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View Full Version : max amps,,, driving leds,



PICMAN
- 1st March 2005, 21:55
does this present a problem,,

run total of 8 superbright leds, directly off pic16f84 pins ( with 330 ohms resistor, ) having posibly 6 on at once,

is the 25 ma rating ,"PER" pin , or cumulitive, does this pose the threat or inevitibility of frying pic when 6 come on at one time ,

egberttheone
- 1st March 2005, 22:37
As far as i know you can balast evry ouput with a rating of 25ma. done this my zelf.

Archilochus
- 1st March 2005, 22:39
Hi Picman,
In the section "electrical specifications" of the data sheet you'll find pin, port, and package specs for absolute power. I don't have the '84 sheet here, so can't check the specs.

Arch

PICMAN
- 1st March 2005, 23:45
ty ach for pulling that out for me, i knew there had to be absolute ratings aswell as the misleading front page saying 25 ms per pin .. knowing where to look put the answers where i could see em,.
and for sake of finishing up the post, :

max out put curent:
port b 100 ma
port a 50 ma

which means stratigic design of what goes on which port, will allow for 6 to be "on" at once, reaching ,, not exceding 50 ma,,,

puting all pins on high with an led stands a very good chance of blowing out the chip , if not a definate one, givin one led = 25 ma , 25 x 4 = 100 ma, over amping port a, rated for 50 ma