AAT3151B
High Efficiency 1X/1.5X Charge Pump
For White LED Applications
™
ChargePump
General Description
Features
The AAT3151B is a low noise, constant frequency
charge pump DC/DC converter that uses a dual
mode load switch (1X) and fractional (1.5X) charge
pump conversion to maximize efficiency for white
LED applications. The AAT3151B is capable of
driving four white LEDs at a total of 120mA from a
2.7V to 5.5V input. The current sinks may be oper-
ated individually or in parallel for driving higher-cur-
rent LEDs. A low external parts count (two 1µF fly-
ing capacitors and two small 1µF capacitors at VIN
and VOUT) makes the AAT3151B ideally suited for
small battery-powered applications.
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VIN Range: 2.7V to 5.5V
Fully Programmable Current with Single Wire
— 16-Step Logarithmic Scale
— 15/20/30mA Max Current
— Four Low-Current Settings Down to 50µA
— Low IQ (50µA) for Low-Current Mode
Dual Mode 1X and 1.5X Charge Pump for
Maximum Efficiency and VF Coverage
Drives Four Channels of LEDs
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
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Built-In Thermal Protection
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AnalogicTech's AS Cwire™ (Advanced Simple
Built-In Auto-Disable for Short-Circuit
Automatic Soft Start
Serial Control™) serial digital input is used to
enable, disable, and set current for each LED with
a 16-level logarithmic scale plus four low-current
settings down to 50µA for optimized efficiency, with
a low housekeeping current of only 50µA.
IQ <1µA in Shutdown
TDFN33-12 Package
The charge pump output of the AAT3151B is
equipped with built-in protection for VOUT. Each
current sink input has short-circuit and auto-disable
to guard against LED failure conditions. Built-in
soft-start circuitry prevents excessive inrush cur-
rent during start-up. A low-current shutdown fea-
ture disconnects the load from VIN and reduces
quiescent current to less than 1µA.
Applications
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Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
The AAT3151B is available in a Pb-free, space-
saving, thermally-enhanced, 12-pin 3x3mm TDFN
package.
Typical Application
VIN
2.7V to 5.5V
C1+
C1
1μF
C
IN
1μF
C1-
C2+
C2
1μF
AAT3151B
C2-
VOUT
COUT
1μF
D1
D2
D3
D4
EN/SET
D1
D2
D3
D4
EN/SET
GND
3151B.2007.09.1.0
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