I am designing a system in which there's a circuit that controls the power applied to a micro SD card (enable/disable).
The circuit is the following:
The power control circuit is done by a P-MOSFET that is deactivated by default.
MICROSD_PWR_EN signal is connected to a pin of a microcontroller configured as open-drain.
The measured voltage on the pin VDD of the micro SD card should be 0V by default. However, this voltage is near +1V, which is neither a logic "0" nor a logic "1". The voltage measured on node "+3.3V" is +3.288V and the one measured on the gate of Q5 P-MOSFET is +3.285V.
Do you have any idea regarding this issue?
Could that be related to the 3mV difference between the source and the gate of the transistor?
Firstly, thank you all for your answers.
It seems that I solved the problem by firmware: by configuring the SD card GPIOs as output open-drain and by setting them to logic "0", the voltage on the VDD pin of the SD card is now near 0V.
As everyone pointed, it is probably related to protection diodes of the SD card chip GPIOs.