DATA SHEET
AAT2822/2823/2824/2825
TFT-LCD DC/DC Converter with WLED Driver and VCOM Buffer
Functional Block Diagram
AAT2822
LX
VIN
EN
Step-up
Controller
COMP
VDD
FB
Charge
Pump
Control
DRVP
FBP
DRVN
FBN
Reference
OP
REF
OPIN
OP-
OUT
WLX
OP+
OVP
WLED
Control
WEN
WCOMP
Brightness
Control
WDIM
WFB
AGND PGND1 PGND2
charge pump inverts the supply voltage (VDD) and pro-
vides a regulated negative output voltage. The VGH
charge pump doubles VDD and provides a regulated posi-
tive output voltage. These outputs use external Schottky
diodes and capacitor multiplier stages (dependent upon
the required output voltage) to regulate up to ±30V.
Integrated soft-start circuitry minimizes the start-up
inrush current and eliminates output voltage overshoot
across the full input voltage range and all load condi-
tions. A constant switching frequency of 1.3MHz mini-
mizes output ripple and capacitor size.
Functional Description
Main Boost Converter
The main boost regulator contains a current-mode,
fixed-frequency PWM architecture to maximize loop
bandwidth and provide fast transient response to pulsed
loads typical of TFT-LCD panel source drivers. The
1.3MHz switching frequency allows the use of low profile,
low value inductors and ceramic capacitors to minimize
the thickness of LCD panel designs.
Dual Charge-Pump Regulator
White LED Backlight Applications
The AAT2822 provides low-power regulated output volt-
ages from two individual charge pumps to provide the
VGH and VGL supplies. Using a single stage, the VGL
The AAT2822 consists of a 1.3MHz fixed-frequency DC/
DC boost controller, and an integrated high voltage
MOSFET power switch. A high-voltage rectifier, power
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
11
202081B
• Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 2, 2012
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
