AAT3105 Datasheet, PDF (11/15 Pages) Advanced Analogic Technologies – Low Cost 1x/2x 4 Channel Charge Pump WLED Driver

ChargePump^TM
PRODUCT DATASHEET
AAT3105178
Low Cost 1x/2x 4 Channel Charge Pump WLED Driver
Additional Applications
The current sources of the AAT3105 can be combined
freely to drive higher current levels through one LED. As
an example, a single LED can be driven at 120mA by
combining together D1 through D4 outputs.
For lower-cost applications, the flying capacitor can be
removed; C+ and C- should be floating. This will force
the AAT3105 to operate in 1x mode. To maintain regu-
lated LED current, the input supply voltage has to be
higher than the charge pump's dropout voltage in 1x
mode plus the forward voltage of the LED at the preset
LED current.
PCB Layout Considerations
When designing a PCB for the AAT3105, the key require-
ments are:
1. Place the flying capacitor C1 as close to the chip as
possible; otherwise 2x mode performance will be
compromised.
2. Place the input and output decoupling capacitors C2
and C3 as close to the chip as possible to reduce
switching noise and output ripple.
Input Voltage
2.7V to 5.5V
IN
OUT
C+
C_IN
1µF
C_P
1µF
AAT3105
D1
C-
D2
EN /PWM
Interface
D3
EN /PWM
D4
GND
C_OUT
1µF
Figure 1: Higher Current, Single LED Application.
Input Voltage
> V_F + V_DROP
C_IN
1µF
EN/PWM
Interface
IN
OUT
C+
AAT3105
D1
C-
D2
D3
EN/PWM
D4
GND
C_OUT
1µF
Figure 2: Lower Cost 1x Mode Application.
3105.2008.10.1.0
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