LINER LT3475 8-channel ã 100ma led driver Datasheet

LT3760
8-Channel × 100mA
LED Driver
Description
Features
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The LT®3760 is an 8-channel LED driver with a step-up
DC/DC controller capable of driving up to 45V of LEDs.
Each channel contains an accurate current sink with ±2%
current matching. Channels follow a master programmable
current to allow between 20mA to 100mA of LED current
per string. Channels can be paralleled for higher LED
current. Output voltage adapts to variations in LED VF for
optimum efficiency and open LED faults do not affect the
operation of connected LED strings.
Up to 45V of LEDs × 100mA, 8-Channel LED Driver
Wide Input Range : 6V to 40V (4.5V to 13V,
VIN Connected to INTVCC)
±2% LED Current Matching at 40mA (Typ ±0.7%)
Up to 3000:1 True Color PWM™ Dimming Range
Single Resistor Sets LED Current (20mA to 100mA)
LED Current Regulated Even for PVIN > VOUT
Output Adapts to LED VF for Optimum Efficiency
Fault Flag + Protection for Open LED Strings
Protection for LED Pin to VOUT Short
Parallel Channels for Higher LED Current
Programmable LED Current Derating vs Temperature
Accurate Undervoltage Lockout Threshold with
Programmable Hysteresis
Programmable Frequency (100kHz to 1MHz)
Synchronizable to an External Clock
The LT3760 allows a PWM dimming range up to 3000:1
and an analog dimming range up to 25:1. Operating
frequency can be programmed from 100kHz up to 1MHz
using a single resistor or synchronized to an external clock.
Additional features include: programmable maximum
VOUT for open LED protection, a fault flag for open LED,
programmable LED current derating vs temperature, micropower shutdown and internal soft-start. The LT3760 is
available in a thermally enhanced 28-pin TSSOP package.
Applications
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Automotive, Notebook and TV Monitor Backlighting
L, LT, LTC and LTM, Linear Technology and the Linear logo 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. Protected by U.S.
Patents, including 7199560, 7321203.
Typical Application
Worst-Case Channels LED Current Matching
(Normalized to 8-Channel Average)
92% Efficient, 36W Backlight LED Driver
4.7µF
VIN
8V TO 14V
10µH
4.7µF
499k
4.7µF
VIN
INTVCC
5×
2.2µF
GATE
••••
SENSE
SHDN/UVLO
0.015Ω
40.2k
VOUT
PWM
LED1
LED2
•
•
•
•
LED7
LED8
LT3760
REF
20k
TSET
30.9k
•
•
•
PGND
CTRL
11k
20k
OVPSET
GND RT
FAULT
ISET
39.2k
1MHz
5.76k
VC
0.8
UP TO 45V OF LEDs PER STRING
•
•
•
•
•
•
•
LED CURRENT MATCHING (%)
PVIN
20V TO 36V
0.4
0.0
–0.4
RISET = 14.7k (I(LED) = 40mA)
–0.8
0
25
100
–50 –25
50 75
JUNCTION TEMERATURE (°C)
•
• 8 CHANNELS × 100mA
•
•
125
3760 TA01
100k
3760 TA01
VIN
SYNC
10k
2.2nF
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LT3760
Absolute Maximum Ratings
Pin Configuration
(Note 1)
TOP VIEW
VOUT, LED1-8.............................................................60V
VIN, SHDN/UVLO, FAULT............................................40V
INTVCC....................................................................... 13V
INTVCC above VIN................................................... +0.3V
PWM, CTRL, SYNC......................................................6V
VC ................................................................................3V
VREF , RT, ISET, TSET, OVPSET........................................2V
SENSE.......................................................................0.4V
Operating Junction Temperature Range
(Notes 2,3)..............................................-40°C to 125°C
Storage Temperature Range...................-65°C to 150°C
Lead Temperature (Soldering, 10 sec).................... 300°C
CTRL
1
28 OVPSET
TSET
2
27 PWM
VREF
3
26 VC
ISET
4
25 RT
NC
5
24 GND
LED1
6
23 LED8
LED2
7
LED3
8
LED4
9
20 LED5
PGND 10
19 PGND
SENSE 11
18 VOUT
GATE 12
17 SYNC
INTVCC 13
VIN 14
29
PGND
22 LED7
21 LED6
16 FAULT
15 SHDN/UVLO
FE PACKAGE
28-LEAD PLASTIC TSSOP
TJMAX = 125°C, θJA = 28°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3760EFE#PBF
LT3760EFE#TRPBF
LT3760FE
28-Lead Plastic TSSOP
–40°C to 125°C
LT3760IFE#PBF
LT3760IFE#TRPBF
LT3760FE
28-Lead Plastic TSSOP
–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.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
3760fc
2
LT3760
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT = 6V, RISET = 14.7k unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
4.2
5.5
4.5
6.0
V
V
13
40
V
V
INPUT BIAS, REFERENCE
Minimum Operational VIN (To Allow GATE Switching)
VC = 1.5V
VIN = INTVCC (Shorted)
VIN ≠ INTVCC
l
l
Operational VIN
VIN = INTVCC (Shorted)
VIN ≠ INTVCC
VIN Quiescent Current
CTRL = 0.1V, PWM = 0V
CTRL = 0.1V, PWM = 1.5V, (Not Switching)
LED1–8 = 1.2V
4.2
9.5
5.7
12
mA
mA
VIN Shutdown Current (VIN ≠ INTVCC) (Not Shorted)
SHDN/UVLO = 0V, VIN =6V
SHDN/UVLO = 0V, VIN = 40V
0.1
2
10
µA
µA
VIN Shutdown Current (VIN = INTVCC (Shorted))
SHDN/UVLO = 0V, VIN = INTVCC = 4.5V
SHDN/UVLO = 0V, VIN = INTVCC = 13V
10
20
20
40
µA
µA
SHDN/UVLO Threshold (Micropower) (Falling) (VSD)
IVIN < 20µA
SHDN/UVLO Threshold (UVLO) (Falling)
(Stop Switching) (VUV)
4.5
6
l
0.3
0.7
l
1.414
1.476
1.538
V
V
SHDN/UVLO Pin Current
SHDN/UVLO = VUV - 50mV
SHDN/UVLO = VUV + 50mV
l
1.6
2.4
0
3.2
µA
µA
VREF Voltage
IVREF = 0µA
l
1.450
1.485
1.524
V
VREF Line Regulation
IVREF = 0µA, 6V < VIN < 40V
0.01
0.05
%/V
VREF Load Regulation
0 < IVREF < 150µA (Max)
2
mV
OSCILLATOR
Frequency: fOSC (100kHz)
RT = 523k
l
92
101
112
kHz
Frequency: fOSC (1MHz)
RT = 39.2k
l
0.90
1
1.10
MHz
fOSC (1MHz) Line Regulation
RT = 39.2k, 6V < VIN < 40V
0.1
0.2
%/V
250
250
nS
nS
2.2
V
RT Pin Voltage
RT = 39.2k
1.6
Minimum Off-Time
Minimum On-Time
(Note 5)
(Note 5)
170
190
SYNC Input High Threshold
SYNC Input Low Threshold
V
0.6
V
SYNC Input Current
SYNC = 0V
SYNC = 5V
0
25
µA
µA
SYNC Frequency Range
RT = 523k
RT = 39.2k
0.12
1.2
INTVCC Regulation Voltage
VIN = 12V
6.65
Dropout (VIN - INTVCC)
IINTVCC = 10mA
250
mV
INTVCC UVLO (+)
(Start Switching)
3.8
V
INTVCC UVLO (-)
(Stop Switching)
1.5
1.5
MHz
MHz
7.35
V
LINEAR REGULATOR (INTVCC)
INTVCC Current Limit
l
40
7
3.4
V
57
mA
4
µmhos
5
V/V
33
µmhos
OVP/LED ERROR AMPLIFIERS
Transconductance (OVP)
∆IVC = ±2.5µA
Voltage Gain (OVP)
Transconductance (LED)
∆IVC = ±2.5µA
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LT3760
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT = 6V, RISET = 14.7k unless otherwise noted.
