Overcome voltage limits on HCT flip-flop

[pozzugno]

I don't know if this is the correct forum section to post this question. Sorry if I'm wrong.

I want to use D-type flip-flop 74HCT74 as a trigger: when I open a switch, the output should change and should stay changed until a reset signal.
The switch is connected between ground and +24V through a pull-up resistor of 2700 ohm.

I don't want to increase the complexity of the clock input, because I'd like a propagation delay as low as possible.

I read on the datasheet from NXP the following note:

The input and output voltage ratings may be exceeded if the input and output current ratings are observed.

The current ratings are +/-25mA and I think I'm inside this limits with 2700 ohm and +24V.

Can I connect the connect input of 74HCT74 to a pull-up resistor to +24V without any risk to damage the IC?

 

[keith1200rs]

Can I connect the connect input of 74HCT74 to a pull-up resistor to +24V without any risk to damage the IC?

Yes, but it won't necessarily work. Either add a zener to the input or maybe a potential divider to scale the input voltage. Which is best depends on how clean your 24V is and the tolerance of it.

Keith.