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 dc1694bfa 1 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. dc1694bfa 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 dc1694bfa 3 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 dc1694bfa 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 dc1694bfa 5 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 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2012