High Efficiency 1X/1.5X/2X Charge Pump with
PWM Control for White LED Applications
General Description
The AAT3143 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 AAT3143 can deliver
current levels up to 80mA to drive white LEDs con-
nected to the four current source outputs from a
2.7V to 5.5V input. The current source outputs may
source up to 20mA each and may be operated indi-
vidually or in parallel for driving 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 AAT3143 ideally suited for small
battery-powered applications.
Output current, and therefore brightness, is con-
trolled via externally applied Pulse Width Modulation
(PWM) control. Typically, PWM frequencies of up to
50kHz can be applied.
The AAT3143 has a thermal management system to
protect the device in the event of a short-circuit con-
dition at the voltage output pin. Built-in soft-start cir-
cuitry prevents excessive inrush current during start-
up. A high charge pump switching frequency allows
the use of very small external capacitors. A low cur-
rent shutdown feature disconnects the load from V
IN
and reduces quiescent current to less than 1µA.
The AAT3143 is available in a Pb-free, space-sav-
ing, 2.85x3.0mm 12-pin TSOPJW package.
AAT3143
Features
•
•
•
•
•
•
•
•
•
•
•
ChargePump
™
Input Voltage Range: 2.7V to 5.5V
PWM Brightness Control
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and V
F
Coverage
Drives Four Low- or High-V
F
Type LEDs
Up to 20mA LED Current per Channel
No Inductors
1MHz Switching Frequency
Small Application Circuit
AutoBias™ Technology
I
Q
<1µA in Shutdown
2.85x3.0mm TSOPJW-12 Package
Applications
•
•
•
Programmable Current Sources
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
2.7V to 5.5V
C
IN
1µF
IN
C1+
C1-
C2+
C1
1µF
C2
1µF
C
OUT
1µF
AAT3143
PWM/EN
EN/PWM
C2-
CP
D1
D2
D3
D4
GND
D4
D3
D2
D1
3143.2006.05.1.0
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
