3.4V VF LEDs operated by 3.3V

[EngIntoHW]

The µC I'm using can source 20mA at 3.3V.

I'd like to use a bi-color green-blue LED (HSMF-C168) which each of its colors has a typical VF of 3.4V and maximal VF of 3.8V.

I'm aware that the LEDs will illuminate more weakly.
I'd like to know whether they will still illuminate.

Thanks.

 

[colin55]

Every LED from each manufacturer has a different characteristic. I have found that LEDs will illuminate weaker and weaker as the voltage drops below their "characteristic" voltage. Many will still illuminate when the voltage drops by as much as 0.5v.

 

[audioguru]

The tiny LEDs are extremely dim. Ordinary LEDs are 1000 times brighter.
You don't know if your LEDs need 3.2V or 3.8V so it is a gamble to see if they will light with only 3.3V.
The output of the micro-c will be less than 3.3V when it has an output of 10mA.
The max current for the LEDs is only 10mA, not 20mA.

 

[EN0]

To me that seems to be a high foreward voltage compared to typical LEDs. I have some that have a foreward voltage of 1.8V. LEDs are cheap, and you should be able to find a foreward voltage lower than 3.3V.

 

[MrAl]

Hello,


Some of the other color LED's (like white) have a much higher forward voltage, like as high as 3.5 volts. Those colors dont come much lower.

Consider pulsing the pin with a square wave and using an external voltage doubler to drive the higher forward voltage LED's.