LT3761_15 Datasheet, PDF (1/28 Pages) Linear Technology – 60VIN LED Controller with Internal PWM Generator

Features
n _{3000:1 True Color PWM™ Dimming for LEDs}
n _{Wide VIN Range: 4.5V to 60V}
n _{Rail-to-Rail Current Sense Range: 0V to 80V}
n _{Programmable PWM Dimming Signal Generator}
n _{Constant Current (±3%) and Constant-Voltage}
(±2%) Regulation
n _{Analog Dimming}
n _{Drives LEDs in Boost, SEPIC, Inverting, Buck Mode,}
Buck-Boost Mode, or Flyback Configuration
n _{Output Short-Circuit Protected Boost}
n _{Open LED Protection and Reporting}
n _{Adjustable Switching Frequency: 100kHz to 1MHz}
n _{Programmable VIN UVLO with Hysteresis}
n _{C/10 Indication for Battery Chargers}
n _{Low Shutdown Current: <1µA}
n _{Thermally Enhanced 16-Lead MSOP Package}
Applications
n _{High Voltage LED Strings >100V with Ground}
Referred Current Sense
n _{Grounded Anode LEDs}
n _{Battery and SuperCap Chargers}
n _{Accurate Current Limited Voltage Regulators}
LT3761
60V_IN LED Controller with
Internal PWM Generator
Description
The LT^®3761 is a DC/DC controller designed to operate as
a constant-current source and constant-voltage regulator.
It features a programmable internal PWM dimming signal.
The LT3761 is ideally suited for driving high current LEDs,
but also has features to make it suitable for charging bat-
teries and supercapacitors. The fixed frequency, current
mode architecture results in stable operation over a wide
range of supply and output voltages. A voltage feedback
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 LT3761 senses output current at the high side or at the
low side of the load. The PWM input can be configured to
self-oscillate at fixed frequency with duty ratio program-
mable from 4% to 96%. When driven by an external
signal, the PWM input provides LED dimming ratios of
up to 3000:1. The CTRL input provides additional analog
dimming capability.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
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
94% Efficient Boost LED Driver for Automotive
Headlamp with 25:1 Internal PWM Dimming
V_IN
8V TO
60V
10µH
2.2µF
×2
499k
90.9k
INTV_CC
1M
140k
V_IN
EN/UVLO
GATE
V_REF
SENSE
LT3761
CTRL
GND
2.2µF ^1M
×4
10mΩ
16.9k
100k
DIM
124k
0.01µF
47nF
300Hz
FB
OPENLED
ISP
DIM/SS
ISN
PWM
PWMOUT
V_C
RT INTV_CC
5.1k
4.7nF
28.7k
350kHz
INTV_CC
1µF
0.25Ω
1A
60W
LED
STRING
I_LED
1A/DIV
PWM Dimming Waveforms at
Various DIM Voltage Settings
0.5ms/DIV
V_DIM = 7.7V
DC_PWM = 96%
V_DIM = 4V
DC_PWM = 50%
V_DIM = 1.5V
DC_PWM = 10%
V_DIM = 0.4V
DC_PWM = 4.3%
3761 TA01b
3761 TA01a
3761f
1