FEATURES
n
n
n
n
n
n
n
n
n
n
LT3743
High Current Synchronous
Step-Down LED Driver with
Three-State Control
DESCRIPTION
The LT
®
3743 is a fixed frequency synchronous step-down
DC/DC controller designed to drive high current LEDs. The
average current mode controller will maintain inductor
current regulation over a wide output voltage range of 0V
to (V
IN
– 2V). LED dimming is achieved through analog
dimming on the CTRL_L, CTRL_H and CTRL_T pins and
with PWM dimming on the PWM and CTRL_SEL pins.
Through the use of externally switched load capacitors,
the LT3743 is capable of changing regulated LED current
levels within several μs, providing accurate, high speed
PWM dimming between two current levels. The switching
frequency is programmable from 200kHz to 1MHz through
an external resistor on the RT pin.
Additional features include voltage regulation and
overvoltage protection set with a voltage divider from the
output to the FB pin. Overcurrent protection is provided
and set by the CTRL_H pin.
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 and others pending.
PWM Dimming Provides Up to 3000:1 Dimming Ratio
CTRL_SEL Dimming Provides Up to 3000:1 Dimming
Ratio Between Any Current
Three-State Current Control for Color Mixing
6% Current Regulation Accuracy
6V to 36V Input Voltage Range
Average Current Mode Control
2μs Maximum Recovery Time Between Any Current
Regulation State
<1μA Shutdown Current
Output Voltage Regulation and Open-LED Protection
Thermally Enhanced 4mm
×
5mm QFN and
28-Pin FE Package
APPLICATIONS
n
n
n
DLP Projectors
High Power Architectural Lighting
Laser Diodes
TYPICAL APPLICATION
92% Efficient 20A LED Driver
EN/UVLO
PWM
CTRL_SEL
82.5k
EN/UVLO
PWM
CTRL_SEL
RT
SYNC
V
REF
LT3743
2nF
R
HOT
45.3k
40k
40k
CTRL_L
CTRL_H
V
IN
1μF
HG
220nF
CBOOT
SW
20μF
V
CC_INT
LG
GND
CTRL_T
R
NTC
680k
SS
10nF
FB
VCL
34k
9nF
VCH
34k
9nF
3743f
4.7μF
4
V
IN
10V TO 36V
1.1μH
2.5mΩ
V
OUT
20A MAXIMUM
CTRL_SEL
5V/DIV
PWM
5V/DIV
SW
20V/DIV
20μF
1mF
1mF
SENSE
+
SENSE
–
PWMGH
PWMGL
51k
1mF
10.0k
3743 TA01a
I
LED
10A/DIV
20μs/DIV
V
IN
= 24V
0A TO 2A TO 20A LED CURRENT STEP
3743 TA01b
1
LINER [ LINEAR TECHNOLOGY ]
