AAT1270_08 Datasheet, PDF (9/18 Pages) Advanced Analogic Technologies – 1A Step-Up Current Regulator for Flash LEDs

SwitchReg^TM
Functional Block Diagram
SW
EN/SET
FLEN
FLINH
200kΩ
PRODUCT DATASHEET
AAT1270
1A Step-Up Current Regulator for Flash LEDs
IN
Control
OUT
FLOUTA
FLOUTB
RSET CT AGND PGND FLGND GND
Functional Description
The AAT1270 is a boost converter with a current regu-
lated output designed to drive high current white LEDs
used in flash/movie light applications. The maximum
flash current is set by an external resistor, R_SET, which not
only sets the flash current but also sets the maximum
movie mode current reduced by a factor of 7.3. A flash
pulse is initiated by switching the FLEN (flash enable) pin
from low to high, which initiates the flash pulse and also
starts the internal timer. The maximum flash time is
determined by an external timing capacitor connected to
the CT pin. The flash duration can be set from 50ms 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
as a safety timer in the event of a control logic malfunc-
tion to prevent the LED 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.
For applications using two flash LEDs, each diode can be
connected to its corresponding current sink (FLOUTA or
FLOUTB) and the output current will be equally shared.
In single flash LED applications, the two current sinks
can be connected together to apply the full output cur-
rent into the LED.
If one sink pin (FLOUTA or FLOUTB) is not used, the
unused current sink must be directly connected to OUT,
which disables that channel.
1270.2008.07.1.5
www.analogictech.com
9