TMUX7308F: Disabled output floats high

Disabled I/Os float and do not have any defined voltage. If you try to measure the voltage anyway, what you get depends on whether there is enough capacitance on the line to keep the old value, and how much leakage currents you have.

In addition to what clemens said, 

To prevent the floating of this device when disabled please tie the output of the device to Ground through a resistor.

This FAQ explains more about this in detail.

Regards,

Kameron

Hello KB,

I believe what you are referring to is overvoltage protection. This means if an Input signal is sent to the mux that is higher than the supply of the mux that signal path  will be disabled( Hi-Z)  and the drain pin will pull up to the supply voltage( or High).

In addition an external resistor(4KOHM) can be added after the drain pin to pull output Low after fault event.

Please let me know if you have nay further questions.

Regards,

Kameron