MOSFET control device power over USB

Other Hardware General Electronics
1

Hello,

I need to control a USB device, to allow the SBC to power it off. The idea is, the USB device is always on, and when it needs, the SBC turn it off over a GPIO. Something like this:

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Any suggestion would be appreciated. Should I add a transistor on MOSFET gate? Or this should be ok? The power of the connected USB device shouldn't go above 1A.

The MOSFET datasheet:

Regards...

PS. The SBC logic of course is 3.3V.

2

I normally do that sort of thing with a logic level MOSFET N-CHAN.

3
  • You need to rethink this schematic.
  • When you need to control the power to an electronic circuit you use a P MOSFET. i.e. configure as a High Side Switch.
2 Likes
4

R9 should be on the other side of R8.
R9 has no function for the gate of the FET.
It's function is to stop the MCU pin from floating during boot-up.
Leo..

1 Like
5
  • To prevent the MOSFET from turning ON when the controller isn’t powered.
3 Likes
6

Ok.

So this schematic should turn ON power to the USB all the time, and I can switch it OFF by writing HIGH on FETpin. Am I right?
The AO3401 should be enough for a 5V/1A.

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Regards.

7

  • Q1 is backwards.
    i.e. Drain and Source are reversed.

  • R9 goes to +5V.

8

Maybe not.
If the 5V is comming From the USB connector, then it is correct and R9 should connect between the gate and source.

1 Like
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10

LOL. My bad.

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The whole idea is to allow the SBC to control the connected USB device by turning it OFF when needs. The connected device should be always ON, unless the condition is met to turn it OFF.

11

I am not exactly sure what is happening but by using the source as your reference the gate needs to be negative for a P-FET, if it is positive it will remain off.

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