AAT3119_07 ANALOGICTECH [Advanced Analogic Technologies], AAT3119_07 Datasheet - Page 13

• Manufacturer Part Number: AAT3119_07
• Description: High Efficiency 2X Charge Pump
• Manufacturer: ANALOGICTECH [Advanced Analogic Technologies]

Flash LED Driver
The AAT3119 can source 250mA for pulsed loads
up to 500ms from an input supply as low as 3.3V.
This makes the device well suited for low-cost flash
LED driver applications in portable products.
Typically the 4.5V output version of the AAT3119
should be selected for photo-flash LED applica-
tions, as it can maintain better voltage regulation at
higher pulsed load current levels (refer to Figure 2).
The limitation of this option is that the greatest flash
LED forward voltage (V
at the maximum set forward current (I
application. Flash LEDs with forward voltage (V
levels up to 5.0V can be driven by the AAT3119
5.0V output option. However, the maximum cur-
rent for a 500ms pulse will be reduced. Refer to
the Typical Characteristics curves for peak output
current levels for a given minimum input voltage.
The forward current (I
be determined with the use of a series ballast resis-
tor. The typical forward voltage (V
LED in a given application should be derived from
the LED manufacturer's datasheet for the desired
3119.2007.02.1.2
V
BATTERY
F
Enable
) through the flash LED may
F
) that can be driven is 4.5V
1μF
C
IN
F
) for the flash
EN
IN
AAT3119
C1+
Figure 1: White LED Driver.
F
) for the
GND
C
1μF
FLY
C1-
OUT
F
)
forward current (I
the forward current has been determined, the flash
ballast resistor can be calculated using the follow-
ing equation:
Where:
R
V
V
I
The flash LED function can be controlled by the
AAT3119 enable pin in most applications.
device start-up time into a maximum load is about
200μs, thus eliminating the need for pre-flash con-
trol synchronization.
F
High Efficiency 2X Charge Pump
OUT
F
F
C
1μF
OUT
=
=
=
=
D1
R
B1
Flash 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
R
D2
B2
R
D3
F
R
B3
) of the flash application. Once
F
=
R
D4
B4
(V
OUT
D5
R
I
B5
F
- V
D6
F
R
)
B6
AAT3119
The
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