In our application, our board can receive +12V from an adapter jack when working in standalone mode. This 12V is fed into a switching regulator to create a 3.3V supply (named 3V3_2 in the schematics below)
The board can also be connected to a host board via an edge connector, in which case, 3.3V should be supplied by the host board (named 3V3_1 in the schematics below)
What we want to do is that, when the user plugs in an adapter jack, we want the board to automatically use the output of the switching regulator. We are using a jack with a switch. The switch is floating when nothing is plugged in, pulled to ground when an adapter jack is inserted. (The switch signal is terminal 2 in the schematics below)
Please take a look at these two circuits. Would any of these work? Do you foresee any problems with either of these circuits? Are there any other alternatives?