PARAMETER
CONDITIONS
MIN
Voltage Gain (LED)
TYP
MAX
UNITS
45
V/V
VC Source Current (Out of Pin)
VC = 1.5V, VLEDx = 0.8V, OVPSET = 1.5V
10
µA
VC Sink Current (OVP)
VC = 1.5V, VLEDx = 0.8V, OVPSET = 0V
15
µA
VC Sink Current (LED)
VC = 1.5V, VLEDx = 1.2V, OVPSET = 1.5V
9
µA
VC Output High (clamp) (VCOH)
2.3
V
VC Output Low (clamp) (VCOL)
0.8
V
VC Switching Threshold (VCSW)
1.1
V
SENSE AMP
SENSE Input Current (Out of Pin)
65
SENSE Current Limit Threshold
Current Mode Gain
l
44
µA
60
6
∆V(VC)/∆V(SENSE)
SENSE Over Current Limit Threshold
52
l
90
100
mV
V/V
110
mV
40.1
41.9
mA
±0.7
±2
%
100.7
105.9
mA
LED CURRENT / CONTROL
ISET Pin Voltage
CTRL = 1.5V
LEDx Current (40mA) (RISET = 14.7k)
VLEDx = 1V, CTRL = 1.5V
LEDx Current Matching (40mA) (RISET = 14.7k)
VLEDx = 1V, CTRL = 1.5V
LEDx Current (100mA) (RISET = 5.76k)
VLEDx = 1V, CTRL = 1.5V
1.00
38.3
l
95.5
V
LED Pin Regulation Voltage
1.1
V
TSET Threshold
630
mV
ANALOG DIMMING
CTRL Input Current (Out of Pin)
CTRL = 1V
CTRL = 0.04V
40
50
LEDx Current (Dimming 25:1)
VLEDx = 1V, CTRL = 0.04V
1.6
200
200
nA
nA
mA
PWM DIMMING
PWM Input Low Threshold
0.7
PWM Input High Threshold
1
1.1
V
1.4
V
PWM Input Current
PWM = 1.5V
PWM = 6V
6
24
µA
µA
VOUT Pin Current in PWM Mode V(VOUT) = 60V
PWM = 1.5V, VLEDx = 1V
PWM = 0V, VLEDx = 1V
370
20
µA
µA
LEDx Leakage Current
(PWM = 0V)
VLEDx = 1V, VOUT = 12V
VLEDx = 50V, VOUT = 60V
0.1
0.1
1
2
µA
µA
FAULT DIAGNOSTICS
FAULT Output Sink Current
LED1 = Open, VFAULT = 0.3V
LEDx Short Threshold (VSH)
(VOUT – VLEDx)
VOUT = 12V
VOUT = 60V
0.3
0.6
6
6
mA
V
LED Open Detection Threshold
VOUT = 12V
0.5
V
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LT3760
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT = 6V, RISET =14.7k unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
GATE DRIVER
GATE Driver Output Rise Time
VIN = 12V, CL = 3300pF (Note 4)
30
nS
GATE Driver Output Fall Time
VIN = 12V, CL = 3300pF (Note 4)
30
nS
GATE Output Low
IGATE= 0µA
GATE Output High
INTVCC = VIN = 7V
IGATE = 0µA
6.95
V
VOUT Over Voltage Protection (OVP) Regulation Voltage
OVPSET = 0.22V
OVPSET = 1V
12.5
57
V
V
OVPSET Input Current (Out of Pin)
OVPSET = 0.22V, VOUT =12V
0.1
V
OUTPUT VOLTAGE
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 LT3760E 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
LED Current
vs CTRL Pin Voltage
110
RISET = 14.7k
100
90
0.4
0.0
–0.4
LED CURRENT (mA)
41
LED CURRENT (mA)
LED CURRENT MATCHING (%)
42
nA
TA = 25°C, unless otherwise noted.
LED Current
vs Junction Temperature
0.8
200
LT3760I is guaranteed to meet performance specifications from
-40°C to 125°C junction temperature.
Note 3: For Maximum Operating Ambient Temperature, see
Thermal Calculations in the Applications Information section.
Note 4: GATE rise and fall times are measured between 10% and 90%
of INTVCC voltage.
Note 5: See Duty Cycle Considerations in the Applications Information.
Typical Performance Characteristics
Worst-Case Channels LED
Current Matching
(Normalized to 8-Channel Average)
40
40
39
80
70
RISET =
5.76k
7.32k
9.76k
14.7k
29.4k
60
50
40
30
20
10
RISET = 14.7k (I(LED) = 40mA)
–0.8
–50 –25
0
25
100
50 75
JUNCTION TEMERATURE (°C)
125
3760 G01
38
–50
–25
0
50
25
75 100
JUNCTION TEMERATURE (°C)
125
3760 G02
0
0.00
0.25
0.50
0.75 1.00
CTRL (V)
1.25
1.50
3760 G03
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LT3760
Typical Performance Characteristics
1.525
(FRONT COVER
APPLICATION)
I(LEDx)
40mA/DIV
SHDN/UVLO Threshold
vs Junction Temperature
VREF vs Junction Temperature
1.525
SHDN/UVLO PIN VOLTAGE (V)
LED Current Waveforms
3000:1 PWM Dimming (100Hz)
TA = 25°C, unless otherwise noted.
1.505
VREF VOLTAGE (V)
1.505
1.485
1.485
I(L1)
1A/DIV
PWM
10V/DIV
1.465
1.465
3760 G04
5µs/DIV
1.445
–50
0
25
50
75 100
–25
JUNCTION TEMPERATURE (°C)
1.445
–50
125
–25
0
25
50
75 100
JUNCTION TEMERATURE (°C)
3760 G05
SHDN/UVLO Pin (Hysteresis)
Current vs Junction Temperature
VIN Shutdown Current
vs Junction Temperature
5
2.70
12
VIN = 6V, SHDN/UVLO = 0V
2.50
2.40
VIN CURRENT (mA)
2.60
3
2
1
2.30
2.20
–50
–25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
RISET = 14.7k
PWM = 1.5V, NO SWITCHING,
V(LED1-8) = 1.2V, CTRL = 0.1V
8
6
4
PWM = 0V, CTRL = 0.1V
2
0
–50
125
VIN Quiescent Current vs VIN
10
4
VIN CURRENT (µA)
SHDN/UVLO PIN CURRENT (µA)
2.80
–25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
3760 G07
0
125
0
5
10
15
3760 G08
VIN Quiescent Current
vs Junction Temperature
2.5
1100
5
PWM = 0V, CTRL = 0.1V
0
–50 –25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
125
3760 G10
1000
RT = 39.2k
950
900
–50 –25
40
35
3760 G09
2.0
1050
VC PIN VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
VIN CURRENT (mA)
PWM = 1.5V, NO SWITCHING,
V(LED1-8) = 1.2V, CTRL = 0.1V
30
VC HIGH CLAMP
VIN = 6V, RISET = 14.7k, CTRL = 0.1V
10
20 25
VIN (V)
VC High Clamp, Active
and Low Clamp Levels
vs Junction Temperature
Switching Frequency
vs Junction Temperature
15
125
3760 G06
1.5
VC ACTIVE (SWITCHING)
1.0
VC LOW CLAMP
0.5
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
125
3760 G11
0.0
–50 –25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
125
3760 G12
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LT3760
Typical Performance Characteristics
INTVCC vs Current,
Junction Temperature
7.0
TA = 25°C, unless otherwise noted.
INTVCC vs Current,
Junction Temperature
6.0
ILOAD = 10mA, 20mA, 30mA
INTVCC, UVLO(+), UVLO(–)
vs Junction Temperature
8
VIN = 6V, PWM = 0V
VIN = 12V
INTVCC (REGULATED)
7
6.9
6
6.8
INTVCC (V)
INTVCC (V)
5.00
ILOAD = 40mA
6.7
VIN = 8V, PWM = 0V
6.6
0
25
50
75 100
–50 –25
JUNCTION TEMPERATURE (°C)
4.5
–50
125
ILOAD = 10mA
ILOAD = 20mA
ILOAD = 30mA
ILOAD = 40mA
–25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
INTVCC Current Limit
vs Junction Temperature
SENSE PIN VOLTAGE (mV)
INTVCC CURRENT (mA)
55
50
45
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
57.5
60
55.0
50.0
INDUCTOR PEAK CURRENT THRESHOLD
(CYCLE-BY-CYCLE)
47.5
40
30
20
45.0
–25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
0
–50
125
0
25
50
75 100
–25
JUNCTION TEMPERATURE (°C)
120
225
100
200
TIME (ns)
GATE Rise/Fall Times
vs GATE Capacitance
250
6.50
125
3760 G18
MINIMUM ON-TIME
VIN = 8V
INTVCC = 7V
80
TIME (ns)
6.75
VOUT = 12V
OVPSET = 0.22V
10
Minimum ON and OFF Times
vs Junction Temperature
6.00
OVPSET = 1.0V
3760 G17
7.00
125
50
52.5
40.0
–50
125
VOUT = 60V
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
Overvoltage Protection (OVP)
Level vs Junction Temperature
70
VOUT - V(LEDx) Short Threshold
vs Junction Temperature
SHORT THRESHOLD (V)
INTVCC UVLO(–)
60.0
3760 G16
5.75
3
3760 G15
42.5
6.25
INTVCC UVLO(+)
SENSE Threshold
vs Junction Temperature
VIN = 6V, INTVCC = 0V
40
–50 –25
4
3760 G14
3760 G13
60
5
2
–50 –25
125
OVP (V)
INTVCC (V)
5.5
175
MINIMUM OFF-TIME
FALL TIME
60
150
40
125
20
RISE TIME
5.50
5.25
5.00
–50
–25
0
25
50
75 100
JUNCTION TEMPERATURE (°C)
125
3760 G18
100
–50
0
25
50
75 100
–25
JUNCTION TEMPERATURE (°C)
125
3760 G20
0
0
5
10
CGATE (nF)
15
20
3760 G21
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LT3760
Pin Functions
CTRL (Pin 1): CTRL pin voltage below 1V controls
LED current. CTRL voltage can be set by a resistor
divider from VIN, VREF or an external voltage source.
LED current derating versus temperature is achievable
if the voltage programmed at the CTRL pin has a negative
temperature coefficient using an external resistor divider
from VREF pin to GND with temperature dependent
resistance.
