Part # Application Notes Power Supply And Power Management L6920 L6926 L6928 L5970D L5973A L5973D L4976 L4973 AN1891 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: APPLICATION IDEAS: DRIVING LEDs USING L497x, L597x, L692x DC-DC CONVERTERS FAMILIES


Part Details:

AN1891 APPLICATION NOTE APPLICATION IDEAS: DRIVING LEDS USING L497X, L597X, L692X DC-DC CONVERTERS FAMILIES This application note, describes the main applications and driving methods for LEDs. Afterthis, several application ideas using ST DC-DC converters are shown. 1 SUMMARY1 SUMMARY ....................................................................................................................... 1 2 INTRODUCTION .............................................................................................................. 2 3 DRIVING LEDS ................................................................................................................ 2 4 APPLICATION IDEAS ...................................................................................................... 44.1 DC BUS SUPPLY.................................................................................................... 4 4.1.1 L5970D APPLICATION IDEA............................................................................. 54.1.2 L4973D APPLICATION IDEA............................................................................. 64.1.3 L6902D APPLICATION IDEA............................................................................. 6 4.2 BATTERY POWERED APPLICATION ................................................................... 7 4.2.1 L6920D APPLICATION IDEA............................................................................. 74.2.2 L6926D BOOST TOPOLOGY APPLICATION IDEA.......................................... 84.2.3 L6926D BUCK-BOOST TOPOLOGY APPLICATION IDEA............................... 94.2.4 L6926D BUCK TOPOLOGY APPLICATION IDEA .......................................... 10 5 CONCLUSION ............................................................................................................... 10 REV. 2 AN1891/0604 1/11 AN1891 APPLICATION NOTE 2 INTRODUCTIONLED (Light Emitting Diode) is a Light Emitted p-n junction Diode, under forward bias. If a for-ward bias is applied between the p-n layers, electrons and holes are meeting in the active lay-er, and recombine themselves, emitting photons. If a reverse bias is applied, they don t movein the active layer, and consequentially, no light is emitted. LEDs generate practically a mono-chromatic light, with a focused beam of a single wavelength. Therefore, there is not wastedenergy, and no filters are required to obtain different colors. The emitted radiation wavelengthdepends on the dopants. Due to their construction technology, LEDs are not subjected toshock, vibrations and heat, and this makes their life very long, measured in order of years(Typically 100.000 hours with an operating temperature comprised between -40°C and+85°C). Thanks to all these characteristics, LEDs are widely used in particular color-specific,power-crucial and high reliability application: Mobile appliances Mobile phone screen and keyboard backlight PDAs, MP3 players and digital camera backlight Signs and displays Advertising signs Traffic variable messages signs Automotive applications Interior application: lights for instrumental panel and dashboard Exterior lighting stop/turn/tail lights Signals Traffic signals Arrows and pedestrian signals Illumination Flashlights Architectural and design lighting Emergency lighting Water features and pools 3 DRIVING LEDSLEDs are devices where the light intensity (brightness), measured in millicandelas, or in Lu-mens, is proportional to the forward current flowing through them. There are two main catego-ries of LEDs: the white-blue LEDs, with a typical voltage drop of 3-4V, and the green-red-yellow ones, with a typical voltage drop, which is about 2V. It is possible to make another dis-tinction based on the forward current:


Please click the following link to download the datasheet:

Application Notes Power Supply And Power Management L6920 L6926 L6928 L5970D L5973A L5973D L4976 L4973 AN1891.pdf Datasheet