QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER LTC3725 / LTC3726 DESCRIPTION Demonstration circuit 1031A-C is a 36V-72Vin, synchronous forward converter featuring the LTC3725/LTC3726. This circuit was designed specifically to attain a high current, low ripple, synchronously rectified forward to efficiently power 5.0V loads at up to 20A from a typical telecom input voltage range. This circuit features secondary-side con- trol of the supply eliminating the need for an optocoupler, self-starting architecture, input undervoltage lockout, and output overvoltage protection. Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. Table 1. Performance Summary (TA = 25°C) PARAMETER CONDITION VALUE Minimum Input Voltage 36V Maximum Input Voltage 72V Output Voltage VOUT VIN = 36V to 72V, IOUT = 0A to 20A 5.0V Maximum Output Current 200LFM Airflow 20A Typical Output Ripple VOUT VIN = 72V, IOUT = 20A 100mVP–P Size Component Area x Top Component Height 2.3” x 0.9” x 0.394” Peak Deviation with Load Step of 10A to 20A (10A/us) ±200mV Settling Time 40us Load Transient Response Nominal Switching Frequency Efficiency 300kHz VIN = 48V, IOUT = 20A 91.5% Typical OPERATING PRINCIPLES The LTC3726 controller is used on the secondary and the LTC3725 driver with self-starting capability is used on the primary. When an input voltage is applied, the LTC3725 begins a controlled soft-start of the output voltage. As this voltage begins to rise, the LTC3726 secondary controller is quickly powered up via T1, D1, and Q27. The LTC3726 then assumes control of the output voltage by sending encoded PWM gate pulses to the LTC3725 primary driver via the small signal transformer, T2. The LTC3725 then operates as a simple driver receiving both input signals and bias power through T2. The transition from primary to secondary control occurs seamlessly at a fraction of the output voltage. From that point on, operation and design simplifies to that of a simple buck converter. Secondary sensing eliminates delays, tames large-signal overshoot and reduces output capacitance while utilizing off-theshelf magnetics and attaining high efficiency. For large values of input inductance, a 100V, 47uF electrolytic capacitor can be added across the input terminals to damp the input filter and provide adequate stability. See Linear Technology Application Note AN19 for a discussion on input filter stability analysis. A recommended part is the Sanyo 100MV39AX. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER QUICK START PROCEDURE Demonstration circuit 1031A-C is easy to set up to evaluate the performance of the LTC3725/LTC3726. Refer to Figure 1 for proper measurement equipment setup and 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 output (or input) voltage ripple by touching the probe tip and probe ground directly across the input or output capacitor. See Figure 2 for proper scope probe technique. 