PROPRIETARY INFORMATION PRODUCT DATASHEET
AAT1271A
SwitchReg
TM
Typical Application
L1
1μH
High Current
Flash LEDs
OUT
V
BAT
C
IN
2.2μF
1.5A Step-Up Current Regulator for Flash LEDs
IN
SW
AAT1271A
Movie-mode
Enable and Set
Flash Enable
Flash Inhibit
FLOUTA
FLEN
FLOUTB
FLINH
CT
RSET
GND AGND PGND FLGND
EN/SET
C
OUT
2.2μF
C
T
R
SET
107kΩ
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
Symbol
CT
EN/SET
FLEN
AGND
IN
SW
PGND
OUT
GND
Function
Flash timer control input. Connect a capacitor between CT and AGND to set maximum duration of the
fl
ash
pulse. To disable the
fl
ash timer, connect CT to AGND.
Enable and Serial Control input. EN/SET is the AS
2
Cwire addressing and programming input to: a) adjust
the movie-mode current level; b) program the
fl
ash timer based on CT; c) select the Flash-to-Movie-mode
ratio; and d) select FLOUTA and FLOUTB’s output configuration.
Flash enable pin. A low-to-high transition on the FLEN pin initiates a
fl
ash pulse and starts the
fl
ash timer.
Analog ground pin. Connect AGND to PGND, GND, and FLGND at a single point as close to the AAT1271A as
possible.
Power input. Connect IN to the input power supply voltage. Connect a 2.2μF or larger ceramic capacitor
from IN to PGND as close as possible to the AAT1271A
Boost converter switching node. Connect a 1μH inductor between SW and IN.
Power ground pin. Connect PGND to AGND, GND, and FLGND at a single point as close to the AAT1271A as
possible.
Power output of the boost converter. Connect a 2.2μF or larger ceramic capacitor from OUT to PGND as
close as possible to the AAT1271A. Connect OUT to the anode(s) of the Flash LED(s).
Ground pin. Connect GND to PGND, AGND, and FLGND at a single point as close to the AAT1271A as pos-
sible.
Flash inhibit pin. FLINH is an active HIGH control input with an internal 200kΩ resistor to AGND. A low-to-
high transition on the FLINH pin reduces FLOUTA and FLOUTB output currents to the maximum (default)
movie-mode current level for the duration of FLINH. Strobing the FLINH pin low to high does not reset the
fl
ash timer.
Flash Output B. Connect cathode of Flash LEDB to FLOUTB. For a single
fl
ash LED, connect FLOUTB &
FLOUTA together. For two
fl
ash LEDs, each output will conduct 50% of the total
fl
ash output current.
Flash ground pin. Connect FLGND to PGND, GND, and AGND at a single point as close to the AAT1271A as
possible
Flash Output A. Connect cathode of Flash LEDA to FLOUTA. For a single
fl
ash LED, connect FLOUTA and
FLOUTB together. For two
fl
ash LEDs, each output will conduct 50% of the total
fl
ash output current.
Flash current setting input. A 107kΩ resistor from RSET to AGND sets the maximum
fl
ash current avail-
able at FLOUTA and FLOUTB to 1.5A. Each FLOUTA and FLOUTB channel will conduct 50% of the maximum
programmed current. The AAT1271A’s
fl
ash-to-movie-mode ratio is
fi
xed at 7.3:1.
Exposed paddle (bottom); Connect EP to PGND as close as possible to the AAT1271A.
10
FLINH
11
12
13
14
EP
FLOUTB
FLGND
FLOUTA
RSET
2
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1271A.2008.07.1.0
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