AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
General Description
The AAT3123/23A/24 is a low noise, constant fre-
quency charge pump DC/DC converter that uses a
dual mode load switch (1X) and fractional (1.5X)
conversion to maximize efficiency for white LED
applications. The device can be used to produce
current levels up to 20mA to drive up to six LEDs
from a 2.7V to 5.5V input. Outputs may be operat-
ed individually or paralleled 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 OUT) make the AAT3123/23A/24 ideally suited
for small battery-powered applications.
AnalogicTech’s Simple Serial Control™ (S
2
Cwire™)
interface is used to enable, disable, and set the
LED drive current with a 32-level logarithmic scale
LED brightness control. The AAT3123/23A/24 has a
thermal management system to protect the device
in the event of a short-circuit condition at the output
pin. Built-in soft-start circuitry prevents excessive
inrush current during start-up. A high charge pump
switching frequency enables the use of very small
external capacitors. A low-current shutdown feature
disconnects the load from V
IN
and reduces quies-
cent current to less than 1µA. The device also inte-
grates a test current/auto-disable feature for each
channel. The AAT3123/23A is available in a very
small, Pb-free 12-pin TSOPJW package. The six
output AAT3124 is available in a Pb-free 16-pin
4x4mm QFN package.
Features
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ChargePump
™
V
IN
Range: 2.7V to 5.5V
Dual Mode 1X and 1.5X Charge Pump for
Maximum Efficiency
Drives Low-V
F
and High-V
F
Type LEDs
Up to Six 20mA Outputs (AAT3124)
Up to Four 20mA Outputs (AAT3123/23A)
32-Position Logarithmic Scale with Digital
Control
Simple Serial Control (S
2
Cwire) Interface
Low Noise Constant Frequency Operation
1MHz Switching Frequency
Small Application Circuit
Regulated Output Current
Automatic Soft Start
No Inductors
I
Q
<1µA in Shutdown
Temperature Range: -40°C to +85°C
12-Pin TSOPJW Package (AAT3123/23A)
16-Pin 4x4mm QFN Package (AAT3124)
Applications
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Color (RGB) Lighting
Programmable Current Source
White LED Backlighting
White Photo Flash for DSCs
Typical Application
VIN
C1+
C1
1µF
V
BATTERY
VOUT
C
IN
1µF
C
OUT
1µF
C1-
C2+
C2
1µF
AAT3124
C2-
D1
D2
D3
D4
D5
D6
EN/SET
EN/SET
GND
D6
D5
D4
D3
D2
D1
3123.2005.12.1.4
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
