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LMH1218: lock of incoming data is unstable

Colin Chen
Mastermind 21121 points
Part Number: LMH1218
Other Parts Discussed in Thread: LMH1219

Hi team,

My customer connect LMH1219 out1 to LMH1218's input, when transmitting 4K60 signal, the lock of incoming data is unstable, have you ever encountered similar problem and how to debug it?

Thanks,

Colin

  • 0
    TI__Guru* 93670 points

    Hi Colin,

    LMH1218 has initialization settings as noted in the data sheet and programming guide. Please make sure your customer follows this procedure. Using this procedure, we have not observed not being able to lock.

    Regards ,, Nasser

  • 0 in reply to Nasser Mohammadi
    TI__Mastermind 21121 points

    Hi Nasser,

    My customer set as the programming guide.

    LMH1219 differentially outputs to LMH1218, and then LMH1218 is abnormally locked. If touch the series capacitor with hand, the signal will be locked. Or connect a large resistor in parallel between the differential lines, about 500 ohms, and it can be locked, but they don’t know if this will have other effects.

    Thanks!

    Colin

  • 0 in reply to Colin Chen
    TI__Guru* 93670 points

    Greetings,

    Given this customer experiment as you noted, this means perhaps there could be some signal integrity issue on the pcb layout.  Suggestion is to use LMH1218 GUI or read HEO/VEO values. Customer can make their changes to get the optimized HEO/VEO values. This should be checked on 5-10 boards to make sure there is no negative side effects.

    Regards,, nasser