I am using a P-Channel Mosfet to control the power of an STM32F103VETE ARM microcontroller (MCU1). The source of the Mosfet is connected to 3.3 V and the drain goes to the MCU1 Vdd pins. The gate of the Mosfet is controlled by another microcontroller (STM32F030RET (MCU2)) which is directly connected to 3.3 V net.
Now the problem is that I can't turn off MCU1:
- When I put a Logic 1 on the gate of the Mosfet, that makes its Vgs = 0 but I still get 2.4 V at the drain of the Mosfet which is enough to turn on MCU1.
- When I put a Logic 0 on the gate of the Mosfet, its Vgs = -3.3 V, it turns on properly and I can read 3.3 V at the drain.
Can anyone please help me to solve this? What can cause such a problem?
Here is the schematic of the circuit I have used:
"POWER_ON" is the signal from MCU2. The Mosfet is STS3DPF20V.