AAT1239-1_0810 Datasheet, PDF (1/23 Pages) Advanced Analogic Technologies – 40V Step-Up Converter for 4 to 10 White LEDs

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PRODUCT DATASHEET
AAT1239-1
40V Step-Up Converter for 4 to 10 White LEDs
General Description
The AAT1239-1 is a high frequency, high efficiency con-
stant current boost converter capable of driving up to
ten (10) series-connected white LEDs or 40V. It is an
ideal power solutions for backlight applications with up
to ten white LEDs in series. 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™
(S²Cwire™) interface. Programmability across 26 dis-
crete current steps provides high resolution, low noise,
flicker-free, constant LED outputs. In programming
AAT1239 operation, LED brightness increases based on
the data applied at the EN/SET pin. The SEL logic pin
changes the feedback voltage between two program-
mable ranges.
The AAT1239-1 features a high current limit and fast,
stable transitions for stepped or pulsed current applica-
tions. The high switching frequency (up to 2MHz) pro-
vides fast response and allows the use of ultra-small
external components, including chip inductors and
capacitors. Fully integrated control circuitry simplifies
design and reduces total solution size. The AAT1239-1
offers a true load disconnect feature which isolates the
load from the power source while in the OFF or disabled
state. This eliminates leakage current, making the devic-
es ideally suited for battery-powered applications.
The AAT1239-1 is available in the Pb-free, thermally-
enhanced 12-pin TSOPJW package.
Typical Application
Features
• Input Voltage Range: 2.7V to 5.5V
• Maximum Continuous Output 40V @ 30mA
• Drives up to 10 LEDs in Series
▪ Constant LED Current with 3.5% Accuracy Over
Temperature and Input Voltage Range
• Digital Control with S²Cwire Single Wire Interface
▪ 26 Discrete Steps
▪ No PWM Control Required
▪ No Additional Circuitry
• Up to 85% 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
Applications
• Color Display Backlight
• Digital Still Cameras (DSCs)
• Digital Photo Frames
• PDAs and Notebook PCs
• White LED Drivers
Li-Ion:
VIN = 2.7V to 4.2V
C1
2.2μF
Enable/Set
Feedback Voltage
Select
PVIN
LIN
VIN
SW
AAT1239-1
OVP
EN/SET
SEL
FB
PGND AGND
L1
2.2μH
DS1
SS16L or equivalent
R2
374k
R3
12k
ILED
20mA
R1 (RBALLAST)
30.1
C2
2.2μF
M673
White LEDs
OSRAM LW M678
or equivalent
1239-1.2008.10.1.2
www.analogictech.com
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