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A8434 6-Channel High Efficiency Charge Pump White LED Driver
Features and Benefits
▪ Proprietary adaptive control scheme (1×, 1.5×, 2×) ▪ 0.5% typical WLED current matching ▪ Drives up to 6 white LEDs ▫ Main display backlight (up to 6 WLEDs) ▫ Main display and sub display backlight ▫ Main display and low-current flash/torch ▪ 30 mA per WLED ▪ 2× serial dimming interfaces ▪ 320 mA charge pump capability ▪ Low EMI design and soft start function ▪ Short circuit, overvoltage, thermal shutdown protection ▪ 0.75 mm nominal height (very thin profile), 3 × 3 mm footprint packages
Description
The A8434 high efficiency charge pump ICs offer a simple, low-cost WLED (white LED) driver solution for driving up to six WLEDs in various application configurations, either all six backlighting a single display, or for multiple displays, such as four WLEDs as the main display backlight, with the other two WLEDs used for backlighting a sub display or a low-current flash/torch. Using a proprietary control scheme (1×, 1.5×, and 2×), the A8434 can deliver well-matched WLED current while maintaining the highest efficiency and low EMI. The WLED current is regulated over the entire range of Li+ battery voltage to provide uniform intensity. WLED brightness and on/off can be controlled for the main display and sub display/torch through 2 single-wire serial interface pins. The A8434 is available in an QFN/MLP-16 space-conserving (3 × 3 mm footprint) ES package. Applications include: ▪ ▪ ▪ ▪ White LED backlights for cellular phones, PDAs Digital cameras, camcorders Portable audio devices and MP3s Other portable device white LED backlighting
Package: 16 pin QFN/MLP (suffix ES)
Approximate scale 1:1
Typical Applications
VBATT 2.7 to 5.5 V VIN CIN 1 µF C1 1 µF C1+ C1– C2 1 µF VOUT LED1 LED2 D1 D2 D3 D4 D5 D6 ENS GND LED6 VBATT 2.7 to 5.5 V VIN CIN 1 µF C1 1 µF C1+ C1– VOUT LED1 D1 D2 D3 D4 D5 D6 ENS GND LED6 COUT 1 µF
RSET On/Off and Dimming Control CIN 1 μF
COUT 1 µF
VIN
VIN C1+ C1–
VOUT LED1 LED2 D1 D2 D3 D4 D5 D6
C2+ A8434 LED3 C2– LED4 ISET ENM LED5
C2+ A8434 LED3 C2– LED4 ISET ENM ENS GND LED5 LED6
RSET On/Off and Dimming Control
VIN>Vf(max)+0.2 V, Vf = LED forward drop
Figure 1.6 × 30 mA WLED display
C2 1 µF
LED2 C2+ A8434 LED3 C2– LED4 ISET ENM LED5
Figure 3. High efficiency current sink
RSET On/Off and Dimming Control
D1-D4 Main Display; D5-D6 Sub Display
Figure 2. 4 × 30 mA main with 2 × 30 mA sub display 8434-DS, Rev. 1
A8434
6-Channel High Efficiency Charge Pump White LED Driver
Functional Block Diagram
C1 1 μF C1+ C1 − C2+ C2 1 μF C2−
VIN Fractional Charge Pump (1×, 1.5×, and 2×) CIN 1 μF ENM Control, Clock, and Reference Minimum Select
+ −
VOUT
COUT 1 μF
ENS
LED1 LED2 LED3 Current Mirror LED4 LED5 LED6
+ −
ISET
+ − + − + − + − + − + −
RSET
GND
Absolute Maximum Ratings
Input or Output Voltage VIN, VOUT, C1+, C1– , C2+, C2– to GND ..................... –0.3 to 6 V All other pins..................................................... –0.3 to VIN + 0.3 V VOUT Short Circuit to GND .................................................... Continuous Operating Ambient Temperature, TA ..................................... –40°C to 85°C Junction Temperature, TJ(max).............................................................. 150°C Storage Temperature, TS ................................................... –55°C to 150°C Part Number A8434EESTR-T
Package Thermal Characteristics ES Package RθJA = 68 °C/W (vendor data, on 4-layer PCB; unverified) Additional information is available on the Allegro website. The device package is lead (Pb) free, with 100% matte tin leadframe plating.
Use the following complete part number when ordering:
Packaging* 7-in. reel, 1500 pieces/reel Package Type ES, 3 × 3 mm MLP-16
*Contact Allegro for additional packing options.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A8434
6-Channel High Efficiency Charge Pump White LED Driver
Pin-out Diagram
ES Package
16 C1+
15 C2–
C2+ VOUT ISET ENS
1 2 3 4 5 6 7 8 EP
13 C1– 12 GND 11 LED1 10 LED2 9 LED3 LED4
ENM
LED6
(Top View)
Terminal List Table
Name C1– C1+ C2– C2+ ENS ENM EP GND ISET LED1, LED2, LED3, and LED4 LED5 and LED6 VIN VOUT Number 13 16 15 1 4 5 – 12 3 8, 9, 10, and 11 6 and 7 14 2 Function Negative terminal of capacitor C1. Connect capacitor C1 between C1+ and C1–. Positive terminal of capacitor C1. Negative terminal of capacitor C2 Positive terminal of capacitor C2. Connect capacitor C2 between C2+ and C2–. Enable and dimming control input for sub display WLED group. Enable and dimming control input for main display WLED group. Exposed metal pad on bottom side. Connect this to ground plane for better thermal performance. Ground. Connect RSET resistor to ground to set desired constant current through main and sub WLEDs. ILED(max) = 220 x 0.6 V / RSET Current sink for main display WLEDs. If not used, connect to VOU.