DEMO MANUAL DC1517A
LT3511: Monolithic
High Voltage Isolated
Flyback Converter
DESCRIPTION
The flyback converter requires a minimum load to maintain good regulation. A Zener diode is placed between
VOUT+ and VOUT– to clamp output voltage to ~7.5V if the
minimum load requirement is not met. Depending on the
input voltage and the output regulation requirement, a
15mA to 20mA minimum load is usually sufficient.
This demo circuit uses a diode-Zener clamp to limit the
peak spike voltage due to transformer leakage inductance.
A diode-Zener clamp is more efficient than a RCD clamp.
The LT3511 operates in boundary mode and also provides
output voltage temperature compensation.
The LT3511 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.
Design files for this circuit board are available at
http://www.linear.com/demo
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.
90
80
70
EFFICIENCY (%)
Demonstration circuit 1517A is a monolithic high voltage
isolated flyback converter featuring the LT3511. This demo
circuit is designed for a 5V isolated output from an input
voltage range of 36V to 75V. The maximum output current
is up to 300mA. The circuit doesn’t require an opto-isolator,
due to the output voltage being sensed directly from the
primary side transformer winding. A third winding off the
transistor is used to bias the LT3511 for highest efficiency.
60
50
40
30
20
VIN = 36V
VIN = 75V
10
0
50
100
150
200
250
LOAD CURRENT (mA)
300
DC1517A F01
Figure 1. DC1517A Efficiency
PERFORMANCE SUMMARY
PARAMETER
(TA = 25°C)
CONDITIONS
Minimum Input Supply Voltage
Maximum Input Supply Voltage
VALUE
UNITS
36
V
75
V
Output Voltage
IOUT = 300mA
5
V
Output Voltage Tolerance
IOUT = 300mA
±5
%
VIN = 36V, IOUT = 300mA
150
kHz
VIN = 75V, IOUT = 300mA
220
kHz
300
mA
84
%
Switching Frequency
Maximum Output Current
Efficiency
VIN = 36V, IOUT = 300mA
dc1517afa
1
DEMO MANUAL DC1517A
QUICK START PROCEDURE
Demonstration circuit 1517A is easy to set up to evaluate the performance of the LT3511. Refer to Figure 2 for
proper measurement equipment setup and to follow the
procedure below:
Note: When measuring the input or output voltage ripple, 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.
Note: Make sure GND and VOUT– are not connected together accidently,
such as by two oscilloscope probes.
1. With power off, connect the input power supply to VIN
and GND.
2. Connect a load of 300mA or less to VOUT+ and VOUT–
terminals (not GND).
3. Turn on the power at the input.
4. Check for the proper output voltage (5V).
Note: If there is no output, temporarily disconnect the load to make
sure that the load is not set too high.
5. Once the proper output voltage is established, adjust the
load and input within the operating ranges and observe
the output voltage regulation, ripple voltage, efficiency
and other parameters.
Figure 2. Proper Measurement Equipment Setup
PARTS LIST
ITEM
QUANTITY
Required Circuit Components
1
1
2
1
3
1
4
1
5
1
6
1
7
1
8
1
9
1
10
1
REFERENCE
DESCRIPTION
MANUFACTURERS PART NUMBER
C2
C3
C5
C9
C10
D1
D2
D4
D5
R3
Capacitor, X7R, 1μF 100V, 10%, 1206
Capacitor, X5R, 47μF 10V, 10%,1210
Capacitor, Electrolytic, 10μF 100V
Capacitor, X7R, 4.7μF 16V, 10%, 0805
Capacitor, X7R, 3300pF, 50V, 0402
Diode, Schottky, SOD-323
Diode, SOD-123
Zener Diode, SOD-123
Zener Diode, SOD-123
Resistor, Chip, 806k, 1%, 0805
Murata, GRM31CR72A105KA01L
Murata, GRM32ER61A476KE20L
SUNCON, 100CE10BS
Taiyo Yuden, EMK212137475KG
AVX, 04025C332KAT2A
Diodes Inc. SBR140S3
Diodes Inc. BAV21W-7-F
ON Semiconductor, MMSZ5266BT1G
Central Semiconductor, CMHZ5236B
Vishay, CRCW0805806KFKEA
dc1517afa
2
DEMO MANUAL DC1517A
PARTS LIST
ITEM
QUANTITY
REFERENCE
11
1
R4
12
2
R5, R7
13
1
R6
14
1
R8
15
1
T1
16
1
U1
Additional Demo Board Circuit Components
1
1
C6
2
0
C7 (Optional)
3
1
D3
4
1
R9
Hardware, for Demo Board Only
1
6
E1-E6
DESCRIPTION
Resistor, Chip, 169k, 1%, 0603
Resistor, Chip, 31.6k, 1%, 0402
Resistor, Chip, 69.8k, 1%, 0402
Resistor, Chip, 10k, 1%, 0402
Transformer
I.C., LT3511EMS, 16-Pin MSOP
MANUFACTURERS PART NUMBER
Vishay, CRCW0603169KFKEA
Vishay, CRCW040231K6FKED
Vishay, CRCW040269K8FKED
NIC, NRC04F1002TRF
Würth, 750311558
Linear Technology, LT3511EMS
Capacitor, X7R, 1000pF 2000V, 10%,1206
Capacitor, 0402
Diode, Schottky, SOD-323
Resistor, Chip, 20, 1%, 0402
AVX 1206GC102KAT1A
Central Semiconductor, CMDSH-3 TR
Vishay, CRCW040220R0FKED
Testpoint, Turret, .095"
MILL-MAX, 2501-2-00-80-00-00-07-0
SCHEMATIC DIAGRAM
5
4
3
2
1
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EN / UVLO
RFB 14
1 EN/UVLO
E5
2
3
D4
7 NC
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D1 SBR140S3
2
1
8
1
D
VOUT+
+5V@300mA
VOUT+
E1
C3
47uF
10V
1210 VOUTE3
VOUT-
Lp = 300uH
D2
BAV21W
R4 169K
D5
CMHZ5236B
7
MMSZ5266BTIG
C6
1000pF
2000V
R5
31.6K
C
6
2
1
LT3511EMS
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2
U1
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5
C2
1uF
100V
1206
1
E4
+ C5
10uF
R3
100V
(OPT) 806K
0805
2
GND
4
E2
VIN 3
VIN
36V - 75V
5(9
1
T1
750311558
D
(&2
C
SW 16
BIAS
11 TC
R6
69.8K
GND
GND
GND
D3
CMDSH-3
1
2
12 RREF
9
8
5
10 VC
BIAS 6
R9 20
BIAS
E6
R7
31.6K
B
C7
(OPT)
R8
10K
C10
3300pF
B
C9
4.7uF
16V
0805
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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.
3
DEMO MANUAL DC1517A
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.
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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
dc1517afa
4
Linear Technology Corporation
LT 0211 REV A • PRINTED IN USA
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