I am driving a MOSFET with AVR using PWM for controlling a motor. I have a 4K7 pull-up resistor on the gate. My question is, do I need a resistor in between the AVR pin and the gate? (The mosfet is NX2301P)
\$\begingroup\$
\$\endgroup\$
Add a comment
|
1 Answer
\$\begingroup\$
\$\endgroup\$
2
No you do not need a series resistor. If you put one in there it would limit the current a bit and might help in case of some layout issue, but it's not necessary.
Why the rather low gate pull down and why a pull down rather than pullup? Normally I'd expect to see more like a 20K pullup so if the AVR output is high impedance the motor turns off. A pull down resistor on a P-channel MOSFET gate means that the motor will turn on if the input is open.
answered Aug 11, 2015 at 12:42
-
\$\begingroup\$ I'm indeed using a pull-up, I'm sorry, I mixed up. Do you think 4K7 is not enough resistance? Also, won't it damage the AVR pin if I leave out the gate resistor? \$\endgroup\$– lszabiCommented Aug 11, 2015 at 12:47
-
\$\begingroup\$ It will work fine, but a bit low value, in my opinion. No it won't damage the AVR pin- it will see a brief pulse of current to charge/discharge the gate charge. If you want to use a resistor probably 50-100 ohms would be okay, but better to put it after the pull-down to get more gate voltage (the part you used is 1.8V though so not much worry). \$\endgroup\$ Commented Aug 11, 2015 at 12:50