Four-String White LED Driver Data Sheet ADD5205 FEATURES FUNCTIONAL BLOCK DIAGRAM White LED driver based on inductive boost converter STEP-UP SWITCHING REGULATOR Input voltage range: 2.8 V to 18 V Internal compensation 4-CHANNEL CURRENT SOURCES 1 MHz fixed operating frequency BRIGHTNESS CONTROL LOGIC 28 V fixed overvoltage protection Built-in soft start for boost converter UNDERVOLTAGE LOCKOUT Drives up to 4 LED current sources SOFT START THERMAL PROTECTION LED current adjustable up to 25 mA for each channel OVERVOLTAGE PROTECTION AUTODISABLE FOR LED OPEN DC current level brightness control with PWM input LED open fault protection Figure 1. General Thermal shutdown Undervoltage lockout 12-lead, 3 mm 3 mm 0.75 mm LFCSP package APPLICATIONS Smart PCs, PMPs, tablet PCs, UMPCs, and notebooks GENERAL DESCRIPTION The ADD5205 is a white LED driver for backlight applications The ADD5205 has multiple safety protection features to prevent based on high efficiency, current mode, step-up converter any damage during fault conditions. If one or more LEDs are open, technology. It is designed with a 0.3 internal switch and 1 MHz the device disables the faulty current regulator automatically. fixed operating frequency. The ADD5205 contains four regulated The internal soft start prevents inrush current during startup. A constant current sources for uniform brightness intensity. Each thermal shutdown protection feature prevents thermal damage. current source is capable of driving up to 25 mA. The ADD5205 is available in a low profile, thermally enhanced 3 mm 3 mm 0.75 mm, 12-lead lead frame chip scale package The ADD5205 has four parallel strings of multiple series connected LEDs with 2% current matching. The device provides adjustable (LFCSP) and is specified over the temperature range of 25C current sources that drive up to 25 mA using an external resistor. to +85C. The LED current can be controlled by a PWM signal input on the PWM pin. An internal circuit translates the PWM signal to an analog signal with an external capacitor and linearly controls the LED current. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 09858-001ADD5205 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Typical Performance Characteristics ..............................................8 Applications....................................................................................... 1 Theory of Operation ...................................................................... 10 Functional Block Diagram .............................................................. 1 Current Mode, Stepup Switching Regulator Operation........ 10 General Description ......................................................................... 1 Current Source............................................................................ 10 Revision History ............................................................................... 2 PWM Dimming Mode .............................................................. 10 Functional Block Diagram .............................................................. 3 Safety Features ............................................................................ 10 Specifications..................................................................................... 4 External Component Selection Guide..................................... 11 Absolute Maximum Ratings............................................................ 6 Layout Guidelines....................................................................... 12 Thermal Resistance ...................................................................... 6 Typical Application Circuit ........................................................... 13 ESD Caution.................................................................................. 6 Outline Dimensions....................................................................... 14 Pin Configuration and Function Descriptions............................. 7 Ordering Guide .......................................................................... 14 REVISION HISTORY 8/11Revision 0: Initial Version Rev. 0 Page 2 of 16