PRODUCT DATASHEET
AAT1231
SwitchReg
TM
Step-Up DC/DC Converters for White LED Backlight Applications
Features
• Input Voltage Range: 2.7V to 5.5V
• Maximum Continuous Output 24V @ 50mA
• Drives 6 LEDs in Series, 12 LEDs in Parallel / Series
Configuration
▪
Constant LED Current with 6% Accuracy
• Digital Control with S
2
Cwire Single Wire Interface
▪
26 Discrete Steps
▪
No PWM Control Required
▪
No Additional Circuitry
• Up to 82% Efficiency
• Up to 2MHz Switching Frequency Allows Small External
Chip Inductor and Capacitors
• Hysteretic Control
▪
No External Compensation Components
▪
Excellent Load Transient Response
▪
High Efficiency at Light Loads
• Integrated Soft Start with No External Capacitor
• True Load Disconnect Guarantees <1.0μA Shutdown
Current
• Selectable Feedback Voltage Ranges for High Resolution
Control of Load Current
• Short-Circuit, Over-Voltage, and Over-Temperature
Protection
• 12-Pin TSOPJW Package
• -40°C to +85°C Temperature Range
General Description
The AAT1231/1231-1 are high frequency, high efficiency
constant current boost converters capable of 24V maxi-
mum output voltage. Both devices are ideal power solu-
tions for backlight applications with up to six white LEDs
in series or up to twelve white LEDs in a parallel/series
configuration. The input voltage is 2.7V to 5.5V for single-
cell lithium-ion/polymer (Li-ion) based portable devices.
The LED current is digitally controlled across a 6x oper-
ating range using AnalogicTech’s Simple Serial Control™
(S
2
Cwire™) interface. Programmability across 26 dis-
crete current steps provides high resolution, low noise,
flicker-free, constant LED outputs. In programming
AAT1231 operation, LED brightness increases based on
the data received at the EN/SET pin. In programming
AAT1231-1 operation, LED brightness decreases based
on the data received at the EN/SET pin. The SEL logic pin
changes the feedback voltage between two program-
mable ranges.
The AAT1231 and the AAT1231-1 feature high current
limit and fast, stable transitions for stepped or pulsed
current applications. The high switching frequency (up to
2MHz) provides fast response and allows the use of
ultra-small external components, including chip induc-
tors and capacitors. Fully integrated control circuitry
simplifies design and reduces total solution size. The
AAT1231 and the AAT1231-1 offer a true load disconnect
feature which isolates the load from the power source
while in the OFF or disabled state. This eliminates leak-
age current, making the devices ideally suited for bat-
tery-powered applications.
The AAT1231 and the AAT1231-1 are available in Pb-free,
thermally-enhanced 12-pin TSOPJW packages.
Applications
•
•
•
•
•
Digital Still Cameras (DSCs)
Mobile Handsets
MP3 Players
PDAs and Notebook PCs
White LED Drivers
Typical Application
L = 2.2μH
DS1
Up to 24V/
50mA max
OSRAM
LW M678
C
2
2.2μF
PVIN
C
1
2.2μF
Li-Ion:
V
IN
= 2.7V to 4.2V
LIN
SW
OVP
R
3
12kΩ
R
2
226kΩ
VIN
PGND
AAT1231/
1231-1
Enable/Set
Select
EN/SET
SEL
FB
AGND
R
1
(R
BALLAST
)
30.1Ω
Capable of Driving
Six LEDs in Series
(see Applications Section)
1231.2008.06.1.5
www.analogictech.com
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