IS31LT3380 40V/1.2A LED DRIVER WITH SWITCH DIMMING OCTOBER 2011 GENERAL DESCRIPTION FEATURES The IS31LT3380 is a continuous mode inductive Multi-modes switch dimming step-down converter, designed for driving a single LED or Up to 1.2A output current multiple series connected LEDs efficiently from a voltage High efficiency (up to 98%) source higher than the LED voltage. The chip operates Wide input voltage range: 8.5V to 40V from an input voltage between 8.5V and 40V and provides an output current up to 1.2A. Internal 40V power switch The IS31LT3380 includes a high-side output current Simple low parts count sensing circuit, which uses an external resistor to set the Typical 5% output current accuracy nominal average output current. The IS31LT3380 Up to 1MHz switching frequency includes an integrated output switch which has a very low Inherent LED open-circuit/short-circuit protection conducting impedance to ensure high system efficiency. The IS31LT3380 has switch dimming function. The chip Thermal shutdown protection circuitry detects external switch action to adjust output current, SOP8 package allowing for dimming functionality to be achieved without changing the original lighting system circuitry. APPLICATIONS The switch dimming is implemented in either two-level MR16, MR11 LED spotlight mode or three-level mode. The output current of every level and the total number of levels are customer LED street lighting selected by setting the corresponding input conditions of PAR LED bulb DIM1 and DIM2 pin. Other LED lighting The output current is set at the initial value the first time that power is supplied to the chip. After the initial power up sequence, the chip adjusts the output current according to the external switch action. After the lowest current level, the current cycles back to the initial value if more switch action is detected. If the power is switched off for longer than 2 seconds, the device will return to its initial state, and the output current will be set to the initial value at the next time that power is applied. Copyright2011IntegratedSiliconSolution,Inc.Allrightsreserved.ISSIreservestherighttomakechangestothisspecificationanditsproductsatany timewithoutnotice.ISSIassumesnoliabilityarisingoutoftheapplicationoruseofanyinformation,productsorservicesdescribedherein.Customersare advisedtoobtainthelatestversionofthisdevicespecificationbeforerelyingonanypublishedinformationandbeforeplacingordersforproducts. IntegratedSiliconSolution,Inc.doesnotrecommendtheuseofanyofitsproductsinlifesupportapplicationswherethefailureormalfunctionofthe productcanreasonablybeexpectedtocausefailureofthelifesupportsystemortosignificantlyaffectitssafetyoreffectiveness.Productsarenot authorizedforuseinsuchapplicationsunlessIntegratedSiliconSolution,Inc.receiveswrittenassurancetoitssatisfaction,that: a.)theriskofinjuryordamagehasbeenminimized b.)theuserassumeallsuchrisks and c.)potentialliabilityofIntegratedSiliconSolution,Incisadequatelyprotectedunderthecircumstances Integrated Silicon Solution, Inc. www.issi.com 1 Rev. A, 09/01/2011 IS31LT3380 APPLICATION CIRCUIT Figure 1-A Figure 1-B Integrated Silicon Solution, Inc. www.issi.com 2 Rev. A, 09/01/2011