TSET (Pin 2): Programs LT3760 junction temperature
breakpoint past which LED current will begin to derate.
Program using a resistor divider from VREF to GND.
VREF (Pin 3): 1.485V Reference Output Pin. This pin can
supply up to 150µA. Can be used to program CTRL, TSET
and OVPSET pin voltages using resistor dividers to GND.
ISET (Pin 4): Resistor to GND Programs LED pin current.
See Table 6 in the Applications Information Section.
NC (Pin 5): No Connect. Okay to leave open or to connect
to GND.
LEDx (Pins 6 to 9, 20 to 23): 8 LED Driver Outputs. Each
output contains an open collector constant current sink. LED
currents are programmable from 20mA to 100mA using a
single resistor at the ISET pin. Connect the cathode of each
LED string to an LED pin. Connect the anode of each LED
string to VOUT. Channels can be paralleled for greater LED
current or individually disabled (connect LED to VOUT).
PGND (Pins 10, 19, Exposed Pad Pin 29): Power grounds
for the IC and the converter. The package has an exposed
pad (Pin 29) underneath the IC which is the best path for
heat out of the package. Pin 29 should be soldered to
a continuous copper ground plane under the device to
reduce die temperature and increase the power capability
of the LT3760.
SENSE (Pin 11): The Current Sense Input for the Control
Loop. Connect this pin to the sense resistor in the source
of the external power MOSFET.
VIN (Pin 14): Input Supply Pin. Must be locally bypassed
with a 1µF capacitor to PGND.
SHDN/UVLO (Pin 15): The SHDN/UVLO pin has an accurate
1.476V threshold and can be used to program an under voltage lockout (UVLO) threshold for system input supply using
a resistor divider from supply to GND. A 2.4µA pin current hysteresis allows programming of UVLO hysteresis.
SHDN/UVLO above 1.476V turns the part on and removes
a 2.4µA sink current from the pin. SHDN/UVLO < 0.7V
reduces VIN current < 20µA. If the shutdown function is
not required, it should be forced above 1.476V or connected directly to VIN.
FAULT (Pin 16): Active low if any or all LED strings have
an open fault. If fault(s) removed, FAULT flag returns high.
Fault status is only updated during PWM high state and
latched during PWM low.
SYNC (Pin 17): Allows synchronization of boost converter
switching frequency to an external clock. RT resistor should
be programmed for fOSC 20% below SYNC frequency. If
unused, connect to GND.
VOUT (Pin 18): Boosted Output Voltage of the Converter.
Connect a capacitor from this pin to PGND. Connect the
anode of each LED (string) to VOUT.
GND (Pin 24): Signal Ground.
RT (Pin 25): A resistor to GND programs switching frequency fOSC between 0.1MHz and 1MHz.
VC (Pin 26): Output of Both Transconductance Error
Amplifiers for the Converter Regulation Loop. The most
commonly used gm error amplifier (LED) regulates VOUT
to ensure no LED pin falls below 1V. The other gm error
amplifier (OVP) is activated if all LEDs fail open and a
regulated maximum VOUT is required. Connect a resistor
and capacitor in series from the VC pin to GND.
GATE (Pin 12): Drives the gate of an N-channel MOSFET
from 0V to INTVCC.
PWM (Pin 27): Input Pin for PWM Dimming Control. Above
1.4V allows converter switching and below 0.7V disables
switching. The PWM signal can be driven from 0V to 6V.
If unused, connect to VREF.
INTVCC (Pin 13): A 7V LDO supply generated from VIN and
used to power the GATE driver and some control circuitry.
Must be bypassed with a 4.7µF capacitor to PGND.
OVPSET (Pin 28): Programs maximum allowed VOUT regulation level if all LEDs are open circuit. Program using a
resistor divider from VREF to GND.
3760fc
8
LT3760
Block Diagram
1.476V
INTVCC
VC
– +
3
1
R
S
+
–
4.2V(+)
3.7V(−)
– +
OSC
SLOPE
PWM
EN
52mV
PEAK
CURRENT
6V
LED CURRENT
CONTROL
EN
1.1V
–
+
18
16
PWM
OVERVOLTAGE
AMP
– +
TSET
11
VOUT
SS
+
+
+
–
LED AMP
2
25
SENSE
FAULT
SOFT
START
CHANNEL X
VPTAT
17
LEDx
6 TO 9, 20 TO 23
LED
LOGIC
1V
100mV
OVER
CURRENT
HICCUP__MODE
VREF
CTRL
12
SYNC
RT
EN
+
–
GATE
Q
EN
1.485V
INTVCC_UV
VIN_UV
SHDN_UV
27
UVLO(+) = 3.8V, UVLO(−) = 3.4V
+
–
REF
1.485V
7V(REGULATED)
4
ISET
24
GND
PGND (10, 19, EXPOSED PAD (29))
26
VC
56R
+
–
600k
+
–
13
VIN
+
–
15
14
SHDN/UVLO
R
28
OVPSET
3760 BD
Figure 1. LT3760 Block Diagram
Operation
The operation of the LT3760 is best understood by referring
to the typical application circuit on the front page and the
Block Diagram in Figure 1. The LT3760 drives 8 strings
of LEDs by using a constant switching frequency, current
mode boost controller to generate a single output voltage
VOUT for the top (anode) of all LED strings. LED string
current is generated and controlled by connection of the
bottom LED in each string (cathode) to a current source
contained in each corresponding LED pin. Each LED pin
contains an accurate current sink to ground, programmable between 20mA to 100mA using a single resistor
at the ISET pin. LED channels can be paralleled to achieve
higher LED currents. For applications requiring less than
8 strings of LEDs, channels can be paralleled or disabled
(connect LED pin to VOUT before startup). For optimum
efficiency, VOUT regulates to the lowest possible voltage
allowable to maintain regulated current in each LED string.
Any OPEN LED fault is indicated by the FAULT pin driven
low without effecting the operation of the connected LED
strings.
The Block Diagram in Figure 1 illustrates the key functions
of the LT3760. It can be seen that two external supplies,
VREF and INTVCC, are generated by the LT3760. The VREF
pin provides a precision 1.485V output for use with external
resistors to program the CTRL, OVPSET and TSET input
pins. The INTVCC pin provides a regulated 7V output to
supply the gate driver for the boost controller GATE pin.
An accurate 1.476V threshold on the SHDN/UVLO pin
combined with a SHDN/UVLO pin current hysteresis allows
a programmable resistor divider from VIN to SHDN/UVLO
3760fc
9
LT3760
Operation
to define the turn on/off voltages for VIN. SHDN/UVLO pin
current switches from 2.4µA to 0µA when SHDN/UVLO
pin voltage exceeds 1.476V.
the LT3760 only allows MOSFET turn-on approximately
every 2ms. This hiccup mode significantly reduces the
power rating required for the MOSFET.
The LT3760 constant switching frequency is programmable
from 100kHz up to 1MHz using a single resistor at the RT
pin to ground. A SYNC pin is also provided to allow an
external clock to define the converter switching frequency.
The GATE output provides a ±0.8A peak gate drive for an
external N-channel power MOSFET to generate a boosted
output voltage VOUT using a single inductor, Schottky
diode and output capacitor. With LED strings connected
from VOUT to every LED pin, the lowest voltage on each
LED pin is monitored and compared to an internal 1V
reference. VOUT is regulated to ensure the lowest LED pin
voltage of any connected LED string is maintained at 1V.
If any of the LED strings are open, the LT3760 will ignore
the open LED pin. If all of the LED strings are open 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 opened and then reconnected.
LED current programming and dimming can be achieved
using the ISET, CTRL and PWM pins. A single resistor at
the ISET pin programs LED current. 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.
Since the LT3760 boost controller uses a current mode
topology, the VC pin voltage determines the peak current
in the inductor of the converter and hence the duty cycle
of the GATE switching waveform. The basic loop uses a
pulse from an internal oscillator to set an RS flip-flop and
turn on the external power MOSFET. Current increases
in the MOSFET and inductor until the VC commanded
peak switch current is exceeded and the MOSFET is then
turned off. Inductor current is sensed during the GATE on
period by a sense resistor RS in the source of the external
N-channel power MOSFET. As with all current mode
converters, slope compensation is added to the control
path to ensure stability for duty cycles above 50%. Any
over current fault condition in the MOSFET turns off the
MOSFET and triggers soft start internally. In this fault mode
For robust operation the LT3760 monitors system
conditions and performs soft start for startup after any of
the following faults: VIN, SHDN or INTVCC voltages too low
or MOSFET current too high. The LT3760, when entering
these faults, discharges an internal soft start node and
prevents switching at the GATE pin. When exiting these
faults the LT3760 ramps up an internal soft start node to
control VC pin voltage rise and hence control MOSFET peak
switch current rise. In addition the soft start period gradually
ramps up switching frequency from approximately 33%
to 100% of full scale.
The LT3760 monitors each LED pin voltage. If the LED
string has an open fault (V(LEDX)<0.5V) the FAULT flag
is pulled low.
For LED protection, the LT3760 CTRL pin allows an LED
current derating curve to be programmed versus the
ambient temperature of the LED strings. An NTC resistor
placed close to the LEDs decreases CTRL pin voltage and
hence decreases LED current as LED ambient temperature
increases.
