ADM8845ACPZ-REEL7 Analog Devices

Charge Pump Driver for LCD White LED Backlights Data Sheet ADM8845 FEATURES GENERAL DESCRIPTION Drives 6 LEDs from 2.6 V to 5.5 V (Li-Ion) input supply The ADM8845 uses charge pump technology to provide the 1/1.5/2 fractional charge pump to maximize power power required to drive up to six LEDs. The LEDs are used for efficiency backlighting a color LCD display, having regulated constant 1% maximum LED current matching current for uniform brightness intensity. The main display can Up to 88% power efficiency over Li-Ion range have up to four LEDs, and the sub display can have one or two Powers main and sub display LEDs with individual shutdown LEDs. The digital CTRL1 and CTRL2 input control pins control 2 Package footprint only 9 mm (3 mm 3 mm) the shutdown operation and the brightness of the main and sub Package height only 0.75 mm displays. Low power shutdown mode Shutdown function To maximize power efficiency, the charge pump can operate in Soft-start limiting in-rush current a 1, 1.5, or 2 mode. The charge pump automatically switches between 1/1.5/2 modes, based on the input voltage, to maintain sufficient drive for the LED anodes at the highest APPLICATIONS power efficiency. Cellular phones with main and sub displays Improved brightness matching of the LEDs is achieved by a White LED backlighting feedback pin to sense individual LED current with a maximum Camera flash/strobes and movie lights Micro TFT color displays matching accuracy of 1%. DSC PDAs FUNCTIONAL BLOCK DIAGRAM C1 C2 1F 1F V ADM8845 CC V OUT CHARGE PUMP C3 C4 1 /1.5 /2 MODE MAIN SUB 2.2 F 4.7 F OSC CTRL1 CONTROL LOGIC CTRL2 V REF FB1 FB2 FB3 FB4 FB5 FB6 LED I SET CURRENT CONTROL R SET CIRCUIT CURRENT CONTROLLED SINKS GND Figure 1. Rev. D Document Feedback 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 20042018 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. CURRENT CONTROL 1 CURRENT CONTROL 2 CURRENT CONTROL 3 CURRENT CONTROL 4 CURRENT CONTROL 5 CURRENT CONTROL 6 04867-0-001ADM8845 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 LED Brightness Control Using a PWM Signal Applied to VPWM ............................................................................................. 13 Applications ....................................................................................... 1 LED Brightness Control Using a DC Voltage Applied to General Description ......................................................................... 1 VBRIGHT .......................................................................................... 13 Functional Block Diagram .............................................................. 1 Applications Information .............................................................. 14 Revision History ............................................................................... 2 Layout Considerations and Noise ............................................ 14 Specifications ..................................................................................... 3 White LED Shorting .................................................................. 14 Absolute Maximum Ratings ............................................................ 4 Driving Fewer than Six LEDs ................................................... 14 Thermal Resistance ...................................................................... 4 Driving Flash LEDs .................................................................... 15 ESD Caution .................................................................................. 4 Driving Camera Light, Main, and Sub LEDs.......................... 15 Pin Configuration and Function Descriptions ............................. 5 Driving Four Backlight White LEDs and Flash LEDs ........... 16 Typical Performance Characteristics ............................................. 6 Power Efficiency ......................................................................... 17 Theory of Operation ...................................................................... 10 Outline Dimensions ....................................................................... 18 Output Current Capability ........................................................ 11 Ordering Guide .......................................................................... 18 Automatic Gain Control ............................................................ 11 Current Matching ....................................................................... 11 Brightness Control with a Digital PWM Signal ..................... 11 REVISION HISTORY 5/2018Rev. C to Rev. D Changes to Figure 16 to Figure 19 ................................................... 8 Changes to Features Section............................................................ 1 Changes to Brightness Control with a Digital PWM Signal Add Thermal Resistance Section .................................................... 4 Section .............................................................................................. 11 Changes to Figure 2 .......................................................................... 5 Added Exposed Pad Notation to Outline Dimensions ............. 18 Updated Outline Dimensions ....................................................... 18 Changes to Ordering Guide .......................................................... 18 Changes to Ordering Guide .......................................................... 18 7/2005Rev. 0 to Rev. A 1/2011Rev. B to Rev. C Changes to Table 3 ............................................................................. 5 Changes to Figure 18 and Figure 19 ............................................... 8 Changes to Table 7 .......................................................................... 12 Updated Outline Dimensions ....................................................... 18 Changes to Ordering Guide .......................................................... 18 Changes to Ordering Guide .......................................................... 18 4/2010Rev. A to Rev. B Changes to Figure 2 .......................................................................... 5 10/2004Revision 0: Initial Version Changes to Figure 4 .......................................................................... 6 Rev. D Page 2 of 18