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I'm having trouble with my circuit. It is supposed to be a load switch to turn on a Wi-Fi module, but it is not working as intended. The idea is to set WIFI_CTRL to high to turn on WIFI_ENABLE.

The components are:

Q3= DMP1045UQ
Q4= TSM250N02CX

I tried reducing the resistance of R10 to 1K and even 100 ohm for a stronger pull-up but still WIFI_Enable is just down to 1.5 V.

Can anyone pinpoint my issue or recommend suitable SOT-23 replacements?

Circuit

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2 Answers 2

Reset to default
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Your P channel MOSFET is upside down. And now the P-channel body diode is always in forward biased and turn-on your WIFI_ENABLE regardless Q4 state.

P-MOSFET body diode

P channel MOSFET source need to be connected to VCC3

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You are missing a pull-down resistor on the gate terminal of Q4. Without this resistor small charges at the gate can keep the MOSFET turned on.

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