I am designing PCB2 & PCB3 but PCB1 & PCB4 are set in stone. My constraints are as follows:
1) The PMIC must be the 1st device to become alive. 2) As much as I would love to, I cannot use the 5V #1 supply for PCB4. PCB4 requires 2A of service but PCB1 can only supply 1A of current.
As you can see, U2 is supplied by 5V #1 and it's output signal is referencing 5V #1 as well, but, U3 is supplied by 5V #2 and it's input signal is (still) referencing 5V #1 (not 5V #2).
Note : All GNDs are common and the VIN (24V) originate from the same external 24V supply.
Can or will this (5V #1/5V #2) referencing mis-match cause excessive ground-loop/s, discontinuity and/or even function?