IS31LT3354-STLS2-TR

IS31LT3354 40V LED DRIVER WITH EXTERNAL SWITCH September 2011 GENERAL DESCRIPTION FEATURES The IS31LT3354 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 required LED voltage. The device operates from an input supply between 6V and 40V and provides an externally adjustable output current of up to 2A or even higher, which is determined by the external MOSFET and inductor.    The IS31LT3354 includes a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. Output current can be adjusted linearly by applying an external control signal to the ADJ pin. The ADJ pin will accept either a DC voltage or a PWM waveform. This will provide either a continuous or a gated output current. Applying a voltage of 0.2V or lower to the ADJ pin turns the output off and switches the chip into a low current standby state. The chip is assembled in SOT23-5 package.        Simple low parts count Wide input voltage range: 6V to 40V Output Current only limited by external component selection High efficiency (up to 98% ) Typical 1200:1 dimming ratio Typical 3% output current accuracy Single pin on/off and brightness control using DC voltage or PWM Up to 1MHz switching frequency Inherent open-circuit LED protection Thermal shutdown protection circuitry APPLICATIONS      Low voltage halogen replacement LEDs Automotive lighting Low voltage industrial lighting LED back-up lighting Illuminated sign TYPICAL APPLICATION CIRCUIT Figure 1 Lumissil Microsystems – www.lumissil.com Rev. A, 09/01/2011 Typical Application Circuit 1 IS31LT3354 PIN CONFIGURATION Package Pin Configuration SOT23-5 PIN DESCRIPTION No. Pin Description 1 GATE Output gate driver for an external NMOSFET. 2 GND Ground (0V). 3 ADJ Multi-function On/Off and brightness control pin: * Leave floating for normal operation.(VADJ = VREF = 1.2V giving nominal average output current IOUT nom =0.1/RS ) * Drive to voltage below 0.2V to turn off output current * Drive with DC voltage (0.3V