LT3743_15 Datasheet, PDF (1/28 Pages) Linear Technology – High Current Synchronous Step-Down LED Driver with Three-State Control

FEATURES
n _{PWM Dimming Provides Up to 3000:1 Dimming Ratio}
n _{CTRL_SEL Dimming Provides Up to 3000:1 Dimming}
Ratio Between Any Current
n _{Three-State Current Control for Color Mixing}
n _{±6% Current Regulation Accuracy}
n _{6V to 36V Input Voltage Range}
n _{Average Current Mode Control}
n _{2µs Maximum Recovery Time Between Any Current}
Regulation State
n _{<1µA Shutdown Current}
n _{Output Voltage Regulation and Open-LED Protection}
n _{Thermally Enhanced 4mm × 5mm QFN and}
28-Pin FE Package
APPLICATIONS
n _{DLP Projectors}
n _{High Power Architectural Lighting}
n _{Laser Diodes}
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 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,
8120335 and others pending.
TYPICAL APPLICATION
92% Efficient 20A LED Driver
EN/UVLO
PWM
CTRL_SEL
82.5k
2.2nF
100k
R_HOT
499Ω
100k
R_NTC
10k
10nF
EN/UVLO
V_IN
PWM
CTRL_SEL
RT
HG
SYNC
CBOOT
V_REF LT3743 SW
CTRL_L
V_{CC_INT}
CTRL_H
LG
GND
CTRL_T
SENSE⁺
SENSE^–
PWMGH
1µF
220nF
22µF
4.7µF
×4
V_IN
10V TO 30V
M1
1.1µH _2.5mΩ
OUTPUT
20A MAXIMUM
4.7µF
330µF
M2
×3
330µF
×3
M3
M4
CTRL_SEL
5V/DIV
PWM
5V/DIV
SW
20V/DIV
I_LED
10A/DIV
SS
PWMGL
FB
V_CL
V_{CH 3743 TA01a}
34k
34k
8.2nF
8.2nF
M1, M2: SiR462DP
M3, M4: Si7234DP
330µF
×3
51.1k
10.0k
V_IN = 24V
20µs/DIV
0A TO 2A TO 20A LED CURRENT STEP
3743 TA01b
3743fd
1