High Current, High Efficiency
Charge Pump with Auto-Timer
General Description
The AAT3171 is a high output current, high effi-
ciency, low noise, low profile charge pump DC/DC
converter. The device is ideal for multi-functional
LED photo-flash applications where solution cost,
size, and efficiency are critical.
The AAT3171 is capable of driving a regulated out-
put current up to 800mA. Output current levels can
be easily programmed in 16 steps through
AnalogicTech's Simple Serial Control™ (S
2
Cwire™)
interface controlled by a single microcontroller
GPIO line. This allows smooth transitions and flexi-
ble adjustment of brightness in flash or other light-
ing modes. The maximum output current can also
be set with an external R
SET
resistor.
The tri-mode (1X/1.5X/2X) operation of the internal
charge pump offers excellent power efficiency
throughout the output current range for both flash
and movie modes. Combined with a low external
parts count (two 1µF flying capacitors and two small
bypass capacitors at V
IN
and OUT), the AAT3171 is
ideally suited for small battery-powered applications.
The AAT3171 has a thermal management system to
protect the device in the event of a short-circuit con-
dition at the output pin. Built-in soft-start circuitry pre-
vents excessive inrush current during start-up. The
shutdown feature disconnects the load from V
IN
and
reduces quiescent current to less than 1µA.
The AAT3171 is available in a Pb-free, thermally-
enhanced 12-pin 3x3mm TDFN package and is spec-
ified over the -40°C to +85°C temperature range.
AAT3171
Features
•
•
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ChargePump
™
Up to 800mA Output Current
Tri-Mode 1X/1.5X/2X in Current Mode
16 Current Level Steps Set by S
2
Cwire
External R
SET
to Set Maximum Current
<1µA of Shutdown
Small Application Circuit
No Inductors
Automatic Soft Start
12-Pin TDFN 3x3mm Package
-40°C to +85°C Temperature Range
Applications
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Camcorders
Camera Phones
Digital Still Cameras
PDAs and Notebook PCs
Smart Phones
Typical Application
1µF
1µF
C1+
2.7V
to 5.5V
C
IN
4.7µF
VIN
C1-
C2+
C2+
OUT
AAT3171
EN/SET
CT
C
OUT
2.2µF
Flash
LED
EN
FL
RSET
GND
187K
0.1µF
3171.2007.03.1.1
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
