I'm using the SN74CB3T3257 as a demux in a circuit I'm working on.
The relevant parts of the circuit is approximately this:
What I want is if I disconnect the external circuit, OUT reads 0.00 V, and if the external circuit is intact, it will read ~VDD. I'll use this to drive a comparator. Keeping it low power is essential as we need to run it off batteries.
When the external circuit is connected it works as expected and reads ~ 0.99*VDD. But when i disconnect the external circuit, it still reads VDD.
I tried with some lower value resistors; everything behaves as expected if R2 is in the 10 - 50 kΩ range; after I disconnect, OUT goes to 0.00 V. But as R2 gets to > 100 kΩ, OUT doesn't fall anymore.
I'm not sure if there is a parameter in the datasheet I'm missing which explains this behavior, but I couldn't find anything. I tried multiple chips to confirm it wasn't a blown chip.
Any ideas why this behavior?
EDIT 1: Fixed schematic and included pin numbers.
EDIT 2: Updated schematic to show where out leads (into comparator). Note, OUT voltage doesn't change whether or not it is connected to the comparator.