The LT3760 also allows it’s own junction temperature
to be monitored and regulated by derating LED currents
when a junction temperature programmed by the TSET
pin is exceeded.
3760fc
10
LT3760
Applications Information
INTVCC Regulator Bypassing and Operation
Inductor
The INTVCC pin is the output of an internal linear regulator driven from VIN and is the supply for the LT3760 gate
driver. The INTVCC pin should be bypassed with a 10V
rated 4.7µF low ESR, X7R or X5R ceramic capacitor to
ensure stability and to provide enough charge for the gate
driver. For high enough VIN levels the INTVCC pin provides
a regulated 7V supply. Make sure INTVCC voltage does
not exceed the VGS rating of the external MOSFET driven
by the GATE pin. For low VIN levels the INTVCC level will
depend on VIN and the voltage drop of the regulator. The
INTVCC regulator has an undervoltage lockout which
prevents gate driver switching until INTVCC reaches 3.8V
and maintains switching until INTVCC falls below 3.4V.
This feature prevents excessive power dissipation in the
external MOSFET by ensuring a minimum gate drive level
to keep RDS(ON) low. The INTVCC regulator has a current
limit of 40mA to limit power dissipation inside the I.C.
This current limit should be considered when choosing the
N‑channel power MOSFET and the switching frequency.
The average current load on the INTVCC pin due to the
LT3760 gate driver can be calculated as:
A list of inductor manufacturers is given in Table 1. 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. Ferrite
cores should be used to obtain the best efficiency. Choose
an inductor that can handle the necessary peak current
without saturating. Also ensure that the inductor has a
low DCR (copper-wire resistance) to minimize I2R power
losses. Values between 2.2µH and 33µH will suffice for
most applications. The typical inductor value required for
a given application (assuming 50% inductor ripple current
for example) can be calculated as:
IINTVCC = Qg • fOSC
where Qg is the gate charge (at VGS = INTVCC) specified
for the MOSFET and fosc is the switching frequency of the
LT3760 boost converter. It is possible to drive the INTVCC
pin from a variety of external sources in order to remove
power dissipation from the LT3760 and/or to remove the
INTVCC current limitation of 40mA. An external supply for
INTVCC should never exceed the VIN pin voltage or the
maximum INTVCC pin rating of 13V. If INTVCC is shorted
to the VIN pin, VIN operational range is 4.5V to 13V.
1
•
1
•V
VOUT fOSC IN
VIN
L=
V
0.5 • OUT • ILEDx • 8
VIN
1-
where:
VOUT = (N • VF) + 1V
(N = number of LEDs per string),
VF = LED forward voltage drop,
ILEDx = LED current per string
Example: For a 12W LED driver application requiring 8
strings of 10 LEDs each driven with 40mA, and choosing VIN = 12V, VOUT = (3.75V • 10) + 1V = 38.5V, ILEDx =
40mA and fOSC = 1MHz the value for L is calculated as
1
1
) • 6 • 12V
3.2 10
L=
= 16.5µH
0.5 • 3.2 • 40mA • 8
(1-
3760fc
11
LT3760
Applications Information
Schottky Rectifier
Table 1. Inductor Manufacturers
Manufacturer
PHONE NUMBER
WEB
Sumida
408-321-9660
www.sumida.com
Würth Elektronik
605-886-4385
www.we-online.com
Vishay
402-563-6866
www.vishay.com
Coilcraft
847-639-6400
www.coilcraft.com
Coiltronics
561-998-4100
www.cooperet.com
Input Capacitor
The input capacitor of the LT3760 boost converter will supply the transient input current of the power inductor. Values
between 2.2µF and 10µF will work well for the LT3760. Use
only X5R or X7R ceramic capacitors to minimize variation
over voltage and temperature. If inductor input voltage is
required to operate near the minimum allowed operational
VIN for the I.C., a larger capacitor value may be required.
This is to prevent excessive input voltage ripple causing
dips below the minimum operating input voltage.
Output Capacitor
Low ESR ceramic capacitors should be used at the LT3760
converter output to minimize output ripple voltage. Use
only X5R or X7R dielectrics as these materials retain their
capacitance over wider voltage and temperature ranges
than other dielectrics. The output capacitance requirements
for several LED driver application circuits are shown in
the Applications Information section for various ILED,
VIN, VOUT, L and fOSC values. Some suggested capacitor
manufacturers are listed in Table 2.
Table 2. Ceramic Capacitor Manufacturers
Manufacturer
PHONE NUMBER
WEB
TDK
516-535-2600
www.tdk.com
Kemet
408-986-0424
www.kemet.com
Murata
814-237-1431
www.murata.com
Taiyo Yuden
408-573-4150
t-yuden.com
AVX
843-448-9411
www.avxcorp.com
The external diode for the LT3760 boost converter must
be a Schottky diode, with low forward voltage drop
and fast switching speed. Table 3 lists several Schottky
manufacturers. The diodes average current rating must
exceed the application’s average output current. The
diode’s maximum reverse voltage must exceed the
maximum output voltage of the application. For PWM
dimming applications be aware of the reverse leakage of
the Schottky diode. Lower leakage current will drain the
output capacitor less during PWM low periods, allowing
for higher PWM dimming ratios. The companies below
offer Schottky diodes with high voltage and current ratings.
Table 3. Schottky Rectifier Manufacturers
Manufacturer
PHONE NUMBER
WEB
Diodes, Inc.
805-446-4800
www.microsemi.com
On Semiconductor
888-743-7826
www.onsemi.com
Zetex
631-360-2222
www.zetex.com
Vishay Siliconix
402-563-6866
www.vishay.com
Power MOSFET Selection
Several MOSFET vendors are listed in Table 4. Consult the
factory applications department for other recommended
MOSFETs. The power MOSFET selected should have a
VDS rating which exceeds the maximum Overvoltage
Protection (OVP) level programmed for the application.
(See “Programming OVP level” in the Applications
Information section). The MOSFET should also have a
low enough total gate charge Qg (at 7V VGS) and a low
enough switching frequency (fOSC) to not exceed the
INTVCC regulator current limit, where loading on INTVCC
pin due to gate switching should obey,
IGATE = Qg • fOSC ≤ 40mA
3760fc
12
LT3760
Applications Information
In addition, the current drive required for GATE switching
should also be kept low in the case of high VIN voltages
(see “Thermal Considerations” in the Applications Information section). The RDS(ON) of the MOSFET will determine
d.c. power losses but will usually be less significant
compared to switching losses. Be aware of the power
dissipation within the MOSFET by calculating d.c. and
switching losses and deciding if the thermal resistance
of the MOSFET package causes the junction temperature
to exceed maximum ratings.
where
IL(PEAK) =
1
0.5
• 8 •ILEDx • 1+
1− D
2
D = MOSFET duty cycle = 1−
(
)
VIN(MIN)
VOUT(MAX)
,
VOUT(MAX) = N • VF(MAX) + 1V
N = number of LEDs in each string,
VF(MAX) = maximum LED forward voltage drop,
Table 4. MOSFET Manufacturers
Manufacturer
PHONE NUMBER
WEB
VIN(MIN) = minimum input voltage to the inductor,
Vishay Siliconix
402-563-6866
www.vishay.com
International Rectifier
310-252-7105
www.irf.com
I LED = current in each LED pin,
Fairchild
972-910-8000
www.fairchildsemi.com
Power MOSFET: Current Sense Resistor
The LT3760 current mode boost converter controls peak
current in the inductor by controlling peak MOSFET current
in each switching cycle. The LT3760 monitors current in the
external N-channel power MOSFET by sensing the voltage
across a sense resistor (RS) connected between the source
of the FET and the power ground in the application. The
length of these tracks should be minimized and a Kelvin
sense should be taken from the top of RS to the sense
pin. A 52mV sense pin threshold combined with the value
of RS sets the maximum cycle-by-cycle peak MOSFET
current. The low 52mV threshold improves efficiency and
determines the value for RS given by:
RS ≤
52mV • 0.7
IL(PEAK)
and the 0.5 term represents an inductor peak-to-peak ripple
current of 50% of average inductor current.
The scale factor of • 0.7 ensures the boost converter
can meet the peak inductor requirements of the loop by
accounting for the combined errors of the 52mV sense
threshold, ILEDx, RS and circuit efficiency.
Example: For a 12W LED driver application requiring 8
strings of 10 LEDs each driven with 40mA, and choosing
VIN(MIN) = 8V, VOUT(MAX) = (4V • 10)+1V = 41V and ILEDx
= 40mA, the value for RS is chosen as:
52mV • 0.7
52mV • 0.7
≤


41
IL(PEAK)
 • 8 • 0.04 • (1+ 0.25)
8

52mV • 0.7
≤
≤ 17.7 mΩ
2.05
RS ≤
3760fc
13
LT3760
Applications Information
The power rating of RS should be selected to exceed
the I2R losses in the resistor. The peak inductor current
should be recalculated for the chosen RS value to ensure
the chosen inductor will not saturate.
