High Efficiency 1X/1.5X/2X Charge
Pump for White LED Applications
General Description
The AAT3167 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 AAT3167 is capable of
driving five LEDs for a total of 135mA from a 2.7V
to 5.5V input. The current sinks may be operated
individually or in parallel for driving higher current
LEDs. A low external parts count (two 1µF flying
capacitors and two small 1µF capacitors at IN and
OUTCP) make this part 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 115µA. For optimized efficiency, low-current set-
tings require only 50µA of housekeeping current.
Each output of the AAT3167 is equipped with built-
in protection for output short circuit and auto-dis-
able for load short-circuit conditions. Built-in soft-
start circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature dis-
connects the load from the input and reduces qui-
escent current to less than 1µA.
The AAT3167 is available in a Pb-free, space-sav-
ing, thermally-enhanced, 14-pin 3x3mm STDFN or
16-pin 4x4mm QFN package and is rated over the
-40°C to +85°C temperature range.
AAT3167
Features
•
•
ChargePump
™
•
•
•
•
•
•
•
•
•
•
•
V
IN
Range: 2.7V to 5.5V
Fully Programmable Current with Single Wire
— 16-Step Logarithmic Scale
— 14/18/27mA Max Current
— Four Low-Current Settings Down to 115µA
— Low I
Q
(50µA) for Single-Channel, Low-
Current Mode
Tri-Mode 1X, 1.5X, 2X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives Up to Five LEDs
Individual Main-Sub (4-1) Group Control
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Built-In Auto-Disable for Open Circuit
Automatic Soft Start
I
Q
<1µA in Shutdown
STDFN33-14 or QFN44-16 Package
Applications
•
•
•
•
•
Color (RGB) Lighting
Programmable Current Sink
Transmissive LCD Display
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
C1+
C1
1µF
C2+
C2
1µF
C1-
2.7V to 5.5V
C
IN
1µF
C2-
OUTCP
IN
AAT3167
GND
D1
D2
D3
D4
D5
D1
D2
D3
D4
D5
C
OUT
1µF
EN/SET
EN/SET
3167.2007.03.1.4
1
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
