AAT3151B Datasheet, PDF (1/15 Pages) Advanced Analogic Technologies – High Efficiency 1X/1.5X Charge Pump For White LED Applications

AAT3151B
High Efficiency 1X/1.5X Charge Pump
For White LED Applications
General Description
Features
ChargePump^™
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 AS²Cwire™ (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.
• 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
VIN
C1+
C1
C_IN
1μF
1μF
C1-
C2+
C2
AAT3151B
1μF
C2-
VOUT
D1 D2 D3 D4
COUT
1μF
EN/SET
EN/SET
D1
D2
D3
D4
GND
3151B.2007.09.1.0
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