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UCC24630: Sink,Source Gate-Drive Capability

Part Number: UCC24630

Hello.

I have a question about UCC 24630.

For the contents, please see the attached document.

thank you.Microsoft PowerPoint - UCC24630-1.pdf

  • Ishii-san,

    The limits of +/-50 mA in the abs max table are the continuous, DC or average limits. These are the maximum current levels that can flow continuously.

    However, larger peak current can flow for shorter time interval, to charge or discharge the FET gate capacitance. This is typical for gate drivers, where the peak current only flows for a short time when the gate capacitance first needs to be charged or discharged. As the voltage on the gate rises/falls, the current flowing out of/into the driver falls.

    As your calculation shows, the average charging/discharging current per the datasheet rise/fall time spec is already far higher than the abs max DC rating.

    I will enquire with the product team for this driver to check what is the driver resistance and max peak source/sink current.

    Thanks,
    Bernard
  • Ishii-san,

    I had another look at the datasheet, and the driver capability is specified in a little more detail on page 5 - the drive pull-down (turn-off) resistance is specified as 1-ohm typical, 2-ohm maximum. So this will ensure a high peak current for fast turn-off of the SR FET.

    The DRV pull-up (turn-on) resistance is not specified explicitly, but I have asked for this typical spec from the product line team.

    Thanks,
    Bernard
  • Hello.

    Bernard-san

    thank you for your answer.

    After that, did you get any answers regarding specs from the product team?

    thank you.

  • Ishii-san,

    Apologies for the delay.

    The only specs that are available are the ones already listed in the datasheet.

    But as noted above, the Abs Max specs are continuous DC ratings, but the transient charge/discharge currents are much higher, as you already calculated.

    The driver is asymmetric, the pull-down/turn-off capability is stronger than the turn-on. So the internal equivalent turn-on pull-up resistance is higher than the turn-off pull-down resistance.

    However, due to the complex internal driver implementation, it's not possible to give a single equivalent pull-up resistance value, since it varies with voltage level, etc.


    Your di/dt based calculation will give the best estimate of the average charging/discharging in order to estimate the time taken to charge/discharge the gate capacitance.


    I hope this is sufficient to address your question.

    Thanks,
    Bernard