AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
General Description
The AAT3151 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-
mode load switch (1X), fractional (1.5X), and dou-
bling (2X) conversion to maximize efficiency for
white LED applications. The AAT3151 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 AAT3151 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 AAT3151 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 AAT3151 is available in a Pb-free, space-saving,
thermally-enhanced, 12-pin 3x3mm TDFN package,
or in the lower-profile STDFN 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
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives Four Channels of LEDs
Individual Main/Sub-Group Control
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 or STDFN33-12 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+
AAT3151
C2-
VOUT
C2
1µF
MAIN
SUB
D1
D2
D3
D4
C
OUT
1µF
EN/SET
EN/SET
D1
D2
D3
GND
D4
3151.2007.03.1.10
1
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
