I'm using an analog switch, ADG1434 to switch some filter components in a circuit. My question is about general best practice for the digital signals going to analog switches. The switch is dual supply so is powered from the analog +/- and uses analog ground. The switch logic input signals however come from the digital part of the circuit, which in my case has its own digital power and digital ground. If I directly connect the digital signals to the switch, then the (very small, maybe < a few nA according to the data sheet) current will flow from my digital side, through to analog ground and return to digital ground elsewhere on the PCB. This seems to me like breaking the rule of trying to keep these signals separate to maximise performance of the analog circuit. Adding optocouplers to each of the logic inputs so they are powered only on the analog side seems to be the only solution I can see.
So what do people generally do? Is there a general best practice for this?