LT3909
2-String × 60mA,
2MHz Step-Up LED Driver
with ±2% Current Matching
DESCRIPTION
FEATURES
Up to 36V of LEDs, 2-String × 60mA LED Driver
nn Wide Input Range: 2.9V to 40V
nn Up to 40,000:1 PWM Dimming (250ns LED On-Time)
(Independent of Leakage at VOUT)
nn ±2% LED Current Matching (Typ ±0.3%)
nn Integrated Schottky Diode
nn Internal 400mΩ, 40V, 1A Switch
nn Single Resistor Sets LED Current (10mA to 60mA)
for Both High-Side Current Sources
nn Output Adapts to LED V for Optimum Efficiency
F
nn LED Current Regulated Even for V > V
IN
OUT
nn Fault Flag + Protection for Open-LED and LED-Shortto-GND (Other String Remains in Regulation)
nn Programmable Maximum V
OUT (Regulated)
nn Internal Compensation, Soft-Start and Thermal
Regulation
nn Accurate EN/UVLO Threshold
nn Fixed 2MHz Switching Frequency
The LT®3909 is a 2-string × 60mA LED driver with a fixed
2MHz step-up DC/DC converter capable of driving up to 36V
of LEDs. Each LED string contains an accurate high-side
current source with ±2% current matching. Output voltage adapts to variations in LED VF for optimum efficiency.
nn
Maximum LED current can be programmed from 10mA
to 60mA per string using a single resistor. LED brightness
can be reduced with analog dimming (up to 10:1) or with
PWM dimming (up to 40,000:1 at 100Hz, up to 160:1 at
25kHz) (independent of leakage at VOUT). The LED pins
can be paralleled for higher LED current.
Additional features include: programmable maximum VOUT
for open LED protection, a fault flag to indicate open-LED
or LED-short-to-GND and an internal regulation loop to
safely limit junction temperature. The LT3909 also includes
internal compensation, internal soft-start and micropower
shutdown. The LT3909 is available in the 12-pin (3mm ×
3mm) DFN and 12-pin MSOP packages.
APPLICATIONS
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
PDAs, Handheld Computers
nn GPS Receivers
nn Automotive Displays
nn High Contrast Instrument Clusters
nn
TYPICAL APPLICATION
2-String × 40mA, 2MHz LED Driver for Ten White LEDs/String
LED Current Waveforms
20,000:1 PWM Dimming (100Hz)
6.8µH
VIN
7V TO 36V
1µF
VIN
SW
VOUT
402k
VIN = 12V
2.2µF
976k
FB
I(LED1)
20mA/DIV
31.6k
LT3909
EN/UVLO
130k
PWM
CTRL
INTVCC
LED1
LED2
FAULT
GND
1µF
ISET
100k
I(LED2)
20mA/DIV
VIN
10 LEDs
PER STRING
24.9k
•
•
•
PWM
2V/DIV
400ns/DIV
3909 TA01b
•
•
•
3909 TA01a
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1
LT3909
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, VOUT, SW............................................................40V
LED1, LED2................................................................40V
VOUT – LED1, VOUT – LED2........................................40V
EN/UVLO, FAULT........................................................40V
CTRL, FB, PWM...........................................................6V
INTVCC, ISET........................................................ (Note 2)
Operating Junction Temperature (Notes 3, 4)
LT3909E, LT3909I.............................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP Package Only.............................................. 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
INTVCC
1
12 SW
VIN
2
11 VOUT
EN/UVLO
3
ISET
4
CTRL
5
FB
6
13
GND
INTVCC
VIN
EN/UVLO
ISET
CTRL
FB
10 LED1
9 LED2
8 FAULT
7 PWM
1
2
3
4
5
6
13
GND
12
11
10
9
8
7
SW
VOUT
LED1
LED2
FAULT
PWM
MSE PACKAGE
12-LEAD PLASTIC MSOP
DD PACKAGE
12-LEAD (3mm × 3mm) PLASTIC DFN
θJA = 43°C/W, θJC = 5.5°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
θJA = 40°C/W, θJC = 5°C/W to 10°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
(http://www.linear.com/product/LT3909#orderinfo)
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3909EDD#PBF
LT3909EDD#TRPBF
LGMY
12-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3909IDD#PBF
LT3909IDD#TRPBF
LGMY
12-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3909EMSE#PBF
LT3909EMSE#TRPBF
3909
12-Lead Plastic MSOP
–40°C to 125°C
LT3909IMSE#PBF
LT3909IMSE#TRPBF
3909
12-Lead Plastic MSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
3909fb
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LT3909
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = VEN/UVLO = 12V, RISET = 49.9k, VOUT = 24V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input, Bias, Reference
Input Voltage Range
l
2.9
40
V
VIN Quiescent Current (Not Switching)
VOUT – VLEDx = 2V, VCTRL = 2.0V, PWM = 1.5V
600
700
µA
VIN Shutdown Current
VEN/UVLO = 0.4V, VIN = 12V
VEN/UVLO = 0.4V, VIN = 40V
0.3
1.5
2
4
µA
µA
Enable/Lockout Threshold
