Hi,
Due to a shortfall in supply, I may have to substitute a 74HCTxxx part that I can get for a 74HCxxx device that I can't get.
The supply voltage is 3.3V. 74HCT is only specified to run from 4.5V to
5.5V, so this would be operating outside the datasheet Recommended Operating Conditions.I understand that 'HCT is just like 'HC but with different W/L ratios on the input P and N ch transistors, and as such, it ought to work at 3.3V. My application doesn't need to be fast or need lots of output drive. The input thresholds do concern me though.
Question 1: What sort of input thresholds should I expect? (I understand it won't be guaranteed, but still...)
Question 2: Are there any gotchas? I'm thinking of things like an (undocumented) brownout detector resetting flip flops when the supply gets low.
Thanks, Allan