AAT1282 Datasheet, PDF (9/22 Pages) Skyworks Solutions Inc. – 2A Driver for High Intensity LED Camera Flash

Functional Block Diagram
DATA SHEET
AAT1282
2A Driver for High Intensity LED Camera Flash
SW
IN
EN
FLEN
SCL
SDA
Control
RSET CT AGND PGND FLGND
OUT
PGND
FLOUTA
FLOUTB
Functional Description
The AAT1282 is a high power, 2A Flash LED driver. This
device utilizes a highly efficient inductive step-up con-
verter to achieve to desired output voltage (Super
Capacitor voltage, 5.5V). The current of two output
channels are regulated evenly which is discharged from
the output Super Capacitor, mainly for camera flash
applications.
The maximum flash current is set by an external resistor,
R_SET, which also sets the maximum movie-mode current.
The maximum movie-mode current is equal to the maxi-
mum programmed flash current reduced by the flash-to-
movie-mode ratio with the default value set to 1:7.3. A
flash pulse is initiated by strobing the FLEN input pin low-
to-high, which initiates a flash pulse and also starts the
internal safety timer. The maximum flash time is deter-
mined by an external timing capacitor connected to the
CT pin. The flash duration can be set from 50ms up to a
maximum of 1s. The flash timer will terminate the flash
current regardless of the status of the FLEN pin. This can
be either used as a simple flash timing pulse or can be
used as a safety timer in the event of a control logic mal-
function to prevent the LEDs from over-heating.
If the safety timer is not needed in the application, it can
be disabled by connecting the CT pin directly to AGND.
Further adjustments to the timeout period can be
obtained by programming through the I²C interface.
When the AAT1282 is enabled, the step-up convertor
operates at 2MHz switching and charged up the Super
Capacitor to 5.5V in seconds. As soon as the Super
Capacitor reaches 5.5V, the AAT1282 automatically
changes to light load mode operation to maintain output
regulation at light load or no load condition. This is dis-
continuous mode operation, and is normal behavior for a
switching regulator. At this point, the LEDs are ready to
be flashed.
During the flash, the boost engine is shut down, and the
two LEDs connected to its corresponding current channel
(FLOUTA or FLOUTB) share the output current supplied
by the Super Capacitor equally. (The duration of the
flash will be further discussed in the Applications
Information section of this datasheet.) In applications
where only one LED is connected to either FLOUTA or
FLOUTB, the unused current channel must be directly
connected to OUT, thereby disabling that channel. For
the single ultra bright LED application which requires
doubling the flash current, the two current channels can
be connected together which allow this ultra bright single
LED getting the full output current (please check with
the LED specification from LED suppliers).
During the movie-mode operation, the safety timer is
disabled. Enabling each output channel (FLOUTA and
FLOUTB can be enabled or disabled individually or
together) and programming the flash-to-movie-mode
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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202305C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013