LT3755_15 Datasheet, PDF (1/26 Pages) Linear Technology – 40VIN, 75VOUT LED Controllers

LT3755/LT3755-1/LT3755-2
40V_IN, 75V_OUT LED Controllers
Features
n _{3000:1 True Color PWM™ Dimming}
n _{Wide Input Voltage Range: 4.5V to 40V}
n _{Output Voltage Up to 75V}
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 _{Improved Open LED Status Pin (LT3755-2)}
n _{Frequency Synchronization (LT3755-1)}
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}
n _{Battery Chargers}
n _{Accurate Current Limited Voltage Regulators}
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.
Typical Application
V_IN
8V TO
40V
50W White Automotive LED Headlamp Driver
22µH
4.7µF 1M
V_IN
SHDN/UVLO
FB
185k
V_REF
ISP
332k
LT3755-2
CTRL
0.1Ω 1A
INTV_CC
40.2k
ISN
GATE
100k
SENSE
OPENLED
0.015Ω
PWM
SS
RT
PWMOUT
0.01µF
V_C
28.7k
375kHz _10k
GND INTV_CC
4.7µF
0.001µF
1M
4.7µF
23.7k
50W
LED
STRING
37551 TA01a
100
96
92
88
84
80
0
Efficiency vs V_IN
10
20
30
40
V_IN (V)
37551 TA01b
37551fd