8-String, White LED Driver with SMBus and PWM Input for LCD Backlight Applications ADD5203 FEATURES FUNCTIONAL BLOCK DIAGRAM White LED driver based on inductive boost converter STEP-UP SWITCHING REGULATOR Integrated 50 V MOSFET with 2.9 A peak current limit Input voltage range: 6 V to 21 V Maximum output adjustable up to 45 V EIGHT CURRENT SOURCES 350 kHz to 1 MHz adjustable operating frequency Overvoltage protection (OVP) up to typical 47.5 V PWM DUTY EXTRACTOR 8-BIT BRIGHTNESS CONTROL LOGIC Built-in soft start for boost converter Drives up to eight LED current strings FIXED DELAY/NO DELAY DIRECT PWM/ DC CURRENT DIMMING CONTROL LED current adjustable up to 30 mA for each channel WITH PWM AND/OR SMBus INTERFACE Headroom control to maximize efficiency Adjustable dimming frequency: 200 Hz to 10 kHz UNDERVOLTAGE LOCKOUT LED open and short fault protection INTERNAL SOFT START THERMAL PROTECTION Selectable dimming control interface methods OVERVOLTAGE PROTECTION AUTODISABLE FOR LED OPEN/SHORT PWM input SMBus serial input Selectable dimming modes Figure 1. Fixed delay PWM dimming control with 8-bit resolution No delay PWM dimming control with 8-bit resolution Direct PWM dimming control DC current dimming control with 8-bit resolution General Thermal shutdown Undervoltage lockout 28-lead, 4 mm 4 mm 0.75 mm LFCSP WQ APPLICATIONS Notebook PCs, UMPCs, and monitor displays GENERAL DESCRIPTION The ADD5203 is a white LED driver for backlight applications provides adjustable output dimming frequency range from based on high efficiency, current-mode, step-up converter tech- 200 Hz to 10 kHz by an external resistor and capacitor. The nology. It is designed with a 0.15 , 2.9 A internal switch and a ADD5203 operates over an input voltage range of 6 V to 21 V, pin-adjustable operating frequency between 350 kHz and 1 MHz. but the device can function with a voltage as low as 5.6 V. The ADD5203 contains eight regulated current sources for The ADD5203 also has multiple safety protection features to uniform brightness intensity. Each current source can be driven prevent damage during fault conditions. If any LED is open or short, the device automatically disables the faulty current source. up to 30 mA, and the LED driving current is pin adjustable by an external resistor. The ADD5203 drives up to eight parallel The internal soft start prevents inrush current during startup. strings of multiple series connected LEDs with a 1.5% current Thermal shutdown protection prevents thermal damage. matching between strings. The ADD5203 is available in a low profile, thermally enhanced, The ADD5203 provides various dimming modes. Each 4 mm 4 mm 0.75 mm, 28-lead, RoHS-compliant lead frame dimming mode is selectable with an external dimming mode chip scale package (LFCSP WQ) and is specified over the selection pin. The LED dimming control interface can be industrial temperature range of 25C to +85C. achieved through PWM input and/or SMBus. The device 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 2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 08717-001ADD5203 TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation ...................................................................... 11 Applications ....................................................................................... 1 Current-Mode, Step-Up Switching Regulator Operation ..... 11 Functional Block Diagram .............................................................. 1 Internal 3.3 V Regulator ............................................................ 11 General Description ......................................................................... 1 Boost Converter Switching Frequency .................................... 11 Revision History ............................................................................... 2 Dimming Frequency (fPWM) ...................................................... 11 Circuit Diagram ................................................................................ 3 Current Source ............................................................................ 11 Specif icat ions ..................................................................................... 4 Dimming Control Interface ...................................................... 11 Step-Up Switching Regulator Specifications ............................. 4 PWM Dimming Mode .............................................................. 12 LED Current Regulation Specifications .................................... 4 Safety Features ............................................................................ 12 SMBus Specifications ................................................................... 5 SMBus Interface.......................................................................... 13 General Specifications ................................................................. 6 SMBus Register Description ..................................................... 15 Absolute Maximum Ratings ............................................................ 7 External Component Selection Guide ..................................... 17 Thermal Resistance ...................................................................... 7 Layout Guidelines....................................................................... 18 ESD Caution .................................................................................. 7 Typical Application Circuits ......................................................... 20 Pin Configuration and Function Descriptions ............................. 8 Outline Dimensions ....................................................................... 23 Typical Performance Characteristics ............................................. 9 Ordering Guide .......................................................................... 23 REVISION HISTORY 5/10Revision 0: Initial Version Rev. 0 Page 2 of 24