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UCC27714: Enable pin not working correctly under simulation

Dylan Bartlett1
Prodigy 60 points
Part Number: UCC27714

Hi,

I am working with the SPICE model for the UCC27714 gate driver in Simetrix 8.10j and have experienced an issue with the EN_NC pin functionality.

I have created a test rig for the part where I am driving the HI input with a 10V 100kHz square wave and the Enable pin with a similar 10 kHz signal. Howver, the HO output does not fall low when the EN input is asserted low. See the below simulation plot.

Is there something I am doing wrong with the model, or does this functionality not exist in the model at all? 

I also attach my simulation schematic if you have Simetrix available to validate my observation.

Thanks in advance for the help,

Dylan

UCC27714_ENABLE_TEST.zip

  • 0
    Prodigy 60 points

    I also attach a capture of the schematic to verify my connections are not incorrect.

  • 0 in reply to Dylan Bartlett1
    TI__Mastermind 22225 points

    Hello Dylan,

    Thank you for the interest in the UCC27714.

    I do have simetrix available and am able to run your schematic. I am seeing the same as your observation, and also connected the LI input to the signal and confirm the LO is not responding as well.

    I will continue to look, so see if there is something I missed so far. From the datasheet curves the EN response time looks similar to the HI and LI response times. Is this Model behavior holding up your evaluation?

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 60 points

    Hi Richard,

    Thanks for getting back to me. It seems a little odd that this part of the model isn't working how I would expect it.

    So far I've had good experience with the model in my design and have gotten it to work in a relativley simple synchonous buck configuration.

    Let me know if you manage to figure out if there is a detail I've missed in handling the EN pin, but the datasheet does suggest its a simple matter of asserting it low.

    Regards,

    Dylan

  • 0 in reply to Dylan Bartlett1
    TI__Mastermind 22225 points

    Hello Dylan,

    Thank you for confirming that most of your simulation is working as expected, with this one exception you indicated.

    I have not found anything regarding how you are using the EN pin in the simulation, it should be a matter of rising or falling voltage beyond the thresholds to enable or disable the device.

    If you need this feature in your sim for detail data, I can provide a basic workaround if needed.

    Confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,

  • 0 in reply to Richard Herring
    Prodigy 60 points

    Hi Richard,

    I am managing to deal with this piece of missing functionality so far by setting the initial conditions of my simulation and providing no input to the driver, but it would be useful to have a workaround to play with.

    Thanks for your help so far,

    Dylan

  • 0 in reply to Dylan Bartlett1
    TI__Mastermind 22225 points

    Hello Dylan,

    I have attached a file with a simple workaround for the enable function. Just adding an and gate on the HI driver input with Enable and the HI signal into the and gate seems to work.

    Confirm if this works, or you can post additional questions on this thread.

    Regards,

    UCC27714_ENABLE_TEST edit.sxsch

  • 0 in reply to Richard Herring
    Prodigy 60 points

    Thanks Richard,

    This works well as a workaround.

    Dylan