QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD LTC3725/LTC3726 DESCRIPTION Demonstration circuit 1032A is a high power isolated synchronous forward converter featuring the LTC3725 and LTC3726 When powered from a 3672V input, a single DC1032A provides an isolated 12V at 12A in a eight-brick footprint. The converter operates at 300kHz and achieves efficiency up to 94.0% with synchronous output rectifiers. Secondary-side control eliminates complex optocoupler feedback, providing fast transient response with a minimum amount of output capacitance. For other output voltages see DC1031A-A/B/C (2.5V/3.3V/5V at 20A). For higher powers see DC888A-A/B/C (3.3V at 50A / 5V at 35A / 12V at 20A) which also support polyphase operation for even higher powers. The simple architecture can be easily modified to meet different input and output voltage requirements. 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 12A 12V Maximum Output Current 200LFM 12A Typical Output Ripple VOUT VIN = 48V, IOUT = 12A, 300kHz 100mVP–P Output Regulation Over All Input Voltages and Output Currents ±1% (Reference) Peak Deviation with 0A to 12A Load Step (10A/us) ±600mV Settling Time 50us Load Transient Response Nominal Switching Frequency 300kHz Efficiency VIN = 48V, IOUT = 12A 93% Typical Isolation BASIC 1500VDC Approximate Size Component Area x Top Component Height 2.3” x 0.9” x 0.34” OPERATING PRINCIPLES – SINGLE PHASE The LTC3726 secondary side controller is used on the secondary and the LTC3725 smart driver with selfstarting capability is used on the primary. When an input voltage is applied, the LTC3725 (U1 in Figure 14), which is powered through R29 and Q28, begins a controlled soft-start of the output voltage by switching MOSFETs Q8 and Q11. As the output voltage begins to rise, the LTC3726 secondary controller is powered up via Q27. The LTC3726 then assumes control of the output voltage by sending encoded PWM gate pulses to the LTC3725 primary driver via 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. From that point on, operation and design simplifies to that of a simple buck converter. The LTC3726 regulates by observing the output voltage directly resulting in superior output voltage regulation and transient response. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD QUICK START PROCEDURE Demonstration Circuit 1032A is easy to set up to evaluate the performance of the LTC3725 and LTC3726. Refer to Figure 1 for proper equipment setup. 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 scope probe. Measure the output (or input) voltage ripple by touching the probe tip and probe ground directly across the +Vout and –Vout (or +Vin and –Vin) terminals. See 0 for proper scope probe technique. 1. 2. 3. The optional input LC filter stage (C2/L1) lowers ac input rms current. A power supply’s complete input filter must have output impedance that is less than the converter input impedance to assure stability. This may require a damping impedance. (See Linear Technology Application Note AN19 for a discussion of input filter stability.) A source with a 50mOhm or higher ESR at the filter resonant frequency is one way of providing damping for the filter elements provided on the DC1032A. For bench testing, adding an 82uF electrolytic capacitor such as a Sanyo 100ME82AX to the input terminals will 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 currents in the filter. Set an input power supply to a voltage of 36V. Make sure that it is capable of 36V to 72V at a current supplying capability of at least 5A. Then, turn off the supply. 