I have a commercial PCB. On it is an IC with a pin that is pulled down to ground by a normally open switch. I want to turn on supply to a load when the switch is closed.
It's not possible to modify the switch as it is in a sealed unit. I can only tap into the cable between the pin and the switch. The cable between the switch and ground is common to 2 other switches which take their respective pins low when closed.
The pin is high at 5V. Battery is a 3S lipo. The load consumes 560 mA at 12V. The load is a set of LEDs, with some circuitry to regulate power and provide some protection.
I don't have any information about the IC, as it is an unlabeled 8 pin package. I measured 1.2 mA between the pin and ground when the switch is closed. The IC is supplied 5V, regulated from the same 12V source.
I want to attach something between the pin and switch that will turn the supply of power to the load, when the switch is closed and the pin is taken low.
I gather I need a P-Channel enhancement mode MOSFET here. Is this appropriate? If the power supply was a constant 12V, then a Vgss of -7V to -12V would be good, however the supply voltage may dip a few volts when the switch is closed. I'm struggling to measure how low, it might be as low as 6V. What components should be placed around the MOSFET to support and protect it?