LT3491_15 Datasheet, PDF (1/16 Pages) Linear Technology – White LED Driver with Integrated Schottky in SC70

LT3491
White LED Driver with
Integrated Schottky in SC70
and 2mm × 2mm DFN
FEATURES
DESCRIPTIO
■ _{Drives Up to Six White LEDs from a 3V Supply}
■ _{High Side Sense Allows “One Wire Current Source”}
■ _{Internal Schottky Diode}
■ _{One Pin Dimming and Shutdown}
■ _{27V Open LED Protection}
■ _{2.3MHz Switching Frequency}
■ _{±5% Reference Accuracy}
■ _{VIN Range: 2.5V to 12V}
■ _{Requires Only 1µF Output Capacitor}
■ _{Wide 300:1 True Color PWM}^TM _{Dimming Range}
■ _{8-Lead SC70 Package}
■ _{Low Profile 6-Lead DFN Package}
(2mm × 2mm × 0.75mm)
U
APPLICATIO S
■ _{Cellular Phones}
■ _{PDAs, Handheld Computers}
■ _{Digital Cameras}
■ _{MP3 Players}
■ _{GPS Receivers}
The LT^®3491 is a fixed frequency step-up DC/DC converter
specifically designed to drive up to six 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 2.3MHz switching frequency allows the use of tiny
inductors and capacitors. A single pin performs both
shutdown and accurate LED dimming control. Few exter-
nal components are needed: open-LED protection and the
Schottky diode are all contained inside the tiny SC70 and
2mm × 2mm DFN packages. With such a high level of
integration, the LT3491 provides a high efficiency LED
driver solution in the smallest of spaces.
, LTC, LT and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
V_IN
3V TO 5V
Li-Ion Driver for Four White LEDs
SHUTDOWN AND
DIMMING CONTROL
L1
10µH
C1
1µF
CTRL
V_IN
CAP
LT3491
SW
LED
GND
R_SENSE
10Ω
C2
1µF
C1: TAIYO YUDEN LMK212BJ105MD
C2: TAIYO YUDEN GMK316BJ105ML
L1: MURATA LQH32CN100
3491 TA01a
Efficiency
80
V_IN = 3.6V
75 ^{4 LEDs}
70
65
60
55
50
45
40
0
5
10
15
20
LED CURRENT (mA)
3491 TA01b
3491fa
1