EN/UVLO Shutdown Threshold
IVIN < 10µA
l
0.4
0.6
EN/UVLO Enable Threshold
Falling
l
1.180
1.215
EN/UVLO Enable Hysteresis
EN/UVLO Pin Current
V
1.250
30
V
mV
VEN/UVLO = 0.4V
VEN/UVLO = 1.15V
VEN/UVLO = 1.3V
l
1.6
0.8
2.0
0
2.4
µA
µA
µA
IINTVCC = 0A to 100µA
l
2.9
3.0
3.1
V
l
1.88
2
2.12
MHz
0.02
0.1
%/V
Linear Regulator (INTVCC)
INTVCC Regulation Voltage
Oscillator
Switching Frequency
fOSC Line Regulation
2.9V ≤ VIN ≤ 40V
Maximum Duty Cycle
l
86
91
%
19.4
20
20.6
±0.3
±1.8
%
50
52.0
mA
±0.3
±1.8
%
60
63.0
mA
±0.3
±2.0
%
LED Current/Control
LEDx Current (20mA)
VOUT – VLEDx = 1.1V, VCTRL = 1.2V, RISET = 49.9k
l
Current Matching (20mA)
VOUT – VLEDx = 1.1V, VCTRL = 1.2V, RISET = 49.9k
l
LEDx Current (50mA)
VOUT – VLEDx = 1.1V, VCTRL = 1.2V, RISET = 20.0k
l
Current Matching (50mA)
VOUT – VLEDx = 1.1V, VCTRL = 1.2V, RISET = 20.0k
l
LEDx Current (60mA) (Note 5)
VOUT – VLEDx = 1.1V, VCTRL = 1.2V, RISET = 16.7k
l
Current Matching (60mA) (Note 5)
VOUT – VLEDx = 1.1V, VCTRL = 1.2V, RISET =16.7k
l
48.0
57.0
VOUT – VLEDx Regulation
1.3
mA
V
Analog Dimming
CTRL Input Current (Out of Pin)
VCTRL = 1V
VCTRL = 0.1V
CTRL Latch-Off Threshold
Falling
CTRL Latch-Off Hysteresis
Rising
LEDx Current (Dimming 10:1)
VOUT – VLEDx = 1.1V, VCTRL = 0.1V, RISET = 49.9k
5
15
200
200
nA
nA
75
80
85
mV
1.87
2.03
0.8
1.1
10
mV
2.19
mA
PWM Dimming
PWM Input Low Threshold
l
PWM Input High Threshold
l
PWM Resistance to GND
1.2
V
1.5
100
V
kΩ
VLEDx = 12V, VOUT = 40V
0.1
1
µA
FAULT Output Low
IFAULT = 100µA
0.1
0.2
V
FAULT Leakage Current
VFAULT = 5V
0.1
1
µA
LEDx Leakage Current (PWM = 0V)
Fault Diagnostics
3909fb
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3
LT3909
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = VEN/UVLO = 12V, RISET = 49.9k, VOUT = 24V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
LEDx Short Threshold VLEDx (Note 6)
VLEDx Falling
5.8
LEDx Open Threshold (VOUT – VLEDx)
(VOUT – VLEDx) Falling
TYP
MAX
UNITS
6.0
6.2
V
0.3
0.4
V
1.215
1.240
V
100
nA
1.2
A
Output Voltage
FB Regulation Voltage
FB Input Current (Out of Pin)
VFB = 1.215V
l
1.190
l
–100
l
1.0
Switch
Switch Current Limit
Switch On-Resistance
ISW = 100mA
Switch Leakage Current
VSW = 40V, VOUT = 40V
1.1
400
mΩ
2
µA
Schottky Diode
Schottky Forward Voltage
ISCHOTTKY = 250mA
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: Do not apply a positive or negative voltage to INTVCC or ISET pins,
otherwise permanent damage may occur.
Note 3: The LT3909 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
0.8
V
Note 4: The LT3909E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3909I is guaranteed over the full –40°C to 125°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 5: The 16.7k is a 0.1% resistor to achieve exactly 60mA LED current.
Note 6: The LED short threshold refers to the LED pin voltage with respect
to GND. This threshold is approximately 25% of VOUT regulation level.
When VLEDx voltage falls below this threshold, the FAULT pin is asserted.
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LT3909
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency
80
75
10
20
30
40
50
60
70
TOTAL LED CURRENT (mA)
RISING
1.240
1.230
FALLING
1.220
1.210
1.200
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
80
3909 G01
VIN SHUTDOWN CURRENT (µA)
9
VIN Shutdown Current
6
VEN/UVLO = 0.4V
4
VIN = 2.9V
VIN = 12V
VIN = 40V
3
2
1
0
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
0.5
0.4
0.3
0.2
RISET = 49.9k
PWM = 1.5V, NO SWITCHING
VCTRL = 2.0V
VOUT – VLEDx = 2.0V
0.1
0
INTVCC Pin UVLO Threshold
0
1.8
10
15 20 25 30
VIN PIN VOLTAGE (V)
35
625
RISING
2.65
FALLING
2.55
2.50
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 G07
VIN Quiescent Current
RISET = 49.9k
PWM = 1.5V, NO SWITCHING
VCTRL = 2.0V
VOUT – VLEDx = 2.0V
600
575
550
VIN = 2.9V
VIN = 12V
VIN = 40V
525
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
40
3909 G06
3909 G05
FB Pin Regulation Voltage
2.70
2.60
5
Switching Frequency
1.240
FB PIN REGULATION VOLTAGE (V)
INTVCC PIN UVLO THRESHOLD (V)
2.75
1.9
650
0.6
3909 G04
2.80
2.0
3909 G03
VIN Quiescent Current vs VIN
7
2.1
1.6
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
0.7
8
2.2
3909 G02
VIN QUIESCENT CURRENT (mA)
10
VEN/UVLO = 1.15V
1.7
VIN QUIESCENT CURRENT (µA)
EFFICIENCY (%)
85
2.3
1.250
EN/UVLO PIN CURRENT (µA)
FRONT PAGE APPLICATION CIRCUIT
VIN = 12V
VPWM = 2.0V
CTRL PIN VOLTAGE SWEEP
90
70
EN/UVLO Pin Current
2.4
2100
1.232
SWITCHING FREQUENCY (kHz)
95
EN/UVLO Pin Threshold
1.260
EN/UVLO PIN THRESHOLD (V)
100
TA = 25°C, unless otherwise noted.
