DEMO CIRCUIT 1557A QUICK START GUIDE LT3748EMS LT3748EMS Non-Opto Isolated Flyback Converter DESCRIPTION Demonstration circuit 1557A is an Non-Opto Isolated Flyback Converter featuring LT3748EMS. It is designed for 12V output from a 30V to 75V DC input. The output current is up to 1A. 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. Table 1 summarizes the performance of the demo board. The demo circuit can be easily modified for applications of different input, and output voltages/currents. Some pre-designed EP10, EP13 transformers from vendors such as Wurth Electronics, Sumida, Pulse Engineering and Coilcraft can be assembled on the board. The LT3748EMS is a high input voltage isolated flyback controller operating with input supply voltages from 5V to 100V. The LT3748EMS utilizes boundary mode operation Table 1. to provide a high efficiency, small size solution with improved load regulation of ±5% over the full line, load and temperature ranges. The LT3748EMS is well suited for a wide variety of industrial, automotive, medical, telecom, data-com applications, where regulated isolated output is required. The LT3748EMS datasheet gives a complete description of the part, operation and application information. The datasheet should be read in conjunction with this quick start guide for Demo Circuit 1557A. Design files for this circuit board are available. Call the LTC Factory. , LTC, LT and LTM are registered trademarks of Linear Technology Corporation. Performance Summary of DC1557A (TA = 25oC) PARAMETER Minimum Input Voltage Maximum Input Voltage Output Voltage, VOUT Output Current, IOUT CONDITION VIN=30V~75V IOUT=20mA~1A VIN=30V~75V VALUE 30V 75V 12.0V ±5% 1.0A QUICK START PROCEDURE Demo circuit 1557A is easy to set up to evaluate the performance of the LT3748EMS. 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 VOUTon the board. Apply 20mA load to the output. 3. Turn on the power at the input. Increase VIN to 30V. 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 connected with correct polarity. 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 current of power supply is below current limit. 1 LT3748EMS 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 VOUTterminals. See Figure 2 for proper scope probe technique. Figure 1. Proper Measurement Equipment Setup Figure 2. Proper Scope Probe Placement for Measuring Input or Output Ripple 2 LT3748EMS 3 LT3748EMS Linear Technology Corporation Bill of Materials LT3748EMS Item Qty Demo Bd. #1557A Reference Part Description REQUIRED CIRCUIT COMPONENTS: Manufacturer / Part # NIC, NACEW100M100V6.3X8TR13F 1 1 C1 CAP., ELECTROLYTIC, 10uF 100V, 6.3x8 2 1 C2 CAP., X7R, 2.2uF 100V, 1210 TDK, C3225X7R2A225M 3 1 C3 CAP., X7R, 47uF 16V, 2220 TDK, C5750X7R1C476M 4 1 C7 CAP., X7R, 0.1uF 16V, 0402 TDK, C1005X7R1C104K 5 1 C8 CAP., C0G, 470pF 50V, 0402 TDK, C1005C0G1H471M 6 1 C10 CAP., X7R, .1uF 100V, 0805 TDK, C2012X7R2A104K 7 1 C11 CAP., X7R, 6800pF 25V, 0402 TDK, C1005X7R1E682K 8 1 C12 CAP., X7S, 1uF 100V, 0805 TDK, C2012X7S2A105K 9 1 C13 CAP., C0G, 10pF 50V, 0402 TDK, C1005C0G1H100M 10 1 C16 CAP., X5R, 4.7uF, 25V, 0805 TDK, 2012X5R1E475K 11 1 D1 SCHOTTKY BARRIER RECTIFIER 2.1A,SMA-DIODE VISHAY, VS-10MQ100NPbF 12 1 D2 SCHOTTKY MINI, SOD323 DIODES/ZETEX., BAV20WS-7-F 13 1 D3 DE, SCHOTTKY MINI, SOD323 DIODES/ZETEX., 1N5711WS-7-F 14 1 Q1 MOSFET N-CH, POWER33 FAIRCHILD SEMI., FDMC2674 15 1 R1 RES., CHIP, 12KΩ, 0402 VISHAY, CRCW040212K0FKED 16 1 R3 RES., CHIP, 357KΩ, 0402 NIC, NRC04F3573TRF 17 2 R4,R8 RES., CHIP, 2KΩ, 1206 VISHAY, CRCW12062K00FKEA 18 1 R5 RES., CHIP, 6.04KΩ, 0402 NIC, NRC04F6041TRF 19 1 R6 RES., CHIP, 16.5KΩ, 0402 VISHAY, CRCW040216K5FKED 20 1 R7 RES., CHIP, 121KΩ, 0603 VISHAY, CRCW0603121KFKED 21 1 R9 RES., CHIP, 57.6KΩ, 0402 VISHAY, CRCW040257K6FKED 22 1 R10 RES., SENSE, 0.03, 0805 VISHAY, WSL0805R0300FEA 23 2 R11,R12 RES., CHIP, 0Ω, 0402 VISHAY, CRCW04020000Z0ED 24 1 T1 XFMR, FLYBACK, TRANS-PULSE-EP13 25 1 LINEAR TECH., LT3748EMS 1 0 U1 IC., LT3748EMS, MSE16(12) ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS: C4 (OPT) CAP., X7R, 0.01uF 50V, 0603 2 0 C5 (OPT) CAP., X7R, 4.7uF 100V, 1210 TDK, C4532X7S2A475M 3 0 C6 (OPT) CAP., 22uF 100V OPT 4 0 C14 (OPT) CAP., 0.033uF, 2220 OPT 5 0 C15 (OPT) CAP., NPO, 47pF 50V, 0402 OPT 6 0 FB1 (OPT) BEAD, 1206 TAIYO YUDEN, FB MJ3216HS800 7 0 L1 (OPT) IND, PWR, 10UH, L-CDRH4D22/HP SUMIDA, CDRH4D22HPNP-100MC 8 0 R2 (OPT) RES., CHIP, 0603 HARDWARE-FOR DEMO BOARD ONLY: OPT 1 5 E1,E2,E3,E4,E5 MILL-MAX, 2501-2-00-80-00-00-07-0 4 TP, TURRET, 0.094" PULSE, PA2467NL, or WURTH, 750311439 TDK, C1608X7R1H103K