Linear Technology DC1739B-C Quick setup guide

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DEMO MANUAL DC1739B-C
DESCRIPTION
LTC3765/LTC3766
120W Isolated Forward Converter
with Synchronous Rectification
Demonstration circuit 1739B-C is a 120W isolated forward
converter with synchronous rectification featuring the
LT C
®
3765/LTC3766 chip set.
This circuit was designed to demonstrate the high level of
performance, efficiency, and small solution size attainable
using this chip set in an active-clamp-reset forward con-
verter power supply. It operates at 240kHz and produces
a regulated 12V, 10A output from an input voltage range
of 9V to 36V: suitable for telecom, industrial, and other
applications.Ithas an eighth-brick footprint area. Synchro-
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.
nous rectificationhelps to attain efficiency exceeding 94%.
Secondary-side control eliminates complex opto-coupler
feedback, providing fast transient response with minimum
output capacitance. For other output requirements, see the
LTC3766 data sheet or contact the LT C factory.
Design files for this circuit board are available at
http://www.linear.com/demo
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range 9 36 V
VOUT Output Voltage 12.0 V
IOUT Output Current Range, Continuous 200LFM 0 10 A
fSW Switching (Clock) Frequency 240 kHz
VOUT(P-P) Output Ripple VIN = 24V, IOUT = 10A (20MHz BW) 40 mVP–P
IREG Output Regulation Line and Load (9VIN to 36VIN, 0AOUT to 10AOUT) ±0.27 %
POUT/PIN Efficiency (See Figure 3) VIN = 24V, IOUT = 10A 92.7 %
Isolation Basic 1500 VDC
Approximate Size Component Area ×Top Component Height 2.3 ×0.9 ×0.47 Inches
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DEMO MANUAL DC1739B-C
OPERATING PRINCIPLES
QUICK START PROCEDURE
The LTC3765 active clamp forward controller and gate
driver is used on the primary and provides start-up, gate
drive, and protection functions. Once start-up is accom-
plished, the LTC3766 high efficiency, secondary-side
synchronous forward controller takes over, and provides
the LTC3765 with timing information and bias power
through a small pulse transformer.
When input voltage is applied, the LTC3765 commences
soft-start of the output voltage. When the secondary bias
source reaches the undervoltage threshold, the LTC3766
comes alive and takes control by sending encoded PWM
gate pulses to the LTC3765 through T3. These pulses
also provide primary bias power efficiently over a wide
input voltage range.
The transition from primary to secondary control occurs
at some fraction of the nominal output voltage. From then
on, operation and design is simplified to that of a simple
buckconverter.Secondarycontroleliminatesdelays,tames
large-signal overshoot, and reduces output capacitance
needed to meet transient response requirements.
An optional LC filter stage on the input lowers rms input
current. The filter must have output impedance that is
less than the converter input impedance to assure stabil-
ity. This may require a damping impedance. (See Linear
Technology Application Note 19 for a discussion of input
filter stability.) A source with a 170mΩ or higher ESR
at the filter resonant frequency (~35kHz) is one way of
providing damping for the filter elements provided on the
DC1739B-C. For bench testing, an electrolytic capacitor
has been added at the input terminals to provide suitable
damping and ripple current capability. The values selected
have a filter resonant frequency that is below the converter
switching frequency, thus avoiding high circulating cur-
rents in the filter.
Demonstration circuit 1739B-C is easy to set up to evalu-
ate the performance of the LTC3765/LTC3766. Refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below:
Note:When measuring the outputvoltage ripple, care must
be taken to avoid a long ground lead on the oscilloscope
probe. Measure the output voltage ripple by touching the
probe tip and ground ring directly across the last output
capacitor as shown in Figure 1.
1. Set an input power supply that is capable of 9V to 36V
to 9V. Then turn off the supply.
2. Direct an airflow of 200lfm across the unit for sustained
operation at full load.
3. Withpower off, connect thesupply to the input terminals
+VIN and –VIN.
a. Input voltages lower than 9V can keep the converter
from turning on due to the undervoltage lockout
feature of the LTC3765 / LTC3766.
b. If efficiency measurements are desired, an ammeter
capable of measuring 10ADC or a resistor shunt can
be put in series with the input supply in order to
measure the DC1739B-C’s input current.
c. A voltmeter with a capability of measuring at least
36V can be placed across the input terminals in order
to get an accurate input voltage measurement.
