LM3551 Datasheet, PDF (1/23 Pages) National Semiconductor (TI) – 1A White LED Driver with Flash Timeout Protection

LM3551, LM3552
www.ti.com
SNVS371D – AUGUST 2005 – REVISED MAY 2013
LM3551 /LM3552 1A White LED Driver with Flash Timeout Protection
Check for Samples: LM3551, LM3552
FEATURES
1
•2 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
• Wide Voltage Range 2.7 to 5.5V
• 1.25MHz Constant Switching Frequency
• Small, Low Profile Package, Non-Pullback
WSON(4mm x 4mm)
APPLICATIONS
• White LED Camera Flash
• White LED Torch (Flashlight)
• DSC (Digital Still Camera) Flash
• Cellular Camera Phone Flash
• PDA Camera Flash
• Camcorder Torch (Flashlight) Lamp
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.
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
TORCH/FLASH pin. A programmable Timeout
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.
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.
Typical Application Circuits
V_BAT
L1
D1
Sharp
GM5BW05340A
Flash LED
SW OVP
C_IN
V_IN
FB
V_C
R_C ^FTO
C_C ^CFTO
LM3551/2
GND
L1
SD/ T/F
EN
D1
R_T
R_F
FET-T
FET-F
SS
C_SS
LUMILED
LXCL-PWF1
Flash LED
C_OUT
V_BAT
V_IN
C_IN
V_C
R_C ^FTO
C_C ^CFTO
SW OVP
FB
LM3551/2
SD/ T/F
EN
R_T
FET-T
FET-F
SS
C_SS
C_OUT
R_F
1
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2
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.
Copyright © 2005–2013, Texas Instruments Incorporated