1. Set an input power supply that is capable of 36V to 72V at a current of at least 3.5A to a voltage of 36V. Then, turn off the supply. 2. With power off, connect the supply to the input terminals +Vin and –Vin. a. Input voltages lower than 36V can keep the converter from turning on due to the undervoltage lockout feature of the LTC3725/LTC3726. b. If efficiency measurements are desired, an ammeter capable of measuring 3.5Adc can be put in series with the input supply in order to measure the DC1031A-C’s input current. c. A voltmeter with a capability of measuring at least 72V can be placed across the input terminals in order to get an accurate input voltage measurement. 3. Turn on the power at the input. NOTE: Make sure that the input voltage never ex- ceeds 72V. 4. Check for the proper output voltage of 5.0V 5. Turn off the power at the input. 6. Once the proper output voltages are established, connect a variable load capable of sinking 20A at 5.0V to the output terminals +Vout and –Vout. Set the current for 0A. 7. a. If efficiency measurements are desired, an ammeter or a resistor current shunt that is capable of handling at least 20Adc can be put in series with the output load in order to measure the DC1031A-C’s output current. b. A voltmeter with a capability of measuring at least 5.0V can be placed across the output terminals in order to get an accurate output voltage measurement. 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 established, adjust the load within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other desired parameters. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER MEASURED DATA Figures 3 through 11 are measured data for a typical DC1031A-C. Figures 12 through 21 are schematics, bill of materials and layout. 94 EFFICIENCY (%) 92 90 36V 88 48V 72V 86 6 8 10 12 14 16 18 20 LOAD CURRENT (A) Figure 3. Efficiency (200lfm airflow) 50mV/div 1us/div Figure 4. Output Ripple Voltage (72Vin, 20Aout) 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Vout 200mV/DIV Iout 10A/div 20us/DIV Figure 5. Output Voltage Transient Response (48Vin, 10A to 20A step) 5 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 6. Temp Data (48Vin, 20A, 25 C, 200LFM airflow – front) Figure 7. Temp Data (48Vin, 20A, 25 C, 200LFM airflow – back) Figure 8. Temp Data (36Vin, 20A, 25 C, 200LFM airflow – front) 6 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 9. Temp Data (36Vin, 20A, 25 C, 200LFM airflow – back Figure 10. Temp Data (72Vin, 20A, 25 C, 200LFM airflow – front) Figure 11. Temp Data (72Vin, 20A, 25 C, 200LFM airflow – back) 7 R22 15.0K R18 365K -Vin 1uF 470pF 3 R3 FB/IN+ 330pF C27 100 C29 33nF SSFLT ULVO U1 FS/IN- LTC3725EMSE VCC R29 100K 10 1uF,100V TDK C3225X7R2A105M (1210) 100uF, 6.3V CER TDK C3225X5R0J107M (1210) C68 Sanyo 6TPE220MI C30 Murata GA343QR7GD222KW01L (1812) L1 Vishay IHLP-2525CZER1R0M-01 L2 Cooper HC1-R87 T1 PA0811 (4:4:2:1) T2 