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OPA994: Looking for simulation model

Patrick Vogelsang
Prodigy 110 points
Part Number: OPA994

Dear support,

Is there a spice model available for the new OPA994? I interested in the cap load behaviour.

Thanks in advanced

Patrick 

  • 0
    TI__Mastermind 28966 points

    Hey Patrick,

    I am currently working on the OPAx994 model. It should be ready early January. There may be some slight discrepancies between the model and silicon behavior, with slightly more optimistic phase margin vs cap load drive for cap loads in the 100's of pF. This is due to a limitation in our spice model architecture.

    Best,
    Jerry

  • 0 in reply to Gerasimos Madalvanos
    Prodigy 110 points

    Thanks Jerry, my use case is to drive a cap load of 2nF in unity gain. I look forward to the model otherwise we have to prototype.

    Patrick

  • 0 in reply to Patrick Vogelsang
    TI__Mastermind 19607 points

    Hey Patrick, 

    Thanks for posting on e2e! 

    For a cap load of 2nF, we expect to see a healthy phase margin of >35 degrees. Ideally a design has between 45 and 90 to fully ensure robustness across lot to lot variation and process corners.

    I recommend implementing a small RISO (between 25 and 50) which will significantly reduce the small signal overshoot: 

    If it ends up not being needed in the prototyping stage, simply replace with a 0 ohm. 

    Does the input signal have a frequency range associated or is it DC? 

    All the best,
    Caro 

  • 0 in reply to Caro Walter
    Prodigy 110 points

    Thanks for the extensive info. The frequency range is 0...100kHz.

    Patrick 

  • 0 in reply to Patrick Vogelsang
    TI__Mastermind 19607 points

    Hey Patrick, 

    As the capacitive load increases, the op amp adjusts the stability by limiting its bandwidth. 

    I think the next revision of the datasheet will include this critical graph but for now we can use the following data I collected on a couple of devices: 

    For 2nF, I expect the OPA994 to have 5MHz of GBWP, since the gain is 1 - I do not expect any bandwidth limitations but I wanted to check. 

    All the best,
    Carolina