Hello,

I am experiencing some strange behavior with my circuit. I am using a 2N7002 MOSFET to drive two types of LEDs, controlled by an STM32WB55. When power is supplied to the system via J2, all LEDs (9,10,12,14,16,18 and D8,D7,D3,D2,D1,D4) turn on. However, when I measure the gate voltage, it is at 0V. The supply voltage is 3.2V, and the drain voltage is 2.3V.

My STM32 is running correctly and functioning as expected. I have tested the D6 LED and successfully transmitted some UART strings.

I am relatively new to PCB design and come from a mechanical engineering background, so please forgive any layout issues or beginner mistakes. I would greatly appreciate any guidance or suggestions!

Thanks in advance!

Best regards,
Tim

 

You have the mosfets totally misswired.

It should be like this, the Source connected to Gnd:

Note: Every led should have own series resistor, not the anodes connected together like in your schematic.

 

who created the schematics and did you check it?
transistor is not wired correctly, schematics clearly shows internal diode which explains your measurements

 

when I measure the gate voltage, it is at 0V. The supply voltage is 3.2V, and the drain voltage is 2.3V.

Yes, that's expected operation for an N-MOSFET the way you have it connected.
To turn off an N-MOSFET, the gate-source voltage (not just the gate voltage) needs to be zero, and the drain source voltage must be positive.
Your circuit has the drain-source voltage negative, so the parasitic substrate diode is conducting, independent of the gate voltage (look at the direction of the substrate diode on the MOSFET symbol).

Normally a P-MOSFET is used for a high-side switch with the source going to the positive supply, and the gate is grounded to turn it on.
To turn on a high-side N-MOSFET the gate must be at a higher voltage than the source.

You need to study a tutorial about how MOSFETs work.