AAT1271A Datasheet, PDF (2/19 Pages) Advanced Analogic Technologies – 1.5A Step-Up Current Regulator for Flash LEDs

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PROPRIETARY INFORMATION PRODUCT DATASHEET
AAT1271A
1.5A Step-Up Current Regulator for Flash LEDs
Typical Application
V_BAT
CIN
2.2μF
Movie-mode
Enable and Set
Flash Enable
Flash Inhibit
RSET
107kΩ
L1
1μH
IN
SW
OUT
AAT1271A
EN/SET
FLEN
FLINH
RSET
FLOUTA
FLOUTB
CT
GND AGND PGND FLGND
High Current
Flash LEDs
COUT
2.2μF
CT
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
EP
Symbol
CT
EN/SET
FLEN
AGND
IN
SW
PGND
OUT
GND
FLINH
FLOUTB
FLGND
FLOUTA
RSET
Function
Flash timer control input. Connect a capacitor between CT and AGND to set maximum duration of the flash
pulse. To disable the flash timer, connect CT to AGND.
Enable and Serial Control input. EN/SET is the AS²Cwire addressing and programming input to: a) adjust
the movie-mode current level; b) program the flash 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 flash pulse and starts the flash 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
flash timer.
Flash Output B. Connect cathode of Flash LEDB to FLOUTB. For a single flash LED, connect FLOUTB &
FLOUTA together. For two flash LEDs, each output will conduct 50% of the total flash 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 flash LED, connect FLOUTA and
FLOUTB together. For two flash LEDs, each output will conduct 50% of the total flash output current.
Flash current setting input. A 107kΩ resistor from RSET to AGND sets the maximum flash 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 flash-to-movie-mode ratio is fixed at 7.3:1.
Exposed paddle (bottom); Connect EP to PGND as close as possible to the AAT1271A.
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1271A.2008.07.1.0