1.223
1.215
1.207
1.198
1.190
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 G08
2060
2020
1980
1940
1900
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 G09
3909fb
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5
LT3909
TYPICAL PERFORMANCE CHARACTERISTICS
VLEDX Short Threshold vs VOUT
Pin Voltage
Maximum Switching Duty Cycle
12.0
91.3
90.7
90.0
89.3
88.7
65
55
50
8.0
6.0
4.0
0
5
3909 G10
70
RISET = 16.7k
RISET = 33.2k
30
RISET = 49.9k
20
RISET = 100k
10
0
0.25
0.50 0.75
1
1.25
CTRL PIN VOLTAGE (V)
40
3909 G11
30
25
3909 G12
1.50
VOUT = 24V, VLEDx = 22.9V
20.3 VCTRL = 2.0V
RISET = 49.9k
RISET = 20.0k
20.2
1.5 2 2.5 3 3.5 4 4.5
VOUT TO VLEDX DIFFERENTIAL (V)
0.2
0
–0.2
–0.4
–0.6
I(LED1)
I(LED2)
19.6
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
5
3909 G15
VVOUT
VLEDX
Regulation
OUT –– V
LEDX REGULATION
Switch Current Limit
1.20
1.18
1.40
1.35
1.30
1.25
1.20
1.15
–0.8
–1.0
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 G16
19.9
19.7
1.45
0.4
20.0
19.8
RISET = 100k
1
20.1
3909 G14
1.50
VOUT = 24V, VLEDx = 22.9V
VCTRL = 2.0V
RISET = 49.9k
RISET = 16.7k
RISET = 49.9k
20
0
LED Current
20.4
RISET = 33.2k
30
10
VOUT – VLEDX REGULATION (V)
LED CURRENT MATCHING (%)
0.6
35
RISET = 24.9k
40
LED Current Matching
(Normalized to 2-String Average)
0.8
VOUT = 24V
VCTRL = 2.0V
50
3909 G13
1.0
15
20
25
30
VOUT PIN VOLTAGE (V)
vs (VCurrent
LED
vs (V)OUT - VLEDx)
OUT – VLEDX
60
RISET = 20.0k
RISET = 24.9k
40
10
SWITCH CURRENT LIMIT (A)
LED CURRENT (mA)
50
35
LED Current
LED CURRENT (mA)
VOUT = 24V
VLEDx = 22.9V
CTRL PIN VOLTAGE RISING
40
15 VOUT = 24V
VLEDx = 22.9V
10
VCTRL = 2.0V
5
10 20 30 40 50 60 70 80 90 100 110
RISET (kΩ)
LED CURRENT (mA)
LED Current
vs CTRL Pin Voltage
60
45
20
2.0
88.0
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
70
LED Current
Current vs
vs R
RISET
ISET
LED
60
10.0
LED CURRENT (mA)
VLEDX PIN SHORT THRESHOLD (V)
MAXIMUM SWITCHING DUTY CYCLE (%)
92.0
0
TA = 25°C, unless otherwise noted.
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
1.10
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 G17
1.00
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 G18
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LT3909
TYPICAL PERFORMANCE CHARACTERISTICS
800
Switch RDS(ON)
LED Current Waveforms
40,000:1 PWM Dimming (100Hz)
Schottky Forward Voltage
1.2
1.0
SCHOTTKY FORWARD DROP (V)
700
RESISTANCE (mΩ)
TA = 25°C, unless otherwise noted.
600
500
400
300
I(LED1)
20mA/DIV
0.8
0.6
I(LED2)
20mA/DIV
0.4
PWM
2V/DIV
0.2
200
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
0
400ns/DIV
0
0.2
3909 G19
0.4
0.6
0.8
1.0
FORWARD CURRENT (A)
FRONT PAGE APPLICATION CIRCUIT
VIN = 12V
1.2
3909 G20
Average LED Current
vs PWM On-Time (100Hz)
LED Current Waveforms
90% PWM Dimming (100Hz)
Average LED Current
vs Low PWM On-Time (100Hz)
44
5.0
FRONT PAGE APPLICATION CIRCUIT
40 V = 12V
IN
36
I(LED2)
20mA/DIV
PWM
2V/DIV
2ms/DIV
FRONT PAGE APPLICATION CIRCUIT
VIN = 12V
3909 G22
4.5
28
24
20
16
12
3.0
2.5
2.0
1.5
1.0
4
0.5
0
1
2
3 4 5 6 7
PWM ON-TIME (ms)
8
9
10
3909 G23
VOUT Transient Response in Fault
Event with Mismatched LED Strings
VOUT
AC–COUPLED
2V/DIV
3.5
8
0
VOUT SMOOTHLY ADAPTS
TO VF of LED1 STRING
I(LED1) = 40mA
I(LED2)
40mA/DIV
LED2 PIN SHORT TO GND
FAULT
12V/DIV
0
0 100 200 300 400 500 600 700 800 900 1000
PWM ON-TIME (ns)
3909 G24
VOUT Regulated to OVP Level in
Fault Event
VOUT
AC-COUPLED
2V/DIV
LED1 PIN SHORT TO GND
I(LED1)
40mA/DIV
I(LED1)
40mA/DIV
FRONT PAGE APPLICATION CIRCUIT
VIN = 12V
4.0
32
LED CURRENT (µA)
LED CURRENT (mA)
I(LED1)
20mA/DIV
3909 G21
LED2 PIN SHORT TO GND
I(LED2)
40mA/DIV
FAULT
12V/DIV
400µs/DIV
FRONT PAGE APPLICATION CIRCUIT
VIN = 12V, VF(LED2) – VF(LED1) = 3.2V
3909 G25
40µs/DIV
FRONT PAGE APPLICATION CIRCUIT
VIN = 12V
3909 G26
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7
LT3909
PIN FUNCTIONS
INTVCC (Pin 1): Internal 3.0V Regulator Bypass Pin. The
internal gate driver and control circuits are powered from
this voltage. Use this pin only for PWM pin connection,
resistor divider setting CTRL pin voltage, and pull-up resistor at FAULT pin. When used, the total current drained
from the INTVCC pin should be kept 1.1A
CC
1.215V
A2
–
13
2
SOFT
START
GND
VIN
–
+
M2
MAX
SELECTOR
1.0V
THERMAL
FOLDBACK
UVLO(+) = 2.75V
UVLO(–) = 2.60V
R1
R2
–
+
–
A4
1.245V (+)
1.215V (–)
10
LED2
9
INTVCC_UVLO
INTVCC
600k
PWM_INT
TJ > 170°C
A3
EN/UVLO
1.3V
1.215V
+
3
+
–
LED1
UVLO
–
1
CTRL_LOW
GM1
SS
CSS
M3
RFB1
S/H
+
RSENSE
6
GM2
A1
UVLO
FB
–
VC
–
Q
1-SHOT
SLOPE
OSCILLATOR
M1
11
+
+
+
+
–
A5
M5
FAULT
80mV
LED OPEN
AND SHORT
DETECTION
CTRL_LOW
8
M6
PWM_INT
M4
PWM_INT VOUT
7
PWM
5
CTRL
4
ISET
3909 BD
RISET
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9
LT3909
OPERATION
The LT3909 integrates a constant-frequency, currentmode boost converter with two high-side current sources.
