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| AAT3119 Datasheet, PDF (14/18 Pages) Advanced Analogic Technologies – High Efficiency 2X Charge Pump | |||
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AAT3119
High Efficiency 2X Charge Pump
CFLY
1μF
V
IN
IN
CIN
1μF
OUT
4.5V
COUT
1μF
AAT3119
RF
Enable
EN
GND
Flash LED
Figure 2: Flash LED Application.
If a "light" or "movie" mode is also needed along
with the flash function, this can be accomplished
with the addition of a second ballast resistor with a
flash function gating MOSFET switch as shown in
Figure 3. Refer to the following equations for the
calculation of flash and light resistors, RF and RL.
RL
=
(VOUT -
IF
VF)
Where:
RL =
VOUT =
VF =
IF
=
Light mode ballast resistor value in
ohms (Ω)
Regulated charge pump output voltage
(typically 4.5V)
Flash LED forward voltage at the
desired forward current
Desired flash LED forward current in
the "light" mode
RF =
(VOUT - VF)
IF
- RDS
Where:
RF =
RDS =
VOUT =
VF =
IF
=
Flash ballast resistor value in ohms (Ω)
Flash gating MOSFET on resistance
Regulated charge pump output voltage
(typically 4.5V)
Flash LED forward voltage at the
desired forward current
Desired flash LED forward current
14
3119.2007.02.1.2
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