I am having an issue with a control signal.
I have a CEP50P03 P channel trench MOSFET that is supposed to switch a 12v power supply.
I am having an issue I can not figure out. When I power the board with 5V everything works as it should.
However when I add the GND connection to the 12v side to use the 7805DT voltage regulator the Mosfet will come on and latch on and will not turn off.
I then tried removing the voltage regulator and power the circuit with only 5v and the fet does not switch at all. I have not been able to figure out this weird behavior.
I attached the shematic below. This circuit is used in an automotive rev limiter module where tach signal is a 0-12v square wave used to read rpm that is then converted to a 0-5v square wave the ATMEGA328P reads and if the frequency is above X ammount the Atmega sends a signal to turn the MOSFET off for X time and the mosfet should turn back on.
However like mentioned above when I have 12V coming in the MOSFET latches on and stays on.