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My goal is to be able to power the RPI from either the internal pin or from the usb-c port, but protect the RPI board in case both sources are connected at the same time.

I’m powering a RPI 4 via the 5v pins directly on the board. If the pi is also accidentally plugged in to a usb-c cable, both sources would be effectively connected in parallel, which will fry the board.

Is there a circuit that can detect that there is already voltage coming in from the 5v pin, and if so, block the internal power source from supplying voltage to the pin?

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  • \$\begingroup\$ For Rpi W (I think similar for other Rpi's), the USB power is isolated/protected from the External power by a Zener diode. See the following schematic from Rpi W datasheet (more details in Chapter 2): imgur.com/a/WIA7VSy. \$\endgroup\$
    – tlfong01
    Commented Dec 3, 2022 at 13:46
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    \$\begingroup\$ @ tlfong01 D1 (MBR120VLSFT1G) is: DIODE SCHOTTKY 20V 1A SOD123FL \$\endgroup\$
    – Rodo
    Commented Dec 3, 2022 at 17:51
  • \$\begingroup\$ @Rodo: Ah, my apologies. It is a Schottky. MBR120VLSFT1G Schottky Power Rectifier, Surface Mount 1.0 A, 20 V, SOD-123 Packag - OnSemi onsemi.com/pdf/datasheet/mbr120vlsft1-d.pdf \$\endgroup\$
    – tlfong01
    Commented Dec 4, 2022 at 2:40

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