LT3755/LT3755-1/LT3755-2
40V
IN
, 75V
OUT
LED Controllers
FeaTures
3000:1 True Color PWM™ Dimming
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Wide Input Voltage Range: 4.5V to 40V
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Output Voltage Up to 75V
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Constant-Current and Constant-Voltage Regulation
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100mV High Side Current Sense
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Drives LEDs in Boost, Buck Mode, Buck-Boost Mode,
SEPIC or Flyback Topology
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Adjustable Frequency: 100kHz to 1MHz
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Open LED Protection
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Programmable Undervoltage Lockout with Hysteresis
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Improved Open LED Status Pin (LT3755-2)
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Frequency Synchronization (LT3755-1)
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PWM Disconnect Switch Driver
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CTRL Pin Provides Analog Dimming
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Low Shutdown Current: <1µA
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Programmable Soft-Start
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Thermally Enhanced 16-Lead QFN (3mm
×
3mm)
and MSOP Packages
n
DescripTion
The LT
®
3755, LT3755-1 and LT3755-2 are DC/DC control-
lers 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 7.15V
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 LT3755/LT3755-1/LT3755-2 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.
L,
LT, LTC, 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.
applicaTions
n
n
n
High Power LED
Battery Chargers
Accurate Current Limited Voltage Regulators
Typical applicaTion
50W White Automotive LED Headlamp Driver
V
IN
8V TO
40V
22µH
4.7µF
1M
185k
V
IN
SHDN/UVLO
V
REF
332k
CTRL
INTV
CC
100k
40.2k
LT3755-2
ISN
GATE
OPENLED
PWM
SS
PWMOUT
RT
V
C
GND INTV
CC
10k
0.001µF
37551 TA01a
Efficiency vs V
IN
100
1M
4.7µF
FB
ISP
0.1
1A
23.7k
96
EFFICIENCY (%)
50W
LED
STRING
92
SENSE
88
0.015
84
80
0.01µF
28.7k
375kHz
4.7µF
0
10
20
V
IN
(V)
30
40
37551 TA01b
37551fd
LINEAR_DIMENSIONS [ LINEAR DIMENSIONS SEMICONDUCTOR ]
