IS31LT3352 40V LED DRIVER WITH TEMPERATURE COMPENSATION September 2011 GENERAL DESCRIPTION FEATURES The IS31LT3352 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 required LED Up to 750mA output current voltage. The chip operates from an input supply High efficiency (up to 95% ) between 6V and 40V and provides an externally 12001 dimming ratio adjustable output current of up to 750mA. Depending Typical 5% output current accuracy upon supply voltage and external components, this Single pin on/off and brightness control using can provide up to 30 watts of output power. DC voltage or PWM The IS31LT3352 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 to protect IC itself average output current. The IS31LT3352 integrates Temperature compensation to protect LEDs temperature compensation function in order to maintain LEDs stable and reliable operation. The APPLICATIONS IS31LT3352 measures the thermistance mounted Low voltage halogen replacement LEDs close to LEDs. When ambient temperature near Automotive lighting LEDs goes too high and the Negative Temperature Coefficient thermistors reach the value of threshold Low voltage industrial lighting resistance connected at RTH pin, output current starts LED back-up lighting to reduce automatically. After the ambient Illuminated sign temperature falls down to a safe temperature the current will return to the set value. The IS31LT3352 can be connected as LED drivers chain with the same temperature compensation percentage. In this chain, every IS31LT3352s ADJO output pin drives next stages IS31LT3352 ADJI input pin with temperature compensation information. So, only one thermistor is needed in the whole IS31LT3352 system. TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit Lumissil Microsystems www.lumissil.com 1 Rev. A, 09/01/2011 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 2 Rev. A, 09/01/2011