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Original question:

LMK03328: output LVPECL to LVDS receiver

LMK03328: LMK03328

Wei Liu89
Prodigy 130 points
Part Number: LMK03328


Hi support,

How are you?

For LMK03328, when output is driving different type, such as LVPECL to LVDS receiver, the customer see the trench at rising edge and falling edge.

https://e2e.ti.com/support/clock-and-timing/f/48/t/711145?tisearch=e2e-quicksearch&keymatch=LMK03328%20LVPECL%20TO

What is the root cause for the trench? Does LMK03328 driver has to match with the receiver clock type?

Thanks,

-Wei

  • 0
    TI__Genius 11900 points

    Hello Wei,

    "Interfacing to LVDS, CML or LVPECL receivers are done with just an external AC-coupling capacitor for each output. No source termination is needed since the on-chip termination is automatically enabled when selecting AC-LVDS, AC-CML, or AC-LVPECL for good impedance matching to 50-Ω interconnects."

    Does LMK03328 driver has to match with the receiver clock type?

    Set the LMK03328 output format to LVDS/LVPECL based on what your receiver requires. You can refer to 8.15 and 8.16 for the output characteristics.

  • 0 in reply to Vibhu Vanjari
    Prodigy 130 points

    Hi Vibhu,

    What is the possible reasons why there is trench in the rise and fall time from the picture?

    Thanks,

    -Wei

  • 0 in reply to Wei Liu89
    TI__Genius 11900 points

    Hello Wei,

    If you are asking why the rising and falling edges have the small irregularity/peak this could be because of a reflection caused by mismatch between the source, cable and input termination. Is this causing any issues, why do you ask?

  • 0 in reply to Vibhu Vanjari
    Prodigy 130 points

    Hi Vibhu,

    OK, thanks for explanation.

    We have seen such waveform from customer and wonder what can cause that. 

    Thanks,

    -Wei