SPDT output voltage for unconnected input

[crazymach]

Noob question.
If I had a 2:1 multiplexer like this one https://assets.nexperia.com/documents/data-sheet/74LVC1G3157.pdf

Input 1 was a normal signal going through it, and input 2 was disconnected and I selected input 2, will the output be connected to input 2, thus be an open? And will this output have a voltage related to the VCC or GND rails?

[David Chamberlain]

Hi Crazymach, do you mind if I rephrase your question....

You are asking if you had a AC signal on Y0 and Y1 was disconnected then what would be the cross talk between Y0 and Z if S were HIGH (meaning Z is connected to Y1)

In that case this is given as ?iso "isolation (OFF-state)" on page 13. Figure 22 on page 14 show the test setup for that.

But just based on your question the potential of the output (Z) with respect to VCC or GND then technically it should be zero (or at least floating with respect to those rails). This is an analog switch not a digital buffer and so they behave more like a 'solid-state relay' some more info can be found in the link below.

https://www.analogictips.com/whats-difference-analog-switch-digital-switch-ics/

[SebG]

Hi
The mux is an analog switch so it acts same as a mechanical toggle switch but with some resistance (~6 Ohms).  So if you select input 2 then the output will be floating.  Each switch is essentially bidirectional pass-through mosfet that is enabled or disabled using S input.

[Ian.M]

There's a little leakage current - up to a maximum of 2uA so a high impedance voltmeter will measure a voltage between VCC and GND on its output, with a source impedance >500K.  The typical leakage is 0.1uA, but that should still be detectable on a 10Meg
DMM.   Don't count on the typical leakage - it will get much worse at elevated temperatures.