How to find out Processor one GPIO pin maximum source current and maximum sink current? In datasheet mentioned IoL and IoH, is it same for GPIO source and sink current also?
How to find out Processor GPIO maximum source current and maximum sink current of that pin
current-source
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What you are describing is covered in "A' and "B" above. Your description for a sink is different. "C" shows perhaps a more common and intuitive description.
This a good question as a good understanding is needed. A current sink/source is not the same thing as a ground which can both sink and source current. This is important as not all components can both sink and source and misusing them can lead to confusion.
If you are selecting a column via a 4515 de-multiplexer, ONLY one column is active therefore it is impossible drive more than 1 LED in the same row at any one moment in time: -
This means, if 25mA will drive 1 LED sufficiently then that's all you need.
EDIT Passerby has made a very good point about the drive capabilities of the 74HC4094 - basically, in a nutshell, the max supply current is 50mA which means that if all 7 row outputs were selected at once, the maximum current deliverable per line is about 7mA and this is somewhat less than what the OP was expecting. There is another serial device that could suit and this is the 74HC595 and its maximum supply current is 70mA; this will deliver 10mA to each of the 7 LEDs but the OP has to decide if this is good enough.
I think the 74AC164 may just do the job however - it has 25mA outputs but I'm struggling to find the max supply current spec - anyone any ideas? Anyway, here's a small diagram that shows it driving a 7 seg display with about 13mA per line: -
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Best Answer
That is one of the most useless datasheets I have ever seen.
The maximum current levels for GPIO pins are not specified in the data sheet. This apparently is intentional on Freescale's part.
This question was brought up in a Freescale forum. A Freescale employee, Yuri Muhin answered. In the last paragraph, he says "Maximum current levels ... are not specified."
Here is the full text of his answer:
Have a great day, indeed.