Pulse PA0297 2(1.4mH):1:1 C24 2 1 8 Q28 FDC2512 (SOT6) C3,C4,C5 3x1.0uF 100V C55 36-72Vin C2 1.0uF 100V 7 1uH 5 4 5.1K C72 R58 R63 100K R61 100 2 VIN 8 1 C30 T2 5 6 4 3 PT- C71 1uF C69 1.5nF R51 50V 2.4 1/4W 7 10 9 11 2.2nF -VOUT 250V C66 1nF 200V R48 0.022 1W C73 0.1uF 470pF Q8 Si7450DP 3 4 5 14 15 VA Q14 Si7336ADP VSW R79 510 PT- PT+ Q34 D29 PT- R69 124K 536 R89 1N4148W R66 100K 10pF VSW C81 -VOUT 2N7002 -VOUT C78 33nF R85 3.01K 100 R55 R76 1K 1/4W VA C67 4.7uF 25V R2 1.2 1/4W C79 2.2nF R68 6.2K Q27 FCX491 (SOT89) FB/PH 220uF 6.3V 4 C77 2.2uF VCC 5.0V/20A C31,C33 2x100uF 6.3V + C68 R46 604 R41 4.42K -Vout +Vout LINEAR TECHNOLOGY HAS MADE A BEST EF FORT 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 CIRUIT BOARD LAYOUT MAY SIGNIF ICANTLY AFF ECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICAT IONS ENGINEERING FOR ASSISTANCE. CUSTOMER NOTICE LINEAR TECHNOLOGY CORPORATION CONFIDENTIAL THIS CIRCUIT IS DISTRIBUTED TO CUSTOMERS ONLY FOR USE WITH LTC PARTS. C75 47pF L2 0.87uH -VOUT D28 MMBZ5236B 7.5V Q12 Si7336ADP CMPSH1-4 D1 LTC3726EGN U2 330pF C70 0.002 1W 100 R54 R50 IS + T1 23.4 x 20.1 x 9.4mm PLANAR 1 SG VIN 8 NDRV V S LMT 9 2 FG G ND 12 13 SW P G ND 10 IS RUN/S S 6 11 S LP 7 16 V CC L1 9 G A TE P G ND 6 FS /S Y NC IS G ND 11 ITH 5 3 MO DE +Vin QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 12. Simplified Schematic 8 E2 C24 1uF C55 470pF Vout/Iout 2.5V/20A 3.3V/20A 5.0V/20A VERSION DC1031A-A DC1031A-B DC1031A-C C5 1.0uF 100V D1 C29 33nF SSFLT ULVO VCC CMPSH1-4 opt. opt. 2 1 8 Q28 FDC2512 3 C4 1.0uF 100V C3 1.0uF 100V * VERSION TABLE R22 15.0K R77 0 R18 365K C2 1.0uF 100V R29 100K U1 10 opt. R86 CMPSH1-4 opt. CMPSH1-4 D25 R88 0 R87 0 330pF C27 100 R3 0 5 4 4.42K 2.74K 1.91K R41 VIN FS/IN- 5678 4 5.1K C72 R58 0.022 0.039 0.039 R48 * R63 R61 100 2 3 4 100K 160K 160K 8 1 * 7 8 10 9 11 124K 0 0 R69 2.2nF 250V R85 3.01K opt opt PT- PT+ T1 PA0811(4:4:2:1) PA0815(6:6:2:1) PA0865(4:4:1:1) R55 100 1% C69 1.5nF 2.2nF 2.2nF Q26 VCC opt. R76 1K 1206 VA * D1 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. 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 CIRUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. C75 47pF * D25 K. Mathews J. WU 12/5/05 12/5/05 DATE C79 2.2nF R68 6.2K Wednesday , August 23, 2006 DESIGNER ENGINEER APPROVED CHECKED DRAWN APPROVALS CONTRACT NO. * R69 1 L2 Q27 FCX491 0.87uH R2 1.2 1/4W C67 4.7uF 25V -VOUT R83 0 D28 R56 opt. MMBZ5236B 7.5V Q32 opt. 321 4 Q12 Si7336ADP 8765 R66 100K CUSTOMER NOTICE 536 910 910 R89 330pF C70 * R85 0.002 1W R50 C78 33nF VSW R79 510 R54 Q25 100 opt. 1% VCC VA -VOUT LTC3726EGN U2 14 15 R84 0 R53 opt. 321 4 Q14 Si7336ADP 8765 Q33 opt. VA PT- C71 1uF -VOUT 5 6 4 3 R52 opt. 1/4W 50V C69 C30 T2 R51 1/4W 2.4 C66 1nF 200V R63 C73 0.1uF 470pF 1W * R48 123 Q11 Q8 Si7450DP opt. R49 FB/IN+ LTC3725EMSE For All The Versions C2-C5 1uF,100V TDK C3225X7R2A105M (1210) C31,C33 100uF, 6.3V CER TDK