AAT1270
1A Step-Up Current Regulator for Flash LEDs
™
SwitchReg
General Description
The AAT1270 is a high-efficiency, high-current boost
converter capable of 1A maximum output current. It
is an ideal power solution for LED photo flash appli-
cations in all single-cell Lithium-ion / polymer battery
operated products.
The AAT1270 is available in a Pb-free, thermally-
enhanced 14-pin 3x3mm STDFN package.
Features
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 induc-
tor and output capacitor, making the AAT1270 ideal-
ly suited for small battery-powered applications.
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Input Voltage Range: 2.7V to 5.5V
Dual Channel Output
— Up to 1A Regulated Output Current
(0.5A per Channel)
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Up to 85% Efficiency with Small Magnetics
2 MHz Switching Frequency
Separate Flash Enable Input
Separate Flash Inhibit Input
2
AnalogicTech’s proprietary S Cwire™ (Simple Serial
Control™) serial digital interface is used to enable,
disable 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 included which reduces flash cur-
rent to movie mode level during high battery demand.
Single Resistor Sets Flash and Movie Mode Current
— Fixed Flash-to-Movie Mode Current Ratio
2
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16-Level Movie Mode Current via S Cwire™
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
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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.
Small Inductor Solution: 1µH (0.9mm in height)
14-pin STDFN 3x3 Package
-40 to +85°C Temperature Range
Applications
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
condition respectively. Built-in circuitry prevents exces-
sive inrush current during start-up. The shutdown fea-
ture reduces quiescent current to less than 1.0µA.
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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
L1
1μH
Flash LEDs
Lumiled LXCL-PWF1 or equivalent
IN
SW
OUT
CIN
2.2μF
VBATTERY
AAT1270
COUT
2.2μF
Movie Mode
EN/SET
FLEN
Enable and Set
Flash Enable
Flash Inhibit
FLOUTA
FLOUTB
FLINH
RSET
CT
CT
47nF
GND AGND PGND FLGND
RSET
162kΩ
1270.2007.07.1.0
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