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PDF A8435 Data sheet ( Hoja de datos )
| Número de pieza | A8435 | |
| Descripción | High Efficiency Charge Pump White LED Driver | |
| Fabricantes | Allegro MicroSystems | |
| Logotipo |  |
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A8435
High Efficiency Charge Pump White LED Driver
Features and Benefits
▪ Proprietary adaptive control scheme (1×, 1.5×)
▪ Maximum efficiency, over 92%
▪ 0.5% LED current matching
▪ 1 MHz operating frequency
▪ Flexible dimming control:
▫ Serial 11-level dimming, down to 5%
▫ PWM
▫ 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
Package: 16 pin QFN/MLP (suffix ES)
Approximate Scale
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
TheA8435 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:
▪ White LED backlights for cellular phones, PDAs
▪ Digital cameras, camcorders
▪ Portable audio devices
▪ Other portable device white LED backlighting
▪ 120 mA WLED flash/torch
Typical Applications
CIN
1 µF
VBATT
2.7 to 5.5 V
C1
1 µF
C2
1 µF
VIN
C1+
C1–
C2+
C2–
EN1
EN2
On/Off and
NC CTRL
Dimming Control
VOUT
LED1
A8435 LED2
LED3
GND
LED4
ISET
COUT
1 µF
RSET
Figure 1. Typical Circuit. Dual wire control configuration: 2-bit
parallel or PWM dimming.
VBATT
2.7 to 5.5 V
CIN
1 µF
C1
1 µF
C2
1 µF
Single-Wire On/Off and
Dimming Control
VIN
C1+
C1-
C2+
C2-
EN1
EN2
CTRL
VOUT
LED1
A8435 LED2
LED3
GND
LED4
ISET
COUT
1 µF
RSET
Figure 2. Typical Circuit. Single wire control configuration.
A8435-DS, Rev. 1
1 page  
A8435
High Efficiency Charge Pump White LED Driver
Performance Characteristics
Tests performed using application circuit shown in figure 1: dual wire control; and
VIN= 3.6 V, EN1 = EN2 = VIN, CIN= C1= C2= COUT= 1 μF, RSET= 7.5 kΩ, TA= 25°C (unless otherwise noted)
Efficiency versus Supply Voltage
Over Range of Dimming Levels, VIN Falling
100
90
80 Dimming Level
(mA)
4.75
9.8
70 17.6 (Full Brightness)
60
50
2.70 2.90 3.10 3.30 3.50 3.70 3.90 4.10
VIN (V)
Supply Current versus Supply Voltage
Over Range of Dimming Levels (mA)
120
100
VIN Falling
VIN Rising
80 17.6 mA
60
VIN Falling
40
20
0
2.70
VIN Falling
2.90
3.10
VIN Rising
VIN Rising
9.8 mA
4.75 mA
3.30
3.50
3.70
3.90
4.10
VIN (V)
LED Current versus Supply Voltage
Matching Between LEDs <1% Over Range of VIN
20
19
18
17
16
15
14
13
12
11
10
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VIN (V)
Allegro MicroSystems, Inc.
5
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet A8435.PDF ] | |
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