digital i/o protection

[alireza7]

hi

i want to connect digital io of my micro controller to a digital ic which it's input capacitance is 15_25 pF ;

do i need any protection here?  like simply connecting my io's  througha series resistor to the ic to prevent sudden current surge ?

[fourtytwo42]

That is not normally a problem, most ic's have that sort of input capacitance.

[danadak]

If the UP is running at 5V, the IC at 3.3, then a series R is advised.

That's because of the parasitic scr problem in CMOS -





https://en.wikipedia.org/wiki/Latch-up


https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwiSndO53M3ZAhXKct8KHTKTDVIQFgg6MAE&url=https%3A%2F%2Fwww.fairchildsemi.com%2Fapplication-notes%2FAN%2FAN-339.pdf&usg=AOvVaw0N7NnjfjppHF0Vl4H16wJm

Note in this case a series R degrades speed, so if you need to maintain
fast rise/fall times then use a logic level translator, many variants from
On Semi, Fairchild, NXP, TI....


Regards, Dana.