AAT3120
3-Channel Charge Pump
For White LED Applications
General Description
The AAT3120 is a low noise, constant frequency
charge pump DC/DC converter that uses fractional
(1.5X) conversion to improve efficiency for white
LED applications. The device can be used to pro-
duce eight current levels up to 20mA per channel
for up to three channels. 1X load switch mode is
also built-in to improve efficiency at low current set-
tings. Low external parts count (two 1µF flying
capacitors and two small 1µF capacitors at V
IN
and
OUT) makes the AAT3120 ideally suited for small
battery-powered applications.
AnalogicTech's S
2
Cwire™ (Simple Serial Control™)
serial digital input is used to enable, disable, and
set current for each LED at eight different levels.
The AAT3120 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 circuit-
ry 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 quiescent current to less
than 1µA. The AAT3120 is available in the very
small Pb-free 12-pin TSOPJW package.
Features
•
•
•
•
ChargePump
™
•
•
•
•
•
•
•
V
IN
Range: 2.7V to 5.5V
Fractional Charge Pump Mode
Drives Low-V
F
and High-V
F
Type LEDs
Up to Three LED Outputs
— Single Wire Programming
— Eight Regulated Current Settings
— Max 20mA per Channel
Low Noise Constant Frequency Operation
No Inductors
1MHz Switching Frequency
Small Application Circuit
Automatic Soft-Start
I
Q
<1µA in Shutdown
12-Pin TSOPJW Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Source
White LED Backlighting
White Photo Flash for DSCs
Typical Application
VIN
C1+
C1
1µF
VOUT
V
BATTERY
C
IN
1µF
C
OUT
1µF
C1-
C2+
C2
1µF
AAT3120
C2-
D1
D2
D3
EN/SET
EN/SET
GND
D3
D2
D1
3120.2005.11.1.1
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
