What is the correct thing to do with unused differential inputs on the ADG707 mux ?
I would tie the inputs to a voltage source that is guaranteed to always be between the rails or to
one of the rails. To be on the safe side, put a resistor in series with the line to Vdd or Vss.
The abs max section on page 5 says to limit the current through an input pin to < 30 mA,
I'd keep it a little bit less, say 10 mA. So 5V/10 mA = 500 ohm. So you could use 1k to
ground and go to all the unused inputs.