Linear LT3748 Quick setup guide

1
dc1860bfa
DEMO MANUAL DC1860B
Description
LT3748
No-Opto Isolated FlybacK
Converter for PSE Applications
Demonstration circuit 1860B is an isolated flyback con-
verter featuring the LT3748. This demo circuit is designed
for Power Sourcing Equipment (PSE) applications with a
52.5V output from a 10V to 15V DC input, with nominal
input voltage of 12V. The output current is from 0mA to
700mA, and is capableof a maximum shortperiod overload
current of 900mA. Table 1 summarizes the performance
of the demo board. This demo circuit can also be easily
modified for different PSE applications with some pre-
designed transformers.
The LT3748 is a high input voltage isolated flyback control-
ler 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
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
efficiency, small size solution with improved regulation.
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.
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 1860B.
Design files for this circuit board are available at
http://www.linear.com/demo
(TA= 25°C)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage Range 10 12 15 V
Output Voltage VIN = 10V – 15V
IOUT = 0V – 700 mA
50 52.5 55 V
Maximum Output Current VIN = 10V – 15V 700 mA
Minimum Output Current VIN = 10V – 15V 0 mA
Output Voltage Ripple (Peak to Peak) VIN = 10V – 15V, IOUT = 0 – 700mA 150 mV
Efficiency VIN = 13.2V, IOUT = 700mA 87.8 %

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dc1860bfa
DEMO MANUAL DC1860B
qUick stArt proceDUre
Demo circuit 1860B is easy to set up to evaluate the
performance of the LT3748. Refer to Figure 1 for proper
equipment setup and follow the procedure below.
1. With power off, connect the input power supply to the
board through VIN (E1) and GND (E2) terminals.
2. Connect the load to the terminals VOUT+(E6) and VOUT–
(E7) on the board.
3. Turn on the power at the input. Increase VIN slowly to
10V.
NOTE: Make sure that the input voltage does not exceed
15V. If higher operating voltage is required, power com-
ponents with higher voltage ratings should be used.
4. Check for the proper output voltages. The output should
be regulated at 52.5V (±5%).
NOTE: The LT3748 requires minimum load to maintain
good output voltage regulation. A zener diode D1 together
with preload resistors R2, R14, R15 and R16 are placed in
the output to clamp the output voltage to ~52.5V without
ex-board preload requirement. The efficiency is higher
than 90% without the preload resistors, but the output
may exceed 57V under no load or transient condition.
5. Once the proper output voltage is established, adjust
the input voltage and load current 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
terminals of the input or output capacitor. See Figure2 for
proper scope probe technique.
NOTE: A gate resistor of less than 10Ω can be added
to the demo circuit to slow down the turning off of the
switch, and reduce the switching node voltage spike. A
RC snubber can be added as well to the primary winding
of the transformer to damp the spike and reduce the EMI.

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dc1860bfa
DEMO MANUAL DC1860B
qUick stArt proceDUre
Figure 1. Proper Measurement Equipment Setup
Figure 2. Proper Scope Probe Placement for Measuring Input or Output Ripple
+ –
VOUT GND
COUT
dc1860b F02

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dc1860bfa
DEMO MANUAL DC1860B
LOAD CURRENT (mA)
0
0
10
EFFICIENCY (%)
70
80
90
50
60
20
30
40
100
600 700200100 300 400 500
dc1860b F03
VIN = 15V
VIN = 13.2V
VIN = 10V
LOAD CURRENT (mA)
0
50.0
Output Voltage (V)
52.0
52.5
50.5
51.0
51.5
53.0
600 700200100 300 400 500
dc1860b F04
VIN = 10V
VIN = 15V
qUick stArt proceDUre
Figure 3. Typical Efficiency Curve, (TA= 25°C)
Figure 4. Load Regulation
Figure 5. Recovery from Short Circuit Fault
VOUT: 20V/DIV
VDS: 20V/DIV

