AAT3151B
High Efficiency 1X/1.5X Charge Pump
For White LED Applications
General Description
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 V
IN
and V
OUT
) makes the AAT3151B ideally suited for
small battery-powered applications.
AnalogicTech's AS
2
Cwire™ (Advanced Simple
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.
The charge pump output of the AAT3151B is
equipped with built-in protection for V
OUT
. 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 V
IN
and reduces
quiescent current to less than 1µA.
The AAT3151B is available in a Pb-free, space-
saving, thermally-enhanced, 12-pin 3x3mm TDFN
package.
Features
•
•
ChargePump
™
•
•
•
•
•
•
•
•
•
•
V
IN
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 I
Q
(50µA) for Low-Current Mode
Dual Mode 1X and 1.5X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives Four Channels of LEDs
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Built-In Auto-Disable for Short-Circuit
Automatic Soft Start
I
Q
<1µA in Shutdown
TDFN33-12 Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
2.7V to 5.5V
C
IN
1μF
VIN
C1+
C1
1μF
C1-
C2+
AAT3151B
C2-
VOUT
C2
1μF
D1
D2
D3
D4
C
OUT
1μF
EN/SET
EN/SET
D1
D2
D3
GND
D4
3151B.2007.09.1.0
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
