Datasheet
LT3497
1
3497f
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
Dual Full Function White
LED Driver with Integrated
Schottky Diodes
The LT
®
3497 is a dual full function step-up DC/DC con-
verter specifi cally designed to drive up to 12 white LEDs
(6 white LEDs in series per converter) from a Li-Ion cell. Se-
ries connection of the LEDs provides identical LED currents
resulting in uniform brightness and eliminating the need
for ballast resistors and expensive factory calibration.
The two independent converters are capable of driving
asymmetric LED strings. Accurate LED dimming and
shutdown of the two LED strings can also be controlled
independently. The LT3497 features a unique high side LED
current sense that enables the part to function as a “one
wire current source;” one side of the LED string can be
returned to ground anywhere, allowing a simpler 1-wire
LED connection. Traditional LED drivers use a grounded
resistor to sense LED current, requiring a 2-wire connec-
tion to the LED string.
The 2.3MHz switching frequency allows the use of tiny
inductors and capacitors. Few external components are
needed for the dual white LED Driver: open-LED protection
and the Schottky diodes are all contained inside the 3mm
× 2mm DFN package. With such a high level of integra-
tion, the LT3497 provides a high effi ciency dual white LED
driver solution in the smallest of spaces.
Li-Ion Power Driver for 4/4 White LEDs
■
Drives Up to 12 White LEDs (6 in Series per
Converter) from a 3V Supply
■
Two Independent Boost Converters Capable of
Driving Asymmetric LED Strings
■
Independent Dimming and Shutdown Control of the
Two LED Strings
■
High Side Sense Allows “One Wire Current Source”
per Converter
■
Internal Schottky Diodes
■
Open LED Protection (32V)
■
2.3MHz Switching Frequency
■
±5% Reference Accuracy
■
V
IN
Range: 2.5V to 10V
■
Dual Wide 250:1 True Color PWM
TM
Dimming
■
Requires Only 1µF Output Capacitor per Converter
■
Available in a 3mm × 2mm 10-Pin DFN Package
■
Cellular Phones
■
PDAs, Handheld Computers
■
Digital Cameras
■
MP3 Players
■
GPS Receivers
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
True Color PWM is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Effi ciency
SW1 V
IN
LT3497
GND
SW2
15µH
10Ω10Ω
1µF
1µF
3497 TA01a
1µF
V
IN
3V TO 5V
15µH
CAP1 CAP2
LED1 LED2
CTRL1
SHUTDOWN
AND DIMMING
CONTROL 1
SHUTDOWN
AND DIMMING
CONTROL 2
CTRL2
OFF ON
OFF ON
LED CURRENT (mA)
0
50
EFFICIENCY (%)
55
60
65
70
75
80
V
IN
= 3.6V
4/4LEDs
5101520
3497 TA01b