AAT3142ITP-T1 AnalogicTech, AAT3142ITP-T1 Datasheet - Page 9

• Manufacturer Part Number: AAT3142ITP-T1
• Description: High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
• Manufacturer: AnalogicTech

Functional Block Diagram
Functional Description
The AAT3142 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 moni-
tors 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 cur-
rent source output voltage. As the battery discharges
over time, the AAT3142 charge pump is enabled when
any of the three 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. Each of
the three current source outputs is independently
ChargePump
3142.2009.07.1.3
TM
EN/SET
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
S
Interface
2
Cwire
w w w . a n a l o g i c t e c h . c o m
Reference
Soft-Start
Oscillator
Voltage
Control
32 x 8 bit
1MHz
ROM
GND
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
nificantly enhances overall device efficiency when the
battery input voltage level is greater than the voltage
required at any current source output.
The AAT3142 requires only four external components:
two 1μF ceramic capacitors for the charge pump flying
capacitors (C
(C
put capacitor (C
(D1 to D3) drive three individual LEDs with a maximum
current of 30mA each. The EN/SET S
face enables the AAT3142 and sets the current source
magnitudes.
IN
), and one 0.33μF to 1μF ceramic charge pump out-
F
Charge
D/A
D/A
D/A
Pump
) can vary as much as 1V, this function sig-
VIN
1.5X
1X
2X
1
and C
CP
). The three constant current outputs
2
PRODUCT DATASHEET
), one 1μF ceramic input capacitor
C1+
C1-
C2+
C2-
CP
D1
D2
D3
AAT3142
2
Cwire serial inter-
9