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LT3491EDC#TRMPBF

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1
LT3491
3491fa
■
Cellular Phones
■
PDAs, Handheld Computers
■
Digital Cameras
■
MP3 Players
■
GPS Receivers
Li-Ion Driver for Four White LEDs
White LED Driver with
Integrated Schottky in SC70
and 2mm × 2mm DFN
■
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
■
V
IN
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)
Efficiency
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
CTRL
V
IN
L1
10µH
V
IN
3V TO 5V
R
SENSE
10Ω
3491 TA01a
LT3491
SHUTDOWN AND
DIMMING CONTROL
SW
CAP
LED
GND
C2
1µF
C1
1µF
C1: TAIYO YUDEN LMK212BJ105MD
C2: TAIYO YUDEN GMK316BJ105ML
L1: MURATA LQH32CN100
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.
LED CURRENT (mA)
0
EFFICIENCY (%)
50
60
20
3491 TA01b
40
5
10
15
80
70
55
65
45
75
V
IN
= 3.6V
4 LEDs
, LTC, LT and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
2
LT3491
3491fa
Input Voltage (V
IN
) ................................................. 12V
SW Voltage ............................................................. 32V
CAP Voltage ............................................................ 32V
CTRL Voltage .......................................................... 12V
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
(Note 1)
LT3491ESC8
LBXQ
T
JMAX
= 125°C, θ
JA
= 270°C/ W
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Operating Voltage 2.5 V
LED Current Sense Voltage (V
CAP
– V
LED
)V
CAP
= 30V ● 190 200 210 mV
CAP, LED Pin Bias Current V
CAP
= 16V, V
LED
= 16V 20 40 µA
V
CAP
, V
LED
Common Mode Minimum Voltage 2.5 V
Supply Current V
CAP
= 16V, V
LED
= 15V, CTRL = 3V 2.6 4 mA
CTRL = 0V 8 10 µA
Switching Frequency 1.8 2.3 2.8 MHz
Maximum Duty Cycle ● 88 92 %
Switch Current Limit ● 260 350 mA
Switch V
CESAT
I
SW
= 200mA 200 mV
Switch Leakage Current V
SW
= 16V 0.1 5 µA
V
CTRL
for Full LED Current V
CAP
= 30V ● 1.5 V
V
CTRL
to Shut Down IC 50 mV
V
CTRL
to Turn On IC ● 100 mV
CTRL Pin Bias Current 100 nA
CAP Pin Overvoltage Protection ● 26 27 28 V
Schottky Forward Drop I
SCHOTTKY
= 100mA 0.8 V
Schottky Leakage Current V
R
= 20V 4 µA
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 3V, V
CTRL
= 3V, unless otherwise specified.
ELECTRICAL CHARACTERISTICS
SW 1
GND 2
GND 3
GND 4
8 CAP
7 LED
6 CTRL
5 V
IN
TOP VIEW
SC8 PACKAGE
8-LEAD PLASTIC SC70
LED Voltage ............................................................ 32V
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Maximum Junction Temperature ......................... 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10sec, SC-70) ......... 300°C
TOP VIEW
CTRL
LED
CAP
V
IN
GND
SW
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
4
5
7
6
3
2
1
T
JMAX
= 125°C, θ
JA
= 102°C/W, θ
JC
= 20°C/ W
EXPOSED PAD (PIN 7) SHOULD BE CONNECTED TO PCB GROUND
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
ORDER PART NUMBER DC PART MARKING
LT3491EDC
LCHJ
ORDER PART NUMBER DC PART MARKING
3
LT3491
3491fa
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Switch Saturation Voltage (V
CESAT
)
Schottky Forward Voltage Drop
Shutdown Current (V
CTRL
= 0V)
Sense Voltage (V
CAP
– V
LED
)
vs V
CTRL
Open-Circuit Output Clamp
Voltage
Input Current in Output Open
Circuit
Switching Waveform
Transient Response
(T
A
= 25°C unless otherwise specified)
SWITCH CURRENT (mA)
0
350
300
250
200
150
100
50
0
150 300
3491 G01
50 100
200 400
250
350
SWITCH SATURATION VOLTAGE (mV)
SCHOTTKY FORWARD DROP (mV)
0
SCHOTTKY FORWARD CURRET (mA)
150
200
250
600
1000
3491 G02
100
50
0
200 400 800
300
350
400
1200
V
IN
(V)
0
SHUTDOWN CURRENT (µA)
9
12
15
12
3491 G03
6
3
0
3
6
9
V
CTRL
(mV)
0
SENSE VOLTAGE (mV)
80
120
2000
3491 G04
40
0
500
1000
1500
240
200
160
V
IN
(V)
0
OUTPUT CLAMP VOLTAGE (V)
27
28
12
3491 G05
26
25
3
6
9
30
29
V
IN
(V)
0
0
INPUT CURRENT (mA)
1
2
3
4
5
6
36 912
3491 G06
V
SW
10V/DIV
V
CAP
50mV/DIV
I
L
100mA/DIV
V
IN
= 3.6V
FRONT PAGE
APPLICATION CIRCUIT
200ns/DIV
3491 G07
V
CTRL
5V/DIV
V
CAP
5V/DIV
I
L
200mA/DIV
V
IN
= 3.6V
FRONT PAGE
APPLICATION CIRCUIT
1ms/DIV
3491 G08
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3491E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
ELECTRICAL CHARACTERISTICS
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LT3491EDC#TRMPBF

Mfr. #:
Buy LT3491EDC#TRMPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
LED Lighting Drivers White LED Driver w/ Integrated Schottky Diode in DFN
Lifecycle:
New from this manufacturer.
Delivery:
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