LM3551, LM3552
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SNVS371D –AUGUST 2005–REVISED MAY 2013
LM3551 /LM3552 1A White LED Driver with Flash Timeout Protection
Check for Samples: LM3551, LM3552
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FEATURES
DESCRIPTION
The LM3551 and LM3552 are fixed frequency,
current mode step-up DC/DC converters with two
integrated NFETs that can be used for precision LED
brightness control. The devices are capable of driving
loads up to 1A from a single-cell Li-Ion battery.
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Up to 1A Total Drive Current
Flash Timeout Protection
Independent Torch/Flash/Shutdown Modes
LED Disconnect in Shutdown
Programmable Soft-Start Limits Inrush Current
Over-Voltage Protection
The LM3551 and LM3552 can drive one or more high
current flash LEDs either in a high power Flash mode
or
a
lower power Torch mode using the
programmable Timeout
Wide Voltage Range 2.7 to 5.5V
1.25MHz Constant Switching Frequency
TORCH/FLASH pin.
A
function on the FTO pin forces the internal NFETs to
turn off after a certain user defined time. An external
SD pin (LM3551) or EN pin (LM3552) is available to
put the device into low power shutdown mode. During
shutdown, the feedback resistors and the load are
disconnected from the input to avoid leakage current
paths to ground.
Small, Low Profile Package, Non-Pullback
WSON(4mm x 4mm)
APPLICATIONS
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White LED Camera Flash
White LED Torch (Flashlight)
DSC (Digital Still Camera) Flash
Cellular Camera Phone Flash
PDA Camera Flash
User programmable soft-start circuitry has been
integrated to eliminate large inrush currents at start-
up. Over-voltage protection circuitry and a 1.25MHz
switching frequency allow for the use of small, low-
cost output capacitors with lower voltage ratings. The
LM3551 and LM3552 are available in a low profile 14-
pin WSON package.
Camcorder Torch (Flashlight) Lamp
Typical Application Circuits
Sharp
GM5BW05340A
Flash LED
D1
L1
SW
OVP
V
BAT
V
IN
FB
C
IN
C
OUT
V
FTO
C
R
T
R
F
LM3551/2
R
C
FET-T
FET-F
C
FTO
C
C
SS
C
GND
SS
T/F
D1
SD/
EN
LUMILED
LXCL-PWF1
Flash LED
L1
SW
OVP
V
BAT
V
IN
FB
C
IN
C
OUT
V
C
R
T
R
F
LM3551/2
FTO
R
C
FET-T
FET-F
C
FTO
C
C
SS
C
SS
SD/
EN
T/F
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PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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