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SLLA385: External Gate Resistor

John Pan
Intellectual 990 points

Hi Mateo,

I enjoy reading your TI TechNotes SLLA385 entitled "External Gate Resistor Design Guide for Gate Drivers." I know it is ideal to place gate driver as close to the MOSFETs as possible. But in some cases, it is difficult to layout a board to achieve that. If the distance between a gate driver and MOSFETs is large, say 40 mm, I am wondering which location of the external gate resistor in a PCB is better, close to the gate driver or close to the MOSFETs, or no effect? I will appreciate if you could provide a reason.

Thanks and I look forward to hearing from you,

John

  • 0
    TI__Guru**** 189401 points

    Hi, John,

    The gate resistor should be placed close to the switch being driven. The reason is the output of the gate driver is very low impedance, whereas the input of the switch is high impedance. If you put the resistor close to the gate driver, you increase the impedance of the track from the resistor to the gate, which could allow noise, ringing, etc, etc to couple in. By placing it closer to the switch, you reduce the amount of trace that is high impedance and likely to pick up noise.

    By the way, the author of this Tech Note, Mateo, is a Mustang! :)

    If this answered your question, please press the Green button. Otherwise, let us know if you have further questions.

  • 0 in reply to Don Dapkus
    Intellectual 990 points

    Hi Don,

    Thank you so much for your insightful explanation. I really appreciate.

    Glad to know Mateo is a Mustang. Go Mustang!

    Best regards,

    John