LT3756-1 Datasheet PDF - Linear Technology

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LT3756-1
Linear Technology

Part Number LT3756-1
Description 100VOUT LED Controller
Page 20 Pages


LT3756-1 datasheet pdf
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FEATURES
n 3000:1 True Color PWMTM Dimming
n Wide Input Voltage Range: 6V to 100V
n Output Voltage Up to 100V
n Constant-Current and Constant-Voltage Regulation
n 100mV High Side Current Sense
n Drives LEDs in Boost, Buck Mode, Buck-Boost Mode,
SEPIC or Flyback Topology
n Adjustable Frequency: 100kHz to 1MHz
n Open LED Protection
n Programmable Undervoltage Lockout with Hysteresis
n Open LED Status Pin (LT3756)
n Frequency Synchronization (LT3756-1)
n PWM Disconnect Switch Driver
n CTRL Pin Provides Analog Dimming
n Low Shutdown Current: <1μA
n Programmable Soft-Start
n Thermally Enhanced 16-Lead QFN (3mm × 3mm)
and MSOP Packages
APPLICATIONS
n High Power LED Applications
n Industrial
n Automotive
LT3756/LT3756-1
100VIN, 100VOUT
LED Controller
DESCRIPTION
The LT®3756 and LT3756-1 are DC/DC controllers designed
to operate as a constant-current source for driving high
current LEDs. They drive a low side external N-channel
power MOSFET from an internal regulated 7V supply. The
fixed frequency, current-mode architecture results in stable
operation over a wide range of supply and output voltages.
A ground referenced voltage FB pin serves as the input for
several LED protection features, and also makes it possible
for the converter to operate as a constant-voltage source.
A frequency adjust pin allows the user to program the
frequency from 100kHz to 1MHz to optimize efficiency,
performance or external component size.
The LT3756/LT3756-1 sense output current at the high
side of the LED string. High side current sensing is the
most flexible scheme for driving LEDs, allowing boost,
buck mode or buck-boost mode configuration. The PWM
input provides LED dimming ratios of up to 3000:1, and the
CTRL input provides additional analog dimming capability.
Both parts are available in the 16-lead QFN (3mm × 3mm)
and MSOP packages.
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners. Protected by U.S. Patents, including 7199560
and 7321203.
TYPICAL APPLICATION
VIN
8V TO 60V
(100V TRANSIENT)
94% Efficient 30W White LED Headlamp Driver
22μH
4.7μF 1M
VIN
SHDN/UVLO
FB
332k
INTVCC
100k
0.01μF
10k
332k
40.2k
VREF
CTRL
LT3756
ISP
ISN
GATE
OPENLED
SENSE
PWM
SS
RT
28.7k VC
400kHz
1% 10k
PWMOUT
GND INTVCC
4.7μF
0.001μF
0.27Ω
0.018Ω
370mA
1M
14k
4.7μF
30W
LED
STRING
3756 TA01a
100
96
92
88
84
80
0
Efficiency vs VIN
20 40 60
VIN (V)
80
37561 TA01b
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ABSOLUTE MAXIMUM RATINGS (Note 1)
VIN ..........................................................................100V
SHDN/UVLO.......................................... 100V, VIN + 0.3V
ISP, ISN ...................................................................100V
INTVCC ...................................................... 8V, VIN + 0.3V
GATE, PWMOUT........................................INTVCC + 0.3V
CTRL, PWM, OPENLED.............................................12V
VC, VREF, SS, FB .........................................................3V
SYNC ..........................................................................8V
RT ............................................................................1.5V
SENSE......................................................................0.5V
Operating Junction Temperature Range
(Note 2) ............................................. –40°C to 125°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range................... –65°C to 125°C
PIN CONFIGURATION
PWMOUT 1
FB 2
ISN 3
ISP 4
VC 5
CTRL 6
VREF 7
PWM 8
TOP VIEW
16 GATE
15 SENSE
14 VIN
13
12
ISNHTDVNCC/UVLO
11 RT
10 SS
9 SYNC OR OPENLED
MSE PACKAGE
16-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 43°C/W, θJC = 4°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
TOP VIEW
16 15 14 13
VREF 1
PWM 2
SYNC OR OPENLED 3
12 FB
11 PWMOUT
17
10 GATE
SS 4
9 SENSE
5678
UD PACKAGE
16-LEAD (3mm s 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = 68°C/W, θJC = 4.2°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3756EMSE#PBF
LT3756EMSE#TRPBF
3756
16-Lead Plastic MSOP
–40°C to 125°C
