LT3591
1
3591f
■
Cellular Phones
■
PDAs, Handheld Computers
■
Digital Cameras
■
MP3 Players
■
GPS Receivers
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
White LED Driver with
Integrated Schottky in
3mm
×
2mm DFN
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.
Li-Ion Driver for Ten White LEDs
■
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
■
80:1 True Color PWM
TM
Dimming Range
■
42V Open LED Protection
■
1MHz Switching Frequency
■
±5% Reference Accuracy
■
V
IN
Range: 2.5V to 12V
■
Requires Only 2.2µF Output Capacitor
■
Low Profi le 8-Lead DFN Package
(3mm
×
2mm
×
0.75mm)
Conversion Effi ciency
CTRL
V
IN
22
µ
H
V
IN
3V TO 5V
R
SENSE
10
Ω
3591 TA01a
LT3591
SHUTDOWN AND
DIMMING CONTROL
SW
CAP
LED
GND
2.2
µ
F
1
µ
F
LED CURRENT (mA)
0
EFFICIENCY (%)
60
20
3591 TA01b
5
10
15
80
70
55
65
75
V
IN
= 3.6V
10 LEDs
, 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.