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. b. If efficiency measurements are desired, an ammeter capable of measuring at least 5Adc per phase can be put in series with the input supply in order to measure the DC1032A’s input current. c. 4. A voltmeter with a capability of measuring • 72V can be placed across the input to get an accurate input voltage measurement. Turn on the power at the input. NOTE: Make sure that the input voltage • 72V. 5. Check for the proper output voltage of 12V. 6. Turn off the power at the input. 7. Once the proper output voltages are established, connect a variable load capable of sinking 12A at 12V to the output terminals +Vout and –Vout. Set current to 0A. 8. a. If efficiency measurements are desired, an ammeter or a resistor current shunt that is capable of handling at least 12Adc can be put in series with the output load in order to measure the DC1032A’s output current. b. A voltmeter with a capability of measuring at least 12V 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, disconnect the load to verify that the load is not set too high. 9. 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 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD MEASURED DATA Figures 3 through 13 are measured data for a typical DC1032A. Figures 14 through 23 consist of schematics, bill of materials, and layout. Figure 3. Efficiency Figure 4. Output Voltage Ripple (72Vin, 12Aout) 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 5. Load Transient Response (48Vin, 0A to 12Aout) Figure 6. Loop Response (48Vin, 12Aout) 5 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 7. Turn-on (48Vin, 12Aout) 6 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 8. Temp Data (36Vin, 12Aout, 25 C, 200LFM airflow – front) Figure 9. Temp Data (36Vin,12Aout, 25 C, 200LFM airflow – back) Figure 10. Temp Data (48Vin, 12Aout, 25 C, 200LFM airflow – front) 7 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 11. Temp Data (48Vin, 12Aout, 25 C, 200LFM airflow – back) Figure 12. Temp Data (72Vin, 12Aout, 25 C, 200LFM airflow – front) Figure 13. Temp Data (72Vin, 12Aout, 25 C, 200LFM airflow – back) 8 R22 15.0K R18 365K E2 C2 1.0uF 100V C24 1uF 1.2nF 2 1 8 C29 33nF R29 100K FB/IN+ R92 150 FS/IN- VSB T1 -VOUT D32 39V 10pF 50V C81 5 6 4 3 Q34 2N7002 R58 5.1K T2 D31 VSW C85 47pF 8 1 7 11 PT- 14 249 1N4148W R89 D29 PT- C71 1uF 15 Q14 HAT2244WP C69 470pF 100V 2.2nF -VOUT 250V C30 R1,R51,R52 3x56=18 1/4W (3/4W) C66 330pF 200V 2 3 4 1N4148W Q35 MMBT2907A VCC C83 47pF R61 100 C73 470pF C72 0.1uF 7.5K R95 R48 0.025 1W Q8,Q11 2xSi7450DP R63 75K 5 4 220pF C27 100 R3 LTC3725EMSE U1 SSFLT ULVO VCC Q28 FDC2512 SOT23-6 C3,C4,C5 3x1.0uF 100V C55 1.0uH 10 NOTE: 1uF, 100V CER TDK C3225X7R2A105M(1210) SG 22uF, 16V CER TDK C3225X5R1C226M(1210) C82 R93 39uF, 100V Sanyo 100ME39AX 47uF, 10V Taiyo Yuden LMK325BJ476MM-B(1210) 150 69uF, 16V Sanyo 6TQC68M 68pF D28 7.5V MMBZ5236B D32 39V MMBZ5259B L1 Vishay IHLP-2525CZER1R0M-01 L2 PULSE PA1393.302 Q26 FMMT618 Q32 FMMT718 T1 Pulse PA0801 (4:4:4) T2 Pulse PA0297 2(1.4mH):1:1 -Vin 36V-72Vin E1 7 5 R54 100 1% PT- PT+ VSW R79 510 U2 1.2nF C70 909 R55 100 1% R85 0.004 1W R50 C78 33nF Q26 SG R56 100 Q32 R66 100K R69 124K C75 47pF L2 R76 1K 2.8uH C79 1.0nF R68 15.0K -VOUT D28 7.5V VSB VCC Q12 HAT2244WP LTC3726EGN IS+ L1 16 Q27 FCX491 VCC 3 NDRV VSLMT 9 2 8 GATE PGND 6 12 FG GND 13 SW PGND 10 ISRUN/SS 6 11 SLP 7 1 SG FS/SYNC 9 IS GND 11 ITH 5 3 FB/PH MODE +Vin 4 R46 604 - +Vout E4 -Vout 12V 12A 2x68uF 16V E3 + C68,C80 E8 R41 11.5K -VOUT C77 47uF 10V VCC -VOUT C31,C33 2x22uF 16V + E7 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 14. Schematic (optional components not shown). 