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LMK03318: LMK03318RTAR Clock fall time adjustment

Jim CHEN
Expert 4795 points

Part Number: LMK03328
Other Parts Discussed in Thread: LMK00338, LMK03318

Dear Team,

We have a question about clock fall time.

According to the spec, 33 ohm is optional. How will it affect if we change from 33ohm to 0 ohm? Or could we change to other value?

 

Because one of our fall time is fail. We ‘re trying to make some adjustment on hardware.

Our Pass/Fail criteria is <900ps.

Attached file is our EA test report for you reference, but I have changed terminate 50 ohm to 86.6 ohm.

I am not sure whether we could fine tune terminate resistor? Please advise.

Thank you.

C01_CLK_EA_Test_Report_0911-17.xlsx

  • 0
    TI__Mastermind 32575 points

    For the series resistor, I suggest they try 0ohms which should help speed-up the clock edge rates.  If there is excessive overshoot/ringing with 0 ohms, then they could consider a small values (e.g. 10 ohms, and increase if needed) to reduce overshoot/ringing.

    For the termination resistor to ground, they should use 49.9 ohms assuming their PCB trace impedance is 50 ohms single-ended (100 ohms differential).

    Also, can you clarify if these test results are for LMK03328 (clock gen) or LMK00338 (HCSL buffer)?

    Regards,
    Alan

  • 0 in reply to Alan O
    TI__Expert 4795 points
    Hi Alan,

    Sorry for the misunderstanding.
    That is LMK03318.