I'm using the ADG5207 8 port differential multiplexer with 0-5Vdc input signals (steady state DC signals at very low current draw through the multiplexer). The differential outputs from the multiplexer are conditioned and routed to a high resolution analog to digital converter (sigma delta type). This ADG5207 chip has a pretty low input leakage on its own in the powered condition (around 200 pA). What happens when I have the 5Vdc input circuits connected to the multiplexer inputs of the chip when it is in an un-powered state (Vdd=Vss=0V)? The data sheet does not seem to characterize the leakage in this non-operating condition. I'm worried about inadvertently discharging or otherwise disturbing my inputs which are sensitive dc level signals that are always on (routed from another unit).
When the ADG5206 is un-powered we are unable to guarantee whether the switch is on or off. If a 5V DC signal is applied to the device when it is powered off, then the diode to VDD on the input of the switch will become forward biased and current will begin to flow to VDD.
If you require a device that is guaranteed powered off with no supplies I would consider using the ADG5209F. It could block the 5V DC with a 0V VDD.