9 E2 R22 15.0K R77 0 R18 365K C2 1.0uF 100V C3 1.0uF 100V C55 C24 1200pF 1uF 3 2 1 8 C5 1.0uF 100V C29 33nF SSFLT ULVO VCC Q28 FDC2512 C4 1.0uF 100V R29 100K 68pF 150 U1 10 VSB MMBT2907A C83 47pF R61 100 2 3 4 7 8 9 10 1 10pF U2 14 PT- PT+ PT- 249 R89 1N4148W D29 -VOUT LTC3726EGN PT- 15 R54 Q25 100 opt. 1% Q33 opt. VA VA 4 C70 909 R85 R55 100 1% 0.004 1W R50 1200pF VSW R79 510 VCC R84 0 R53 opt. 321 8765 Q14 HAT2244WP C69 470pF 100V C71 1uF -VOUT 5 6 4 3 VSW C81 2.2nF 250V C30 R58 5.1K -VOUT 2N7002 Q34 8 1 T2 R51 R52 1/4W 1/4W 56 56 C66 330pF 200V C85 47pF C73 470pF D31 1N4148W -VOUT R1 1/4W 56 C72 0.1uF 7.5K R95 R48 0.025 1W 123 D32 MMBZ5259B 39V VSW FS/IN- 5 4 R63 75K 220pF C27 100 R3 0 4 5678 Q11 Q8 Si7450DP Si7450DP R49 FB/IN+ LTC3725EMSE NOTE: 1uF, 100V CER TDK C3225X7R2A105M(1210) 22uF, 16V CER TDK C3225X5R1C226M(1210) 39uF, 100V Sanyo 100ME39AX 47uF, 10V Taiyo Yuden LMK325BJ476MM-B(1210) 69uF, 16V Sanyo 6TQC68M L1 Vishay IHLP-2525CZER1R0M-01 L2 PULSE PA1393.302 VCC Q26 FMMT618 Q32 FMMT718 T1 Pulse PA0801 (4:4:4) R92 T2 Pulse PA0297 2(1.4mH):1:1 150 SG C82 R93 Q35 -Vin 36V-72Vin 6 5 2 1 4 1.0uH 7 E1 3 NDRV VS LMT 9 10 11 C78 33nF R66 100K 4 Q26 VCC 1 R76 1K 1 2.8uH L2 R83 R94 opt. D28 opt. R56 100 MMBZ5236B 7.5V SG -VOUT Q32 321 8765 Q12 HAT2244WP VSB IS + 5 8 GA TE PGND 6 2 FG GND 12 SW PGND 13 IS RUN/S S 6 11 SLP 7 1 R69 124K SG L1 9 IS GND 11 FS/S Y NC +Vin 3 2 ITH C75 47pF 5 C79 1.0nF R68 15.0K 16 4 VCC 2 3 3 C33 22uF 16V 4 Q27 FCX491A FB/PH MODE T1 PA0801 C76 opt. C77 47uF 10V VCC 0 R91 -VOUT C31 22uF 16V R46 604 R41 11.5K E8 - C23 opt. R75 opt. 68uF 16V + C68 + E7 E4 68uF 16V + C80 E3 -Vout 12V 12A +Vout QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 15. Full Schematic (optional components shown). 10 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Item Qty Reference Part Description Manufacture / Part # 1 REQUIRED CIRCUIT COMPONENTS 1 4 C2,C3,C4,C5 2 2 C71,C24 3 1 C27 4 2 C29,C78 5 1 C30 6 2 C31,C33 7 1 C69 8 1 C73 9 1 C66 10 2 C68,C80 11 2 C55,C70 12 1 C72 13 3 C75,C83,C85 14 1 C77 15 1 C79 16 1 C81 17 1 C82 18 1 D28 19 2 D29,D31 20 1 D32 21 1 L1 22 1 L2 23 2 Q8,Q11 24 2 Q12,Q14 25 1 Q26 26 1 Q27 27 1 Q28 28 1 Q32 29 1 Q34 30 1 Q35 31 3 R3,R56,R61 32 1 R18 33 2 R22,R68 34 1 R29 35 1 R41 36 1 R46 37 1 R48 38 1 R50 39 3 R1,R51,R52 40 2 R54,R55 41 1 R58 42 1 R63 43 1 R66 44 1 R69 45 1 R76 46 1 R79 CAP., X7R, 1.0uF, 100V, 20%, 1210 CAP., X7R, 1uF, 16V 10%, 0805 CAP., X7R, 220pF, 25V, 10%, 0603 CAP., X7R, 33nF, 25V, 10%, 0603 CAP., X7R, 2.2nF, 250V, 10%, 1812 CAP., X5R, 22uF, 16V, 20%, 1210 CAP., C0G, 470pF, 100V, 10%, 0805 CAP., C0G, 470pF, 25V, 10%, 0603 CAP., C0G, 330pF, 200V, 10%, 1206 CAP., POSCAP, 68uF, 16V, 20% 7343 CAP., X7R, 1200pF, 50V, 10%, 0603 CAP., X7R, 0.1uF, 25V, 10%, 0805 CAP., C0G, 47pF, 25V, 10%, 0603 CAP., X7S, 47uF, 10V, 20%, 1210 CAP., X7R, 1.0nF, 50V, 10%, 0603 CAP., C0G, 10pF, 50V, 10%, 0603 CAP., C0G, 68pF, 25V, 10%, 0603 DIODE, MMBZ5236B, SOT23 DIODE, 1N4148W, SOD-123 DIODE, MMBZ5259B, SOT23 INDUCTOR, 