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dc1860bfa
DEMO MANUAL DC1860B
pArts list
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 2 C2, C3 Cap., X5R, 22µF, 16V, 20%, 1210 Taiyo Yuden EMK325BJ226MN
2 1 C5 Cap., X7S, 0.22µF, 100V, 10%, 0805 TDK C2012X7S2A224KT
3 3 C6, C7, C8 Cap., X7S, 4.7µF, 100V, 20%, 1812 TDK C4532X7S2A475MT
4 1 C9 Cap., Elect. 470µF, 63V, 20%, J16-PANASONIC PANASONIC EEVFK1J471M
5 1 C10 Cap., X5R, 4.7µF, 16V, 20%, 0805 Taiyo Yuden EMK212BJ475MG
6 1 C11 Cap., X5R, 0.33µF, 10V, 20%, 0603 AVX 0603ZD334MAT1A
7 1 C12 Cap., NPO, 470pF, 25V, 10%, 0603 AVX 06033A471KAT2A
8 1 C13 Cap., Ceramic 2.2nF, 250V, 10%, 1812 Murata GA343QR7GD222KW01L
9 2 C14, C15 Cap,, X7R, 6800pF, 25V, 20%, 0603 AVX 06033C682MAT2A
10 1 D1 Diode Zener 62V ON Semi. 1SMB5943BT3
11 1 D2 Schottky Diode 1A/100V, PowerDItm123 Diodes Inc. DFLS1100
12 1 D3 Schottky Diode 3A, PowerDi5 Diodes Inc. PDS3200-13
13 1 L1 Inductor, 1.8µH Würth Electronik 744318180
14 1 Q1 Mosfet N-Channel, 100V, LFPAK Renesas HAT2173H-EL-E
15 2 R1, R13 Res., Chip, 16k, 0.25W, 5%, 1206 Vishay CRCW120616K0JNED
16 4 R2, R14, R15, R16 Res., Chip, 11.8k, 0.25W, 1%, 1206 Vishay CRCW120611K8FKEA
17 2 R3, R7 Res/Jumper, Chip, 0Ω, 1/16W, 1 AMP 0603 Vishay CRCW06030000Z0EA
18 1 R4 Res., Chip, 200k, 0.06W, 1%, 0603 Vishay CRCW0603200KFKEA
19 1 R5 Res., Chip, 36k, 0.06W, 5%, 0603 Vishay CRCW060336K0JNEA
20 1 R6 Res., Chip, 82.5k, 0.06W, 1%, 0603 Vishay CRCW060382K5FKEA
21 1 R8 Res., Chip, 22, 0.06W, 5%, 0603 Vishay CRCW060322R0JNEA
22 1 R9 Res., Chip, 270k, 0.06W, 5%, 0603 Vishay CRCW0603270KJNEA
23 1 R10 Res., Chip, 40.2k, 0.06W, 1%, 0603 Vishay CRCW060340K2FKEA
24 1 R11 Res., Chip, 6.04k, 0.06W, 1%, 0603 Vishay CRCW06036K04FKEA
25 1 R12 Res., 0.005, 0.25W, 1%, 1206 Vishay Dale WSL-1206-5L000-1%
26 1 T1 Transformer, XFMR Würth Elektronik 750311591
27 1 U1 I.C., LT3748EMS Linear Tech. Corp. LT3748EMS
Hardware For Demo Board Only
1 2 E1, E2 Connector, Banana Jack Keystone 575-4
2 3 E5, E6, E7 Turret, Testpoint Mill Max 2501-2-00-80-00-00-07-0
3 1 JP1 Headers, Sgl. Row, 3 Pins, 2mm Ctrs. Samtec TMM-103-02-L-S
4 4 MH1, MH2, MH3, MH4 STAND-OFF, NYLON 0.25" tall KEYSTONE, 8831(SNAP ON)
5 1 XJP1 Shunt, 2mm Ctrs. Samtec 2SN-BK-G
6 1 FAB, 1860B, Rev 3.PCB DEMO CIRCUIT 1860B
7 2 STENCILS - TOP & BOTTOM STENCIL DC1860B
Additional Demo Board Circuit Components
1 0 C1 (Opt) Cap., Alum 330µ,F 25V, 10%, 25cv330gX SANYO 25CV330gX
2 0 C16 (Opt) Cap., Alum. Elect. 100µF, 63V, ±20%, NipponChemi-Con/JA0 Nippon Chemi-Con EMZA630ADA101MJA0G
3 0 L2 (Opt) Inductor, 47µH, IHLP4040 VISHAY IHLP-4040DZ-ER-470-M11
4 0 T2 (Opt) Transformer, XFMR Würth Elektronik 750311456
5 0 T3 (Opt) Transformer, XFMR Würth Elektronik 750311604
6 0 E3, E4 (Opt) Turret, Testpoint Mill Max 2501-2-00-80-00-00-07-0

