LED resistor selection G120TH

NETMF & Gadgeteer
1

Hi,

A simple design issue that trobles me. In the G120 manual has been stated for GPIO:

“Individual pins can source or sink up to 4 mA (see the processor’s documentation for advanced information).”

But in schematics I see a 330 ohm resitor on PIN controlling a led.
I = U/R = > 3.3V/330 ohm = 10 mA.
10 mA > 4 mA ???

What goes wrong here?

BR

jari

2

And where is the voltage drop due to the LED in your equation?
Blue LED have a quite high offset, see some datasheet.

3

Yes I shall take into account the voltage drop on LED (~2.5V)

Something like this:

I = U/R = > 3.3V- 2.5 V /330 ohm = ~2.4 mA.

2.4 mA < 4 mA, this should do and candelas should also be fine on this current.