LT3756IMSE#PBF
LT3756IMSE#TRPBF
3756
16-Lead Plastic MSOP
–40°C to 125°C
LT3756EMSE-1#PBF
LT3756EMSE-1#TRPBF 37561
16-Lead Plastic MSOP
–40°C to 125°C
LT3756IMSE-1#PBF
LT3756IMSE-1#TRPBF 37561
16-Lead Plastic MSOP
–40°C to 125°C
LT3756EUD#PBF
LT3756EUD#TRPBF
LDMQ
16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C
LT3756IUD#PBF
LT3756IUD#TRPBF
LDMQ
16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C
LT3756EUD-1#PBF
LT3756EUD-1#TRPBF LDMR
16-Lead (3mm × 3mm) Plastic QFN –40°C to 125°C
LT3756IUD-1#PBF
LT3756IUD-1#TRPBF
LDMR
16-Lead (3mm × 3mm) Plastic QFN –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/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
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LT3756/LT3756-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temp-
erature range, otherwise specifications are at TA = 25°C. VIN = 24V, SHDN/UVLO = 24V, CTRL = 2V, PWM = 5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VIN Minimum Operating Voltage
VIN Shutdown IQ
VIN Tied to INTVCC
SHDN/UVLO = 0V, PWM = 0V
SHDN/UVLO = 1.15V, PWM = 0V
6
0.1 1
5
V
μA
μA
VIN Operating IQ (Not Switching)
VC = 0V, RT = 100k to GND
1.4 1.7
mA
VREF Voltage
VREF Line Regulation
SENSE Current Limit Threshold
100μA ≤ IVREF ≤ 0μA
6V ≤ VIN ≤ 100V
l 1.965
98
2.00
0.006
108
2.045
118
V
%/V
mV
SENSE Input Bias Current
Current Out of Pin
40 μA
SS Pull-Up Current
Current Out of Pin
8 10.5 13
μA
Error Amplifier
LED Current Sense Threshold (VISP – VISN)
FB = 0V, VISP = 48V
LED Current Sense Threshold at CTRL = 0V (VISP – VISN) CTRL = 0V, FB = 0V, VISP = 48V
CTRL Threshold Linear Programming Range
l 96 100 103
–13 –10
–8
0 1.1
mV
mV
V
CTRL Input Bias Current
Current Out of Pin
50 100
nA
LED Current Sense Amplifier Input Common Mode
Range (VISP)
ISP/ISN Short-Circuit Threshold (VISP – VISN)
VISN = 0V
2.9 100
115 150 200
V
mV
ISP/ISN Short-Circuit Fault Sensing Common Mode
Range (VISN)
ISP/ISN Input Bias Current
LED Current Sense Amplifier gm
VC Output Impedance
VC Standby Input Bias Current
PWM = 5V (Active), VISP = 48V
PWM = 0V (Standby), VISP = 48V
VISP – VISN = 100mV
1V < VVC < 2V
PWM = 0V
03
50
0 0.1
120
15000
–20 20
V
μA
μA
μS
nA
FB Regulation Voltage (VFB)
FB Amplifier gm
VISP = VISN
FB = VFB, VISP = VISN
l 1.220
1.232
1.250
1.250
480
1.270
1.265
V
V
μS
FB Pin Input Bias Current
FB Open LED Threshold
Current Out of Pin
OPENLED Falling (LT3756 Only)
VFB
60mV
40
VFB
50mV
100
VFB
40mV
nA
V
FB Overvoltage Threshold
PWMOUT Falling
VFB + VFB + VFB +
50mV 60mV 70mV
V
VC Current Mode Gain – ΔVVC/ΔVSENSE
Oscillator
4 V/V
Switching Frequency
Minimum Off-Time
RT = 100k
RT = 10k
l 90
925
105 125
1000 1050
170
kHz
kHz
ns
Linear Regulator
INTVCC Regulation Voltage
Dropout (VIN – INTVCC)
INTVCC Undervoltage Lockout
IINTVCC = –10mA, VIN = 7V
7 7.15 7.3
1
3.9 4.1 4.3
V
V
V
INTVCC Current Limit
INTVCC Current in Shutdown
SHDN/UVLO = 0V, INTVCC = 7V
14 18 23
mA
8 12
μA
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ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temp-
erature range, otherwise specifications are at TA = 25°C. VIN = 24V, SHDN/UVLO = 24V, CTRL = 2V, PWM = 5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Logic Inputs/Outputs
PWM Input High Voltage
1.5 V
PWM Input Low Voltage
0.4 V
PWM Pin Resistance to GND
45 60
PWMOUT Output Low (VOL)
PWMOUT Output High (VOH)
SHDN/UVLO Threshold Voltage Falling
SHDN/UVLO Rising Hysteresis
SHDN/UVLO Input Low Voltage
SHDN/UVLO Pin Bias Current Low
SHDN/UVLO Pin Bias Current High
OPENLED Output Low (VOL)
SYNC Pin Resistance to GND
IVIN Drops Below 1μA
SHDN/UVLO = 1.15V
SHDN/UVLO = 1.30V
IOPENLED = 0.5mA (LT3756 Only)
LT3756-1 Only
INTVCC
– 50mV
l 1.185
0
1.220
20
1.7 2.05
10
30
50
1.245
0.4
2.5
100
200
mV
V
V
mV
V
μA
nA
mV
SYNC Input High
LT3756-1 Only
1.5 V
SYNC Input Low
LT3756-1 Only
0.4 V
Gate Driver
tr GATE Driver Output Rise Time
tf GATE Driver Output Fall Time
GATE Output Low (VOL)
GATE Output High (VOH)
CL = 3300pF
CL = 3300pF
35
35
INTVCC
– 50mV
0.05
ns
ns
V
V
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 LT3756E and LT3756E-1 are 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 LT3756I and LT3756I-1 are guaranteed to meet performance
specifications over the –40°C to 125°C operating junction temperature
range.
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