Each high-side current source regulates and modulates
the current in each LED string. For optimum efficiency,
VOUT is regulated to the lowest possible voltage required
to maintain those regulated currents in each LED string.
Operation is best understood by referring to the typical
application circuit on the front page and the Block Diagram.
Start-Up
The LT3909 enters shutdown mode and draws almost
zero current when the EN/UVLO pin is lower than 0.6V
(typical). Once the EN/UVLO pin is above 0.6V, the part
starts to wake up internal bias currents, generates various
references, and charges the INTVCC pin towards a 3.0V
regulation voltage.
For the LT3909 to exit undervoltage lockout (UVLO) mode,
EN/UVLO pin needs to be above 1.245V and INTVCC pin
needs to be above 2.75V. A 1.215V falling threshold on
the EN/UVLO pin, combined with an EN/UVLO pin current
hysteresis, allows a programmable resistor divider from
VIN to EN/UVLO to define the UVLO threshold for VIN.
EN/UVLO pin current switches from 2.0μA to 0μA when
EN/UVLO pin voltage exceeds 1.245V.
After exiting UVLO, if the PWM pin voltage is high, the
boost converter enables switching action, and the internal
soft-start node is charged up, thereby smoothly ramping
up the inductor current. During the soft-start period,
the switching frequency also gradually ramps up from
approximately 15% of full-scale, and immediately steps
up to 100% of full-scale once the soft-start period ends.
Constant Current Source
Each string has a local current source regulating its own
LED current. These high-side current sources are connected between the VOUT pin and each LED pin. With the
top LED in each string (anode) connected to the LED pin
and the bottom LED (cathode) connected to any available
ground, this high-side current source structure allows a
simple one wire LED connection per LED string.
LED Current Modulation and Regulation
LED current programming and dimming is achieved using the ISET, CTRL and PWM pins. A single resistor at the
ISET pin programs LED current between 10mA to 60mA.
Analog dimming of LED brightness is achieved using the
CTRL pin below 1V. PWM dimming of LED brightness is
achieved by controlling the duty cycle of the PWM pin.
LED pins can be paralleled to achieve higher LED currents.
For applications requiring only 1 string of LEDs, parallel
both LED pins and program for half of the full current.
Fault Detection and Protection
The LT3909 monitors the voltage drop across each highside current source and also each LED pin voltage. If an
LED string has an open-LED fault [(VOUT – VLEDx) < 0.3V]
or an LED-short-to-GND fault (VLEDx < 0.25 • VOUT), the
FAULT flag is pulled low, and the remaining LED string is
not affected.
For LED protection, the LT3909 CTRL pin allows an LED
current derating curve as a function of LED ambient
temperature. An NTC resistor placed close to the LEDs
decreases the CTRL pin voltage and hence decreases LED
current as LED ambient temperature increases (see Figure
5). The LT3909 also features an internal thermal regulation
loop to regulate its own maximum junction temperature
by derating LED currents.
Boost Converter Operation
The LT3909 has an internal N-channel DMOS power switch
and an internal Schottky diode to generate a boosted output
voltage VOUT using a single inductor and an output capacitor.
For optimum efficiency, VOUT is regulated to the lowest
possible voltage required to maintain regulated current in
each LED string. This is achieved by the GM1 loop, which
monitors and regulates the lower voltage drop across the
two high-side current sources (between VOUT and each LED
pin) to 1.3V. If one of the LED strings has an open-LED or
LED-short-to-GND fault, the LT3909 regulation loop will
ignore the LED pin with the fault.
3909fb
10
For more information www.linear.com/LT3909
LT3909
OPERATION
When both of the LED strings have either an open-LED or
LED-short-to-GND fault, VOUT charges up until a user programmable OVP (overvoltage protection) level is reached.
This programmable OVP level allows the user to protect
against LED damage when the LED strings are open and
then reconnected. The OVP regulation is implemented
by the GM2 loop, which regulates the FB pin voltage to
1.215V. The GM2 loop is also activated during the PWM
low periods when PWM Dimming is applied. During PWM
high, VOUT is regulated to the optimum level for the LED
driver. At the PWM low edge, the FB pin voltage is sampled
to store that optimum VOUT level. VOUT is then regulated
during PWM off time to maintain the optimum VOUT level.
This regulation of VOUT during PWM off time prevents
VOUT droop due to leakages. This allows fast LED current
recovery at the rising edge of the PWM dimming pulse.
