IS31LT3380

IS31LT3380 40V/1.2A LED DRIVER WITH SWITCH DIMMING OCTOBER 2011 GENERAL DESCRIPTION The IS31LT3380 is a continuous mode inductive step-down converter, designed for driving a single LED or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The chip operates from an input voltage between 8.5V and 40V and provides an output current up to 1.2A. The IS31LT3380 includes a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. The IS31LT3380 includes an integrated output switch which has a very low conducting impedance to ensure high system efficiency. The IS31LT3380 has switch dimming function. The chip detects external switch action to adjust output current, allowing for dimming functionality to be achieved without changing the original lighting system circuitry. The switch dimming is implemented in either two-level mode or three-level mode. The output current of every level and the total number of levels are customer selected by setting the corresponding input conditions of DIM1 and DIM2 pin. The output current is set at the initial value the first time that power is supplied to the chip. After the initial power up sequence, the chip adjusts the output current according to the external switch action. After the lowest current level, the current cycles back to the initial value if more switch action is detected. If the power is switched off for longer than 2 seconds, the device...