I had posted a question earlier but I was using a BJT at the time and the solution provided led me to use a MOSFET for my application instead. I switched to the FET but still unable to provide stable Power to my Pi. Is my ATtiny10 pin current too low to drive the Gate of this FET? Is there something wrong with my circuit design? I get at most 120mA to the Pi but my source current is providing 3A.


simulate this circuit – Schematic created using CircuitLab


You're not driving the FET with a high enough voltage. Remember, the threshold voltage \$V_{th}\$ is the voltage at which the FET just barely begins to allow current through--not the voltage at which it's fully on. If you look on page 4 of the datasheet:

enter image description here

you'll see that the on-state resistance is specified at a \$V_{GS}\$ of 10V, twice what you have. And some of the other specifications are rated at a \$V_{GS}\$ of 13V!

  • \$\begingroup\$ I had no idea about that spec. I know the site frowns on requesting part suggestions but since I have been trying to get this to work for a while now would you be able to point me in the right direction? \$\endgroup\$ – SChand May 14 at 0:34
  • \$\begingroup\$ The trick is to search for "logic-level" FETs. Hopefully that search term helps! \$\endgroup\$ – Hearth May 14 at 0:37
  • \$\begingroup\$ If the drain-source on-state resistance spec says Vgs=5V and Id=1.1A, does that mean my load can only receive 1.1A at most? \$\endgroup\$ – SChand May 14 at 0:51
  • \$\begingroup\$ @SChand That just means that's the current at which it was tested. \$\endgroup\$ – Hearth May 14 at 0:52
  • \$\begingroup\$ Rds is also important for this application. You don't want to drop more than a few tenths of a volt. \$\endgroup\$ – Mattman944 May 14 at 1:20

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