Attached is a circuit from the National data sheet. I want to drive a super-flux LED (well, 2 or 3) with a 317 wired for constant current. The data sheet was a little light on material, so hoping to see if I'm on the right track here.
The LEDs are 2.2 volts 70mA Max, amber (if anybody cares), power from NiCd battery pack, 4.8v, but can add more if needed.
They gave an equation for output current as: Iout=Vref/R1
I took Vref to mean 1.25 volts, from the beginning of the data sheet.
.07=1.25/R1 R1= about 18 ohms
Now, does mean I'll get 4.8v @ 70mA max output?
Since 2 LEDs in series will use 4.4 volts, will the remaining .4 volts be a concern?
Or do I loose 1.25 volts in the LM317, and only get 3.55 volts out?
The LEDs are 2.2 volts 70mA Max, amber (if anybody cares), power from NiCd battery pack, 4.8v, but can add more if needed.
They gave an equation for output current as: Iout=Vref/R1
I took Vref to mean 1.25 volts, from the beginning of the data sheet.
.07=1.25/R1 R1= about 18 ohms
Now, does mean I'll get 4.8v @ 70mA max output?
Since 2 LEDs in series will use 4.4 volts, will the remaining .4 volts be a concern?
Or do I loose 1.25 volts in the LM317, and only get 3.55 volts out?