C3225X5R0J107M (1210) C68 Sanyo 6TPE220MI L1 Vishay IHLP-2525CZER1R0M-01 or COOPER HCP0703-1R0-R L2 Coil Tronics HC1-R87 T2 Pulse PA0297 2(1.4mH):1:1 -Vin 36-72Vin 1.0uH 6 5 2 1 4 E1 7 * T1 10 5 IS+ 3 9 1 SG 2 3 16 FB/PH 4 Q34 C77 2.2uF + E8 - PT- * E4 220uF 6.3V opt. E3 + C80 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 R89 C23 opt. R75 opt. 1N4148W D29 R46 604 220uF 6.3V + C68 E7 * R41 TECHNOLOGY -VOUT 1 10pF VSW C81 C76 opt. VCC -VOUT C31 100uF 6.3V 2N7002 C33 100uF 6.3V +VOUT FILENAME: CAGE CODE SCALE: SIZE DWG NO SHEET DC1031A 1 OF 1 A REV -Vout +Vout LTC3725EMSE, LTC3726EGN, 36V - 72Vin Forward Converter TITLE VCC VIN 8 NDRV VSLMT 2 FG GND 12 SW PGND 13 ISRUN/SS 6 11 SLP 7 GATE PGND 6 FS/SYNC 9 IS GND 11 ITH 5 3 MODE L1 3 2 +Vin QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 13. Full Board Schematic 9 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Item Qty Reference Part Description Manufacture / Part # 1 REQUIRED CIRCUIT COMPONENTS 1 4 C2,C3,C4,C5 2 2 C71,C24 3 2 C27,C70 4 2 C29,C78 5 1 C30 6 2 C31,C33 7 2 C73,C55 8 1 C66 9 1 C67 10 1 C68 11 1 C69 12 1 C72 13 1 C75 14 1 C77 15 1 C79 16 1 C81 17 1 D1 18 1 D28 19 1 D29 20 1 L1 0 L1 (second source) 21 1 L2 22 1 Q8 23 2 Q12,Q14 24 1 Q34 25 1 Q27 26 1 Q28 27 1 R2 28 2 R54,R55 29 1 R18 30 1 R22 31 1 R29 32 1 R41 33 1 R46 34 1 R48 35 1 R50 36 1 R51 37 1 R58 38 2 R3,R61 39 2 R63,R66 40 1 R68 41 1 R69 42 1 R76 43 1 R79 44 1 R85 CAP., X7R, 1.0uF, 100V, 20%, 1210 CAP., X7R, 1uF, 16V 10%, 0805 CAP., X7R, 330pF, 25V, 10%, 0603 CAP., X7R, 33nF, 25V, 10%, 0603 CAP., X7R, 2.2nF, 250V, 10%, 1812 CAP., X5R, 100uF, 6.3V, 20%, 1210 CAP., C0G, 470pF, 25V, 10%, 0603 CAP., C0G, 1nF, 200V, 10%, 1206 CAP., X7R, 4.7uF, 25V, 20%, 1206 CAP., POSCAP, 220uF, 6.3V, 20% 7343 CAP., NPO, 1.5nF, 50V, 10%, 0805 CAP., X7R, 0.1uF, 25V, 10%, 0805 CAP., NPO, 47pF, 25V, 10%, 0603 CAP., X7R, 2.2uF, 16V, 20%, 1206 CAP., X7R, 2.2nF, 25V, 10%, 0603 CAP., C0G, 10pF, 50V, 5%, 0603 DIODE, Schottky, CMPSH1-4, 40V, SOT23 Diode, MMBZ5236B, SOT23 Diode, 1N4148W SOD-123 INDUCTOR, 1.0uH INDUCTOR, 1.0uH INDUCTOR, 0.87uH FET, N-CH,. Si7450DP, POWERPAK SO-8 FET, N-CH,. Si7336ADP, POWERPAK SO-8 N-CH., Transistor. 2N7002 SOT23 NPN TRANSISTOR, FCX491 N-CH FET, 150V, FDC2512, Super SOT-6 RES., CHIP, 1.2, 1/4W, 5%, 1206 RES., CHIP, 100, 1/16W, 1%, 0603 RES., CHIP, 365K, 1/8W, 1%, 0805 RES., CHIP, 15.0K, 1/16W, 1%, 0603 RES., CHIP, 100K, 1/8W, 5%, 0805 RES., CHIP, 4.42K, 1/16W,1%, 0603 RES., CHIP, 604, 1/16W, 1%, 0603 RES., CHIP, 0.022, 1W, 2%, 2010 RES., CHIP, 0.002, 1W, 1%, 2512 RES., CHIP, 2.4, 1/4W, 5%, 1206 RES., CHIP, 5.1K, 1/16W, 5%, 0603 RES., CHIP, 100, 1/16W, 5%, 0603 RES., CHIP, 100K, 1/16W, 5%, 0603 RES., CHIP, 6.2K, 1/16W, 5%, 0603 RES., CHIP, 124K, 1/16W, 1%, 0603 RES., CHIP, 1K, 1/4W, 5%, 1206 RES., CHIP, 510, 1/8W, 5%, 0805 e3 RES., CHIP, 3.01K, 1/16W, 1%, 0603 TDK, C3225X7R2A105M TAIYO YUDEN, EMK212BJ105KG AVX, 06033C331KAT2A AVX, 