Linear Technology DC2339A Quick setup guide

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DEMO MANUAL DC2339A
Description
LT3744
High Current Synchronous
Step-Down LED Driver
Demonstrationcircuit2339Aisahighcurrentsynchronous
step-down LED driver featuring the LT
®
3744. The unique
drive stage used on the LT3744 allows the anodes of three
LEDs to be connected together for better heat sinking. This
connection will work in both the step-down configuration
and the inverting buck-boost configuration. The pros and
cons of each configuration can be found in the data sheet.
This demonstration circuit 2339A is for customers to test
thestep-downconfiguration only.Theinvertingbuck-boost
configuration is shown in aseparate demonstration circuit.
The input of the demo board is up to 36V. The components
are optimized for the efficiency, thermal and PWM dim-
ming for a 12V input. Each of the three outputs is up to
5V, 20A with a 6.05V maximum output voltage limit. The
PWM1, PWM2 and PWM3 pins are set to low by default.
A DC or PWM signal is required to connect to at least one
of the PWM pins to enable the circuit. At any giving time,
output current only passes through one LED determined
by settings of PWM pins.
The CTRL1, CTRL2 and CTRL3 pins can be adjusted to
provide accurate analog dimming down to 20:1 ratio.
The minimal input voltage for the LT3744 to operate is
3.3V. However, to maintain the output current regulation
in a step down regulator, the minimum input voltage is
determinedbytheLEDvoltageandthemaximum dutycycle.
For a 5V output, the demo board minimum input voltage
will be around 5.5V at room temperature. The load to be
used with this demo board is high current LEDs or laser
diodes. Smaller LEDs may not be able to handle the high
current, even for a short period of time. It is necessary
to mount the LED load on a proper heat sink. A fan may
become necessary to avoid exceeding LED’s maximum
temperate rating.
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.
The typical efficiency of the demo board is 93.5% from
a12V input to 5V, 20A load. The lower the input voltage,
the higher the efficiency tends to be for a given load. At
output power level of 100W, even one percent of efficiency
improvement is abig advantage in minimizing temperature
rise. If an efficiency measurement is needed in an applica-
tion, the output voltage must be measured at the output
capacitors instead of the LED load. This prevents cable
loss from being counted as a loss of the board.
The demo circuit DC2399A achieves fast current rise time
from 0A to 20A in 5µs. To see the real rise time, connecting
wires between the LED and the board should be as short as
possible to minimize the wire inductance and resistance. It
is recommended to measure the voltage across R32 with
a short 50Ω coax cable directly into a BNC connector on
the oscilloscope. The current can be calculated from the
measured voltage. Figure 1 shows the current rise time. A
current probe adds more delays to the rise time so using
a current probe is not recommended unless rise time is
not a concern.
The LT3744 data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 2339A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2339A

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DEMO MANUAL DC2339A
Quick start proceDure
Demonstration circuit 2339A is easy to set up to evalu-
ate the performance of the LT3744. Refer to Figure 2 for
proper measurement equipment setup and follow the
procedure below:
1. With power off, connect the input power supply to PVIN
and GND. Note: make sure PVIN is below 36V. Con-
nect a DC supply or a PWMsignal to PWM1, PWM2
and/or PWM3.
2. With power off, connect the LED load to VLED+ and
proper LED1–, LED2–, LED3–according to the setting
of the PWM pins.
3. Turn on the power at the input. Turn on PWM1, PWM2
and/or PWM3.
4. Carefully evaluate other design parameters as needed.
performance summary
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
PVIN Input Supply Voltage VLED+ = 5V 5.5 36 V
VLED+ Maximum Output Voltage 6.05 V
IOUT Output Current CTRL1, CTRL2, CTRL3 = 1.5V 19 20 21 A
fSW Switching Frequency 380 425 470 kHz
EFF Efficiency at DC VIN = 12V, IOUT = 20A, VOUT = 5V 93.5 %
Figure 1. DC2339A Current Rise Time. VIN = 12V, LED Voltage = 4.2V when ON. Total LED Current = 20A
2.00µs/DIV
PWM
2V/DIV
PWM
(YELLOW)
2V/DIV
LED CURRENT
(GREEN)
6.67A/DIV
Description

