IS31LT3350-V1STLS2-TR ISSI

IS31LT3350 40V LED DRIVER WITH INTERNAL SWITCH October 2011 GENERAL DESCRIPTION FEATURES The IS31LT3350 is a continuous mode inductive Simple low parts count step-down converter, designed for driving a single Internal 40V power switch LED or multiple series connected LEDs efficiently Wide input voltage range: 6V to 40V from a voltage source higher than the LED voltage. Up to 750mA output current (SOT89-5 package) The chip operates from an input supply between 6V High efficiency (up to 95% ) and 40V and provides an externally adjustable output Typical 12001 dimming ratio current of up to 750mA. Depending upon supply Typical 5% output current accuracy voltage and external components, this can provide Single pin on/off and brightness control using up to 30 watts of output power. DC voltage or PWM The IS31LT3350 includes an integrated output Up to 1MHz switching frequency switch and a high-side output current sensing circuit, Inherent open-circuit LED protection which uses an external resistor to set the nominal Thermal shutdown protection circuitry average output current. Two packages available for different current Output current can be adjusted linearly by applying APPLICATIONS an external control signal to the ADJ pin. The ADJ pin will accept either a DC voltage or a PWM Low voltage halogen replacement LEDs waveform. This will provide either a continuous or a Automotive lighting gated output current. Applying a voltage of 0.2V or Low voltage industrial lighting lower to the ADJ pin turns the output off and switches LED back-up lighting the chip into a low current standby state. Illuminated sign The chip is assembled in SOT23-5 and SOT89-5 package. SOT23-5 is available for 350mA output current application. SOT89-5 is available for 750mA output current application. TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit Lumissil Microsystems www.lumissil.com 1 Rev. A, 10/18/2011 IS31LT3350 PIN CONFIGURATION Package Pin Configuration SOT23-5 LX 1 5 VIN SOT89-5 GND 2 Thermal Pad ADJ 34 ISENSE PIN DESCRIPTION No. Pin Description SOT23-5 SOT89-5 1 LX Drain of power switch. 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 R from this pin to VIN to define nominal S 4 ISENSE average output current I =0.1/R OUT NOM S. Input voltage (6V ~ 40V). Decouple to ground with 0.1F 5 VIN X7R ceramic capacitor as close to device as possible. Thermal - Connect to GND. Pad Lumissil Microsystems www.lumissil.com 2 Rev. A, 10/18/2011