AAT1270_08 Datasheet, PDF (1/18 Pages) Advanced Analogic Technologies – 1A Step-Up Current Regulator for Flash LEDs

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PRODUCT DATASHEET
AAT1270
1A Step-Up Current Regulator for Flash LEDs
General Description
The AAT1270 is a high-efficiency, high-current boost con-
verter capable of 1A maximum output current. It is an ideal
power solution for LED photo flash applications in all single-
cell Lithium-ion / polymer battery operated products.
The AAT1270 maintains output current regulation by
switching the internal high-side and low-side switch
transistors. The transistor switches are pulse-width
modulated at a fixed frequency of 2MHz. The high
switching frequency allows the use of a small inductor
and output capacitor, making the AAT1270 ideally suited
for small battery-powered applications.
AnalogicTech’s proprietary S²Cwire™ (Simple Serial
Control™) serial digital interface is used to enable, dis-
able and set the movie mode current level for the flash
LEDs to one of 16 levels. The AAT1270 also includes a
separate Flash Enable input to initiate both flash/strobe
operation and the default timer, which can be used to
terminate a flash event after a user-programmed delay
or as a safety feature. A Flash Inhibit pin is also includ-
ed which reduces flash current to movie mode level dur-
ing high battery demand.
The maximum flash and movie mode current is set by one
external resistor; the ratio between flash and movie mode
current is set at approximately 7.3:1. One or two LEDs can
be connected to the AAT1270; when two LEDs are used,
the output current is matched between each diode.
The AAT1270 contains over-voltage protection and a
thermal management system to protect the device in the
event of an output open-circuit and short-circuit condi-
tion respectively. Built-in circuitry prevents excessive
inrush current during start-up. The shutdown feature
reduces quiescent current to less than 1.0μA.
The AAT1270 is available in a Pb-free, thermally-enhanced
14-pin 3x3mm STDFN package.
Features
• Input Voltage Range: 2.7V to 5.5V
• Dual Channel Output
▪ Up to 1A Regulated Output Current (0.5A per
Channel)
• Up to 85% Efficiency with Small Magnetics
• 2 MHz Switching Frequency
• Separate Flash Enable Input
• Separate Flash Inhibit Input
• Single Resistor Sets Flash and Movie Mode Current
▪ Fixed Flash-to-Movie Mode Current Ratio
• 16-Level Movie Mode Current via S²Cwire™
• User-Programmable Safety Timer
• True Load Disconnect
• Input Current Limit
• Over-Voltage (Open LED, Open Circuit), Short-Circuit,
and Over-Temperature Protection
• Shutdown Current: < 1.0μA
• Small Inductor Solution: 1μH (0.9mm in height)
• 14-pin STDFN 3x3 Package
• -40 to +85°C Temperature Range
Applications
• Camcorder Video Light (Torch Light)
• Cellphones / Smartphones
• Digital Still Cameras (DSC)
• LED Photo Flash Light (Strobe Light)
• Mobile Handsets
• MP3 Players
• PDAs and Notebook PCs
Typical Application
VBATTERY
Movie Mode
Enable and Set
Flash Enable
Flash Inhibit
CIN
2.2μF
RSET
162kΩ
L1
1μH
IN
SW
OUT
AAT1270
EN/SET
FLEN
FLINH
FLOUTA
FLOUTB
RSET
CT
GND AGND PGND FLGND
Flash LEDs
Lumiled LXCL-PWF1 or equivalent
COUT
2.2μF
CT
47nF
1270.2008.07.1.5
www.analogictech.com
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