kawai-san,

    I don't think LMH1983 has this protection function, this is not a standard function of LVDS interface.
  • 0 in reply to Noel Fung
    Guru 19785 points
    Hi Noel-san,

    Understood. Thanks for your comment.

    Best Regards,
    Kawai