AAT2847
Four-Channel Backlight Driver with Dual LDOs
General Description
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.
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.
AnalogicTech’s AS
2
Cwire™ (Advanced Simple
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.
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.
The AAT2847 is available in the thermally
enhanced 20-pin 3x4x0.75mm TQFN package.
Features
•
•
•
ChargePump
™
•
•
•
•
•
•
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
— Dual 200mA LDOs (w/Separate Enables)
Single-Wire AS
2
Cwire Serial Interface for
Configuration/Control
— Four Addressable Registers
— Fast, 1MHz Serial Interface
> 90% Peak Efficiency
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
Applications
•
•
•
•
Camera Function Power Supplies
Camera Phone Displays
LCD Modules
White LED Backlighting
C1
1μF
C2
1μF
C2+
OUT
C
OUT
1μF
WLEDs
OSRAM LW M673
or equivalent
Typical Application
C1
1μF
C2
1μF
C2+
C1- C1+ C2-
C1- C1+ C2-
OUT
C
OUT
1μF
D1
D2
D3
D4
IN
LDOA
IN
WLEDs
OSRAM LW M673
or equivalent
IN
AAT 2847-EE
V
BAT
3.6V
C
IN
2.2μF
V
BAT
3.6V
C
IN
2.2μF
AAT 2847-QI
D1
D2
D3
D4
200mA
IN
LDOA
C
LDOA
2.2μF
C
LDOA
2.2μF
AS
2
Cwire
Backlight Control
LDO A Enable
LDO B Enable
FBA
EN/SET
ENA
ENB
FBB
GND
PGND
LDOB
200mA
C
LDOB
2.2μF
V
OUTA
2.8V, 200mA
AS Cwire
Backlight control
LDO A Enable
LDO B Enable
2
EN/SET
ENA
ENB
LDOB
V
OUTB
1.8V, 200mA
C
LDOB
2.2μF
GND
PGND
2847.2007.09.1.0
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
