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UCC28180: Gate Drive Resistor Physical Size

Garret Holt
Intellectual 1050 points
Part Number: UCC28180

Hi Team,

What is the recommended physical size/power for the gate drive resistor? In the EVM/datasheet the resistor is sized at 1210/0.5W while in the design calculator lists 1/10W. Any recommendation for required size/power rating would be helpful. We are trying to save on board size but wouldn't want to put too much power through it or add substantial parasitic capacitance from too small of a package. Thank you!


Regards,


Garret

  • 0
    TI__Guru* 86286 points

    Hello,

    The gate drive resistor is generally used to reduce ringing at the gate drive.  The current is need to turn on and turn off the FET goes through it. 

    Igate = Qg*fsw

    PRgate = Igate^2*Rgate

    Regards,

  • 0 in reply to Mike O'
    TI__Intellectual 1050 points

    Hi Mike,

    We are familiar with the purpose of the gate drive resistor. Are you able to recommend a physical size/power rating of the gate resistor to be used with UCC28180? 


    Regards,


    Garret

  • 0 in reply to Garret Holt
    TI__Guru* 86286 points

    Hello Garret,

    This resistor is generally less than 10 ohms.  When you select the FET for your design the data sheet will have a gate charge specification Qg.

    First you calculate the current coming out the gate drive to drive the FET (Igate):

    Igate = Qg*fsw

    Second based on the gate resistance you have chosen (Rgate) you calculated the power dissipated by the Rgate:

    PRgate = Igate^2*Rgate

    To keep things cool I would select a resistor that is rated for 2X the PRgate.

    Regards,

  • 0 in reply to Mike O'
    TI__Mastermind 25570 points

    Hello Garrett

    The first consideration is the static power dissipation that Mike has calculated.

    The second consideration is whether the resistor can tolerate the high peak current pulses as the gate is charged and discharged. We have seen in some applications where a 0603 sized part degraded slowly over a period of months and eventually its resistance increased to the point where the MOSFET was not being driven correctly and failed - in the field.

    So - see if you can get a peak pulse current rating from the resistor manufacturer that would be ideal. If you can't then I would normally suggest that a 1206 size part will be large enough that there won't be any problems.

    Regards

  • 0 in reply to Colin Gillmor
    TI__Intellectual 1050 points

    Hi Collin, Mike,

    Thank you both for your feedback, this was very helpful!

    Regards,


    Garret