High Efficiency 1.5X Fractional Charge
Pumps For White LED Applications
General Description
The AAT3113/4 are low noise, constant frequency
charge pump DC/DC converters that use fractional
(1.5X) conversion to increase efficiency in White
LED applications. The devices can be used to pro-
duce current levels up to 20mA for each output from
a 2.7V to 5.5V input. Low external parts counts (two
1µF flying capacitors and two small bypass capaci-
tors at V
IN
, and OUT) make the AAT3113/4 ideally
suited for small battery-power applications.
AnalogicTech™’s Simple Serial Control™
(S
2
Cwire™) interface is used to enable, disable
and set the LED drive current for a 32 level loga-
rithmic scale LED brightness control. The
AAT3113/4 have a thermal management system to
protect the device in the event of a short circuit
condition on any of the output pins. Built-in soft-
start circuitry prevents excessive inrush current
during start-up. 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 AAT3113 provides 4 LED current source out-
puts, and the AAT3114 provides 6. The AAT3113/4
are available in 16-pin quad QFN packages, and
the AAT3113 is also available in the 12-pin
TSOPJW package.
AAT3113/4
Features
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ChargePump
™
White LED Backlighting
AAT3113 - 4 Outputs
AAT3114 - 6 Outputs
20mA Full Scale Current
32 Position Logarithmic Scale with Digital
Control
Simple Serial Control™ (S
2
Cwire™) interface
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
VIN Range: 2.7V to 5.5V
No Inductors
600kHz Switching Frequency
Iq < 1µA in Shutdown
Temperature Range -40 to 85°C.
16-Pin QFN, 12-Pin TSOPJW Package
Applications
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White LED Backlighting
Programmable Current Source
Typical Application
V
IN
C1+
C1
1µF
V
OUT
V
BATTERY
C
IN
1µF
C
OUT
1µF
C1-
C2+
C2
1µF
AAT3114
C2-
D1
D2
D3
D4
D5
D6
EN/SET
EN/SET
GND
D6
D5
D4
D3
D2
D1
3113.2004.07.1.4
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ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
