PRODUCT DATASHEET
AAT3151B
ChargePump
TM
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Features
• 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
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 conver-
sion 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 operated individually or in parallel for driv-
ing higher-current LEDs. A low external parts count (two
1μF flying 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 current during start-up. A low-current
shutdown feature 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.
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.2008.02.1.1
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