Linear Technology LT3591 Datasheet

FEATURES
Drives Up to Ten White LEDs from a 3V Supply
■
■ High Side Sense Allows "One Wire Current Source"
Internal Schottky Diode
■
One Pin Dimming and Shutdown
■
TM
■ 80:1 True Color PWM
42V Open LED Protection
■
1MHz Switching Frequency
■
±5% Reference Accuracy
■
V Range: 2.5V to 12V
■
IN
Requires Only 2.2µF Output Capacitor
■
Low Profi le 8-Lead DFN Package
■
(3mm × 2mm × 0.75mm)
APPLICATIONS
Cellular Phones
■
PDAs, Handheld Computers
■
■ Digital Cameras
MP3 Players
■
GPS Receivers
■
TYPICAL APPLICATION
Li-Ion Driver for Ten White LEDs
SHUTDOWN AND
DIMMING CONTROL
CTRL
V
IN
V
IN
3V TO 5V
22µH LT3591
SW
GND
1µF
Dimming Range
CAP
R
SENSE
10Ω
LED
3591 TA01a
White LED Driver with
Integrated Schottky in
DESCRIPTION
®
The LT 3591 is a fi xed frequency step-up DC/DC converter
specifi cally designed to drive up to ten white LEDs in series
from a Li-Ion cell. Series connection of the LEDs provides
identical LED currents resulting in uniform brightness
and eliminating the need for ballast resistors. The device
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 one wire LED connection. Traditional
LED drivers use a grounded resistor to sense LED current,
requiring a 2-wire connection to the LED string.
The high switching frequency allows the use of tiny induc-
tors and capacitors. A single pin performs both shutdown
and accurate LED dimming control. Few external compo-
nents are needed: open-LED protection and the Schottky
diode are all contained inside a low profi le 3mm × 2mm
DFN package.
, 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.
80
V = 3.6V
IN
10 LEDs
75
70
65
2.2µF
60
55
0
LT3591
3mm × 2mm DFN
Conversion Effi ciency
5 10 15
20
LED CURRENT (mA)
3591 TA01b
3591f
1