I'm designing a Split keyboard where each half can be connected to USB, or to the other half, or both. If one half is not connected to USB, it receives its power from the other half. 99% of the time these will probably be connected to the same computer, so simply connecting all 5V together only has the effect of connecting the 5V and Ground of two USB ports on the same computer (potentially on different USB hubs/controllers). This doesn't feel very safe, especially since I might connect each half to a different computer while the halves are connected to each other.
While the USB port will only supply 5V (if plugged in), J2 and J3 can either supply or recieve 5V depending on whether the other side is plugged in to USB.
I investigated using an ideal diode solution, but the problem comes when supplying the power back to the other side: The LM66100 datasheet is available here. If +5V were connected to EXT_5V, I'm not sure of the effects on IC2 as VOUT is connected to VIN. Perhaps with a resistor it would be okay?
Essentially there are three situations that each half can be in:
- This half has USB power: it should use the USB power, and supply USB power to the other side. This half should not accept power from the other side.
- This half does not have USB power: it should accept power from the other side
- Both halves have USB power: they should run off their own USB power, and the two power supplies should not be connected.
Is this possible over a single shared 5V conductor? I'm open to all suggestions, not just modifications to the ideal diode setup. It would be very inconvenient to use a different connector to the TRRS shown, but if that's what it takes... The 5V will be used for a 3.3V regulator for the microcontroller, as well as powering WS2812b LEDs. If the LEDs will work off a slightly reduced voltage then solutions involving a diode might be okay.
Thanks in advance for your helpful responses :)