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Thread: Internal Pullup resistor as a Mosfet gate resistor

  1. #1

    Internal Pullup resistor as a Mosfet gate resistor

    Are the internal pullup resistors suitable for mosfet gate resistors? For 5v Arduino, it seems 220 ohm resistor is appropriate for a gate resistor. If the internal pullup resistors are not suitable would the 220 ohm resistor be suitable for 3.3v Teensy?

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by Elf View Post
    Are the internal pullup resistors suitable for mosfet gate resistors?
    Generally, no. The internal pullups are about 50K, which will be very slow for driving a mosfet.

    ... would the 220 ohm resistor be suitable for 3.3v Teensy?
    That's probably fine. The pins are rated for 9 mA constant, 20 mA short duration. 220 ohms will limit the current to 15 mA.

    MOSFET transistors come in many different types with widely varying specs. Since we don't even know the part number of the transistor you're using, very hard to say if this is appropriate.

    But I can tell you most of them are designed for 5V or 10V drive signals. Some are designed to work with only 3.3V input, but those are fairly rare. If you have the more common types that need 5V, it might not fully turn on with only 3.3V, no matter what resistor you use.

  3. #3
    Thanks for the response. I'm working on a board that will drive 3 DRV8825s. The MOSFETs aren't really necessary for this, but they may be useful in a future project, so I'm adding the footprints now.

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