Since the LT3909 boost converter uses a peak current
mode topology, the VC node voltage determines the peak
current in the inductor and hence the duty cycle of the SW
pin switching waveform. The basic loop uses a pulse from
an internal oscillator to set an RS flip-flop and turn on the
internal power switch. Current increases in the switch and
the inductor until the VC commanded peak switch current
is exceeded and the switch is then turned off. As with
all peak current mode converters, slope compensation
is added to the control path to ensure stability for duty
cycles above 50%. The LT3909 features an accurate 1.1A
cycle-by-cycle current limit for the protection of the internal
switch, the internal Schottky diode and the inductor. If this
current limit is exceeded, the SR latch is reset regardless
of the state of A1.
APPLICATIONS INFORMATION
Inductor Selection
Inductors with values between 3.3µH and 10µH will suffice
for most LT3909 applications. Choose an inductor that can
handle the necessary peak current without saturating. Also
ensure that the inductor has low core losses at 2MHz and a
low DCR (copper-wire resistance) to obtain the best efficiency.
Table 1 lists several inductors that work well with the
LT3909. However, there are many other manufacturers and
inductors that can be used. Consult each manufacturer for
more detailed information and their entire range of parts.
Input and Output Capacitor Selections
The input capacitor for the LT3909 boost converter will
supply the transient input current of the power inductor.
A 50V, 1.0μF input capacitor is sufficient for most LT3909
applications. Use only X5R or X7R ceramic capacitors to
minimize variation over voltage and temperature. If the
IC is required to operate near the minimum operational
VIN, a larger capacitor value may be required. This is to
prevent excessive input voltage ripple from causing dips
below the minimum operating input voltage. The output
capacitor at the LT3909 boost converter output should
be a low ESR ceramic capacitor, to minimize output ripple
voltage. Use only X5R or X7R ceramic capacitors as they
retain their capacitance over wider voltage and temperature
ranges than other dielectrics. A 50V, 1µF output capacitor
is recommended for VOUT < 20V applications, and a 50V,
2.2µF output capacitor for VOUT > 20V applications. Table 2
shows a list of several recommended 50V capacitors.
Consult the manufacturer for more detailed information
and their entire range of parts.
Schottky Diode
The LT3909 has a built-in Schottky diode. The internal
Schottky saves PCB area in space constrained applications. For better efficiency, an external Schottky diode can
be connected between the SW node and the VOUT node.
It is important to use a properly rated Schottky diode
that can handle the peak switch current of the LT3909.
In addition, the Schottky diode must have a breakdown
voltage of at least 40V along with a low forward voltage
in order to achieve higher efficiency. One recommended
external Schottky diode for the LT3909 is the Diodes Inc.
SBR1A40S3.
3909fb
For more information www.linear.com/LT3909
11
LT3909
APPLICATIONS INFORMATION
Shutdown and Programming Undervoltage Lockout
The LT3909 has an accurate 1.215V shutdown threshold at the EN/UVLO pin. This threshold can be used in
conjunction with a resistor divider from the system input
supply to define an accurate undervoltage lockout (UVLO)
threshold for the system (Figure 1). An internal hysteresis
voltage (30mV) and current (2.0μA) at the EN/UVLO pin
allows programming of hysteresis voltage for this UVLO
threshold. Calculation of the turn on/off thresholds for a
system input supply using the LT3909 EN/UVLO pin is
as follows:
R1
VSUPPLY(OFF) = 1.215V • 1+
R2
R1
VSUPPLY(ON) = 1.245V • 1+ + (2.0µA • R1)
R2
An open drain transistor can be added to the resistor divider
network at the EN/UVLO pin to independently control the
turn-off of the LT3909.
INTVCC Regulator Bypassing and Operation
The INTVCC pin is the output of an internal linear regulator driven from VIN and is the supply for the internal gate
driver and control circuits. The INTVCC pin should be
bypassed with a 4V or higher rated 1.0µF low ESR, X7R
or X5R ceramic capacitor to ensure stability and provide
charge for the gate driver. For VIN ≥ 3.3V, the INTVCC pin
provides a regulated 3V supply. The INTVCC regulator has
an undervoltage lockout which prevents gate driver switching until INTVCC reaches 2.75V and maintains switching
until INTVCC falls below 2.6V.
Table 1. Recommended Inductors
PART
L
(μH)
MAX CURRENT
DCR RATING
(Ω)
(A)
VENDOR
74437324100
74437324082
74437324068
74437324056
74437324047
74437324033
10
8.2
6.8
5.6
4.7
3.3
0.243
0.180
0.172
0.125
0.105
0.076
1.5
1.6
1.75
2.0
2.2
2.5
Würth Elektronik
www.we-online.com
LPS5030-103MR
LPS5030-822MR
LPS5030-682MR
LPS5030-562MR
10
8.2
6.8
5.6
0.127
0.125
0.099
0.089
1.4
1.6
1.6
1.8
Coilcraft
www.coilcraft.com
VLCF5020T-100MR87
VLF5014ST-6R8M1R4
VLF5014ST-4R7M1R7
10
6.8
4.7
0.182
0.2
0.12
1.56
1.6
2.0
TDK
www.tdk.com
Table 2. Recommended Output Capacitors
PART
C (μF) VOLTAGE TEMP. VENDOR
C2012X7R1H105K085AC
1.0
50V
X7R
C3216X7R1H225K160AB
2.2
50V
X7R
GJ821BR71H105KA12#
1.0
50V
X7R
GRM31CR71H225KA88#
2.2
50V
X7R
TDK
www.tdk.com
Murata
www.murata.com
The INTVCC regulator is not intended to supply external
circuitry, except for PWM pin connection, resistor divider
setting CTRL pin voltage, and pull-up resistor at the FAULT
pin. When used, the total current drained from the INTVCC
pin should be kept 1.1V)
RISET
See Table 3 for resistor values and corresponding programmed LED current.
