PMP8379 is a constant current source used to drive 1 to 6 LEDs. The topology is integrated switch hysteretic buck using the economical MC33063A.The input voltage can be from 5 to 24 volts provided that the input voltage is greater than the forward voltage drop of the number of LEDs selected.The current is programmed by the current sense resistor R2 and is roughly .3/R2.