LM3555 PRODUCT BRIEF Synchronous Boost Converter with 500 mA High Side LED Driver and Dual-Mode Control Interface General Description Features The LM3555 is a 2 MHz fixed frequency, current mode synchronous boost converter designed to drive either a single flash LED at 500 mA or two series flash LEDs at 400 mA. A high-voltage current source allows the LEDs to be terminated to the GND plane eliminating the need for an additional return trace back to the IC. A dual mode control interface allows the user to configure the LM3555 with a general purpose interface using two enable pins for control or an I2C allowing a higher level of control. Both interfaces allow access to the indicator, assist light and flash modes. A dedicated Strobe pin provides a direct interface to trigger the flash event, while an external Torch pin provides an additional method for enabling the LEDs in a constant current mode. The LM3555 can adaptively scale the maximum flash level delivered to the LED/LEDs based upon the flash configuration, whether it be a single LED or two LEDs in series. Eight protection features are available on the LM3555 ranging from over-voltage protection, to broken inductor detection. The LM3555 has four selectable inductor current limits to help the user select an inductor that is appropriate for the design. ■ High Voltage High-Side Current Source Allows for Grounded Cathode LED Operation ■ Synchronous Boost Converter ■ Peak Converter Efficiency >90% ■ Accurate and Programmable LED Current ranging from ■ ■ ■ ■ ■ ■ ■ ■ ■ 60mA to 500mA Adaptive LED Current Range Based on LED Configuration Dedicated Indicator Current Source Dedicated Torch and Strobe Pins Dual Mode Control (General Purpose or I2C) Broken Inductor Detection Output Over-Voltage Protection Output and LED Short-Circuit Protection 400kHz I2C Compatible Interface 12–Bump, 1.575 mm x 2.1 mm x 0.6 mm micro SMD Package (TLA12BCA) Applications ■ Camera Phone LED Flash Typical Application Circuits 30079401 © 2009 National Semiconductor Corporation 300794 www.national.com LM3555 PRODUCT BRIEF January 15, 2009 LM3555 PRODUCT BRIEF Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy PowerWise® Solutions www.national.com/powerwise Solutions www.national.com/solutions Serial Digital Interface (SDI) www.national.com/sdi Mil/Aero www.national.com/milaero Temperature Sensors www.national.com/tempsensors Solar Magic® www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless Analog University® www.national.com/AU THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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