Table 3. LED Current vs RISET
(1% Resistors Unless Otherwise Noted)
LED CURRENT PER STRING (mA)
RISET (kΩ)
10
100
20
49.9
30
33.2
40
24.9
50
20.0
60
16.7 (0.1% Resistor)
Analog Dimming
The LT3909 allows for LED brightness control by analog
dimming or by PWM dimming. Analog dimming uses the
CTRL pin voltage below 1V to reduce LED current. For a
CTRL pin voltage below 1V, the current in each LED pin
is given by:
ILEDx ≈ CTRL •
1000
, (0.1V < CTRL < 1V)
RISET
ILEDx = 0 for CTRL < 80mV
When changing the CTRL pin voltage for analog dimming,
especially when ramping up, use 80mV for ~4µs.
2) In the case of actual open-LED or LED-short-to-GND
faults, VOUT has reached 95% of its programmed OVP
level.
Once either condition is met, the LT3909 enables the FAULT
flag and correctly reports LED-short-to-GND faults. Also
at this time the switching frequency immediately steps up
to 100% of full-scale.
It is important to note that even though the FAULT pin is
disabled during start-up, a true LED-short-to-GND fault
will keep the LED current source off to protect that current
source. The LT3909 correctly reports actual open-LED
faults ~12ms after the very first PWM rising edge.
3909fb
For more information www.linear.com/LT3909
15
LT3909
APPLICATIONS INFORMATION
To avoid errant faults during PWM dimming edges (where
LED pins can possibly ring and trip fault detection levels), the LT3909 only monitors/updates fault conditions
during PWM high (and only after a 1μs blanking following each PWM rising edge). Similarly, the LT3909 only
monitors/updates fault conditions during CTRL higher
than the latch-off threshold (and only after a 1µs blanking
following the CTRL rising edge).
When an LED-short-to-GND fault is detected, the current
source for that string is immediately turned off. If only one
string has a fault, the LT3909 regulation loop will regulate
VOUT to the optimum level for the remaining valid string. If
both strings have faults, the regulation loop will regulate
VOUT to the programmed OVP level.
Programming Maximum VOUT (Regulated):
Overvoltage Protection (OVP) Level
If the LED display faults open, VOUT will rise. When the
display is reconnected, the LEDs and their high-side current sources must be protected from excessively high VOUT
levels. To achieve this protection the LT3909 allows an
overvoltage protection (OVP) level to be programmed for
VOUT. During an open display fault, VOUT will be regulated
to this OVP level. The OVP level must be programmed high
enough to drive the largest expected LED string voltage
and to allow at least 1.3V across each high-side current
source. This ideal level would represent the largest VOUT
in regulation during a connected display, given by,
VOUT(REG)(MAX) = 1.3V + N • VF(MAX)
N = the number of diodes in each string
VF(MAX) = the maximum expected forward voltage drop
of the LEDs
As stated in the LED Open and Short Circuit section, the
LT3909 during startup does not monitor the LED pins for
open-LED faults until each LED current source has 1.3V
across it or, in the case of an actual open-LED fault, until
VOUT has risen to 95% of its programmed OVP level. For
this startup procedure to operate correctly, 95% of the
programmed OVP level must be high enough to satisfy
the VOUT regulation equation above. Hence OVP should
be programmed to satisfy:
Required VOUT(OVP) =
VOUT(REG)(MAX)
0.95
= (1.3V + N • VF(MAX) ) / 0.95
OVP is programmed using a resistor divider from VOUT
to GND connected to the FB pin. The required OVP level
should be calculated from the equation above. Once known,
OVP resistors can be programmed by,
R
Programmed VOUT(OVP) = 1.215V • 1 + FB2
RFB1
Thermal Protection
The LT3909 contains a thermal regulation loop that limits
the internal junction temperature of the part. Since the
LT3909 topology consists of a single boost controller
with two linear current sources, any LED string voltage
mismatch will cause additional power to be dissipated
in the package. This topology provides excellent current
matching between LED strings and allows a single power
stage to drive a large number of LEDs, but at the price
of additional power dissipation inside the part (which
means a higher junction temperature). Being able to limit
the maximum junction temperature allows the benefits of
this topology to be fully realized. This thermal regulation
feature provides important protection at high ambient
temperatures, with the assurance that the LT3909 will
automatically protect itself and the LED strings.
The operation of the thermal loop is simple. As the ambient temperature increases, so does the internal junction
temperature of the part. Once the junction temperature
reaches approximately 160°C, the LT3909 begins to
linearly reduce the LED current, to maintain the junction
temperature at around 160°C. If the junction temperature
continues to rise past 160°C, LED current will be reduced
to approximately 5% of full LED current. The LT3909
stops switching when thermal shutdown is actuated (approximately 170°C).
3909fb
16
For more information www.linear.com/LT3909
LT3909
APPLICATIONS INFORMATION
Thermal Considerations
For higher ambient temperatures, care should be taken in
the layout of the PCB to ensure good heat sinking of the
LT3909. The exposed pad on the bottom of the package
must be soldered to a ground plane. This ground should be
tied to large copper layers below with thermal vias; these
layers will spread heat dissipated by the LT3909. Placing
additional vias can reduce thermal resistance further.
Power dissipation within the LT3909 can be estimated
by calculating the total power loss from an efficiency
measurement and subtracting the inductor loss. The die
temperature is calculated by multiplying the LT3909 power
dissipation by the thermal resistance of the package (see
the Pin Configuration). See the Thermal Protection section.