4. Turn on the power at the input.
Note: Make sure that the input voltage never exceeds 36V.
5. Check for the proper output voltage of 12V. Turn off
the power at the input.
6. Once the proper output voltages are established, con-
nect a variable load capable of sinking 10A at 12V to
the output terminals +VOUT and –VOUT. Set the current
for 0A.
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DEMO MANUAL DC1739B-C
QUICK START PROCEDURE
a. If efficiency measurements are desired, an ammeter
or a resistor shunt that is capable of handling 10ADC
can be put in series with the output load in order to
measure the DC1739B-C’s output current.
b. Avoltmeterwithacapabilityofmeasuringat least 12V
can be placed across the output terminals in order
to get an accurate output voltage measurement.
7. Turn on the power at the input.
Note: If there is no output, temporarily disconnect the load
to make sure that the load is not set too high.
8. Once the proper output voltage is again established,
adjust the load within the operating range and observe
the output voltage regulation, ripple voltage, efficiency
and other desired parameters.
OUTPUT CURRENT (A)
0
EFFICIENCY (%)
POWER DISSIPATION (W)
92
94
96
8
90
88
86
6
8
10
12VIN
24VIN
4
2
0
24610
PD 12VIN
PD 24VIN
Figure 1. Proper Measurement Equipment Setup
Figure 2. Efficiency and Power Dissipation
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DEMO MANUAL DC1739B-C
QUICK START PROCEDURE
Figure 3. Output Ripple at 24VIN and 10AOUT (50mV, 5A, 2µs/Div, 20MHz)
Figure 4. Transient Response Waveform at 24VIN and 5A – 7.5A – 5AOUT (5A, 100mV, 100µs/Div)
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DEMO MANUAL DC1739B-C
QUICK START PROCEDURE
Figure 5. Thermal Map, Front Side at 24VIN and 10AOUT (TA= 25°C, 200LFM)
Figure 6. Thermal Map, Back Side at 24VIN and 10AOUT (TA= 25°C, 200LFM)
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DEMO MANUAL DC1739B-C
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 1 C1 CAP., AL., TH,100uF, 50V, ME-PX SERIES SUNCON, 50ME100PX
2 4 C2, C3, C4, C5 CAP., X7R, 10µF, 50V, 10%, 1210 MURATA, GRM32ER71H106KA12
3 1 C6 CAP., C0G, 47pF, 200V, 5%, 1206 AVX, 12062A470JAT2A
4 1 C7 CAP., C0G, 15pF, 200V, 5%, 0805 AVX, 08052A150JAT2A
5 2 C8, C9 CAP., POSCAP, 68µF, 16V, 20%, 7343 SANYO, 16TQC68M
6 1 C10 CAP., X7R, 2.2nF, 630V, 5%, 1206 MURATA, GRM31A7U2J222JW31
7 2 C12, C27 CAP., X7R, 10µF, 16V, 20%, 1206 MURATA, GRM31CR71C106MA12
8 1 C13 CAP., X7R, 1.0µF, 100V, 10%, 1206 MURATA, GRM31CR72A105KA01
9 1 C14 CAP., X7R, 0.1µF, 250V, 10%, 1206 MURATA, GRM31CR72E104KW03
10 1 C16 CAP., C0G, 1000pF, 25V, 5%, 0402 TDK, C1005C0G1E102J
