I'm working on a driver for a solenoid and just want to make sure I got it right, or somewhat. So this is how it works, or supposed to. The signal to the gate driver U55 goes fully on (high) for 10ms before it enters PWM at 24kHz. So for this 10ms Q40 will see a max current of 2A and it's power dissipation will be (2*2*Rds(on)) = 100mW. I used Rds(on) = 0.025. Then 100mW * RθJA = 10. I used 100 for RθJA since my pad will be smaller than 1" and 1oz. With a max ambient of 40C this 10C rise should not be a problem. That's if I didn't miss anything that you guys can catch here.
Now since I'm doing PWM at 24kHz (42us period, 50%DC) I figure I would need 60nc/21us = 3mA current to the gate of Q40. I have not worked with gate drivers before, so I think I might need a limiting resistor on the gate of Q40 to give a current of at least 20mA. So with this the driver will be dissipating (.02*.02*200) = 80mW. 80mW*200 = 16C. Again this 16C rise on a 40C ambient wouldn't be a problem.
If anyone has any suggestions or I missed anything I would appreciate any feedback.
Now since I'm doing PWM at 24kHz (42us period, 50%DC) I figure I would need 60nc/21us = 3mA current to the gate of Q40. I have not worked with gate drivers before, so I think I might need a limiting resistor on the gate of Q40 to give a current of at least 20mA. So with this the driver will be dissipating (.02*.02*200) = 80mW. 80mW*200 = 16C. Again this 16C rise on a 40C ambient wouldn't be a problem.
If anyone has any suggestions or I missed anything I would appreciate any feedback.