Circuit Layout Considerations
As with all switching regulators, careful attention must be
given to PCB layout and component placement to achieve
optimal thermal, electrical and noise performance. The
exposed pad of the LT3909 is the only ground connection
for the IC. The exposed pad should be soldered to a continu-
ous copper ground plane underneath the device to reduce
die temperature and maximize the power capability of the
IC. An analog ground is connected to the exposed pad near
the CTRL and FB pins. ISET, CTRL and FB components
should be connected to an area of ground copper near
these pins. The internal power switch current escapes
through the exposed pad near the SW pin. This area of
copper should be the power ground (PGND) connection for
the inductor input capacitor, INTVCC capacitor and output
capacitor. A separate bypass capacitor for the VIN pin of
the IC may be required close to the VIN pin and connected
to the copper area associated with analog ground. To reduce the effects of both radiated and conducted noise, the
length and area of the copper trace for the SW pin should
be kept as small as possible. Use a ground plane under
the switching regulator to minimize interplane coupling.
The optional Schottky diode and output capacitor should
be placed as close as possible to the SW pin to minimize
this high switching frequency path. To achieve the best
PWM dimming ratio, minimize the trace capacitance on
each LED pin.
3909fb
For more information www.linear.com/LT3909
17
LT3909
TYPICAL APPLICATIONS
2-String × 20mA Driver for Five White LEDs/String
OPTIONAL
1.0
1µF
VIN
SW
61.9k
LED1
LED2
FAULT
PWM
PWM DIMMING
ANALOG DIMMING
FB
LT3909
EN/UVLO
CTRL
INTVCC
GND
1µF
1M
VOUT
LED CURRENT MATCHING (%)
4.7µH
VIN
3V TO 5V
LED Current Matching (Normalized
to 2-String Average)
100k
ISET
VIN
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
49.9k
1µF
VIN = 3.0V
0.8 VCTRL = 2.0V
VPWM = 2.0V
0.6
3909 TA02b
3909 TA02a
2-String × 50mA Driver for Five White LEDs/String
LED Current Waveforms
20,000:1 PWM Dimming (100Hz)
10µH
VIN
10V
TO
14V
1µF
VIN
SW
590k
100k
1M
VOUT
ANALOG DIMMING
EN/UVLO
PWM
CTRL
INTVCC
61.9k
LED1
LED2
FAULT
GND
1µF
I(LED1)
25mA/DIV
FB
LT3909
PWM
DIMMING
VIN = 12V
VCTRL = 2.0V
1µF
ISET
I(LED2)
25mA/DIV
100k
PWM
2V/DIV
VIN
400ns/DIV
3909 TA03b
20k
3909 TA03a
3909fb
18
For more information www.linear.com/LT3909
LT3909
TYPICAL APPLICATIONS
2-String × 60mA Driver for Six White LEDs/String
LED Current Waveforms
20,000:1 PWM Dimming (100Hz)
6.8µH
VIN
10V
TO
14V
1µF
VIN
SW
976k
VOUT
232k
ANALOG DIMMING
52.3k
EN/UVLO
PWM
LED1
LED2
FAULT
CTRL
INTVCC
GND
I(LED1)
30mA/DIV
FB
LT3909
PWM
31.6k DIMMING
VIN = 12V
VCTRL = 2.0V
2.2µF
ISET
I(LED2)
30mA/DIV
100k
PWM
2V/DIV
VIN
400ns/DIV
3909 TA04b
16.7k (0.1%)
1µF
3909 TA04a
1 String × 100mA Driver for Ten White LEDs
LED Current Waveforms
20,000:1 PWM Dimming (100Hz)
10µH
VIN
10V
TO
14V
1µF
VIN
SW
VOUT
590k
100k
976k
FB
ANALOG DIMMING
EN/UVLO
PWM
CTRL
INTVCC
LED1
LED2
FAULT
GND
1µF
I(LED)
50mA/DIV
31.6k
LT3909
PWM
DIMMING
VIN = 12V
VCTRL = 2.0V
2.2µF
ISET
100k
PWM
2V/DIV
VIN
400ns/DIV
3909 TA05b
20k
10 LEDs •
•
•
3909 TA05a
3909fb
For more information www.linear.com/LT3909
19
LT3909
TYPICAL APPLICATIONS
2-String × 40mA Buck-Boost Mode Driver for Five White LEDs/String
VIN
3V TO 18V
VIN Transient Response
I(LED1)
20mA/DIV
6.8µH
1µF
VIN
SW
31.6k
CTRL
INTVCC
LED1
LED2
FAULT
GND
1µF
ISET
I(LED1) = 40mA
I(LED2) = 40mA
VOUT
10V/DIV
FB
LT3909
EN/UVLO
PWM
2.2µF
976k
VOUT
I(LED2)
20mA/DIV
VIN BETWEEN 3V AND 14V
VIN
10V/DIV
100k
VIN
1ms/DIV
3909 TA06a
3909 TA06b
Protection in High VIN Event
24.9k
VIN
15V/DIV
VOUT
10V/DIV
VIN RISES FROM 14V
TO 38V IN 1ms
VIN RECOVERS
I(LED1) + I(LED2)
80mA/DIV
IL
80mA/DIV
2ms/DIV
3909 TA06c
3909fb
20
For more information www.linear.com/LT3909
LT3909
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LT3909#packaging for the most recent package drawings.
DD Package
12-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1725 Rev A)
DD Package
12-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1725 Rev A)
0.70 ±0.05
3.50 ±0.05
2.10 ±0.05
2.38 ±0.05
1.65 ±0.05
PACKAGE
OUTLINE
0.25 ±0.05
0.45 BSC
2.25 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
3.00 ±0.10
(4 SIDES)
R = 0.115
TYP
7
0.40 ±0.10
12
2.38 ±0.10
1.65 ±0.10
PIN 1 NOTCH
R = 0.20 OR
0.25 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
6
0.200 REF
1
0.23 ±0.05
0.45 BSC
0.75 ±0.05
2.25 REF
0.00 – 0.05
(DD12) DFN 0106 REV A
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD AND TIE BARS SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
3909fb
For more information www.linear.com/LT3909
21
LT3909
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LT3909#packaging for the most recent package drawings.
