IS31LT3354-STLS2-TR ISSI

IS31LT3354 40V LED DRIVER WITH EXTERNAL SWITCH September 2011 GENERAL DESCRIPTION FEATURES The IS31LT3354 is a continuous mode inductive Simple low parts count step-down converter, designed for driving a single LED Wide input voltage range: 6V to 40V or multiple series connected LEDs efficiently from a Output Current only limited by external voltage source higher than the required LED voltage. component selection The device operates from an input supply between 6V High efficiency (up to 98% ) and 40V and provides an externally adjustable output Typical 1200:1 dimming ratio current of up to 2A or even higher, which is determined Typical 3% output current accuracy by the external MOSFET and inductor. Single pin on/off and brightness control using The IS31LT3354 includes a high-side output current DC voltage or PWM sensing circuit, which uses an external resistor to set Up to 1MHz switching frequency the nominal average output current. Output current can Inherent open-circuit LED protection be adjusted linearly by applying an external control signal to the ADJ pin. The ADJ pin will accept either a Thermal shutdown protection circuitry DC voltage or a PWM waveform. This will provide either APPLICATIONS a continuous or a gated output current. Low voltage halogen replacement LEDs Applying a voltage of 0.2V or lower to the ADJ pin turns Automotive lighting the output off and switches the chip into a low current standby state. Low voltage industrial lighting LED back-up lighting The chip is assembled in SOT23-5 package. Illuminated sign TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit Lumissil Microsystems www.lumissil.com 1 Rev. A, 09/01/2011 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). 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 3 ADJ * Drive with DC voltage (0.3V<VADJ <1.2V) to adjust output current from 25% to 100% of IOUTnom * Drive with PWM signal to adjust output current. * When driving the ADJ pin above 1.2V, the current will be clamped to 100% brightness automatically. Connect resistor RS from this pin to VIN to define nominal average 4 I SENSE output current IOUTnom =0.1/RS . Input voltage (6V to 40V). Decouple to ground with 1 F or higher X7R 5 V IN ceramic capacitor close to device. Lumissil Microsystems www.lumissil.com 2 Rev. A, 09/01/2011