PRODUCT DATASHEET
AAT3194
ChargePump
TM
High Efficiency 1.5X Fractional Charge Pump For White LED Applications
Features
• V
IN
Range: 2.7V to 5.5V
• 20mA Full-Scale Current
• Simple Serial Control (S
2
Cwire) Interface
▪
32-Position Logarithmic Scale with Digital Control
• Low Noise Constant Frequency Operation
• 33% Less Input Current Than Doubler Charge Pump
• High Accuracy Brightness Matching
• Small Application Circuit
• Regulated Output Current
• Automatic Soft Start
• No Inductors
• 600kHz Switching Frequency
• I
Q
<1µA in Shutdown
• Temperature Range: -40°C to 85°C
• 12-Pin TSOPJW Package
General Description
The AAT3194 is a low noise, constant frequency charge
pump DC/DC converters that use fractional (1.5X) conver-
sion to increase efficiency in white LED applications. The
devices can be used to produce current levels up to 20mA
for each output from a 2.7V to 5.5V input. A low external
parts count (two 1µF flying capacitors and two small
bypass capacitors at IN and OUT) makes these devices
ideally suited for small, battery-powered applications.
AnalogicTech’s Simple Serial Control™ (S
2
Cwire™) inter-
face is used to enable, disable, and set the LED drive
current for 32-level logarithmic scale LED brightness
control. The AAT3194 has a thermal management sys-
tem for protection in the event of a short-circuit condi-
tion on any of the output pins. Built-in soft-start circuitry
prevents excessive inrush current during start-up. A high
switching frequency enables the use of small external
capacitors. A low-current shutdown feature disconnects
the load from V
IN
and reduces quiescent current to less
than 1µA. The AAT3194 is available in a Pb-free 12-pin
TSOPJW package.
Applications
• Programmable Current Source
• White LED Backlighting
Typical Application
IN
C1+
C1
1µF
OUT
V
BATTERY
C
IN
1µF
C
OUT
1µF
C1-
C2+
C2
1µF
AAT3194
C2-
D1
D2
D3
EN/SET
EN/SET
GND
D4
D4
D3
D2
D1
3194.2008.05.1.1
www.analogictech.com
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
