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G120 Pin current 4ma?


#1

According to the data sheet a G120 can source or sink 4ma on a GPIO. However, according to this diagram of the Cobra 3. Pins 1.14 and 1.19 are being used to drive a pair of LEDs that appear to pull 10ma?
I have two pins left on my board to use to drive a status led, P1.16 and P1.17. I’m pretty much out of room to add a transistor or mosfet to drive the thing. Can someone who knows more than me :-[ recommend a resistor value to use, I’d like it to be as bright as possible without risking the pin. I’ve got a bunch of these laying around https://www.digikey.com.au/product-detail/en/lite-on-inc/LTST-C230EKT/160-1187-1-ND/269259.
But if someone were to recommend a different led and resistor pair. I could live with that. I’ve got DigiKey orders I need to do next week any way.

Thanks in advance,
I’ve nearly finished this project and I just couldn’t have done it with out the generous support of this community.


#2

@ stotech - Drive the led with a mosfet.


#3

I’ve been moving parts around for the last hour trying to squeeze one in there, I should have said that I was cramped for space. But yeah I’m afraid I might have to. Still, I’m interested to see what ghi’s reason was for pulling more power out of the pins. Do they know something we don’t?


#4

@ stotech - Your calculation that the LEDs pull 10 mA seems to be not correct. You have to consider the voltage drop over the LED
which can be estimated between 1.2 and 2.5 Volts. You can look in the datasheet of the LED or you can measure the voltage in your circuit. If we take for exampe 1.5 V you have to calculate with the difference 3.3V - 1.5V = 1.8 V
and with a resistor of 330 Ohm you see that the current is only 5.5 mA.

Edit: According to the data sheet of the LED you have you can calculate with a forward voltage of about 1.6 to 1.7 Volts.


#5

:-[ :-[ :-[ :-[ :-[ :-[ so embarrassing.


#6

So I’ve crammed in an nch mosfet to make it work. Sorry for the stupid question.

Thanks again.

BTW. I vote the new platform under consideration has a reward system of some sort. That way I wouldn’t fell so guilty every time I stuff up.


#7

@ stotech - Well at least you didn’t release the blue smoke and then feel guilty. That would be way worse.