AAT2847
Four-Channel Backlight Driver with Dual LDOs
™
ChargePump
General Description
Features
The AAT2847 is a highly integrated power solution
for single cell Li-Ion/Polymer based liquid crystal
display (LCD) display applications. It includes a
four channel light emitting diode (LED) backlight
driver and two integrated 200mA low dropout volt-
age regulators (LDOs) as additional power sup-
plies for display and camera related chipsets.
•
•
Input Supply Voltage Range: 2.7V to 5.5V
Tri-Mode (1X/1.5X/2X) Charge Pump:
— Delivers up to 120mA of Output Current
Integrated LCD Display Solution:
•
— Four-Channel WLED Backlight
•
User-Programmable WLED Current
Scales: 30mA, 20mA and 15mA.
— Sixteen Programmable Current
Level Settings
User Selectable Low Level Current Scale
— Four Programmable Current
Level Settings
The backlight driver in the AAT2847 is a low noise
tri-mode DC/DC charge pump converter. Each of
the four channels of the backlight driver is capable
of delivering up to 20mA of bias currents for white
LEDs. The white LED (WLED) backlight bias cur-
rent matching is 1% which helps provide uniform
display brightness.
•
— Dual 200mA LDOs (w/Separate Enables)
2
•
Single-Wire AS Cwire Serial Interface for
Configuration/Control
2
AnalogicTech’s AS Cwire™ (Advanced Simple
— Four Addressable Registers
— Fast, 1MHz Serial Interface
> 90% Peak Efficiency
Serial Control™) serial digital interface is used to
enable, disable, and set the current for each back-
light LED channel. Each LED channel has sixteen
available current level settings in three separate
current scales, plus four available current level set-
tings on a low level current scale.
•
•
LDO Output Voltages:
— AAT2847-EE: User-Programmable
— AAT2847-QG: 2.8V and 1.5V
— AAT2847-QI: 2.8V and 1.8V
Over-Temperature Protection
Available in 3x4x0.75mm TQFN34-20 Package
-40°C to +85°C Temperature Range
•
•
•
Each LED channel is equipped with built-in short
circuit protection and auto disable functionality. A
low shutdown current feature disconnects the load
from the input and reduces quiescent current to
less than 1µA.
Applications
The AAT2847 is available in the thermally
enhanced 20-pin 3x4x0.75mm TQFN package.
•
•
•
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Camera Function Power Supplies
Camera Phone Displays
LCD Modules
White LED Backlighting
Typical Application
C1
1μF
C2
1μF
C1
1μF
C2
1μF
C1- C1+ C2- C2+
OUT
C1- C1+ C2- C2+
OUT
WLEDs
WLEDs
OSRAM LW M673
OSRAM LW M673
or equivalent
COUT
1μF
or equivalent
COUT
1μF
IN
IN
AAT 2847-EE
AAT2847-QI
VBAT
3.6V
D1
D2
D3
D4
VBAT
3.6V
D1
D2
D3
D4
CIN
2.2μF
CIN
2.2μF
200mA
VOUTA
IN
LDOA
IN
LDOA
2.8V, 200mA
CLDOA
2.2μF
AS2Cwire
Backlight control
CLDOA
2.2μF
EN/SET
FBA
AS2Cwire
EN/SET
ENA
ENB
LDO A Enable
LDO B Enable
Backlight Control
LDO A Enable
LDO B Enable
200mA
VOUTB
1.8V, 200mA
LDOB
PGND
LDOB
ENA
ENB
CLDOB
2.2μF
CLDOB
2.2μF
GND
FBB
GND
PGND
2847.2007.09.1.0
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