One ACM 7135 provides 350mA. Nine can fully power Cree XM-L2 U3. But that's 10W.
ACM7135 only have Vin, Vout and GND pins. People are using them with ATtiny (example), apparently without any other electronic there. It's hard to believe they are pushing 10W of power thorough micro controller. So how do they do it? How should it be done?
Transistors would be inconvenient, because at around 5V, voltage drop on transistor might mean a significant amount of power to dissipate. Or am I wrong here? Also, it seems there are no transistors on flashlight drivers anyway.