IS31LT3352-V1GRLS2-TR

IS31LT3352 40V LED DRIVER WITH TEMPERATURE COMPENSATION September 2011 GENERAL DESCRIPTION FEATURES The IS31LT3352 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 chip operates from an input supply between 6V and 40V and provides an externally adjustable output current of up to 750mA. Depending upon supply voltage and external components, this can provide up to 30 watts of output power.         The IS31LT3352 includes an integrated output switch and a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. The IS31LT3352 integrates temperature compensation function in order to maintain LEDs’ stable and reliable operation. The IS31LT3352 measures the thermistance mounted close to LEDs. When ambient temperature near LEDs goes too high and the Negative Temperature Coefficient thermistors reach the value of threshold resistance connected at RTH pin, output current starts to reduce automatically. After the ambient temperature falls down to a safe temperature，the current will return to the set value.     Simple low parts count Internal 40V power switch Wide input voltage range: 6V to 40V Up to 750mA output current High efficiency (up to 95% ) 1200：1 dimming ratio Typical 5% 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 to protect IC itself Temperature compensation to protect LEDs APPLICATIONS      Low voltage halogen replacement LEDs Automotive lighting Low voltage industrial lighting LED back-up lighting Illuminated sign The IS31LT3352 can be connected as LED drivers’ chain with the same temperature compensation percentage. In this chain, every IS31LT3352’s ADJO output pin drives next stage’s IS31LT3352 ADJI input pin with temperature compensation information. So, only one thermistor is needed in the whole IS31LT3352 system. TYPICAL APPLICATION CIRCUIT Figure 1 Lumissil Microsystems – www.lumissil.com Rev. A, 09/01/2011 Typical Application Circuit 1 IS31LT3352 SYSTEM APPLICATION Note: Each IS31LT3352 can driver up to three slave chips in the next stages, and it is recommend no more than three stages are used for the current coherence, therefore, up to thirteen IS31LT3352s are allowed in one system Lumissil Microsystems – www.lumissil.com Rev. A, 09/01/2011 2 IS31LT3352 PIN CONFIGURATION Package Pin Configuration SOP-8 PIN DESCRIPTION No. Pin Description 1 VIN Input voltage (6V to 40V). Decouple to ground with 1μF or higher X7R ceramic capacitor close to device 2 ISENSE Connect resistor RS from this pin to VIN to define nominal average output current IOUTnom =0.1/RS 3 RTH The pin set the starting temperature of temperature compensation by connecting an external resistor. 4 RNTC 5 ADJO 6 ADJI 7 GND The output currents reduction slope set pin by connecting an external thermistor in temperature compensation mode. LED drivers chain application pin. * When R3(NTC)>R2,VADJO=VADJI * When R3(NTC)