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Charge-Pump, Parallel Backlight Driver with Image Content PWM Input
ADP8870
FEATURES
Charge pump with automatic gain selection of 1x, 1.5x, and 2x for maximum efficiency Two high accuracy (5%) phototransistor inputs for automated ambient light sensing (ALS) 5 programmable ambient light-sensing zones for optimal backlight power savings Independent ALS control of D7, for automated response of keypad lighting to ambient light levels PWM input can be used for content adaptive brightness control (CABC) of any, or all, of the LEDs PWM input scales the LED output current 7 independent, programmable LED drivers 6 drivers capable of 30 mA (maximum) 1 driver capable of 60 mA (maximum) Programmable maximum current limit (128 levels) Standby mode for <1 A current consumption 16 programmable fade-in and fade-out times (0.1 sec to 5.5 sec) with choice of square or cubic rates Fading override I2C-compatible interface for all programming Dedicated reset pin and built-in power-on reset (POR) Short-circuit, overvoltage, and overtemperature protection Internal soft start to limit inrush currents Input-to-output isolation during faults or shutdown Operates down to VIN = 2.5 V, with undervoltage lockout (UVLO) at 2.0 V. Available in a small, 2.15 mm x 2.36 mm x 0.6 mm wafer level chip scale package (WLCSP) or a 4 mm x 4 mm x 0.75 mm lead frame chip scale package (LFCSP)
APPLICATIONS
Mobile display backlighting Mobile phone keypad backlighting RGB LED lighting LED indication General backlighting of small format displays
TYPICAL OPERATING CIRCUIT
VDD_ALS OPTIONAL PHOTOSENSOR VOUT PHOTOSENSOR 0.1F D1 VIN 1F VOUT VDDIO 1F D2 D3 D4 D5 D6 D7 CMP_IN 0.1F
C1+ nRST SDA C2+ SCL nINT PWM C2- GND C2 1F
ADP8870
C1-
C1 1F
Figure 1.
GENERAL DESCRIPTION
The ADP8870 combines a programmable backlight LED charge-pump driver with automatic phototransistor control of the brightness (LED current) and a PWM input to control the scale of the output current. This combination allows significant power savings because it automatically changes the current intensity based on the sensed ambient lighting levels and the display image content. It performs this function automatically, eliminating the need for a processor to monitor the phototransistor. The light intensity thresholds are fully programmable via the I2C interface. The ADP8870 allows up to six LEDs to be independently driven up to 30 mA (maximum). An additional seventh LED can be driven to 60 mA (maximum). All LEDs are individually programmable for minimum/maximum current and fade-in/fade-out times through an I2C interface. These LEDs can also be combined into groups to reduce the processor instructions during fade-in and fade-out. Driving these components is a two-capacitor charge pump with gains of 1x, 1.5x, and 2x. This setup is capable of driving a maximum IOUT of 240 mA from a supply of 2.5 V to 5.5 V. A full suite of safety features, including short-circuit, overvoltage, and overtemperature protection, allows easy implementation of a safe and robust design. Additionally, input inrush currents are limited via an integrated soft start combined with controlled input-to-output isolation.
For more information about the ADP8870, including the complete data sheet, contact your local Analog Devices, Inc., sales office at www.analog.com/sales.
Rev. Sp0
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 rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2010 Analog Devices, Inc. All rights reserved.
08829-001
ADP8870 OUTLINE DIMENSIONS
2.190 2.150 2.110
4 3 2 1 A
BALL 1 IDENTIFIER 2.395 2.355 2.315
B
1.60 REF
C D E
0.40 REF TOP VIEW
(BALL SIDE DOWN)
BOTTOM VIEW
(BALL SIDE UP)
0.645 0.600 0.555
SIDE VIEW
0.415 0.400 0.385 COPLANARITY 0.05
1.20 REF
SEATING PLANE
Figure 2. 20-Ball Wafer Level Chip Scale Package [WLCSP] (CB-20-7) Dimensions shown in millimeters
4.10 4.00 SQ 3.90 0.50 BSC 0.30 0.25 0.20
16 15 EXPOSED PAD 20 1
PIN 1 INDICATOR
PIN 1 INDICATOR
2.65 2.50 SQ 2.35
5 6
11
TOP VIEW 0.80 0.75 0.70 SEATING PLANE
0.50 0.40 0.30
10
0.25 MIN
BOTTOM VIEW FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET.
0.05 MAX 0.02 NOM COPLANARITY 0.08 0.20 REF
COMPLIANT TO JEDEC STANDARDS MO-220-WGGD.
Figure 3. 20-Lead Lead Frame Chip Scale Package [LFCSP_WQ] 4 mm x 4 mm Body, Very Very Thin Quad (CP-20-10) Dimensions shown in millimeters
08829-031
061609-B
110609-A
0.287 0.267 0.247
0.230 0.200 0.170
Figure 4. Tape and Reel Orientation for WLCSP Units
(c)2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08829F-0-6/10(Sp0)
Figure 5. Tape and Reel Orientation for LFCSP Units
Rev. Sp0 | Page 2 of 2
08829-032

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