The PT4115 is a continuous conduction mode inductive  step-down converter, designed for driving single or  multiple series connected LED efficiently from a  voltage source higher than the total LED chain voltage.  The device operates from an input supply between 6V  and 30V and provides an externally adjustable output  current of up to 1.2A. Depending upon the supply  voltage and external components, the PT4115can  provide more than 30 watts of output power.  

The PT4115 includes the power switch and a high-side  output current sensing circuit, which uses an external  resistor to set the nominal average output current, and a  dedicated DIM input accepts either a DC voltage or a  wide range of pulsed dimming. Applying a voltage of  0.3V or lower to the DIM pin turns the output off and  switches the device into a low current standby state.  The PT4115 is available in SOT89-5 and ESOP8  packages.