Four-Channel Backlight Driver with Dual LDOs
General Description
The AAT2845 is a highly integrated power solution
for single-cell lithium-ion-based LCD display appli-
cations. It includes a four-channel LED backlight
driver and two integrated 200mA LDOs as addi-
tional power supplies for display and camera-relat-
ed chipsets.
The backlight driver is a low noise, constant fre-
quency charge pump DC/DC converter that uses a
tri-mode load switch (1X), fractional (1.5X), and
doubling (2X) conversion to maximize efficiency.
Each of the four channels is capable of driving up
to 20mA per channel.
AnalogicTech's S
2
Cwire™ (Simple Serial Control™)
serial digital input is used to enable, disable, and
set current for each LED with 16 available settings
down to 50µA. The low current mode supply current
can be as low as 50µA to save power and maintain
high efficiency.
Each LED output is equipped with built-in protec-
tion for short-circuit and auto-disable functions.
Built-in soft-start circuitry prevents excessive
inrush current during start-up. A low current shut-
down feature disconnects the load from V
IN
and
reduces quiescent current to less than 1µA.
The AAT2845 is available in a Pb-free, thermally-
enhanced 20-pin 3x4mm TQFN package.
AAT2845
Features
•
•
ChargePump
™
•
•
•
•
•
Input Voltage Range: 2.7V to 5.5V
Four-Channel LED Driver:
— Tri-Mode Charge Pump
— Up to 20mA/Channel
— Easy Control with Single Wire Interface
— 16 Current Levels
— Four Low Current Settings Down to 50µA
— Low I
Q
(50µA) for Low Current Mode
— >90% Peak Efficiency
Dual 200mA LDOs
Automatic Soft-Start
Over-Temperature Protection
Available in 3x4mm TQFN34-20 Package
-40°C to +85°C Temperature Range
Applications
•
•
•
•
Camera Function Power Supplies
Camera Phone Displays
LCD Modules
White LED Backlighting
Typical Application
CF1
1µF
C1-
CF2
1µF
C2+
C1+ C2-
IN
V
BAT
3.6V
C
IN
2.2µF
OUT
AAT2845
D1
D2
D3
D4
IN
LDOA
FBA
C
OUT
1µF
200mA
Co
1
S
2
Cwire Backlight Control
LDO Enable
C
BYP
0.1µF
EN/SET
ENLDO
CBP
GND
LDOB
200mA
Co
2
FBB
2845.2006.12.1.0
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