Power MOSFET: Overcurrent and Hiccup Mode
For severe external faults which may cause the external
MOSFET to reach currents greater than the peak current
defined by RS and the 52mV sense pin threshold described
above, the LT3760 has an overcurrent comparator which
triggers soft start and turns off the MOSFET driver for
currents exceeding,
I(OVERCURRENT ) =
100mV
RS
In this fault mode the LT3760 only allows MOSFET turn
on for approximately 100ns every 2ms. This hiccup mode
significantly reduces the power rating required for the
MOSFET.
Soft Start
To limit inductor inrush current and output voltage during
startup or recovery from a fault condition, the LT3760 provides a soft start function. The LT3760 when entering these
faults will discharge an internal soft start node and prevent
switching at the GATE pin for any of the following faults: VIN,
SHDN/UVLO or INTVCC voltages too low or MOSFET current
too high (see the timing diagram in Figure 2). When exiting
these faults the LT3760 ramps up an internal soft start
node at approximately 0.5V/ms to control VC pin voltage
rise and hence control MOSFET switch current rise. In addition the soft start period gradually ramps up switching
frequency from approximately 33% to 100% of full scale.
The conditions required to exit all faults and allow a soft
start ramp of the VC pin are listed in Figure 2. An added
feature of the LT3760 is that it waits for the first PWM pin
active high (minimum 200ns pulse width) before it allows
GATE
VC
VC MIN
CLAMP
0.5V/ms
0.4V + VBE (VC SWITCHING
THRESHOLD)
0.1V + VBE
SS
(INTERNAL)
0.5V/ms
0.4V
0.1V
ANY OF THE FOLLOWING FAULTS
TRIGGERS SOFT START LATCH
WITH GATE TURNED OFF
IMMEDIATELY:
VIN < 3.7V, SHDN < 1.476V,
INTVCC < 3.4V
IDSS (EXTERNAL MOSFET) > 100mV/RS
SOFT-START
LATCH SET:
SOFT-START LATCH RESET REQUIRES
ALL CONDITIONS SATISFIED:
SS (INTERNAL) < 0.2V, VIN ≥ 4.2V,
SHDN > 1.476V, INTVCC > 3.8V,
IDSS (EXTERNAL MOSFET) < 100mV/RS,
PWM > 1.4V (FOR AT LEAST 200ns)
3760 F02
Figure 2. LT3760 Fault Detection and Soft Start Timing for VC Pin and Internal SS Node
3760fc
14
LT3760
Applications Information
the soft start of VC pin to begin. This feature ensures that
during startup of the LT3760 the soft start ramp has not
timed out before PWM is asserted high. Without this ‘wait
for PWM high’ feature, systems which apply PWM after VIN
and SHDN/UVLO are valid, can potentially turn on without
soft start and experience high inductor currents during
wake up of the converter’s output voltage. It is important
to note that when PWM subsequently goes low, the soft
start ramp is not held at its present voltage but continues
to ramp upwards. If the soft start ramp voltage was held
every time PWM goes low, this would cause very slow
startup of LED displays for applications using very high
PWM Dimming ratios.
Shutdown and Programming Undervoltage Lockout
The LT3760 has an accurate 1.476V shutdown threshold
at the SHDN/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 3). An internal hysteresis
current at the SHDN/UVLO pin allows programming of
hysteresis voltage for this UVLO threshold. Just before
part turn on, an internal 2.4µA flows from the SHDN/
OFF ON
VSUPPLY ON = VSUPPLY OFF + (2.4µA • R1)
An open drain transistor can be added to the resistor
divider network at the SHDN/UVLO pin to independently
control the turn off of the LT3760.
Programming Switching Frequency
The switching frequency of the LT3760 boost converter
can be programmed between 100kHz and 1MHz using a
single resistor (RT) connected from the RT pin to ground
(Figure 4). Connect the RT resistor as close as possible to
the RT pin to minimize noise pick up and stray capacitance
(see “Circuit Layout Considerations” in the Applications
Information section). Table 5 shows the typical RT values
required for a range of frequencies.
1000
1.476V
SWITCHING FREQUENCY (kHz)
15 SHDN/UVLO
600k
R2
 R1 
VSUPPLY OFF = 1.476 1+ 
 R2 
900
VSUPPLY
R1
UVLO pin. After part turn on, 0µA flows from the SHDN/
UVLO pin. Calculation of the turn on/off thresholds for a
system input supply using the LT3760 SHDN/UVLO pin
can be made as follows :
–
+
800
700
600
500
400
300
200
100
3760 F03
Figure 3. Programming Undervoltage
Lockout (UVLO) with Hysteresis
0
100
200
300
400
RT (kΩ)
500
600
3760 F04
Figure 4. Switching Frequency vs RT
3760fc
15
LT3760
Applications Information
Selecting the optimum frequency depends on several
factors. Higher frequency allows reduction of inductor
size but efficiency drops due to higher switching losses.
Lower frequency allows higher operational duty cycles to
drive a larger number of LEDs per string from a low input
supply but require larger magnetics. In each application
the switching frequency can be tailored to provide the
optimum solution.
Table 5. Switching Frequency vs. RT (1% resistors)
SWITCHING FREQUENCY (kHz)
RT (kΩ)
100
523
200
249
300
158
400
115
500
90.9
600
73.2
700
60.4
800
51.1
900
44.2
1000
39.2
Duty Cycle Considerations
When designing the LT3760 LED driver for a given
application, the duty cycle requirements should be
considered and compared to the minimum/maximum
achievable duty cycles for the LT3760 GATE pin. If required,
the LT3760 switching frequency can be programmed to a
lower value to meet the duty cycle requirements. In general,
the minimum/maximum GATE duty cycles required for a
particular application are given by:
MIN Duty Cycle = GATE Minimum On-Time • Switching
Frequency fOSC
MAX Duty Cycle = 1 – (GATE Minimum Off-Time •
Switching Frequency fOSC)
Table 6. LED Current vs. RISET (1% resistors)
LED CURRENT PER CHANNEL (mA)
RISET (kΩ)
20
29.4
40
14.7
60
9.76
80
7.32
100
5.76
An extra 50ns should be added to these tested timings to
account for errors in the rise/fall times of the GATE and
DRAIN of the external MOSFET and the d.c. resistance of
the external MOSFET and inductor.
Synchronizing to an External Clock
The SYNC pin allows the LT3760 oscillator to be synchronized to an external clock. The SYNC pin can be driven
from a logic level output, requiring less than 0.6V for a
logic level low and greater than 2.2V for a logic level high.
SYNC pin high or low periods should exists for at least
100ns. If unused, the SYNC pin should be tied to ground.
To avoid loss of slope compensation during synchronization, the free running oscillator frequency (fOSC) of the
LT3760 should be programmed to 80% of the external
clock frequency.
Programming LED Current
The current source to ground at each LED pin is programmed
using a single resistor RISET connected from the ISET pin
to ground according to the following equation:
I (LEDX ) ≈
590 ( )
A (CTRL > 1.1V )
RISET
See Table 6 for resistor values and corresponding programmed LED.
The typical values for LT3760 GATE pin minimum on
and off times versus temperature are shown in the Typical Performance Characteristics. The range of GATE pin
minimum on time and off times are given in the electrical
specifications.
3760fc
16
LT3760
Applications Information
Analog Dimming
The LT3760 allows for LED dimming (brightness reduction)
by analog dimming or by PWM dimming. Analog dimming
uses the CTRL pin voltage below 1V to reduce LED
brightness by reducing LED current. For CTRL pin voltage
below 1V, the current in each LED pin is given by:
590
I (LEDX ) ≈ CTRL •
(0.04 < CTRL < 1V )
RISET
For CTRL pin voltages below 40mV (greater than 25:1
dimming) the LED current will approach zero current. The
CTRL pin voltage can be derived from a resistor divider
from VREF pin to ground or generated from an external
source. If analog dimming is not required, the pin can be
directly connected to the VREF pin. The only drawback of
analog dimming is that reducing LED current to reduce
the brightness of the LED also changes the perceived
color of the LED.
turn LED currents on/off as quickly as possible. For PWM
low, the LT3760 turns off the boost converter, turns off
all LED channel currents and disconnects the VC pin and
internal VOUT resistor divider connected to the OVP error
amplifier. This allows the part to quickly return to the last
state of operation when the PWM pin is returned high.
Some general guidelines for LED current dimming using
the PWM pin (see Figure 5):
(1) PWM Dimming Ratio (PDR) = 1/(PWM Duty Cycle) =
1/TON(PWM) • fPWM
(2) Lower PWM frequency (fPWM) allows higher PWM
dimming ratios (Typically choose 100Hz to maximize PDR
and to avoid visible flicker which can occur for display
systems with refresh rates at frequencies below 80Hz)
(3) Higher fOSC value improves PDR (allows lower TON(PWM))
but will reduce efficiency and increase internal heating. In
general, minimum operational TON(PWM) = 3 • (1/fOSC)
PWM Dimming
(4) Lower inductor value improves PDR
Many applications require an accurate control of the brightness of the LED(s). In addition, being able to maintain a
constant color over the entire dimming range can be just
as critical. For constant color LED dimming the LT3760
provides a PWM pin and special internal circuitry to achieve
up to a 3000:1 wide PWM dimming range. This is achieved
by operating the LED at it’s programmed current and then
controlling the on time of that LED current. The duty cycle
of the PWM pin controls the on time of each LED pin
current source (Figure 5). For maximum PWM dimming
ratios (low PWM duty cycles) it is important to be able to
(5) Higher output capacitor value improves PDR
(6) Choose the Schottky diode for the LT3760 boost converter for minimum reverse leakage current.
