Let's say I want to put an existing CPU board with an onboard LM1117-33 linear regulator on top of a larger motherboard. Now the motherboard should provide the 3V3 voltages for the whole system including the CPU board and the 5V supply of the CPU board (Vin of the LM1117-33) is left disconnected. So the 3V3 supply from the mainboard is directly connected to the output (Vout) of the LM1117-33 on the CPU board.
My question is: could this damage the LM1117-33 or have other unfavorable side effects?
From what I can see in the LM1117's datasheet, a floating Vin should mean that all the bipolar transistors are inactive and so nothing bad should happen. I also did a small experiment with a LD1117V33 I had at hand: the (open) input could be measured at ~2.9V with 3.3V connected to the output, which I guess is the voltage drop over the NPN transistor between Vin and Vout. I measured ~4.8mA going into the output. On a scope, the output looked flat (no oscillation).
So does anybody have either the insight or experience to tell me if there are issues to be expected with this constellation?