AAT3132 Datasheet, PDF (13/14 Pages) Advanced Analogic Technologies – High Efficiency 1.5X Fractional Charge Pump for White LED Applications

AAT3132/32A
High Efficiency 1.5X Fractional Charge
Pump for White LED Applications
However, if the diodes are dramatically different in
type comprising a mix of high-V_F type and low-V_F
type LEDs, the AAT3132/32A has the capability to
optimally drive up to four LEDs of one type and up
to two LEDs of another type simultaneously. This
feature can be useful for driving different color
LEDs, driving both display backlight and photo-
flash LEDs, or for driving main and sub-LCD dis-
play LED backlights from a single charge pump IC.
For example, when driving independent RGB
LEDs, the green and blue LEDs typically require a
high V_F to operate (e.g., 3.7V), while the red LED
needs a low forward voltage (e.g., 2V). By con-
necting the green and blue diodes to outputs D1 to
D3 and the red diodes to D4, good control and uni-
formity in brightness is maintained despite the 2V
difference in the diode forward voltages.
Similarly, if a 4V photo-flash LED array is connect-
ed to outputs D1 through D3 (with the outputs short-
ed together) and two 3.3V sub-LCD display back-
light LEDs are connected to output D4, then the
AAT3132/32A can optimally drive each set of LEDs
at the programmed current level (see Figure 2).
V_BATTERY
VIN
C1+
C1
1µF
VOUT
C1-
C2+
C_IN
C_OUT
AAT3132
C2
1µF
1µF
AAT3132A
1µF
C2-
D1
D2
D3
EN/SET
EN/SET D4
GND
D1
D2
D3
D4
D5
D6
Figure 2: AAT3132/32A Driving Two Groups of Paralleled White LEDs
(e.g., main and sub-LCD backlights).
3132.2005.12.1.4
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