iliketux the penguin

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9 years, 8 months ago.

FRDM-K64F: Wrong power specs in technical reference?

Hi there,

I was looking at the specs for the FRDM-K64F board and I recognized that the power specifications on the platform page (http://mbed.org/platforms/FRDM-K64F/) seem to be wrong. The datasheet (http://cache.freescale.com/files/microcontrollers/doc/data_sheet/K64P144M120SF5.pdf) states in chapter 1.4 that a digital I/O pin can source or sink 25 mA at maximum. Your technical reference says only 4 mA.

Furthermore table 4 in chapter 2.2.3 states a maximum output current of 100 mA for all ports together which is much lower than the 400 mA listed in the platform reference. Maybe I'm wrong but I don't think that you simply can add up all the output high and output low currents to achieve the 400 mA since chapter 1.4 limits the maximum digital supply current to 185 mA.

And as a bonus it would be nice to see an explicit list of 5V tolerant inputs. I think it would be very useful for beginners to know where they can put 5V on and where not without studying the manual.

Regards, Tobi

1 Answer

Dave M
9 years, 6 months ago.

Hi Tobi, I recall there being 5V tolerant inputs on the FRDM-K64F. I thought all were, but clearly that's not the case. Can you point me to the page in the datasheet that mentions which are 5V tolerant? I have gone over it twice, and I could only find footnote 1 on page 7 that says, "All 5 V tolerant digital I/O pins are internally clamped to VSS through an ESD protection diode", but I couldn't find anything regarding such inputs elsewhere in the datasheet.

I wish I could delete my post, because I accidentally posted it as an answer, instead of a comment to your question. Sorry about that.

posted by Dave M 01 Oct 2014

Hello Dave,

in chapter 1.4 (page 6) you will find a table that states a maximum digital input voltage (V_DIO / row 3) of 5.5V. But you have to be careful because row 5 (V_AIO) says that pure analog pins only tolerate up to 3.6V. Footnote 1 clarifies what is meant by analog. Knowing this you can go to chapter 5.1 where you will find a very big table. There you have to search the ALTn columns whether you find an entry that starts with PT (e.g. PTA1, PTB3, ...). If there is such an entry that pin can be used as an GPIO and therefore tolerates 5V. Out of that I would conclude that you can put 5V on every pin that is on the outer rows of one of the headers (AREF, GND, ... exclusive) and has an associated name that starts with PT. With the inner rows you have to be more careful. The ADC0x, ADC1x and DAC0x pins do not tolerate 5V. To be really sure you should take a look in the schematics and then into the table in chapter 5.1 before you start to barbecue your board ;-)

Cheers, Tobi

posted by iliketux the penguin 02 Oct 2014

Thanks, Tobi, that was a very detailed bit of help to piece together the puzzle. I could follow exactly what you said!

posted by Dave M 03 Oct 2014

Indeed, thanks Tobi.

posted by Vladimir Akopyan 09 Apr 2016