DC1694B - Demo Manual

DEMO MANUAL DC1694B
LT3748
100V Isolated
Flyback Converter
DESCRIPTION
Demonstration circuit 1694B is an isolated flyback converter featuring the LT®3748. The demo circuit is designed
for a 12V output from a 22V to 75V DC input. The output
current is up to 2.5A. The part senses the isolated output
voltage directly from the primary side flyback waveform
during the off time of the power switch. No third winding,
opto-coupler, or signal transformer is required for regulation. A minimum load of approximately 2% of maximum
load is required on the output to maintain regulation.
The LT3748 is a high input voltage isolated flyback controller operating with input supply voltages from 5V to
100V, and 1.9A average gate drive source and sink current.
The LT3748 utilizes boundary mode operation to provide
a high efficiency, small size solution with improved load
regulation of ±5% over the full line, load and temperature
ranges. The LT3748 can be used in a wide variety of industrial, automotive, medical, telecom, data-com applications,
where regulated isolated output is required.
The demo circuit can be easily modified for applications
of different input, and output voltage/current, with some
pre-designed transformers from vendors such as Würth
Electronics, Sumida, Pulse Engineering and Coilcraft. Both
EP13 and EFD20 core transformers can be assembled on
the board. A two-stage filter is optional for applications
requiring very small output ripple.
The LT3748 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 1694B.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1694B
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.
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
PARAMETER
CONDITIONS
MIN
TYP
22
48
75
V
Output Voltage
VIN = 22V to 75V
IOUT = 50mA to 2.5A
11.4
12
12.6
V
Maximum Output Current
VIN = 22V to 75V
2.5
Output Voltage Ripple (Peak-to-Peak)
VIN = 22V to 75V, IOUT = 2.5A
Switching Frequency
VIN = 48V, IOUT = 2.5A
289
kHz
Efficiency
VIN = 48V, IOUT = 2.5A
86.5
%
Input Voltage Range
MAX
UNITS
A
420
mV
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DEMO MANUAL DC1694B
QUICK START PROCEDURE
Demo circuit 1694B is easy to set up to evaluate the
performance of the LT3748. Refer to Figure 1 for proper
measurement equipment setup and follow the procedure
below.
1.With power off, connect the input power supply to VIN
and GND.
2.Connect the load to the terminals VOUT+ and VOUT– on
the board. Apply a load between 100mA to 2.5A to the
output.
3.Turn on the power at the input. Increase VIN to 22V.
NOTE: Make sure that the input voltage does not exceed
75V.
4.Check for the proper output voltages. The output should
be regulated at 12V (±5%).
NOTE: If there is no output, temporarily disconnect
the power supply. Make sure that the load is properly
connected. If the output voltage is out of spec, make
sure minimum load current is applied to the output,
the load is not set too high, and the DC power supply
does not hit the current limit.
2
NOTE: If higher operating voltage is required, power
components with higher voltage ratings should be used.
NOTE: The LT3748 requires minimum load to maintain
good regulation. A Zener diode D4 is placed between
VOUT+ and VOUT– to clamp the output voltage to ~13V
if minimum load requirement is not met. Depending on
input voltage and output regulation, a 100mA minimum
load is usually sufficient.
5.Once the proper output voltage is established, adjust the
input and load within the operating range and observe
the output voltage regulation, ripple voltage, efficiency
and other parameters.
NOTE: When measuring the input or output voltage
ripples, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or output
voltage ripple by touching the probe tip directly across
the VIN and GND, or VOUT+ and VOUT– terminals. See
Figure 2 for proper scope probe technique.
