AAT3140_07 ANALOGICTECH [Advanced Analogic Technologies], AAT3140_07 Datasheet - Page 10

• Manufacturer Part Number: AAT3140_07
• Description: High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
• Manufacturer: ANALOGICTECH [Advanced Analogic Technologies]

Functional Block Diagram
Functional Description
The AAT3140 is a tri-mode load switch (1X) and
high-efficiency (1.5X or 2X) charge pump device
intended for white LED backlight applications. To
maximize power conversion efficiency, an internal
sensing circuit monitors the voltage required on
each constant current source output and sets the
load switch and charge pump modes based on the
input battery voltage and the current source output
voltage. As the battery discharges over time, the
AAT3140 charge pump is enabled when any of the
four current source outputs nears dropout. The
charge pump initially starts in 1.5X mode. If the
charge pump output drops enough for any current
source output to become close to dropout, the
charge pump will automatically transition to 2X
mode.
10
EN/SET
S
Interface
2
Cwire
Reference
Soft-Start
Oscillator
Voltage
Control
32 x 8 bit
1MHz
ROM
High Efficiency 1X/1.5X/2X Charge Pump
GND
AutoBias Technology
Each of the four current source outputs is inde-
pendently switched between the battery input (1X)
or the charge pump output (1.5X or 2X), depending
on the voltage at the current source output. Since
the LED-to-LED forward voltage (V
much as 1 volt, this function significantly enhances
overall device efficiency when the battery input
voltage level is greater than the voltage required at
any current source output.
The AAT3140 requires only four external compo-
nents: two 1µF ceramic capacitors for the charge
pump flying capacitors (C
ceramic input capacitor (C
1µF ceramic charge pump output capacitor (C
The four constant current outputs (D1 to D4) drive
four individual LEDs with a maximum current of
30mA each. The EN/SET S
enables the AAT3140 and sets the current source
magnitudes.
Charge
D/A
D/A
D/A
D/A
Pump
VIN
1.5X
1X
2X
for White LED Applications
C1+
C1-
C2+
C2-
CP
D1
D2
D3
D4
IN
1
2
), and one 0.33µF to
Cwire serial interface
and C
AAT3140
F
) can vary as
2
3140.2007.03.1.3
), one 1µF
CP
).