LT3741/LT3741-1
High Power, Constant
Current, Constant Voltage,
Step-Down Controller
FEATURES
DESCRIPTION
n
Control Pin Provides Accurate Control of Regulated
The LT 3741 and LT3741-1 are fixed frequency synchro-
Output Current
nous step-down DC/DC controllers designed to accurately
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1.5% Voltage Regulation Accuracy
regulate the output current at up to 20A. The average current-
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6% Current Regulation Accuracy
mode controller will maintain inductor current regulation
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6V to 36V Input Voltage Range
over a wide output voltage range of 0V to (V 2V). The
IN
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Wide Output Voltage Range Up to (V 2V) regulated current is set by an analog voltage on the CTRL
IN
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Average Current Mode Control pins and an external sense resistor. Due to its unique
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<1A Shutdown Current topology, the LT3741 is capable of sourcing and sinking
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Up to 94% Efficiency current. If sinking current is not required, or for parallel
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Additional Pin for Thermal Control of Load Current applications, use the LT3741-1. The regulated voltage and
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overvoltage protection are set with a voltage divider from
Thermally Enhanced 4mm 4mm QFN and 20-Pin
the output to the FB pin. Soft-Start is provided to allow a
FE Package
gradual increase in the regulated current during startup.
The switching frequency is programmable from 200kHz to
APPLICATIONS
1MHz through an external resistor on the RT pin or through
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the use of the SYNC pin and an external clock signal.
General Purpose Industrial
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Super-Cap Charging
Additional Features include an accurate external reference
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Applications Needing Extreme Short-Circuit Protec-
voltage for use with the CTRL pins, an accurate UVLO/EN
tion and/or Accurate Output Current Limit
pin that allows for programmable UVLO hysteresis, and
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Constant Current or Constant Voltage Source
thermal shutdown.
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. Patents including 7199560, 7321203 and others pending.
TYPICAL APPLICATION
10V/20A Constant Current, Constant Voltage Step-Down Converter
V vs I
V
IN OUT OUT
EN/UVLO EN/UVLO V
IN
14V TO 36V
12
RT 1F 100F
SYNC
82.5k
HG
10
LT3741
220nF
V
REF
CBOOT
2.2H
V
10nF 2.5m
OUT
8
10V
SW
20A
CTRL1
6
V
CC_INT
VC
22F
39.2k
4
R
LG
HOT 150F
45.3k
2
5.6nF
GND
V = 18V
2 IN
+
CTRL2 SENSE V = 10V
OUT
88.7k I = 20A
SENSE
LIMIT
0
R
NTC SS FB
0 2 4 6 8 10 12 14 16 18 20 22
10nF
12.1k
I (A)
OUT
3741 TA01b
3741 TA01a
37411fg
1
For more information www.linear.com/LT3741
V (V)
OUTLT3741/LT3741-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
V Voltage ................................................................40V RT Voltage ..................................................................3V
IN
EN/UVLO Voltage ........................................................6V FB Voltage ...................................................................3V
V Voltage ...............................................................3V SS Voltage ..................................................................6V
REF
CTRL1 and CTRL2 Voltage ..........................................3V V Voltage ...........................................................6V
CC_INT
+
SENSE Voltage ........................................................40V SYNC Voltage ..............................................................6V
SENSE Voltage ........................................................40V Storage Temperature Range .................. 65C to 150C
VC Voltage ..................................................................3V Lead Temperature (Soldering, 10 sec)
SW Voltage ...............................................................40V TSSOP ..............................................................300C
CBOOT ......................................................................46V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 20 LG
CC_INT
GND 2 19 CBOOT
20 19 18 17 16
V 3 18 SW
IN
EN/UVLO 1 15 HG
EN/UVLO 4 17 HG
V 2 14 GND
REF
V 5 16 GND
REF
21
21
CTRL2 3 13 SYNC
GND
GND
CTRL2 6 15 SYNC
GND 4 RT
12
GND 7 14 RT
CTRL1 GND
5 11
CTRL1 8 13 VC
6 7 8 9 10 SS 9 12 SENSE
+
FB 10 11 SENSE
FE PACKAGE
20-LEAD PLASTIC TSSOP
UF PACKAGE
20-LEAD (4mm 4mm) PLASTIC QFN
T = 125C, = 38C/W
JMAX JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
T = 125C, = 37C/W
JMAX JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB