Usually MOSFETs stay in switched-off state by default and get switched on by a signal. But I want to use MOSFET the opposite way:
1) it should pull down a line to GND all the time by default, after power supply is ON
2) if needed, should be turned-off by signal from MCU, so that the line gets automatically floating
Is this possible?
In the schematics below R24 should either be connected to GND to enable charging or let float to disable it (according to datasheet MCP73833, chapters 3.4 and 4.2). As per chapter 1.0 the resistor R24 could be at least 200K to disable charging.
If the PROG pin is open or floating, the MCP73833/4 is disabled and the battery reverse discharge current is less than 2 µA. In this manner, the PROG pin acts as a charge enable and can be used as a manual shutdown.