T6319A Taiwan Memory Technology, T6319A Datasheet - Page 7

• Manufacturer Part Number: T6319A
• Description: High Efficiency 2X charge Pump
• Manufacturer: Taiwan Memory Technology

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Flash LED Driver
The T6319A 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 poducts.
Typically the 4.5V output version of the T6319A should be selected for photo-flash LED
applications, as it can maintain better voltage regulation at higher pulsed load current levels (refer to
figure “Flash LED Application”). The limitation of this option is that the greatest flash LED forward
voltage (V
Flash LEDs with forward voltage (V
option. However, the maximum current 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
resistor. The typical forward voltage (V
from the LED manufacturer's datasheet for the desired forward current (I
Once the forward current has been determined, the flash ballast resistor can be calculated using the
following equation:
The flash LED function can be controlled by the T6319A enable pin in most applications. The
device start-up time into maximum load is about 200µs, this eliminating the need for pre-flash
control synchronization. If “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 “Flash LED Driver with Gated Flash Application”. Refer to
the following equations for the calculation of flash and light resistors, R
TM Technology Inc. reserves the right
to change products or specifications without notice.
R
R
R
F
L
F
=(V
=(V
=[(V
F
) that can be driven is 4.5V at the maximum set forward current (I
CH
TE
OUT
OUT
OUT
-V
-V
-V
F
F
F
)/I
)/I
)/I
F
F
F
F
) through the flash LED may be determined with the use of a series ballast
] - R
DS
Where: R
Where: R
Where: R
V
V
V
V
F
F
V
V
R
) levels up to 5.0V can be driven by the T6319A 5.0V output
OUT
F
I
I
OUT
= Flash LED forward voltage at the desired forward current
DS
OUT
F
F
F
=Flash LED forward voltage at the desired forward current
F
I
) for the flash LED in a given application should be derived
L
= Flash LED forward voltage at the desired forward current
F
=Desired LED forward current
=Desired LED forward current in “light” mode
= flash gating MOSFET on resistance
=Desired LED forward current
F
=Regulated charge pump output voltage (typically 4.5V)
=Light mode ballast resistor value in ohms
=Regulated charge pump output voltage (typically 4.5V)
=Regulated charge pump output voltage (typically 4.5V)
=Flash ballast resistor value in ohms
F
= Flash ballast resistor value in ohms
P. 7
F
Publication Date: MAY. 2007
and R
F
) of the flash application.
F
L
) for the application.
.
T6319A
Revision: A