MSE Package
12-Lead Plastic MSOP, Exposed Die Pad
MSE
Package
(Reference LTC
DWG
# 05-08-1666 Rev G)
12-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1666 Rev G)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 ±0.102
(.112 ±.004)
5.10
(.201)
MIN
2.845 ±0.102
(.112 ±.004)
0.889 ±0.127
(.035 ±.005)
6
1
1.651 ±0.102
(.065 ±.004)
1.651 ±0.102 3.20 – 3.45
(.065 ±.004) (.126 – .136)
12
0.65
0.42 ±0.038
(.0256)
(.0165 ±.0015)
BSC
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
0.35
REF
4.039 ±0.102
(.159 ±.004)
(NOTE 3)
0.12 REF
DETAIL “B”
CORNER TAIL IS PART OF
DETAIL “B” THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
7
NO MEASUREMENT PURPOSE
0.406 ±0.076
(.016 ±.003)
REF
12 11 10 9 8 7
DETAIL “A”
0° – 6° TYP
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
1.10
(.043)
MAX
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
1 2 3 4 5 6
0.650
(.0256)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL
NOT EXCEED 0.254mm (.010") PER SIDE.
0.86
(.034)
REF
0.1016 ±0.0508
(.004 ±.002)
MSOP (MSE12) 0213 REV G
3909fb
22
For more information www.linear.com/LT3909
LT3909
REVISION HISTORY
REV
DATE
DESCRIPTION
A
04/16
Clarified Title, Description and Features
Clarified Absolute Maximum Ratings
Removed H-Grade Parts from Order Information
Clarified Electrical Specifications
Clarified Notes
Clarified Graphs
Clarified LED Current Waveforms Graph
Clarified Pin Functions
Clarified Block Diagram
Clarified LED Current Modulation/Regulation and Boost Converter Sections
Clarified Table 3
Clarified LED Open and Short Circuit Section
Clarified Programming Maximum VOUT Section
Clarified Applications Schematics
PAGE NUMBER
B
08/16
Revised graph G13
Revised ISET resistance tolerance
1
2
2
3
4
6
7
8
9
10
13
15
16
18, 19, 22
6
13, 19
3909fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
For more
information
www.linear.com/LT3909
23
LT3909
TYPICAL APPLICATION
2-String × 20mA, 2MHz LED Driver for Ten White LEDs/String
LED Current Matching (Normalized
to 2-String Average)
10µH
1.0
1µF
VIN
SW
976k
VOUT
402k
2.2µF
0.8
LED CURRENT MATCHING (%)
VIN
7V TO 36V
FB
31.6k
LT3909
EN/UVLO
130k
PWM
CTRL
INTVCC
LED1
LED2
FAULT
GND
ISET
100k
VIN
10 LEDs
PER STRING
49.9k
1µF
•
•
•
•
•
•
VIN = 12V
VPWM = 2.0V
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3909 TA07b
3909 TA07a
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT3476
Quad Output 1.5A, 2MHz High Current LED Driver with
5,000:1 Dimming
VIN(MIN) = 2.8V, VIN(MAX) = 16V, VOUT(MAX) = 36V, 5,000:1 True Color
PWM Dimming, ISD < 10μA, 5mm × 7mm QFN-38
LT3496
Triple Output 750mA, 2.1MHz High Current LED Driver with VIN(MIN) = 3.0V, VIN(MAX) = 30V, VOUT(MAX) = 40V, 3,000:1 True Color
PWM Dimming, ISD < 1μA, 4mm × 5mm QFN-28, TSSOP-28E
3,000:1 Dimming
LT3591
Constant Current, 1MHz, White LED Boost Regulator with
Integrated Schottky Diode
VIN(MIN) = 2.5V, VIN(MAX) = 12V, VOUT(MAX) = 40V, IQ = 4mA, 80:1 True
Color PWM Dimming, ISD < 11μA, 2mm × 3mm DFN-8
LT3595A
45V, 2MHz Buck 16-Channel 50mA LED Driver
VIN(MIN) = 4.5V, VIN(MAX) = 45V, VOUT(MAX) = 45V, 5,000:1 True Color
PWM Dimming, ISD < 40μA, 5mm × 9mm QFN-56
LT3598
44V, 1.5A, 2.5MHz Boost 6-String 20mA LED Driver
VIN(MIN) = 3.2V, VIN(MAX) = 30V, VOUT(MAX) = 44V, 3,000:1 True Color
PWM Dimming, ISD < 1μA, 4mm × 4mm QFN-24, TSSOP-24E
LT3599
44V, 2A, 2.1MHz Boost 4-String 120mA LED Driver
VIN(MIN) = 3.1V, VIN(MAX) = 30V, VOUT(MAX) = 44V, 3,000:1 True Color
PWM Dimming, ISD < 1μA, 5mm × 5mm QFN-32, TSSOP-28E
LT3745
16-String 50mA LED Driver with Buck Controller
VIN(MIN) = 6.0V, VIN(MAX) = 55V, VOUT(MAX) = 36V, 0.5μs Minimum PWM
Dimming On-Time, ISD < 2μA, 6mm × 6mm QFN-40
LT3754
16-String × 50mA LED Driver
VIN(MIN) = 6.0V, VIN(MAX) = 40V, VOUT(MAX) = 45V, 3,000:1 True Color
PWM Dimming, ISD < 10μA, 5mm × 5mm QFN-32
LT3760
8-String × 100mA LED Driver
VIN(MIN) = 6.0V, VIN(MAX) = 40V, VOUT(MAX) = 45V, 3,000:1 True Color
PWM Dimming, ISD < 10μA, TSSOP-28E
3909fb
24 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LT3909
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LT3909
LT 0816 REV B • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2015
工商网监
湘ICP备2023018690号