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dc1860bfa
DEMO MANUAL DC1860B
scheMAtic DiAgrAM
A A
B B
C C
D D
E E
4 4 3 3 2 2 1 1
VIN SW
VOPT
DIODE
VOUT+
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CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
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CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
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SHEET OF
TITLE:
APPROVALS
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APP ENG.
TECHNOLOGY
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CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
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REVISION HISTORY
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REVISION HISTORY
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Oct 01, 2012
R16
11.8k 1% 1206
R16
11.8k 1% 1206
D2
DFLS1100
D2
DFLS1100
JP1
SHDN
RUN
SHDN
JP1
SHDN
RUN
SHDN
1 3 2
+
C9
470uF
63V
+
C9
470uF
63V
U1 LT3748EMS U1 LT3748EMS
VIN
1
EN/UVLO
3
INTVCC
5
RFB
16
GATE
6
SENSE
7
GND
9
GND
8
SS
10
TC
12
VC
11
REF
14
R10
40.2k
1%
R10
40.2k
1%
R1
16k 1206
R1
16k 1206
E6 VOUT+
[email protected]
E6 VOUT+
[email protected]
C7
4.7uF
100V 1812 C7
4.7uF
100V 1812
C8
4.7uF
100V 1812 C8
4.7uF
100V 1812
R4 200k
1%
R4 200k
1%
E1
VIN
10V-15V
E1
VIN
10V-15V
E2
GND
E2
GND
D3
PDS3200-13
D3
PDS3200-13
1 2
3
C10
4.7uF
16V
0805
C10
4.7uF
16V
0805
C14 6800pF C14 6800pF
C11
0.33uF
C11
0.33uF R8
22 R8 22
C12
470pF
C12
470pF
D1
1SMB5943BT3
D1
1SMB5943BT3
R9 270k R9 270k
R15
11.8k 1% 1206
R15
11.8k 1% 1206
C13
2.2nF
250V 1812
C13
2.2nF
250V 1812
C6
4.7uF
100V 1812 C6
4.7uF
100V 1812
E4
VOPT-
(Opt)
E4
VOPT-
(Opt)
R12
0.005
1206
R12
0.005
1206
C2 22uF
16V 1210
C2 22uF
16V 1210
+
C1 330uF
25V
SANYO (Opt)
+
C1 330uF
25V
SANYO (Opt) E7
VOUT-
E7
VOUT-
C3 22uF
16V 1210
C3 22uF
16V 1210
R5
36k
R5
36k
Q1 HAT2173H-EL-E Renesas Q1 HAT2173H-EL-E Renesas
L1
1.8uH
744318180
Wurth Electronik
L1
1.8uH
744318180
Wurth Electronik
R14
11.8k 1% 1206
R14
11.8k 1% 1206
E5
EXT_EN
E5
EXT_EN
R7
0 Ohm
R7
0 Ohm
C5
0.22uF
100V 0805
C5
0.22uF
100V 0805
R2
11.8k 1% 1206
R2
11.8k 1% 1206
R3 0 Ohm R3 0 Ohm
T1
750311591
T1
750311591
6 5
8 9 3
1
11 12
4 210
7
R6
82.5k
1%
R6
82.5k
1%
R13
16k 1206
R13
16k 1206
R11 6.04k 1% R11 6.04k 1%
C15
6800pF
C15
6800pF
E3 VOPT+
[email protected]
(Opt)
E3 VOPT+
[email protected]
(Opt)

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dc1860bfa
DEMO MANUAL DC1860B
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.
scheMAtic DiAgrAM
A A
B B
C C
D D
E E
4 4 3 3 2 2 1 1
Optional Circuit
VIN
SW
VOPT
DIODE
VOPT VOUT+
SIZE DATE:
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TITLE:
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APP ENG.
TECHNOLOGY

 


CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
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ZHONGMING Y.
C:\PADS PROJECTS\1860B\REV_B(09-17-12)\SCH\1860B_REV1.DSN
SIZE DATE:
IC NO. REV.
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TITLE:
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APP ENG.
TECHNOLOGY

 


CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
1


22




ZHONGMING Y.
C:\PADS PROJECTS\1860B\REV_B(09-17-12)\SCH\1860B_REV1.DSN
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY

 


CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
1

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22




ZHONGMING Y.
C:\PADS PROJECTS\1860B\REV_B(09-17-12)\SCH\1860B_REV1.DSN
C16
100uF
63V
(Opt)
C16
100uF
63V
(Opt)
L2
47uH
VISHAY
IHLP-4040DZ-ER-470-M11
(Opt)
L2
47uH
VISHAY
IHLP-4040DZ-ER-470-M11
(Opt)
T2
750311456
(Opt)
T2
750311456
(Opt)
3 5 2 1
9 6 7
10
T3
750311604
(Opt)
T3
750311604
(Opt)
6 5
93
112 4 211
8

8
dc1860bfa
DEMO MANUAL DC1860B
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2011
LT 0213 REV A • PRINTED IN USA
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 applica-
tion engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation

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