74ACXX running on 3,3v

[dacen]

Will a 74ACXX circuit running on 3,3volt be 5volt input logic tolerant?

 

[rayma]

On Semi rates the 74AC00 as follows, so you will need to level shift the input.

Absolute Maximum Ratings:
VI DC Input Voltage –0.5V to VCC + 0.5V

Recommended Operating Conditions:
VI Input Voltage 0V to VCC

https://www.onsemi.com/pub/Collateral/74ACT00-D.PDF

 

[dacen]

I know the datasheet parameters. I also know that 74LVXX running on3,3v is 5volt logic tolerant. I just seem to remember reading somewhere that 74AC will behave likewise despite that the datasheet does not tell. May be I have to test it first.

 

[rayma]

Using devices not in accord with the data sheet is undefined and unpredictable.
Never do this for commercial purposes, or for any critical application. Also,
different mfr devices can behave differently.

 

[dacen]

Thanks

 

[dacen]

Obviously no golden rule here. Found this. Answers my question: When running at 3.3V, families that ARE 5V-tolerant:
LV-A, AHC (except transceivers?), LVX, LVC, LCX, LVT

When running at 3.3V, families that are NOT 5V-tolerant:
LV, HC, AC, ALVC

 

[dacen]

That is correct. It is not AC but AHC that is tolerant to 5V when running on 3,3V. The datasheet says : Inputs accepts voltages higher than VCC. Page 2 here:

 

[Mark Tillotson]

Note that 5V tolerant families may be more static sensitive, lacking protection diodes.


I've used LVC and LCX before.


Datasheets should always give the input voltage limits.