National Semiconductor LM3424 Manual
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LM3424August 22, 2009Constant Current N-Channel Controller with ThermalFoldback for Driving LEDsGeneral DescriptionThe LM3424 is a versatile high voltage N-channel MosFETcontroller for LED drivers . It can be easily configured in buck,boost, buck-boost and SEPIC topologies. In addition, theLM3424 includes a thermal foldback feature for temperaturemanagement of the LEDs. This flexibility, along with an inputvoltage rating of 75V, makes the LM3424 ideal for illuminatingLEDs in a very diverse, large family of applications.Adjustable high-side current sense voltage allows for tightregulation of the LED current with the highest efficiency pos-sible. The LM3424 uses standard peak current-mode controlproviding inherent input voltage feed-forward compensationfor better noise immunity. It is designed to provide accuratethermal foldback with a programmable foldback breakpointand slope. In addition, a 2.45V reference is provided.The LM3424 includes a high-voltage startup regulator thatoperates over a wide input range of 4.5V to 75V. The internalPWM controller is designed for adjustable switching frequen-cies of up to 2.0 MHz and external synchronization is possible.The controller is capable of high speed PWM dimming andanalog dimming. Additional features include slope compen-sation, softstart, over-voltage and under-voltage lock-out, cy-cle-by-cycle current limit, and thermal shutdown.Features■ VIN range from 4.5V to 75V■ High-side adjustable current sense■ 2Ω, 1A Peak MosFET gate driver■ Input under-voltage and output over-voltage protection■ PWM and analog dimming■ Cycle-by-cycle current limit■ Programmable slope compensation■ Programmable, synchronizable switching frequency■ Programmable thermal foldback■ Programmable softstart■ Precision voltage reference■ Low power shutdown and thermal shutdownApplications■ LED Drivers - Buck, Boost, Buck-Boost, and SEPIC■ Indoor and Outdoor Area SSL■ Automotive■ General Illumination■ Constant-Current RegulatorsTypical Application Circuit300857k9300857b6© 2009 National Semiconductor Corporation 300857 www.national.comLM3424 Constant Current N-Channel Controller with Thermal Foldback for Driving LEDs |
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