AAT2856
High Current Charge Pump with
Dual LDO for BacklightApplications
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 back-
light. 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 regu-
lators. Both regulators use individual enable inputs
and each will supply up to 200mA load current. LDO
ground pin current 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 cir-
cuitry prevents excessive inrush current at start-up
and mode transitions.
The AAT2856 is available in a Pb-free TQFN44-28
package and operates over the -40°C to +85°C
ambient temperature range.
Features
•
•
ChargePump
™
•
•
•
•
•
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
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
2856.2007.06.1.0
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