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DEMO MANUAL DC2339A
Figure 2. Proper Measurement Equipment Setup
INPUT
SUPPLY
DC or
PWM
DC or
PWM
DC or
PWM
+
–
+
–
+ –
Quick start proceDure

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DEMO MANUAL DC2339A
parts List
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 6 C1, C2, C24, C25, C30, C31 CAP., X7R, 10µF, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12L
2 2 C4, C5 CAP., ALUM., ELECT., 56µF, 50V SUN ELECT., 50HVT56M
3 1 C6 CAP., X7R, 0.22µF, 25V, 10% 0603 MURATA, GRM188R71E224KA88D
4 1 C7 CAP., X7R, 1µF, 50V, 10% 0805 AVX, 08055C105KAT2A
5 1 C8 CAP., X7R, 22µF, 6.3V, 10% 0805 AVX, 08056D226KAT2A
6 1 C9 CAP., X5R, 47µF, 10V, 10% 1206 MURATA, GRM31CR61A476KE15L
7 3 C11, C12, C16 CAP., POSCAP, 470µF, 6.3V, D4D PANASONIC, 6TPF470MAH
8 1 C14 CAP., X5R, 2.2µF, 25V, 10% 0603 MURATA, GRM188R61E225KA12D
9 4 C18, C21, C22, C23 CAP., X7R, 10nF, 25V, 10% 0603 AVX, 06033C103KAT2A
10 5 C26-C29, C19 CAP., X7R, 1nF, 25V, 10% 0603 AVX, 06033C102KAT2A
11 1 D1 SCHOTTKY RECTIFIER, 40V, SOD523 NXP, PMEG4002EB
12 2 D3, D4 DIODE, BAT54A SOT23 DIODES INC., BAT54A-7-F
13 1 L1 INDUCTOR, 0.82µH Würth Elektronik, 744355182
14 2 Q1, Q2 N-CH., 40-V, PG-TDSON-8 INFINEON, BSC035N04LS G
15 2 Q3, Q5 N-CH., 40-V, PG-TDSON-8 INFINEON, BSC026N04LS
16 3 Q4, Q6, Q7 N-CH., 12-V, PowerPAK SO-8 VISHAY, Si7234DP-T1-GE3
17 3 Q8-Q10 N-CH., 40-V, PG-TDSON-8 FL INFINEON, BSC010N04LS
18 6 R1, R4, R12, R13, R33, R36 RES., CHIP., 0Ω, 1/10W, 0603 VISHAY, CRC06030000Z0EA
19 10 R3, R6-R8, R10, R20-R23, R25 RES., CHIP., 100K, 1/10W, 1% 0603 VISHAY, CRCW0603100KFKEA
20 2 R5, R32 RES., CHIP., 0.003Ω, 3W, 1%, KRL6432 SUSUMU, KRL6432E-M-R003-F
21 1 R14 RES., CHIP., 4.02K, 1/10W, 1% 0603 VISHAY, CRCW06034K02FKEA
22 1 R16 RES., CHIP., 82.5K, 1/10W, 1% 0603 VISHAY, CRCW060382K5FKEA
23 3 R17, R18, R19 RES., CHIP., 309K, 1/10W, 1% 0603 VISHAY, CRCW0603309KFKEA
24 1 R27 RES., CHIP., 1k, 1/10W, 1% 0603 VISHAY, CRCW06031K00FKEA
25 3 R29, R30, R31 RES., CHIP., 25.5k, 1/10W, 1% 0603 VISHAY, CRCW060325K5FKEA
26 1 U1 I.C. LT3744EUHE 36PIN, UHE LINEAR TECH., LT3744EUHE#PBF
Additional Demo Board Circuit Components
1 0 C10, C13, C15(OPT) CAP., D4D
2 0 C17 (OPT) CAP., 0603
3 0 D2(OPT) DIODE, DI123
4 0 R2, R9(OPT) RES., CHIP., 0603
Hardware: For Demo Board Only
1 16 E1-E16 TESTPOINT, TURRET, 0.094" MILL-MAX, 2501-2-00-80-00-00-07-0
2 8 J1-J8 JACK BANANA KEYSTONE, 575-4
3 4 STAND-OFF STAND-OFF, NYLON, 0.25" (SNAP ON) KEYSTONE, 8831

