I remember a while back someone posted a lil circuit for getting a boost voltage for driving LEDs out of a low voltage uP pin. I need to drive two high-brightness yellow LEDs from a single 3-3.5 volt output with ability to PWM the intensity (doesn't need to be different PWM values for both)
So just maybe silicon diode anode to the supply, the two LEDs in series with a boost cap from one output pin to the junction, and a PWM capable output pin sinking current to ground from the lower diode cathode?
I feel like there's some detail I'm missing