DC2339A - Demo Manual

DEMO MANUAL DC2339A
LT3744
High Current Synchronous
Step-Down LED Driver
Description
Demonstration circuit 2339A is a high current synchronous
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
the step-down configuration only. The inverting buck-boost
configuration is shown in a separate demonstration circuit.
The input of the demo board is up to 36V. The components
are optimized for the efficiency, thermal and PWM dimming 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
determined by the LED voltage and the maximum duty cycle.
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.
The typical efficiency of the demo board is 93.5% from
a 12V 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 a big advantage in minimizing temperature
rise. If an efficiency measurement is needed in an application, 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
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.
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1
DEMO MANUAL DC2339A
Description
PWM
2V/DIV
PWM
(YELLOW)
2V/DIV
LED CURRENT
(GREEN)
6.67A/DIV
2.00µs/DIV
Figure 1. DC2339A Current Rise Time. VIN = 12V, LED Voltage = 4.2V when ON. Total LED Current = 20A
Performance Summary
Specifications are at TA = 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
PVIN
Input Supply Voltage
VLED+ = 5V
5.5
VLED+
Maximum Output Voltage
IOUT
Output Current
fSW
Switching Frequency
EFF
Efficiency at DC
TYP
MAX
36
6.05
CTRL1, CTRL2, CTRL3 = 1.5V
19
380
VIN = 12V, IOUT = 20A, VOUT = 5V
UNITS
V
V
20
21
A
425
470
kHz
93.5
%
Quick Start Procedure
Demonstration circuit 2339A is easy to set up to evaluate 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. Connect a DC supply or a PWM signal to PWM1, PWM2
and/or PWM3.
2
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.
dc2339af
DEMO MANUAL DC2339A
Quick Start Procedure
++
–
+
DC or
PWM
DC or
PWM
INPUT
SUPPLY
–
–
DC or
PWM
Figure 2. Proper Measurement Equipment Setup
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3
DEMO MANUAL DC2339A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
CAP., X7R, 10µF, 50V, 10%, 1210
MURATA, GRM32ER71H106KA12L
Required Circuit Components
1
6
C1, C2, C24, C25, C30, C31
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
4
dc2339af
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
A
B
C
C27
1nF
SYNC
PWM3
PWM2
PWM1
CTRL3
CTRL2
CTRL1
EN/UVLO
SGND
SGND
SGND
SGND
PVIN
C29
1nF
R21
100K
R3
R22
100K
C14
2.2uF
SGND
R8
R16
C26
R9
E8
100K
1nF
7
5
4
2
6
3
1
36
E9
82.5K
OPT
100K
0805
C7
1uF
50V
R33
0
R17
309K
E7
E14
5
100K
R25
13
14
VIN
RT
SS
FAULT
SYNC
PWM3
PWM2
PWM1
CTRL3
CTRL2
CTRL1
CTRLT
VREF
EN/UVLO
VIN
U1
LT3744EUHE
C24
C30
10uF
50V
1210
1. ALL RESISTORS ARE 0603.
ALL CAPACITORS ARE 0603.
NOTE: UNLESS OTHERWISE SPECIFIED
R19
309K
R23
100K
C18 10nF
11
10
9
R20
100K
R2
OPT
C2
C1
10uF
50V
1210
8
R18
309K
R7
100K
C4
56uF,50V
50HVT56M
E13
C28
1nF
R10
100K
+
E12
E11
R6
100K
E16
E15
E2
E1
E10
E6
E4
J2
J1
4
C25
C31
10uF
50V
1210
C5
56uF,50V
50HVT56M
10nF
10nF
10nF
C23
0
LED_ISN
LED_ISP
FB
PWM_OUT3
PWM_OUT2
PWM_OUT1
ISN
ISP
VF NEG
BG
SW
INTVCC
C8
22uF
6.3V
0805
C6
0.22uF
4
15
16
17
PWM3
23
0
R13
PWM2
0
R12
PWM1
4
25
C17
OPT
R36
0
27
21
22
24
32
Q3 Q5
BSC026N04LS
30
34
D1
PMEG4002EB
R4
0
R1
3
D3-1
BAT54A
D2
OPT
744355182
L1
0.82uH
KRL6432
R5
0.003
Q1
Q2
BSC035N04LS G
D3-2
4
2
BAT54A
3
2
+
Si7234DP
Q6
8
7
5
6
C10
OPT
C11
470uF
4
2
D4-2
BAT54A
3
2
Figure 3. F. DC2339A Demo Circuit Schematic
C22
R30
R31
25.5K 25.5K
C21
R29
25.5K
+
29
*
12
SGND
31
BOOST
2
1
5
6
7
8
1
2
3
5
6
7
8
1
2
3
PVIN
1
3
3.3V - 36V
1
3
D
3
1
+
Q4
Si7234DP
8
7
5
6
C15
OPT
C12
470uF
2
R32
0.003
KRL6432
4
2
D4-1
BAT54A
3
1
2
1
3
3
+
Si7234DP
Q7
8
7
5
6
C13
OPT
C16
470uF
4
R27
1k
R14
4.02K
C19
1nF
J4
J6
LED1-
LED+
Q8
BSC010N04LS
PWM1
C9
47uF
10V
1206
5
6
7
8
1
2
3
SEE DEMO MANUAL
4
4
Q9
BSC010N04LS
PWM2
J7
LED2-
LED+
J5
1
5
6
7
8
4
LED+
1
J3
J8
LED3-
Q10
BSC010N04LS
PWM3
1
2
3
*
VEE
28
VEE
26
VEE
33
VEE
35
VEE
37
VC1
20
TG
VC2
19
VC3
18
5
6
7
8
1
2
3
5
E5
E3
SGND
LED+
A
B
C
D
DEMO MANUAL DC2339A
Schematic Diagram
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5
DEMO MANUAL DC2339A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) 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 LTC 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 LTC 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. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC 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 LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
6
dc2339af
Linear Technology Corporation
LT 0215 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2015
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