I’m using a DMP2045U P-channel MOSFET as a high-side switch to control 3.3V power to an ESP32-S3-WROOM module. The gate is driven by an STM32. Connections Source → 3.3V (measured 3.289V) Drain → ESP32 3V3 pin Gate → STM32 GPIO 10k pull-up from gate to 3.3V Measurements When gate is LOW (~0.009V): Source = 3.289V Gate = 0.009V Drain = 3.289V Vgs ≈ −3.28V → MOSFET turns fully ON (as expected) When gate is HIGH (3.287V): Source = 3.289V Gate = 3.287V Vgs ≈ 0V → MOSFET should be OFF However: Drain measures ~2.89V I added a 47k pulldown resistor from drain to GND. This reduced the drain voltage to ~2.4V — but not to 0V. All STM32 GPIOs connected to the ESP32 are driven LOW. If I completely remove the MOSFET, the ESP32 3V3 rail stays at 0V (no floating voltage). Question Is this expected off-state leakage/floating behavior for a discrete P-MOSFET in this configuration, or is there something wrong with my circuit?

P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

arvindsa 4 days ago

I’m using a DMP2045U P-channel MOSFET as a high-side switch to control 3.3V power to an ESP32-S3-WROOM module. The gate is driven by an STM32.

When gate is LOW (~0.009V):

When gate is HIGH (3.287V):

However:

I added a 47k pulldown resistor from drain to GND. This reduced the drain voltage to ~2.4V — but not to 0V.

All STM32 GPIOs connected to the ESP32 are driven LOW.
If I completely remove the MOSFET, the ESP32 3V3 rail stays at 0V (no floating voltage).

Is this expected off-state leakage/floating behavior for a discrete P-MOSFET in this configuration, or is there something wrong with my circuit?