Teensy 4.0 Schematic Question

[chefcurrypot]

I was looking at the teensy 4.0 schematic, and I noticed that there was a transistor with its gate connected to ground attached to the USB power supply line that goes to the processor. If the gate is tied to ground, wouldn't this just act as a diode? Is there any reason this was chosen over a diode, or is it performing some function I am unaware of?


Links to relevant parts:

Teensy 4.0 Schematic
Transistor datasheet

 

[duff]

I think it's for reverse polarity protection, also the mosfet design has a lower voltage drop than a diode and would have less wasted heat and more voltage for the USB controller on the T4.

 

[PaulStoffregen]

Is there any reason this was chosen over a diode

Yes. It has much lower forward voltage drop, which is better for running from a 3.6V battery.