Max input current

Hi all I need to connect a button to my Arduino Due so i can use it as a start/stop signal. My intention is to connect it to the 3.3V line and make a pulldown resistance (like this, but with the 3.3V line) so that I don't break my board. Anyway, I can't exactly find the maximum amount of current that each pin can recieve. I mean: the resistance connected to the ground will be something like 10 kOhm, but I need to know the max receivable mAmperes in order to put another correct resistance between the button and the input pin. The official support isn't very specific about this:

Each pin can provide (source) a current of 3 mA [u]or[/u] 15 mA, [u]depending on the pin[/u], or receive (sink) a current of 6 mA [u]or[/u] 9 mA, [u]depending on the pin[/u].

Can you please provide me any exact value?

Thanks in advance, Michele

P.s: sorry for my bad english ;)

Providing you don't go over 3v ....

You'll be fine, but as a precaution a 10k resistor can be used.

but I need to know the max receivable mAmperes in order to put another correct resistance between the button and the input pin.

A pin when it is an input is very high impedance so the current does not matter, you need not be concerned about it. That means you can remove R1 altogether and replace it with a wire.

The purpose of R1 is to act as a bit of protection in case pin 8 gets set as an output and that output gets set to be low and you push the button. In that case that pin will be sinking current. To keep below the maximum of the pin you should use a value of :- 3.3 / 0.006 = 550 ohms But I would not bother with it as it spoils the noise margin of the input pin. How likely are you to make those three errors all at once?

Grumpy_Mike:

but I need to know the max receivable mAmperes in order to put another correct resistance between the button and the input pin.

A pin when it is an input is very high impedance so the current does not matter, you need not be concerned about it. That means you can remove R1 altogether and replace it with a wire.

The purpose of R1 is to act as a bit of protection in case pin 8 gets set as an output and that output gets set to be low and you push the button. In that case that pin will be sinking current. To keep below the maximum of the pin you should use a value of :- 3.3 / 0.006 = 550 ohms But I would not bother with it as it spoils the noise margin of the input pin. How likely are you to make those three errors all at once?

Thank you very much, I was going crazy searching over the internet :D I have only a doubt: you put 6mA in the Ohm's law, but the quotation I did before says that, depending on the pin, it may accept also 9mA. The same is when proving current (3 or 15mA). Is there any table which tells precisly the max amount of current for every pin? The "depending on the pin" seems to me very vague.

Why are you obsessed with sinking the maximum current into a pin in the event of an accident? As I said that resistor is not needed at all.

The high current pins are in the data sheet or in the excellent diagram that GreyNomad has drawn, see the sticky post at the start of this section.

Grumpy_Mike:
Why are you obsessed with sinking the maximum current into a pin in the event of an accident?
As I said that resistor is not needed at all.

The high current pins are in the data sheet or in the excellent diagram that GreyNomad has drawn, see the sticky post at the start of this section.

My question was also for the use of the pins as output. Anyway I found the specific values in the pinout diagram, thank you very much for the help :slight_smile: