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LMH1297: IBIS Model Termination Resistance

Don Schelle
Expert 4150 points
Part Number: LMH1297

Hello,

After downloading the LMH1297 IBIS model from the TI website we tested in a Hyperlynx simulation.  The resulting TDR on a single ended SDI_IO input shows termination resistance as 50 ohms instead of 75 ohms.

 

Why does the model show 50 ohm termination when the expected LMH1297 termination is 75 ohms?

Don

  • 0
    TI__Guru* 93670 points

    Hi Don,

    We use Agilent ADS environment to validate LMH1297 IBIS-AMI file and indeed we do pass SMPTE return loss with margin. We've done ADS simulation and all look fine.

    At the moment Michael and i are looking into this and will let you know.

    Regards,,nasser

  • 0
    TI__Mastermind 29655 points

    Hi Don,

    I just implemented a TDR in ADS for the LMH1297 SDI_IO, and I am seeing the termination impedance settling at 75 Ohms for SDI_IO and SDI_OUT. In ADS, one of the key parameters to input when simulating TDR is to specify the reference impedance. This reference impedance for SDI_IO and SDI_OUT should be set to 75-Ohms. Please see an example of a simulation with an example board BNC and trace below:

    • S11_TDR = SDI_IO
    • S22_TDR = SDI_OUT

    If the reference impedance is set to, say, 50-Ohms, the SDI_IO and SDI_OUT will give the appearance of being centered around 50-Ohms. Please check to see whether this may be the case.

    Thanks,

    Michael