1.0uH INDUCTOR, 2.8uH FET, N-CH,. Si7450DP, POWERPAK SO-8 FET, N-CH,. HAT2244WP, WPAK NPN TRANSISTOR, SOT23 NPN TRANSISTOR, FCX491A N-CH FET, 150V, FDC2512, SuperSOT-6 PNP TRANSISTOR, SOT23 N-FET, 2N7002 SOT23 PNP TRANSISTOR, SOT23 RES., CHIP, 100, 1/16W, 5%, 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, 11.5K, 1/16W,1%, 0603 RES., CHIP, 604, 1/16W, 1%, 0603 RES., CHIP, 0.025, 1W, 2%, 2010 RES., CHIP, 0.004, 1W, 1%, 2512 RES., CHIP, 56, 1/4W, 5%, 1206 RES., CHIP, 100, 1/16W, 1%, 0603 RES., CHIP, 5.1K, 1/16W, 5%, 0603 RES., CHIP, 75K, 1/16W, 5%, 0603 RES., CHIP, 100K, 1/16W, 5%, 0603 RES., CHIP, 124K, 1/16W, 1%, 0603 RES., CHIP, 1.0K, 1/4W, 5%, 0603 RES., CHIP, 510, 1/8W, 5%, 0805 TDK, C3225X7R2A105M TAIYO YUDEN, EMK212BJ105KG AVX, 06033C221KAT2A AVX, 06033C333KAT2A MURATA, GA343QR7GD222KW01L TDK, C3225X5R1C226M AVX, 08051A471KAT2A AVX, 06033A471KAT2A AVX, 12062A331KAT2A SANYO, 16TQC68M AVX, 06035C122KAT2A AVX, 08053C104KAT2A AVX, 06033A470KAT2A TAIYO YUDEN, LMK325BJ476MM-TQ AVX, 06035C102KAT2A AVX, 06035A100KAT2A AVX, 06033A680KAT2A DIODES INC., MMBZ5236B DIODES INC., 1N4148W-7-F DIODES INC., MMBZ5259B VISHAY DALE, IHLP2525CZER1R0M01 PULSE, PA1393.302 VISHAY, Si7450DP RENESAS, HAT2244WP-EL-E ZETEX, FMMT618 ZETEX, FCX491A FAIRCHILD, FDC2512 ZETEX, FMMT718 ZETEX, 2N7002 DIODES., MMBT2907A-7-F AAC, CR16-101JM AAC, CR10-3653FM AAC, CR16-1502FM AAC, CR10-104JM AAC, CR16-1152FM AAC, CR16-6040FM IRC, LRC-LRF2010-01-R025-G PANASONIC, ERJM1WSF4M0U VISHAY, CRCW120656R0JNEA VISHAY, CRCW0603100RFKEA AAC, CR16-512JM VISHAY, CRCW060375K0JNEA AAC, CR16-104JM AAC, CR16-1243FM VISHAY, CRCW06031K00JNEA VISHAY, CRCW0805510RJNEA 11 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD 47 48 49 50 51 52 53 54 1 1 2 1 1 1 1 1 R85 R89 R92,R93 R95 T1 T2 U1 U2 RES., CHIP, 909, 1/16W, 1%, 0603 RES., CHIP, 249, 1/16W, 1%, 0603 RES., CHIP, 150, 1/16W, 5%, 0603 RES., CHIP, 7.5K, 1/16W, 5%, 0603 TRANSFORMER, PA0801 TRANSFORMER, PA0297 I.C., LTC3725EMSE, EMSE I.C., LTC3726EGN SSOP16GN VISHAY, CRCW0603909RFKEA VISHAY, CRCW0603249RFKEA VISHAY, CRCW0603150RJNEA VISHAY, CRCW06037K50JNEA PULSE, PA0801 PULSE, PA0297 LINEAR TECH., LTC3725EMSE#PBF LINEAR TECH., LTC3726EGN 2 ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS 1 0 C23,C76 (OPT.) CAP., 0603 2 0 Q25,Q33 (OPT.) NPN/PNP Transistor, SOT23 3 3 R49,R84,R91 RES., CHIP, 0, 1/16W, 0603 4 0 R53,R75,R83,R94 (OPT.) RES., CHIP, 0603 5 1 R77 RES., CHIP, 0, 1/8W, 1%, 0805 1 2 3 4 5 6 7 2 2 2 4 2 2 4 HARDWARE-FOR DEMO BOARD ONLY: E1,E2 TESTPOINT, TURRET, .094" E8,E7 TESTPOINT, TURRET, .061" E3,E4 STUD E3,E4 (2 EACH) NUT, BRASS, #10-32 E3,E4 Ring, Lug Ring #10 E3,E4 WAHSER, STAR #10 BRASS NICKEL (STAND-OFF) STAND-OFF, NYLON 0.5" AAC, CR16-000M AAC, CR10-0000FM MILL-MAX, 2501-2 MILL-MAX, 2308-2-00-44 PEM, KFH-032-10 ANY KESTONE, 8205 ANY 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 16. Bill of Materials 12 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 17. Top 13 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 18. Layer 2 14 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 19. Layer 3 15 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 20. Layer 4 16 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 21. Layer 5 17 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 22. Bottom 18 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1032A 36V-72VIN, ISOLATED SYNCHRONOUS FORWARD Figure 23. Bottom Mirrored 19