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Pic Current Limits

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Wp100

Well-Known Member
Hi,

Am using the pic18Fs to control various led arrays etc, which will always present an even-ish load by the nature of the layout.

The i/o pin currents are 25ma max and the total current per chip is quoted as Vdd 250ma, Vss 300ma.

Any suggestions as to what practical maximum load should be applied though the chip to ensure good life ?

( Want to keep the use of extra chips / transistors to a minimum. )


Thanks
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi,

Am using the pic18Fs to control various led arrays etc, which will always present an even-ish load by the nature of the layout.

The i/o pin currents are 25ma max and the total current per chip is quoted as Vdd 250ma, Vss 300ma.

Any suggestions as to what practical maximum load should be applied though the chip to ensure good life ?

( Want to keep the use of extra chips / transistors to a minimum. )


Thanks

hi,
This for the 16F877, but the 18F datasheet has the info fo the 18F.
https://www.electro-tech-online.com/blogs/ericgibbs/attachments/126d1255799243-files-aaesp03.gif
 

Wp100

Well-Known Member
Hi Eric,

Thanks, but had seen those pages for the 16 and 18F chips, I'm after the real world maximum current I can safely use ?

I generally derate my power devices by 50% to keep on the safe side, don't know if this is a good thing to use on the Pics as I have never used them at higher loadings ?
 

Pommie

Well-Known Member
Most Helpful Member
Note that there is a limit of 100mA per port. So, use all 8 pins and you get (are limited to) 12mA per pin. If you are multiplexing then you will have fairly dim LEDs.

Mike.
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi Eric,

Thanks, but had seen those pages for the 16 and 18F chips, I'm after the real world maximum current I can safely use ?

I generally derate my power devices by 50% to keep on the safe side, don't know if this is a good thing to use on the Pics as I have never used them at higher loadings ?

hi,
In addition what Pommie has explained, note the total power dissipation is 1Watt and the warning given in Note #1.
 
Last edited:

Wp100

Well-Known Member
Hi,

Thanks guys, looks like I have no real option but to use a buffer like the good old uln2803 - worth checking though.
 
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