PRODUCT DATASHEET
AAT2856
ChargePump
TM
High Current Charge Pump with Dual LDO for Backlight Applications
Features
• Input Voltage Range: 2.7V to 5.5V
• Tri-Mode Charge Pump:
▪
Drives up to Six Backlight LEDs
▪
32 Programmable Backlight Current Settings
Ranging from 115μA to 30mA
▪
2MHz Switching Frequency
• Two Linear Regulators:
▪
200mA Output Current
▪
200mV Dropout Voltage
▪
Output Voltage Adjustable from 1.2V to V
BATTERY
▪
Output Auto-Discharge for Fast Shutdown
▪
Individual LDO Enable Inputs
• Built-In Thermal Protection
• Automatic Soft Start
• -40°C to +85°C Temperature Range
• TQFN44-28 Package
General Description
The AAT2856 is a highly integrated charge pump with
dual linear regulators optimized for systems powered
from lithium-ion/polymer batteries. The charge pump
provides power for white LED backlight. Six backlight
LEDs can be driven at up to 30mA. AnalogicTech’s
AS
2
Cwire™ (Advanced Simple Serial Control™) single-
wire interface is used to enable, disable, and set the
current to one of 32 levels for the backlight. Backlight
current matching is 1% for uniform display brightness.
The AAT2856 offers two high-performance low-noise
MicroPower™ low dropout (LDO) linear regulators. Both
regulators use individual enable inputs and each will
supply up to 200mA load current. LDO ground pin cur-
rent is only 80μA, making the AAT2856 ideal for battery-
operated applications.
The AAT2856 is equipped with built-in short-circuit and
over-temperature protection. The soft start circuitry pre-
vents excessive inrush current at start-up and mode
transitions.
The AAT2856 is available in a Pb-free TQFN44-28 pack-
age and operates over the -40°C to +85°C ambient
temperature range.
Applications
• Camera-Enabled Mobile Devices
• Digital Still Cameras
• Multimedia Mobile Phones
Typical Application
C
1
1μF
C1+ C1-
IN
C
IN
4.7μF
C
2
1μF
C2+ C2-
OUT
C
OUT
2.2μF
IN
BL1
BL2
BL3
BL4
BL5
BL6
OUTA
C
BYP
0.1μF
REF
FBA
R
1A
R
2A
C
OUTA
2.2μF
V
OUTA
V
OUT
V
BAT
WLEDs
OSRAM LW M673
or equivalent
AAT2856
ENABLE/SET
ENS
EN_LDOA
EN_LDOB
ENA
ENB
AGND
OUTB
R
2B
FBB
PGND
R
1B
V
OUTB
C
OUTB
2.2μF
2856.2008.02.1.3
www.analogictech.com
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