Programming LED Current Derating (Breakpoint and
Slope) versus LED Ambient Temperature (CTRL Pin)
LED data sheets provide curves of maximum allowed
LED current versus ambient temperature to warn against
damaging of the LED (Figure 6). The LT3760 LED driver
improves the utilization and reliability of the LED(s) by al90
TON(PWM)
IF - FORWARD CURRENT (mA)
80
TPWM
(= 1/fPWM)
PWM
INDUCTOR
CURRENT
RESISTOR
OPTION A
70
60
50
LT3760
PROGRAMMED LED
CURRENT DERATING
CURVE
40
30
20
10
LED
CURRENT
MAX ILED
0
3760 F05
Figure 5. PWM Dimming Waveforms
0
10
20 30 40 50 60
TA-TEMPERATURE (°C)
70
80
3760 F06
Figure 6. LED Current Derating vs LED Ambient Temperature
3760fc
17
LT3760
Applications Information
lowing the programming of an LED current derating curve
versus the ambient temperature of the LED(s). Without the
ability to back off LED currents as temperature increases,
many LED drivers are limited to driving the LED(s) at 50%
or less of their maximum rated currents. This limitation
requires more LEDs to obtain the intended brightness
for the application. The LT3760 allows the LED(s) to be
programmed for maximum allowable current while still
protecting the LED(s) from excessive currents at high temperature. The temperature breakpoint and the slope of LED
current versus ambient temperature can be programmed
using a simple resistor network shown in Figure 7.
This is achieved by programming a voltage at the CTRL
pin with a negative temperature coefficient using a resistor
divider with temperature dependent resistance (Figures 7
and 8). A variety of resistor networks and NTC resistors
with different temperature coefficients can be used to
achieve the desired CTRL pin voltage behavior versus
temperature. The current derating curve in Figure 6 uses
the resistor network shown in option A of Figure 7.
Table 7 shows a list of NTC resistor manufacturers/ distributors. There are several other manufacturers available and
the chosen supplier should be contacted for more detailed
information. To use an NTC resistor to monitor the ambient
temperature of the LED(s) it should be placed as close as
possible to the LED(s). Since the temperature dependency
of an NTC resistor can be non-linear over a wide range of
temperatures it is important to obtain a resistor’s exact
values over temperature from the manufacturer. Hand
calculations of CTRL voltage can then be performed at
each given temperature and the resulting CTRL voltage
plotted versus temperature.
Table 7. NTC Resistor Manufacturers
Manufacturer
WEB
Murata Electronics North America
www.murata.com
TDK Corporation
www.tdk.com
Digi-key
www.digikey.com
If calculation of CTRL voltage at various temperatures gives
a downward slope that is too strong, alternative resistor
networks can be chosen (B,C,D in Figure 7) which use
temperature independent resistance to reduce the effects
of the NTC resistor over temperature. Murata Electronics
provides a selection of NTC resistors with complete data
over a wide range of temperatures. In addition, a software
tool is available which allows the user to select from different resistor networks and NTC resistor values and then
simulate the exact output voltage curve (CTRL pin behavior) over temperature. Referred to on the website as the
‘Murata Chip NTC Thermistor Output Voltage Simulator’,
1.50
R1
1
VREF
1.25
LT3760
CTRL VOLTAGE (V)
3
CTRL
OPTION A TO D
R2
RY
RNTC
RNTC
RX RNTC
RESISTOR
OPTION A
0.75
0.50
RY
RNTC
1.00
RX
0.25
0
10 20 30 40 50 60 70
TA - AMBIENT TEMPERATURE (°C)
80
3760 F08
A
B
C
D
3760 F07
Figure 7. Programming LED Current Derating Curve
vs Ambient Temperature (RNTC Located on LED PCB)
Figure 8. Programmed CTRL Voltage vs Temperature
3760fc
18
LT3760
Applications Information
users can log onto www.murata.com/designlib and download the software followed by instructions for creating an
output voltage ‘VOUT’ (LT3760 CTRL pin voltage) from a
specified VCC supply (LT3760 VREF pin voltage). At any
time during selection of circuit parameters the user can
access data on the chosen NTC resistor by clicking on
the link to the Murata catalog. For a detailed example of
hand calculations using an NTC type resistor divider to
program CTRL pin voltage, read the LT3478 LED driver
data sheet section Programming LED Current Derating vs
Temperature under Applications Information.
Using the TSET Pin for Thermal Protection
While this feature is intended to directly protect the LT3760,
it can also be used to derate the LED current at high temperatures. Since there is a direct relationship between the
LED temperature and LT3760 junction temperature, the
TSET function also provides some LED current derating
at high temperatures.
Two external resistors program the maximum IC junction
temperature using a resistor divider from the VREF pin,
as shown in Figure 9. Choose the ratio of R1 and R2 for
the desired junction temperature. Figure 10 shows the
relationship of TSET voltage to junction temperature, and
Table 8 shows commonly used values for R1 and R2.
The LT3760 contains a special programmable thermal
regulation loop that limits the internal junction temperature
of the part. Since the LT3760 topology consists of a single
boost controller with eight 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, and allows a given application to be optimized
for typical, not worst-case, ambient temperatures with
the assurance that the LT3760 will automatically protect
itself and the LED strings under worst-case conditions.
The operation of the thermal loop is simple. As the ambient temperature increases, so does the internal junction
temperature of the part. Once the programmed maximum
junction temperature is reached, the LT3760 begins to
linearly reduce the LED current, as needed, to try and
maintain this temperature. This can only be achieved
when the ambient temperature stays below the desired
maximum junction temperature. If the ambient temperature continues to rise past the programmed maximum
junction temperature, the LEDs current will be reduced
to approximately 5% of the full LED current.
3
R2
VREF
LT3760
2
TSET
R1
3760 F09
Figure 9. Programming the TSET Pin
950
VTSET THRESHOLD (mV)
900
850
800
VPTAT
750
700
650
600
550
500
0
25
50
75
100
125
JUNCTION TEMPERATURE (°C)
150
3760 F10
Figure 10. Programing the TSET Pin Threshold
Table 8. Resistor Values to Program Maximum IC Junction
Temperature (VREF (Typical) = 1.485V)
TJ (°C)
R1 (kΩ)
R2 (kΩ)
TSET (V)
100
24.9
20
0.824
115
28.0
20
0.866
130
30.9
20
0.902
3760fc
19
LT3760
Applications Information
Programming Overvoltage Protection (OVP) Level
The LT3760 LED driver provides optimum protection to
the LEDs and the external MOSFET by providing a programmable maximum regulated output voltage limit using
the OVPSET pin. The Overvoltage Protection (OVP) level
is programmed as:
OVP(maximum regulated VOUT) = 57 • OVPSET
If every LED string fails open or the multiple string LED
display becomes disconnected the LT3760 LED driver loop
regulates to the programmed OVP level. The OVP level
should be programmed to a level high enough to regulate
the LED strings but low enough to prevent damage to the
power switch and to minimize the voltage across the LED
pins upon reconnection of the LED strings. Recommended
OVP level is given by:
OVP(RECOMMENDED) = 1.2 • ((N • VF) + 1V)
where:
N = number of LEDs in each string,
VF = maximum LED forward voltage drop
and the scaling factor of 1.2 accounts for variation in the
generation of OVP from OVPSET pin voltage and startup
logic requirements.
Example: For a converter operating with 10 LEDs per string
at a maximum forward voltage of 4V per LED, the OVP
level should be programmed to:
OVP(RECOMMENDED) = 1.2 • ((10 • 4) + 1V ) = 49.2V
For OVP = 49.2V, OVPSET =
49.2
= 0.863V
57
The OVPSET pin voltage can be generated using a resistor
divider from the REF pin.
LED Open Circuit and PWM Dimming Ratios
The LT3760 monitors each LED pin voltage to determine if
the LED string has an open fault (LED pin voltage < 0.5V).
If an open LED fault occurs, the FAULT flag is pulled low.
To avoid false detection of faults during the initial converter
startup when VOUT is low, the LT3760 ignores low LED
pin voltages until VOUT reaches 90% of its maximum allowed OVP level. Once this condition is met, the LT3760
monitors all LED pins for open LED faults. To avoid false
detection of faults during PWM dimming edges (where
LED pins can possibly ring and trip fault detection levels)
the LT3760 only monitors/updates fault conditions during
PWM high (and only after a blank duration of 2µs following
each PWM rising edge).
LED Short Circuit
A short circuit fault between the positive terminal of an
LED string (VOUT) and the negative terminal of the LED
string (LEDx pin) causes the channel to be disabled in
order to protect the internal current source. A resistive
short is allowed as long as (VOUT -VLEDx) < 6V.
