LT3497 Datasheet, PDF (1/20 Pages) Linear Integrated Systems – Dual Full Function White LED Driver with Integrated Schottky Diodes

FEATURES
■ _{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}
■ _{VIN 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}
APPLICATIONS
■ _{Cellular Phones}
■ _{PDAs, Handheld Computers}
■ _{Digital Cameras}
■ _{MP3 Players}
■ _{GPS Receivers}
LT3497
Dual Full Function White
LED Driver with Integrated
Schottky Diodes
DESCRIPTION
The LT^®3497 is a dual full function step-up DC/DC con-
verter specifically 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 efficiency dual white LED
driver solution in the smallest of spaces.
, 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.
TYPICAL APPLICATION
Li-Ion Power Driver for 4/4 White LEDs
V_IN
3V TO 5V
15µH
1µF
15µH
SW1 V_IN SW2
CAP1
CAP2
10Ω
LT3497
10Ω
1µF
1µF
LED1
LED2
CTRL1 GND CTRL2
OFF ON
SHUTDOWN
AND DIMMING
CONTROL 1
OFF ON
SHUTDOWN
AND DIMMING
CONTROL 2
3497 TA01a
80
V_IN = 3.6V
4/4LEDs
75
Efficiency
70
65
60
55
50
0
5
10
15
20
LED CURRENT (mA)
3497 TA01b
3497f
1