A8435
High Efficiency Charge Pump White LED Driver
Features and Benefits
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Proprietary adaptive control scheme (1×, 1.5×)
Maximum efficiency, over 92%
0.5% LED current matching
1 MHz operating frequency
Flexible dimming control:
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Serial 11-level dimming, down to 5%
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PWM
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2-bit parallel
Drives up to 4 white LEDs
30 mA per LED
120 mA total continuous output
Low input ripple and EMI
Soft-start limits inrush current
Short circuit protection
Overvoltage protection
Thermal shutdown protection
Space-saving MLP-16 package: 3 × 3 mm footprint
Very thin 0.75 mm nominal height package
Description
The A8435 high efficiency charge pump IC offers a simple,
low-cost white LED driver solution for portable electronics
display applications. Using a proprietary control scheme (1×,
1.5×), the A8435 can output well-matched currents for up to
4 LEDs, while maintaining the highest efficiency over most
of the Li-ion battery lifetime.
The A8435 accepts an input range of 2.7 to 5.5 V and delivers
up to 30 mA for each of the four regulated current sources. The
A8435 can deliver a total continuous output current of 120 mA,
meeting the requirements of most Li-ion battery-powered white
LED backlight applications. Outputs can also be tied together
for WLED flash/torch applications.
The A8435 offers flexible options for LED current driving.
The LED current can be set by any of the following methods:
(a) choosing an appropriate value for RSET, (b) 2-bit
parallel control with 3 levels, (c) PWM control, or (d) serial
programming
The A8435 is available in a very thin profile 0.75 mm (nominal
height) 3 × 3 mm QFN/MLP-16 package (ES), fitting the needs
of space-conscious applications.
Applications include:
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White LED backlights for cellular phones, PDAs
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Digital cameras, camcorders
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Portable audio devices
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Other portable device white LED backlighting
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120 mA WLED flash/torch
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Package: 16 pin QFN/MLP (suffix ES)
Approximate Scale
Typical Applications
V
BATT
2.7 to 5.5 V
VIN
VOUT
V
BATT
2.7 to 5.5 V
VIN
VOUT
C1+
LED1
C1–
CIN
1 µF
C1
1 µF
C2
1 µF
COUT
1 µF
CIN
1 µF
C1
1 µF
C2
1 µF
C1+
LED1
C1-
COUT
1 µF
C2+
A8435
LED2
C2+
A8435
LED2
C2–
EN1
EN2
NC CTRL
On/Off and
Dimming Control
GND
LED3
C2-
LED3
Single-Wire On/Off and
Dimming Control
LED4
ISET
EN1
EN2
CTRL
GND
LED4
ISET
RSET
RSET
Figure 1. Typical Circuit. Dual wire control configuration: 2-bit
parallel or PWM dimming.
Figure 2. Typical Circuit. Single wire control configuration.
A8435-DS, Rev. 1
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