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DEMO MANUAL DC1694B
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup
INPUT OR OUTPUT CAPACITOR
Figure 2. Proper Scope Probe Placement for Measuring Input or Output Ripple
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DEMO MANUAL DC1694B
PARTS LIST
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART #
Required Circuit Components
1
1
C1
CAP., ELECTRO., 100µF, 100V
CHEMI-CON, EMVY101ARA101MKE0S
2
2
C2, C3
CAP., X7R, 2.2µF, 100V, 20% 1210
TDK C3225X7R2A225M
3
1
C6
CAP., X7R, 1.0µF, 100V, 20% 1206
AVX, 12061C105MAT2A
4
1
C7
CAP., X7R, 0.1µF, 16V, 10% 0402
TDK, C1005X7R1C104K
5
1
C8
CAP., C0G, 470pF, 50V, 5% 0402
TDK, C1005COG1H471J
6
1
C9
CAP., X5R, 4.7µF, 16V, 20% 0805
AVX, 0805YD475MAT2A
7
1
C10
CAP., C0G, 220pF, 100V, 5% 0805
AVX, 08051A221JAT2A
8
1
C11
CAP., X7R, 22nF, 25V, 10% 0402
MURATA, GRM155R71E223KA61D
9
1
C12
CAP., X7R, 2200pF, 250V, 10% 1812
MURATA, GA343QR7GD222KW01L
10
3
C16, C17, C18
CAP., X7R, 22µF,16V, 20% 1210
TDK, C3225X7R1C226M
11
1
C20
CAP., COG, 270pF, 100V, 5% 0805
MURATA, GRM2165C2A271JA01D
12
1
D1
DIODE., PDS5100, Power DI-5
DIODE INC., PDS5100-13
13
1
D3
Schottky Barrier Rec., BAT41, SOD523
ST, BAT41KFILM
14
1
D4
ZENER DIODE, DFLZ13, 13V, PowerDI-123
DIODE INC., DFLZ13-7
15
1
Q1
N-MOSFET, SI7450DP, PowerPAK
VISHAY, SI7450DP-T1-GE3
16
1
R1
RES., CHIP, 12.1k, 1% 0402
VISHAY, CRCW040212K1FKED
17
1
R3
RES., CHIP, 402k, 1% 0402
VISHAY, CRCW0402402KFKED
18
1
R5
RES., CHIP, 6.04k, 1% 0402
NIC, NRC04F6041TRF
19
1
R6
RES., CHIP, 32.4k, 1% 0402
VISHAY, CRCW040232K4FKED
20
1
R7
RES., CHIP, 150k, 1% 0603
VISHAY, CRCW0603150KFKED
21
2
R8, R13
RES., CHIP, 0, 1% 0603
VISHAY, CRCW06030000Z0EA
22
1
R9
RES., CHIP, 63.4k, 1% 0402
VISHAY, CRCW040263K4FKED
23
1
R10
RES., CHIP, 0.015Ω, 1/8W, 1% 0805
VISHAY, WSL0805R015F
24
2
R11, R12
RES., CHIP, 43Ω, 1/4W, 5% 1206
VISHAY, CRCW120643R0JNEA
25
1
R14
RES., CHIP, 10, 1% 0603
VISHAY, CRCW060310R0FKED
26
1
R15
RES., CHIP, 22, 1/8W, 5% 0805
VISHAY, CRCW080522R0JNEA
27
1
T1
TRANSFORMER
Midcom, Inc. 750311607
28
1
U1
I.C. LT3748EMS, MSOP-16
LINEAR TECH., LT3748EMS#TRPBF
Additional Demo Board Circuit Components
1
0
C4, C5, C13, C14, C15 ( OPT.) CAP., 1210
2
0
C19 (OPT.)
CAP., 0603
3
0
D5 (OPT.)
Schottky Barrier Rec., SOD-323
4
0
L1 (OPT.)
INDUCTOR
5
0
ROUT (OPT.)
RES., 1210
Hardware – For Demo Board Only
1
4
E1, E2, E5, E6
TESTPOINT, TURRET, .094” pbf
MILL-MAX, 2501-2-00-80-00-00-07-0
2
1
JP1
3 PIN 0.079 SINGLE ROW HEADER
SAMTEC, TMM103-02-L-S
3
1
XJP1
SHUNT, .079” CENTER
SAMTEC, 2SN-BK-G
4
4
MTG 4 CORNERS
STAND-OFF, NYLON (SNAP ON), 0.25” TALL
KEYSTONE, 8831
4
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VIN
GND
22V - 75V
E2
E1
EN
JP1
SHDN
250V
1812
3
2
1
C2 C3
2.2uF
100V
1210
C12
2200pF
SHDN
100uF
100V
+ C1
C4
C5
1210
OPT
C7
0.1uF
R6
32.4k
R3
402k
TC
SS
C11
22nF
R1
12.1k
EN/UVLO
R9
63.4K
12
10
3
C6
1uF
100V
1206
11
VC
1
VIN
GND
8
SENSE
GATE
RFB
INTVCC
C8
470pF
7
6
16
5
R13
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.
R7
0
0603
0
4
R10
0.015
0805
1 2 3
Q1
SI7450DP
5 6 7 8
10
0603
R14
0805
100V
7
PDS5100
D1
100V
0805
0805
C16 C17 C18
22uF
16V
1210
22
R15
D4
DFLZ13
13V
1. ALL RESISTORS ARE 0402.
ALL CAPACITORS ARE 0402.
NOTE: UNLESS OTHERWISE SPECIFIED
6
8
10
4
5
12
9
11
Midcom
750311607
T1
3
2
1
270pF
Figure 3. DC1694B Demo Circuit Schematic
C19
OPT.
0603
0603
OPT.
D5
220pF
C10
BAT41KFILM
SOD523
D3
1206
1206
150K
R8
43
R12
43
R11
C9
4.7uF
16V
0805
0603
R5
6.04K
U1
LT3748EMS
GND
9
RREF
14
C20
ROUT
OPT
1210
L1
0.47uH
OPT.
C13 C14 C15
OPT
1210
VOPT
E6
E5
VOUT-
12V / 2.5A
VOUT+
DEMO MANUAL DC1694B
SCHEMATIC DIAGRAM
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DEMO MANUAL DC1694B
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 © 2014, Linear Technology Corporation
6
dc1694bfa
Linear Technology Corporation
LT 0914 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
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 LINEAR TECHNOLOGY CORPORATION 2012
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