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### Topic: Is there an input current limit in the digital pins on DUE? (Read 809 times)previous topic - next topic

#### F1_

##### Aug 22, 2017, 03:18 pmLast Edit: Aug 22, 2017, 03:49 pm by F1_
Hi,

Following this page there is a max current sink in some digital pins of up to 9mA, this means if one of those digital pins are selected as an input and receive 3.3V 100mA it will only let 9mA go by without damaging the board?

"I don't think a success factor of a novel is determined by the tools used by the writer, it can be notepad, ms word, or just pencil and paper, but CREATIVITY IS." ~DuckfaceNinja, Construct2 Forum user

#### dougcl

#1
##### Aug 22, 2017, 06:14 pmLast Edit: Aug 23, 2017, 07:19 pm by dougcl
this means if one of those digital pins are selected as an input and receive 3.3V 100mA it will only let 9mA go by without damaging the board?
No, it does not mean that. The Due will not restrict the current to 9mA. What the spec means is that you must restrict the current yourself, using a resistor external to the Due. If you do not restrict the current, and the current exceeds 9mA, then the pin will be damaged.

Edit: my mistake, as Whandall points out below, if the pin is configured as input, it has high impedance, and will not draw very much current. External resistors are not needed in this case.

Doug

#### F1_

#2
##### Aug 22, 2017, 06:23 pm
Okay, so I will apply resistors or something else to reduce the current, thank you.
"I don't think a success factor of a novel is determined by the tools used by the writer, it can be notepad, ms word, or just pencil and paper, but CREATIVITY IS." ~DuckfaceNinja, Construct2 Forum user

#### Whandall

#3
##### Aug 23, 2017, 08:10 am
there is a max current sink in some digital pins of up to 9mA, this means if one of those digital pins are selected as an input and receive 3.3V 100mA it will only let 9mA go by without damaging the board?
If configured as input the pins do not draw any significant current,
you do not need resistors for inputs to delimit the current.
Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of. (D.Adams)

#### F1_

#4
##### Sep 12, 2017, 02:31 pm
Thanks!
"I don't think a success factor of a novel is determined by the tools used by the writer, it can be notepad, ms word, or just pencil and paper, but CREATIVITY IS." ~DuckfaceNinja, Construct2 Forum user

#### GolamMostafa

#5
##### Sep 23, 2017, 09:45 pmLast Edit: Sep 24, 2017, 01:24 pm by GolamMostafa
The value of current limiting resistor for maximum sink current as Output Port:

Given for PA0 (as per data sheets):
VDD = 3.3V, VOL = 0.4V, and IOL = 9 mA

R = (3.3 - 0.4)/9*10-3 =~ 320 ohm.

Q  How much current would PA0-pin of DUE sink when driving a typical TTL load?

IOL = (3.3 - 0.7-0.4)/4*10-3 = 550 uA.

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