I have a board (A) which exposes a parallel bus. I want to make a second board (B) which connects to (A) but does not draw too much current from it. I want (B) to come on only when (A) is powered, to avoid having logic gates on (B) that are powered to feed current to (A) through the parallel bus lines. (B) maximum current draw is around 500 mA, so a small mosfet should be ok to power it.
I came up with the following schematic. 5V_pwr is where (B) draws current from, while 5V_sense is from (A). Do you see any problems / possible improvements?