I am designing a system that has 2 power inputs and has to be working as long as these power supplies are fine. I mean, the system starts working with power supply #1 but if it fails, switches to power supply #2.
I've read some threads and noticed of LTC4417 CI, that does exactly what I want.
The circuits I've found in many threads (as done too in eval board DC1717A) suggests to connect all grounds lines together (http://cds.linear.com/docs/en/demo-board-manual/dc1717af.pdf page 6).
Knowing that every power supply has a ground reference (in essence, a ground line has an electric potential lower to positive terminal), is there any risk connecting all ground terminals together?
Do I have to put any kind of filter between this physical lines?
Thanks in advance.
PD: as an example of a circuit that does this function: Switching between power supplies - USB dominant.