LT3744_15 Datasheet, PDF (1/32 Pages) Linear Technology – High Current Synchronous Step-Down LED Driver

LT3744
High Current Synchronous
Step-Down LED Driver
Features
Description
n _{Ideal for Driving Up to 40A LEDs}
n _{Up to 3000:1 PWM Dimming}
n _{20:1 Analog Dimming}
n _{±3% Current Regulation Accuracy}
n _{±3% Voltage Regulation Accuracy}
n _{Unique Inverting Buck-Boost Topology Allows}
Grounded Heat Sink to Be Used for RGB LEDs
n _{3.3V to 36V Input Voltage Range}
n _{Peak Current Mode with DC LED Current Sensing}
n _{Open and Shorted LED Protection and Fault Reporting}
n _{Floating LED Driver Allows Single Power Solution}
to Drive Multicolor LEDs or Single LED with Three
Different Regulated Currents
n _{Thermally Enhanced 5mm × 6mm QFN 36-Lead}
Package
Applications
n _{LED Driver for DLP Projectors}
n _{Heads-Up Displays}
n _{High Power LED}
The LT^®3744 is a fixed frequency synchronous step-down
DC/DC controller designed to drive a LED load at up to 20A
continuous or 40A pulsed. The peak current mode controller
will maintain ±3% LED current regulation over a wide output
voltage range, from VEE to V_IN. By allowing VEE to float
to negative voltages, several LEDs in series can be driven
from a single Li-Ion battery with a simple, single step-down
output stage. PWM dimming is achieved with the PWM pins.
The regulated LED current is set with analog voltages at the
CTRL pins. Regulated voltage and overvoltage protection
are set with a voltage divider from the output to the FB pin.
The switching frequency is programmable from 100kHz to
1MHz through an external resistor on the RT pin.
Additional features include an accurate external reference
voltage, a control input for thermally derating regulation
current, an accurate EN/UVLO pin, an open-drain output
fault flag, OVLO, frequency synchronization, and thermal
shutdown.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 7199560, 7321203, 8120335 and 8901904.
Typical Application
LED Driver for DLP Projectors
EN/UVLO
2V
2.2µF _100k
45.3k
680k
1nF
82.5k
4.7nF
51k
4.7nF
51k
4.7nF
51k
EN/UVLO
V_IN
PWM1
PWM2
PWM3
TG
CTRL1
CTRL2
CTRL3
BOOST
SW
LT3744
V_REF
INTV_CC
FAULT
BG
CTRLT
VEE
SGND
ISP
ISN
SYNC
SS
RT
VEE
PWM_OUT1
PWM_OUT2
V_FNEG
PWM_OUT3
V_C1
LED_ISP
LED_ISN
V_C2
FB
V_C3
20µF
VEE
220nF
V_IN
220µF ^{3.3V TO 12V}
0.47µH _1mΩ
22µF
330µF
330µF
330µF
VEE
20A MAXIMUM
51k
GREEN
10µF
3mΩ
10k
3744 TA01a
For more information www.linear.com/LT3744
LED Current Waveforms
(2000:1) 0A to 6.7A to 13.3A to 20A
PWM1
5V/DIV
PWM2
5V/DIV
PWM3
5V/DIV
I_LED
6.7A/DIV
25µsec/DIV
3744 TA01b
3744f
1