Loop Compensation
Be sure to check the stability of the loop with the LEDs
connected (LED regulation loop) and disconnected
(Overvoltage Protection (OVP) regulation loop). Various
application circuits are shown in the data sheet which
cover a range of VIN, VOUT, fOSC, output power and inductor
current ripple values. For application requirements which
deviate from the circuits shown in the data sheet be sure
to check the stability of the final application over the full
VIN range, LED current range (if analog dimming) and
temperature range. Be aware that if the VC pin components
represent a dominant pole for the converter loop and they
have been adjusted to achieve stability, the VC pin might
move more slowly during load transient conditions such
as an all-LEDs-open fault. A slower moving VC pin will
add to VOUT overshoot during an all-LEDs-open fault.
An alternative compensation approach is to place the
dominant pole of the converter loop at the output. This
requires an increased output capacitor value but will allow
a much reduced Vc capacitor. The combination will allow
VC to move more quickly and VOUT to move more slowly
resulting in less overshoot during an all-LEDs-open fault.
3760fc
20
LT3760
Applications Information
Thermal Considerations
The internal power dissipation of the LT3760 comes from 3
main sources: VIN quiescent current (IQ total), VIN current
for GATE switching (IGATE) and the LT3760 LED current
sources. Since the maximum operational VIN voltage is
40V, care should be taken when selecting the switching
frequency and type of external power MOSFET since the
current required from VIN for GATE switching is given by,
IGATE = fOSC • Qg
where Qg is the gate charge (at VGS = INTVCC) specified
for the MOSFET and fOSC is the programmed switching
frequency for the LT3760. A low Qg MOSFET should always be used when operating the LT3760 from high VIN
voltages. The internal junction temperature of the LT3760
can be estimated as:
TJ = TA + [VIN • (IQTOTAL + (fOSC • Qg)) + (8 • I(LEDX) • 1.1V)]
• θJA
where, TA is the ambient temperature for the LT3760
IQTOTAL represents the VIN quiescent current for the LT3760
(not switching, PWM = 1.5V and CTRL = 0.1V) - illustrated
in the Typical Characteristics Graphs – plus the base currents of active channels (typically 8 • I(LED)/75). θJA is
the thermal resistance of the package (28°C/W for the
28-pin TSSOP package).
Example : For a 12W LED driver application requiring 8
strings of 10 LEDs each driven with 40mA, VIN = 24V, fOSC
= 1MHz, Qg (at 7V VGS) = 15nC, I(LEDX) = 40mA, and an
85°C ambient temperature for the LT3760 IC, the LT3760
junction temperature can be approximated as:
TJ = 85°C + [24 • (9.5mA + (8 • 40mA/75) + (1MHz
• 15nC)) + (8 • 40mA • 1.1V)] • 34
= 85°C + [(24 • 28.8mA) + (320mA • 1.1V)] • 34
= 85°C + (0.691W + 0.35W) • 34
= 85°C + 35°C
The exposed pad on the bottom of the package must be
soldered to the ground plane. The ground plane should
be connected to an internal copper ground plane with vias
placed directly under the package to spread out the heat
generated by the LT3760.
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 LT3760 should be soldered to a
continuous copper ground plane underneath the device
to reduce die temperature and maximize the power capability of the IC. The signal ground (GND, pin 24) is down
bonded to the exposed pad near the RT and VC pins.
ISET, RT and VC components should be connected to an
area of ground copper connected to pin 24. The OVPSET
track should be kept away from fast moving signals and
not loaded with an external capacitor. GATE pin turn off
currents escape through a downbond to the exposed pad
and exit the PGND, pin 10. This area of copper and pin
10 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 the VIN pin and connected to
the copper area associated with signal ground, pin 24. To
minimize MOSFET peak current sensing errors the sense
resistor (RS) should have Kelvin connections to the SENSE
pin and the power ground copper area near the pin. The
MOSFET drain rise and fall times are designed to be as
short as possible for maximum efficiency. To reduce the
effects of both radiated and conducted noise, the area of
the copper trace for the MOSFET drain should be kept as
small as possible. Use a ground plane under the switching
regulator to minimize interplane coupling. The Schottky
diode and output capacitor should be placed as close as
possible to the drain node to minimize this high switching
frequency path.
TJ = 120°C
3760fc
21
LT3760
Typical Applications
92% Efficient, 36W LED Driver, 1MHz Boost, 8 Strings, 100mA Per String
PVIN
20V TO 36V
4.7µF
50V
VIN
8V TO 14V
L1
10µH
D1
UP TO 45V OF LEDs PER STRING
4.7µF
25V
VIN
4.7µF
10V
INTVCC
GATE
M1
SENSE
VIN
499k
2.2µF
100V
×5
100k
•
•
•
0.015Ω
LT3760
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
PGND
FAULT
VOUT
SHDN/UVLO
40.2k
GND
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
SYNC
PWM
PWM DIMMING
ANALOG DIMMING
CTRL
3760 TA03
VREF
20k
LED Current Waveforms
3000:1 PWM Dimming (100Hz)
TSET
30.9k
11k
OVPSET RT
20k
39.2k
ISET
5.76k
VC
10k
(FRONT COVER
APPLICATION)
I(LEDx)
40mA/DIV
2.2nF
L1: SUMIDA CDRH8D38
M1: VISHAY SILICONIX Si7850DP
D1: DIODES, INC. PDS360
I(L1)
1A/DIV
PWM
10V/DIV
5µs/DIV
3760 G04
3760fc
22
LT3760
Typical Applications
28W LED Driver, 750kHz Boost, 8 Strings, 80mA Per String
L1
10µH
VIN
11V TO 18V
D1
UP TO 44V OF LEDs PER STRING
4.7µF
25V
VIN
4.7µF
10V
INTVCC
GATE
M1
SENSE
0.0125Ω
1M
LT3760
100k
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
VOUT
SHDN/UVLO
ANALOG
DIMMING
•
•
•
PGND
FAULT
SHDN
2.2µF
100V
×7
CTRL
GND
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
SYNC
PWM DIMMING
PWM
3760 TA04
VREF
20k
TSET
10k
OVPSET RT
30.9k
16.9k
56.2k
ISET
7.32k
VC
10k
4.7nF
L1: SUMIDA CDRH8D38
M1: VISHAY SILICONIX Si7308DN
D1: DIODES, INC. DFLS160
3760fc
23
LT3760
Typical Applications
15W LED Driver, 750kHz Boost, 8 Strings, 55mA Per String
L1
7.3µH
VIN
8V TO 21V
D1
UP TO 34V OF LEDs PER STRING
4.7µF
50V
VIN
4.7µF
10V
INTVCC
GATE
M1
2.2µF
50V
×5
SENSE
0.015Ω
1M
LT3760
100k
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
PGND
FAULT
SHDN
VOUT
SHDN/UVLO
ANALOG
DIMMING
CTRL
GND
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
SYNC
PWM DIMMING*
PWM
3760 TA05
VREF
20k
TSET
10k
OVPSET RT
30.9k
10k
56.2k
ISET
10.7k
VC
5.1k
4.7nF
L1: SUMIDA CDRH8D28
M1: VISHAY SILICONIX Si7308DN
D1: DIODES, INC. DFLS160
*MAXIMUM PWM DIMMING RATIO:
(a) fPWM = 20kHz
= 20:1 (VIN > 10V)
= 5:1 (VIN = 8V)
(b) fPWM = 100Hz
= 3000:1 (VIN > 10V)
= 750:1 (VIN = 8V)
3760fc
24
LT3760
Typical Applications
29W LED Driver, 400kHz Boost, 2 Strings, 350mA Per String
L1
10µH
VIN
8V TO 36V
D1
UP TO 42V OF LEDs PER STRING
4.7µF
50V
VIN
4.7µF
10V
INTVCC
GATE
M1
SENSE
0.007Ω
100k
1M
LT3760
PGND
2.2µF
100V
×10
•
•
•
•
•
•
FAULT
VOUT
SHDN/UVLO
232k
GND
LED1
LED2
LED3
LED4
SYNC
PWM
