AAT3131 Datasheet, PDF (13/14 Pages) Advanced Analogic Technologies – High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications

AAT3131
High Efficiency 1X/1.5X Fractional
Charge Pump for White LED Applications
V_BATTERY
VIN
C1+
C1
1µF
D1
D2
D3
D4
VOUT
C1-
C2+
C_IN
1µF
C_OUT
1µF
AAT3131
C2
1µF
RB*
RB*
RB*
RB*
C2-
D1
D2
D3
EN/SET
EN/SET D4
GND
D5
D6
RB*
RB*
*In some applications, white LED forward voltages (V_F) can vary significantly. Ballast resistors between the LED cathodes and ground are recommended
for balancing the forward voltage differences. The ballast resistor value may be approximated by the following equation:
RB
=
VSOURCE
IF
-
VF
Figure 2: AAT3131 Driving Two Groups of Paralleled White LEDs
(e.g., main LCD and sub-LCD backlights).
3131.2005.12.1.2
13