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DEMO MANUAL DC2339A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Figure 3. F. DC2339A Demo Circuit Schematic
schematic Diagram
5
5
4
4
3
3
2
2
1
1
D
D
C
C
B
B
A
A
1. ALL RESISTORS ARE 0603. ALL CAPACITORS ARE 0603. NOTE: UNLESS OTHERWISE SPECIFIED
*
SEE DEMO MANUAL
*
PWM1 PWM2 PWM3
PWM1
PWM2
PWM3
E10
CTRL2
R16 82.5K
J2
SGND
C19
1nF
D3-2
BAT54A
3 2
C30 1210 10uF
50V
R27
1k
E14
PWM3
E2
SGND
E1
PVIN
R10
100K
C23
10nF
R12 0
R14
4.02K
R3
100K
Q1
BSC035N04LS G
3
2
1
4
5
6
7
8
C25
1210 10uF
50V
E7
SYNC
C18 10nF
+
C15 OPT
Q5
3
2
1
4
5
6
7
8
R29
25.5K
R2
OPT
J7
LED2-
J5
LED+
E12
PWM1
R22
100K
Q6
Si7234DP
3
4
1
27
8 6 5
C1
50V
+
C16 470uF
E9
VIN
Q8
BSC010N04LS
3
2
1
4
5
6
7
8
U1 LT3744EUHE
EN/UVLO
1
VREF
3
CTRLT
6
CTRL1
2
CTRL2
4
SS
14
FB 17
ISP 22
ISN 21
LED_ISN 15
LED_ISP 16
RT
13
SYNC
10
PWM1
7
CTRL3
5
PWM_OUT3 23
TG 29
SW 30
BOOST 31
BG 32
INTVCC 34
VIN
36
VEE
33
PWM2
8
PWM3
9
FAULT
11
VEE
35
VC1
20
VC2
19
VC3
18
VEE
26
PWM_OUT1 27
VF NEG 24
PWM_OUT2 25
VEE
28
SGND 12
VEE
37
J6
LED1-
D1
PMEG4002EB
1 2
D3-1
BAT54A
31
C17
OPT
R33 0
D4-1
BAT54A
3 1
R7
100K
R13 0
Q7 Si7234DP
3
4
1
27
8 6 5
+
C5
56uF,50V
50HVT56M
E13
PWM2
R5
0.003
KRL6432
D2
OPT
C27 1nF
R18
309K
L1
0.82uH
744355182 C9
47uF
1206
10V
R9 OPT
R19 309K
R1
0
E3
LED+
R21
100K
J3
LED+
R8 100K
E8
SGND
+
C4
56uF,50V
50HVT56M
R17
309K
R30
25.5K
R4 0
Q9
BSC010N04LS
3
2
1
4
5
6
7
8
E6
CTRL1
E15
SGND
+
C10 OPT
R36
0
C2
10uF 1210
C24
1210 10uF
50V
E5
SGND
R31
25.5K
E16
SGND
C22
10nF
Q2
3
2
1
4
5
6
7
8
C8
22uF
6.3V
0805
+
C13 OPT
C31
1210 10uF
50V
J1
PVIN
3.3V - 36V
+
C12 470uF
D4-2
BAT54A
3 2
J4
LED+
J8
LED3-
C14
2.2uF
R6
100K
E11
CTRL3
C26 1nF
Q4
Si7234DP
3
4
1
27
8 6 5
R23
100K
E4
EN/UVLO
R20
100K
C29 1nF
Q3
BSC026N04LS
3
2
1
4
5
6
7
8
R25
100K
C7 1uF 50V
0805
C6
0.22uF
C28 1nF
+
C11 470uF
Q10
BSC010N04LS
3
2
1
4
5
6
7
8
R32 0.003
KRL6432
C21
10nF

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DEMO MANUAL DC2339A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2015
LT 0215 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LT C ) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LT C for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LT C from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LT C assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LT C currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LT C applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation

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