The SN74AHC240 Datasheet lists the Vin max as -0.5V to 7V,
with a Note 1 saying these can be exceeded as long as the current into the pin is kept below the ABS MAX values of -20mA.
Given the above statement, I assume the 20mA limit is "constant current limit of 20mA" and not a transient rating, correct?
The real question is:
"Is an undershoot on the input (pin2 / pin4) that reaches beyond -0.5V (max = -0.7V) for <1ns, acceptable given the datasheet phrasing?"
Personally, I think 1ns is too fast for the ESD structure to respond so it doesn't look like an issue from that side either, but if you have any comments?
Thanks,
Darren