11 3 C17, C20, C35 CAP., X7R, 0.1µF, 25V, 10%, 0603 AVX, 06033C104KAT2A
12 1 C18, C33 CAP., C0G, 2200pF, 50V, 5%, 0603 MURATA, GRM1885C1H222JA01D
13 1 C19 CAP., X7R, 12nF, 50V,10%, 0805 AVX, 08055C123KAT2A
14 2 C21, C23 CAP., X7R, 1.0µF, 16V 10%, 0805 MURATA, GRM21BR71C105KA01L
15 2 C22 CAP., C0G, 220pF, 25V, 5%, 0603 AVX, 06033A221JAT2A
16 1 C24 CAP., X7R, 2200pF, 250V, 10%, 1812 MURATA, GA343QR7GD222KW01L
17 1 C25 CAP., COG, 0.033uF, 25V, 5%, 0805 TDK, C2012C0G1E333J
18 1 C28 CAP., X7R, 0.010µF, 50V, 10%, 0603 AVX, 06035C103KAT2A
19 1 C29 CAP., X7R, 0.033µF, 25V, 10%, 0603 AVX, 06033C333KAT2A
20 1 C32 CAP., C0G, 47pF, 25V, 5%, 0603 AVX, 06033A470JAT2A
21 2 C37, C44 CAP., C0G, 1000pF, 25V, 5%, 0603 AVX, 06033A102JAT2A
22 1 C36 CAP., X7R, 1500pF, 50V,10%, 0402 AVX, 04025C152KAT2A
23 1 C39 CAP., X7R, 1.0uF, 50V, 10%, 0805 MURATA, GRM21BR71H105KA12
24 1 D1 DIODE ULTRA FAST 1A 200V SMP VISHAY, ES1PD-M3 / 84A
25 2 D3, D5 DIODE SCHOTTKY 40V 0.4A SOD323 DIODES INC., ZHCS400TA
26 1 L1 INDUCTOR, 0.56µH 20% VISHAY, IHLP2525EZERR56M01
27 1 L4 INDUCTOR, 16µH CHAMPS PQA2050-16-LT C
28 1 Q1 MOSFET N-CH 60V POWERPAK-SO-8 INFINEON, BSC028N06NS
29 1 Q3 MOSFET N-CH POWERPAK-SO-8 INFINEON, BSC057N08NS3G
29 1 Q4 MOSFET N-CH 150V POWERPAK-SO-8 INFINEON, BSC190N15NS3
30 1 Q5 MOSFET, P-CH, IRF6217, SO-8 IR, IRF6217TR
31 1 Q6 MOSFET, N-CH, SUPER SOT23 FAIRCHILD, 2N7002
32 1 R1 RES., CHIP, 12.4Ω, 1/4W, 1%, 1206 VISHAY, CRCW120612R4FKEA
33 2 R4 RES., CHIP, 15k, 1W 2512 VISHAY, CRCW251215KJNEG
34 1 R7, R37 RES., CHIP, 909Ω, 1/8W, 1%, 0805 VISHAY, CRCW0805909RFKEA
35 1 R10 RES., CHIP, 0.005Ω, 1W, 1%, 2512 PANASONIC, ERJ-M1WTF5M0U
36 1 R11 RES., CHIP, 51.1Ω, 1/8W, 1%, 0805 VISHAY, CRCW080551R1FKEA
37 1 R14 RES., CHIP, 0.004Ω, 3W, 5%, 1225 SUSUMU, KRL6432D-C-R004-F-T5
38 1 R17 RES., CHIP, 28.7k, 1/8W, 1%, 0805 VISHAY, CRCW080528K7FKEA
39 1 R18 RES., CHIP, 100k, 1/8W, 5%, 0805 VISHAY, CRCW0805100KJNEA
40 4 R19, R20, R23, R24 RES., CHIP, 100Ω, 1/16W, 1%, 0402 VISHAY, CRCW0402100RFKEA
41 1 R22 RES., CHIP, 1.82k, 1/4W, 1%, 1206 VISHAY, CRCW12061K82FKEA
42 1 R25 RES., CHIP, 10k, 1/10W, 1%, 0603 VISHAY, CRCW060310K0FKEA
43 1 R26 RES., CHIP, 2.21k, 1/10W, 1%, 0603 VISHAY, CRCW06032K21FKEA
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DEMO MANUAL DC1739B-C
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
44 1 R27 RES., CHIP, 0.750Ω, 1/3W, 1%, 0805 SUSUMU, RL1220S-R75-F
45 1 R29 RES., CHIP, 20.0k, 1/10W, 1%, 0603 VISHAY, CRCW060320K0FKEA
46 1 R35 RES., CHIP, 1.82k, 1/10W, 1%, 0603 VISHAY, CRCW06031K82FKEA
47 1 R36 RES., CHIP, 11.5k, 1/10W, 1%, 0603 VISHAY, CRCW060311K5FKEA
