It should be a continuous mode with voltage supply of say 3.3V. I would like to be able to adjust the current through the LED from 10mA to 100mA.
For that, I am planning to use the trimmer resistor in series with a 10 Ohm resistor in place of the Rext, where the 10 Ohm on its own will drive the Iout to about 90mA, and additional resistance from the trimmer will allow to drop the current to 10mA, according to the plot below:
- Should I care about the Vout value? It seems to me like a chicken and an egg problem. Vout depends on the voltage drop across the LED and Rext, and determines the current Iout, according to the plot. It the same time, the current through the LED depends on the voltage drop across the LED, which also dictates the Vout that determines the Iout. Well, I can not seem to get out of this loop. So, what determines all the other?
- How do I determine the current through the Rext, or the Vdrop? Is it correct to assume that for low Rext values the current through it is ~Iout?
- What is the advantage of this circuit as opposed to simple resistor-diode in series (except the EN pin that allows fast switching)?