I am worried that my MOSFET may be slowly damaged from negative voltage spikes from inductance (solenoid).
My MOSFET: IRL540Nchannel http://www.mouser.com/ds/2/196/irl540npbf-936642.pdf
I dont know what area I can check to see what is the maximum negative voltage spike is safe for my MOSFET.
I have a 1N5401 diode to drain the flyback current.
MOSFET is switching at 97,000Hz
I get spikes around -12V based on this picture:
The initial spike is very large and then there are two smaller ones. Is this ok?
Another question I have is what resistor to put between my PWM source and the gate of my MOSFET.
I wish to put the lowest possible resistor because my MOSFET will switch cleaner and wont overheat.
My pwm driver is a PCA9635, it is capable of "totem-pole, or open drain" Totem pole is 10mA. The output voltage is 5V. I dont know how to get open drain to work. So I am using totem pole.
Based on V=IR, I have to use a 500ohm resistor or else I will surpass the 10mA limit?? However, When I use any resistor above 100ohms, the Mosfet will get too hot.
What can I do? Will going to open drain give me cleaner square waves so that my mosfet gets clean switches?