48 1 R38, R39, R56 RES., CHIP, 100Ω, 1/10W, 1%, 0603 VISHAY, CRCW0603100RFKEA
48 1 R40 RES., CHIP, 464k, 1/10W, 1%, 0603 VISHAY, CRCW0603464KFKEA
49 1 R41 RES., CHIP, 14.7k, 1/10W, 1%, 0603 VISHAY, CRCW060314K7FKEA
49 1 R42 RES., CHIP, 78.7k, 1/10W, 1%, 0603 VISHAY, CRCW060378K7FKEA
50 1 R44 RES., CHIP, 102k, 1/10W, 1%, 0603 VISHAY, CRCW0603102KFKEA
51 1 R46 RES., CHIP, 60.4k, 1/10W, 1%, 0603 VISHAY, CRCW060360K4FKEA
52 1 R47 RES., CHIP, 15.0k, 1/10W, 1%, 0603 VISHAY, CRCW060315K0FKEA
53 1 R48 RES., CHIP, 4.99k, 1/10W, 1%, 0603 VISHAY, CRCW06034K99FKEA
54 1 R49 RES., CHIP, 1.87k, 1/10W, 1%, 0603 VISHAY, CRCW06031K87FKEA
55 1 R50 RES., CHIP, 604Ω, 1/10W, 1%, 0603 VISHAY, CRCW0603604RFKEA
56 1 R51 RES., CHIP, 16.2k, 1/10W, 1%, 0603 VISHAY, CRCW060316K2FKEA
57 1 R52 RES., CHIP, 21.5k, 1/10W,1%, 0603 VISHAY, CRCW060321K5FNEA
58 1 R53 RES., CHIP, 8.25k, 1/10W, 1%, 0603 VISHAY, CRCW06038K25FKEA
49 1 T1 TRANSFORMER, 3T:6T CHAMPS, G45R2-0603-xx
50 1 T3 TRANSFORMER, 1.25T:1T COILCRAFT, CT8281-BL
51 1 U1 I.C. LTC3765EMSE, MSOP-16PIN LINEAR TECH., LTC3765EMSE
52 1 U2 I.C. LTC3766EGN28, SSOP-GN28 LINEAR TECH., LTC3766EGN
Additional Demo Board Circuit Components
53 0 C42, C43 CAP., OPT, 0402 OPT
54 0 C15, C30, C31, C41 CAP., OPT, 0603 OPT
55 0 C38, C40 CAP., OPT, 0805 OPT
56 1 C26 0Ω JUMPER 0603 VISHAY, CRCW06030000Z0EA
57 0 C11, C34 CAP., OPT, 1206 OPT
58 1 D2 DIODE 4148 SOD323 DIODES INC., 1N4148WS
59 0 D4 DIODE OPT 220AA OPT
60 0 D7, D8, D9, D10 DIODE OPT SOD323 OPT
61 0 D11 DIODE OPT SOT23 OPT
62 0 L5 INDUCTOR, OPT 1608 OPT
63 0 Q2 MOSFET OPT POWERPAK-SO-8 OPT
64 0 Q7,Q9 TRANSISTOR, NPN, OPT SOT23 OPT
65 0 Q8 TRANSISTOR, NPN/PNP, OPT SOT23-6 OPT
66 12 R8, R9, R21, R28, R30-R34, R45,
R54, R59
0Ω JUMBER 0402 VISHAY, CRCW04020000Z0ED
67 1 R6 0Ω JUMBER 0603 VISHAY, CRCW06030000Z0ED
68 0 R2, R3, R12, R43, R58 RES., OPT, 0402 OPT
69 0 R55, R57, R60 RES., OPT, 0805 OPT
70 0 T4 TRANSFORMER, OPT OPT
Hardware For Demo Board Only
71 5 E1, E2, E3, E4, E5 TESTPOINT, TURRET, 0.090" PBF MILL-MAX, 2501-2-00-80-00-00-07-0
72 4 J1, J2, J3, J4 CONNECTOR, BANANA JACK Keystone, 575-4
73 4 MTGS AT 4 CORNERS STANDOFF, NYLON 0.5 1/2" KEYSTONE, 8833(SNAP-ON)
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DEMO MANUAL DC1739B-C
SCHEMATIC DIAGRAM
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DEMO MANUAL DC1739B-C
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-COMPLETE PCB
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DEMO MANUAL DC1739B-C
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2013
LT 0813 • 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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