Pin input current limits

Neighborhood Physicist

How much current will an input·pin draw at 3.3 V?

I have an input·signal that will be split among several pins and I wanted to make sure that I will not draw too much current.

Thanks.

Nick Mueller

On page 25, the data-sheet says +/- 1µA

Nick

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Neighborhood Physicist

Thanks.

crgwbr

Don't forget to take into account a pull-up or pull-down resister (if you included one). Pull downs especially, can draw quite a bit of current.

Regards,
Craig

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Peter Jakacki

Fan-out was always a concern with TTL logic but CMOS presents a capacitive load rather than resistive. The non-switching 1ua figure is not typical at all but certainly it will never be above this unless the device was damaged. Because it is a capacitive load it does present a greater load the higher the switching frequency, so there is a limit if you are driving a lot of inputs at high frequency. At slow speed there is practically no limit though.

If you are interested here is a cool link to a demonstration of CMOS technology:
tech-www.informatik.uni-hamburg.de/applets/cmos/cmosdemo.html


*Peter*

deSilva

Neighborhood Physicist said...
How much current will an input pin draw at 3.3 V?

A generally more important question is: "How much will it draw at 5V?"
I hope you are aware of the working of the ESD diodes, and that the answer to my question is: Infinite