PWM DIMMING
ANALOG DIMMING
LED5
LED6
LED7
LED8
CTRL
VREF
3760 TA06
20k
TSET
15k
OVPSET RT
30.9k
23.2k
115k
ISET
VC
6.65k
5.1k
4.7nF
L1: COOPER BUSSMANN HC9-100-R
M1: VISHAY SILICONIX Si7850DP
D1: DIODES, INC. PDS560
3760fc
25
LT3760
Typical Applications
25W LED Driver, 400kHz Boost, 3 Strings, 200mA Per String
L1
10µH
VIN
8V TO 36V
D1
UP TO 42V OF LEDs PER STRING
4.7µF
50V
VIN
4.7µF
10V
INTVCC
GATE
M1
SENSE
0.007Ω
100k
1M
LT3754
•
•
•
•
•
•
VOUT
SHDN/UVLO
LED8
LED7
232k
GND
LED1
LED2
SYNC
PWM
ANALOG DIMMING
•
•
•
PGND
FAULT
PWM DIMMING
2.2µF
100V
×10
LED3
LED4
CTRL
VREF
LED5
LED6
20k
TSET
3760 TA07
15k
OVPSET RT
30.9k
23.2k
115k
ISET
VC
5.76k
5.1k
4.7nF
L1: COOPER BUSSMANN HC9-100-R
M1: VISHAY SILICONIX Si7850DP
D1: DIODES, INC. PDS560
3760fc
26
LT3760
Typical Applications
29W LED Driver, 700kHz Boost, 4 Strings, 160mA Per String
L1
15µH
VIN
10V TO 18V
D1
UP TO 45V OF LEDs PER STRING
4.7µF
25V
VIN
4.7µF
10V
INTVCC
GATE
SENSE
VIN
1M
M1
0.02Ω
LT3760
100k
PGND
FAULT
GND
•
•
•
•
•
•
LED3
LED4
PWM
ANALOG DIMMING
•
•
•
LED1
LED2
SYNC
PWM DIMMING
•
•
•
VOUT
SHDN/UVLO
SHDN
2.2µF
100V
×5
CTRL
LED5
LED6
VREF
20k
LED7
LED8
TSET
11k
OVPSET RT
30.9k
20k
60.4k
ISET
7.32k
3760 TA08
VC
7.5k
4.7nF
L1: SUMIDA CDRH8D38
M1: VISHAY SILICONIX Si7308DN
D1: DIODES, INC. DFLS160
3760fc
27
LT3760
Typical Applications
14W LED Driver, 700kHz Boost, 4 Strings, 80mA Per String (For Machine Vision Systems with Very Long Off-Times)
L1
15µH
VIN
10V TO 28V
D1
4.7µF
10V
INTVCC
GATE
0.02Ω
LT3760
100k
PGND
FAULT
•
•
•
•
•
•
•
•
•
CTRL
LED5
LED6
VREF
20k
LED7
LED8
TSET
20.5k
OVPSET RT
30.9k
•
•
•
LED3
LED4
PWM
ANALOG DIMMING
2.2µF
100V
×5
LED1
LED2
SYNC
PWM DIMMING
5V/0V
ON/OFF
VOUT
SHDN/UVLO
GND
140k
M1
SENSE
SHDN
10k
Q1
1k
VIN
1M
UP TO 45V OF LEDs PER STRING
M2
4.7µF
50V
VIN
M3
1.5k
20k
60.4k
ISET
7.32k
3760 TA09
VC
10k
820pF
200pF
L1: SUMIDA CDRH8D38
M1: VISHAY SILICONIX Si7308DN
M2: VISHAY SILICONIX Si2309DS
M3: VISHAY SILICONIX Si2312DS
Q1: MMBTA42
D1: DIODES, INC. DFLS160
3760fc
28
LT3760
Typical Applications
13W LED Driver, 1MHz SEPIC, 8 Strings, 100mA Per String (Survives VOUT Short to PGND)
PVIN
10V TO 32V
4.7µF
50V
4.7µF
25V
L1B
15µH
VIN
4.7µF
10V
INTVCC
GATE
D1
VOUT
UP TO 16V OF LEDs PER STRING
499k
M1
•
4.7µF
25V
×4
SENSE
VIN
1M
2.2µF
50V
×2
•
VIN
8V TO 14V
L1A
15µH
0.015Ω
LT3760
100k
PGND
FAULT
VOUT
SHDN/UVLO
100k
CTRL
GND
110k
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
SYNC
PWM
PWM DIMMING
ANALOG DIMMING
CTRL
3760 TA10
VREF
20k
TSET
30.9k
20k
OVPSET RT
6.34k
39.2k
ISET
5.76k
VC
7.5k
4.7nF
L1A, L1B: 15µH COUPLED INDUCTOR DRQ125
M1: VISHAY SILICONIX Si7850DP
D1: DIODES, INC. PDS560
3760fc
29
LT3760
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
FE Package
28-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation EB
9.60 – 9.80*
(.378 – .386)
4.75
(.187)
4.75
(.187)
28 2726 25 24 23 22 21 20 19 18 1716 15
6.60 ±0.10
2.74
(.108)
4.50 ±0.10
SEE NOTE 4
0.45 ±0.05
EXPOSED
PAD HEAT SINK
ON BOTTOM OF
PACKAGE
6.40
2.74
(.252)
(.108)
BSC
1.05 ±0.10
0.65 BSC
RECOMMENDED SOLDER PAD LAYOUT
4.30 – 4.50*
(.169 – .177)
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN MILLIMETERS
(INCHES)
3. DRAWING NOT TO SCALE
1 2 3 4 5 6 7 8 9 10 11 12 13 14
0.25
REF
1.20
(.047)
MAX
0° – 8°
0.65
(.0256)
BSC
0.195 – 0.30
(.0077 – .0118)
TYP
0.05 – 0.15
(.002 – .006)
FE28 (EB) TSSOP 0204
4. RECOMMENDED MINIMUM PCB METAL SIZE
FOR EXPOSED PAD ATTACHMENT
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
3760fc
30
LT3760
Revision History
REV
DATE
DESCRIPTION
A
1/11
Revised FAULT pin description.
8
B
10/11
Updated Features section.
1
Updated equation in “Power MOSFET: Current Sense Resistor” section.
13
Updated “Programming LED Current Derating (Breakpoint and Slope) versus LED Ambient
Temperature (CTRL Pin)” section.
18
Corrected the inductor value formula.
11
C
3/12
PAGE NUMBER
3760fc
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.
31
LT3760
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LT3755/LT37551/
LT3755-2
High Side 40V, 1MHz LED Controller with True Color
3,000:1 PWM Dimming
VIN = 4.5V to 40V, VOUT(MAX) = 75V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, 3mm × 3mm QFN-16 MSOP-16E
LT3756/LT37561/
LT3756-2
High Side 100V, 1MHz LED Controller with True Color
3,000:1 PWM Dimming
VIN = 6V to 100V, VOUT(MAX) = 100V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, 3mm × 3mm QFN-16 MSOP-16E
LT3598
44V, 1.5A, 2.5MHz Boost 6-Channel 20mA LED Driver
VIN = 3V to 30V (40VMAX), VOUT(MAX) = 44V, 1,000:1 True Color PWM
Dimming, ISD = <1µA, 4mm × 4mm QFN-24
LT3599
44V, 2A, 2.5MHz Boost 4-Channel 100mA LED Driver
VIN = 3V to 30V (40VMAX), VOUT(MAX) = 44V, 1,000:1 True Color PWM
Dimming, ISD = <1µA, 4mm × 4mm QFN-24
LT3595
45V, 2.5MHz 16-Channel Full Featured LED Driver
VIN = 4.5V to 45V, VOUT(MAX) = 45V, 5,000:1 True Color PWM Dimming,
ISD = <1µA, 5mm × 9mm QFN-56
LTC3783
High Side 36V, 1MHz LED Controller with True Color
3,000:1 PWM Dimming
VIN = 3V to 36V, VOUT(MAX) = 40V, 3,000:1 True Color PWM Dimming,
ISD = <20µA, 4mm × 5mm DFN-16 TSSOP-16E
LT3517
1.5A, 2.5MHz High Current LED Driver with 3,000:1
Dimming
VIN = 3V to 30V, VOUT(MAX) = 45V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, 4mm × 4mm QFN-16
LT3518
2.3A, 2.5MHz High Current LED Driver with 3,000:1
Dimming
VIN = 3V to 30V, VOUT(MAX) = 45V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, 4mm × 4mm QFN-16
LT3519/LT35191/
LT3519-2
750mA, 2.2MHz High Current LED Driver
VIN = 3V to 30V, VOUT(MAX) = 45V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, MSOP-16E
LT3486
Dual 1.3A, 2MHz High Current LED Driver
VIN = 3V to 40V, VOUT(MAX) = 36V, 1,000:1 True Color PWM Dimming,
ISD = <1µA, 5mm × 3mm DFN, TSSOP-16E
LT3478/LT3478-1 4.5A, 2MHz High Current LED Driver with 3,000:1
Dimming
VIN = 2.8V to 36V, VOUT(MAX) = 60V, 3,000:1 True Color PWM Dimming,
ISD = <10µA, 5mm × 7mm QFN-10
LT3496
VIN = 3V to 30V, VOUT(MAX) = 40V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, 4mm × 5mm QFN-28
Triple Output 750mA, 2.1 MHz High Current LED Driver
with 3,000:1 Dimming
LT3474/LT3474-1 36V, 1A (ILED), 2MHz, Step-Down
LED Driver
VIN = 4V to 36V, VOUT(MAX) = 13.5V, 400:1 True Color PWM Dimming,
ISD = <1µA, TSSOP-16E
LT3475/LT3475-1 Dual 1.5A(ILED), 36V, 2MHz, Step-Down LED Driver
VIN = 4V to 36V, VOUT(MAX) = 13.5V, 3,000:1 True Color PWM Dimming,
ISD = <1µA, TSSOP-20E
LT3476
Quad Output 1.5A, 2MHz High Current LED Driver with
1,000:1 Dimming
VIN = 2.8V to 16V, VOUT(MAX) = 36V, 1,000:1 True Color PWM Dimming,
ISD = <10µA, 5mm × 7mm QFN-10
LT3754
16-Channel × 50mA LED Driver
VIN = 6V to 40V, VOUT(MAX) = 60V, 3,000:1 True Color PWM Dimming,
ISD = <2µA, 5mm × 5mm QFN-32
3760fc
32 Linear Technology Corporation
LT 0312 REV C • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
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www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2009