Hello,
We're using the CD74HC4067 in an ADC mux application.
In some cases, the design can have voltage at an input pin when the IC is powered.
When this happens, we get a voltage showing up on VCC pin.
We have a work-around, but want to understand if this is expected behavior? (put a diode between VCC and input voltage to it)
Can the IC be damaged if operated in this manner?
Thank you, Keith
I believe what you're trying to describe is the injection current
There's a good TI Precision Lab video that explains this: Switches and Muxes : Prevent crosstalk with injection current control
So here the internal protection diode will be forward biased, and the supply rail voltage will have current injected into it when you try to run a current into the unused pin. This is normal behavior for devices that don't have injection current control. If you have this problem mitigated in your design, you shouldn't need to worry about the device itself, as long as you stay within the recommended range of operation.for the signal input.
We do have some devices that provide the injection current control to resolve this but unfortunately nothing in a 16:1 configuration yet.
Thanks,
Rami Mooti
