LT3755 Datasheet, PDF (1/24 Pages) Linear Technology – 40VIN, 75VOUT LED Controller

LT3755/LT3755-1
40V_IN, 75V_OUT LED Controller
FEATURES
n _{3000:1 True Color PWM}^TM _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 _{Open LED Status Pin (LT3755)}
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 Applications}
n _Industrial
n _Automotive
DESCRIPTION
The LT^®3755 and LT3755-1 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 LT3755/LT3755-1 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 (3mm × 3mm) QFN
and MSOP packages.
L, 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.
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
CTRL
0.1Ω 1A
INTV_CC
40.2k
ISN
GATE
100k
OPENLED
SENSE
0.015Ω
PWM
SS
D2
0.01μF
RT
PWMOUT
V_C
GND INTV_CC
28.7k
10k
400kHz _10k
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
37551fa
1