I want to drive a 3W LED. I can use a TIP120 or MOSFET to switch it from the teensy.

But what's the best practise to drive it, I suppose constant current source?

I did find a LDD-600LW, which works with a HiV or higher input :

Or I can just a a sufficient resistor in series with the LED and power the led with a bit safer lower voltage?

Is there another solution or any recommendations?

BTW. It will be battery powered, probably a few AA Nimh's .