06033C333KAT2A MURATA, GA343QR7GD222KW01L TDK, C3225X5R0J107M AVX, 06033A471KAT2A AVX, 12062A102KAT2A TDK, C3216X7R1E475M SANYO, 6TPE220MI AVX, 08055A152KAT2A AVX, 08053C104KAT2A AVX, 06033A470KAT2A TDK, C3216X7R1C225M AVX, 06033C222KAT2A AVX, 06035A100JAT2A CENTRAL SEMI., CMPSH1-4-LTC DIODES INC., MMBZ5236B-7 DIODES INC., 1N4148W-7-F VISHAY DALE, IHLP2525CZER1R0M01 COOPER, HCP0703-1R0-R COOPER, HC1-R87 VISHAY, Si7450DP VISHAY, Si7336ADP DIODES INC., 2N7002-7-F ZETEX, FCX491 FAIRCHILD, FDC2512 AAC, CR18-1R2JM VISHAY, CRCW06031000FRT6 VISHAY, CRCW0805365KFKEB AAC, CR16-1502FM AAC, CR10-104JM AAC, CR16-4421FM AAC, CR16-6040FM IRC, LRC-LRF2010-01-R022-G PANASONIC, ERJM1WTF2M0U AAC, CR18-2R4JM AAC, CR16-512JM AAC, CR16-101JM AAC, CR16-104JM AAC, CR16-622JM AAC, CR16-1243FM AAC, CR18-102JM AAC, CR10-511JM AAC, CR16-3011FM 10 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER 45 46 47 48 49 1 1 1 1 1 R89 T1 T2 U1 U2 RES., CHIP, 536, 1/16W, 5%, 0603 TRANSFORMER, 1750VDC BASIC, PA0811 TRANSFORMER, 1500VRMS BASIC, PA0297 I.C., LTC3725EMSE, MS10E I.C., LTC3726EGN, SSOP16GN AAC, CR16-5360FM PULSE, PA0811 PULSE, PA0297 LINEAR TECH., LTC3725EMSE LINEAR TECH., LTC3726EGN 2 ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS 1 0 C23,C76 (opt.) CAP., 0603 2 0 C80 (opt.) CAP., POSCAP, 220uF, 6.3V, 20% 7343 3 0 D25 (opt.) DIODE, Schottky, CMPSH1-4, 40V, SOT23 4 0 Q11 (opt.) FET, N-CH, POWERPAK SO-8 5 0 Q25,Q26 (opt.) NPN Transistor, FMMT619, SOT23 6 0 Q32,Q33 (opt.) PNP Transistor, FMMT718, SOT23 7 5 R49,R83,R84,R87,R88 RES., CHIP, 0, 1/16W, 0603 8 0 R52 (opt.) RES., CHIP, 1206 9 0 R53,R56,R75 (opt.) RES., CHIP, 0603 11 1 R77 RES., CHIP, 0, 1/8W, 0805 12 0 R86 (opt.) RES., CHIP, 0805 1 2 3 4 5 6 7 2 2 4 2 2 2 4 HARDWARE-FOR DEMO BOARD ONLY: E1,E2 TESTPOINT, TURRET, .094" E3,E4 STUD E3,E4 (2 EACH) NUT, BRASS, #10-32 E3,E4 Ring, Lug Ring # 10 E3,E4 WASHER, STAR #10 BRASS NICHEL E8,E7 TURRET, (STAND-OFF) STAND-OFF, NYLON 0.50" Panasonic, ERJ3GEY0R00V AAC, CJ10-000M MILL-MAX, 2501-2 PEM, KFH-032-10 ANY KEYSTONE 8205 ANY MILL-MAX2308-2-00-44 KEYSTONE 8833 (SNAP ON) Notes: 1. Required Circuit Components are those parts that are required to implement the circuit function 2. Additional Demo Board Circuit Components are those parts that provide added functionality for the demo board but are not required in the actual circuit. Figure 14. Bill of Materials 11 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 15. Top 12 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 16. Layer 2 13 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 17. Layer 3 14 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 18. Layer 4 15 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 19. Layer 5 16 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 20. Bottom 17 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1031A-C 36V-72VIN, SYNCHRONOUS FORWARD CONVERTER Figure 21. Bottom Mirrored 18