Application Note 1717 ISL6726EVAL2Z: 24V to 12V 90W Active Clamp Forward DC/DC Converter Introduction Design Specifications The board is a 24V input to 12V output DC/DC converter that can output current up to 7.5A. It is implemented with Intersil’s Active Clamp Forward (ACF) current-mode PWM controller, ISL6726. It demonstrates fundamental functions of ISL6726, including soft-start/soft-stop, peak current protection, average current protection, slope compensation, flux limit, minimum duty ratio clamp, etc. The circuit operates at fixed frequency with peak current mode control. The converter adopts ACF and synchronous rectifier to obtain high efficiency. Typical efficiency is about 92% at full load. This application note covers the test setup, test report, schematics, layout and BOM etc. • Input Voltage VIN: 18V to 36V • Output Voltage VO: 12V • Output Curent IO: 7.5A (90W) • Switching Frequency: 160kHz • UVLO with Hysteresis, (18V/19V) • Board Dimensions: 120×60×30mm3 (L×W×H) 2 8 Q2 P1 Vo 5 C2 L1 12 P2 C22 P3 12V Q3 R5 P4 T1 U1 10 20 CS 1 SY NC OUTM 2 MODE EN DELAY 18 RTC VREF CT VERR U2 R32 Vo C20 R34 8 R35 C7 9 ISET FB 12 SLOPE IOUT 14 VDD R20 17 7 C9 VREF 19 UV 4 6 T4 OUTAC 3 C6 Q5 15 13 DC LIM R 14 5 T3 Q4 SS VDD GND U3 11 R17 R36 16 R18 ISL6726 FIGURE 1. SIMPLIFIED SCHEMATIC Figure 2 shows the test setup. DC SOURCE IIN ISL6726EVAL2Z P3 + P1 + VIN - P2 EUT VO - IO + LOAD - P4 FIGURE 2. TEST SETUP February 2, 2012 AN1717.0 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. Copyright Intersil Americas Inc. 2012. All Rights Reserved. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries. All other trademarks mentioned are the property of their respective owners. Application Note 1717 FIGURE 3. TOP/BOTTOM VIEW OF THE EVALUATION BOARD 95 Figures 4 and 5 show the efficiency curves; line and load regulation are shown in Figures 6 and 7. 90 ISL6726 supports the brick-wall current limit protection feature shown in Figure 8. TABLE 1. EFFICIENCY vs. LOAD CURRENT IIN (A) PIN (W) VO (V) IO (mA) PO (W) LOAD (%) η (%) 24 0.243 5.8 12.05 0 0 0 - 23.99 0.530 12.7 12.048 0.755 9 10 71.5 23.98 0.894 21.4 12.047 1.5 18 20 84.2 23.97 1.289 30.8 12.047 2.246 27 30 87.5 23.95 1.689 40.4 12.046 3.006 36.2 40 89.5 23.94 2.080 49.7 12.045 3.752 45.1 50 90.7 23.93 2.480 59.3 12.044 4.499 54.1 60 91.3 23.92 2.884 68.9 12.043 5.245 63.1 70 91.5 23.9 3.297 78.7 12.042 6.005 72.3 80 91.7 23.99 3.690 88.5 12.04 6.744 81.1 90 91.7 23.98 4.093 98.1 12.038 7.472 89.9 99 91.6 24Vi/160kHz 85 80 75 70 0 1.5 PIN (W) VO (V) IO (mA) PO (W) LOAD (%) η (%) 19.06 5.136 97.8 12.033 7.468 89.8 99 91.7 21.47 4.562 97.9 12.033 7.468 89.8 99 91.7 23.98 4.093 98.1 12.033 7.468 89.8 99 91.5 26.47 3.717 98.3 12.033 7.468 89.8 99 91.3 29.07 3.397 98.7 12.032 7.468 89.8 99 90.9 31.97 3.102 99.1 12.031 7.468 89.8 99 90.5 34.07 2.92 99.4 12.031 7.468 89.8 99 90.3 12.03 2 7.468 89.8 7.5 92.0 91.8 91.6 91.4 91.2 91.0 90.8 90.6 90.4 90.2 90.0 89.8 18 7.5A/160kHz 23 28 LINE VOLTAGE VIN (V) 33 99 89.9 12.052 OUTPUT VOLTAGE VO (V) IIN (A) 99.8 6.0 FIGURE 5. EFFICIENCY vs. LINE VOLTAGE VIN (V) 2.773 4.5 FIGURE 4. EFFICIENCY vs. LOAD CURRENT TABLE 2. EFFICIENCY vs. INPUT VOLTAGE 36 3.0 LOAD CURRENT IO (A) EFFICIENCY h (%) VIN (V) EFFICIENCY h (%) Steady State Test 24Vi/160kHz 12.050 12.048 12.046 12.044 12.042 12.040 12.038 12.036 0 1.5 3.0 4.5 6.0 7.5 LOAD CURRENT IO (A) FIGURE 6. LOAD REGULATION AN1717.0 February 2, 2012 Application Note 1717 OUTPUT VOLTAGE VO (V) 12.0335 12.0330 12.0325 7.5A/160kHz 12.0320 12.0315 12.0310 Vds2 12.0305 12.0300 12.0295 18 23 28 33 LINE VOLTAGE VIN (V) CS FIGURE 7. LINE REGULATION OUTPUT VOLTAGE VO (V) 14 12 10 VIN = 20V FIGURE 10. SIGNAL WAVEFORM ON CS PIN VIN = 24V 8 VIN = 36V 6 4 2 0 0 2 4 6 LOAD CURRENT IO (A) 8 10 Vds2 FIGURE 8. BRICK-WALL CURRENT LIMIT Typical waveforms are shown in Figures 9~11. Test conditions: VIN = 24V. Vgs2 Vgs3 Vds2 FIGURE 11. Q2 AND Q3 SWITCHING WAVEFORMS (IO = 7.5A) For Figures 9~11: Vgs2 Ch1: Vgs of Q2; Ch3: Vgs of Q3; Vgs3 Ch2: CS signal of ISL6726; Ch4: Vds of Q2. FIGURE 9. Q2 AND Q3 SWITCHING WAVEFORMS (I O = 1.6A) 3 AN1717.0 February 2, 2012 Application Note 1717 Figure 12 and 13 are waveforms of Q4 (Rectifier/Forward switch) Figures 14 and 15 are Waveforms of Q5 (Freewheeling Switch). Vds Vds Vgs Vgs FIGURE 14. Q5 TURN ON, NO LOAD FIGURE 12. Q4 TURN ON, NO LOAD Vgs Vgs Vds Vds FIGURE 13. Q4 TURN OFF , NO LOAD 4 FIGURE 15. Q5 TURN OFF, NO LOAD AN1717.0 February 2, 2012 Application Note 1717 Table 3 shows the output ripple voltage. TABLE 3. VOUT RIPPLE; CH3: 50mV/DIV; TIME: 4µs/DIV No Load Full Load VIN = 18V VIN = 24V VIN = 36V Dynamic Response Test Table 4 shows the dynamic response at different input conditions.The load current slew rate is 0.2A/µs for the step transient. TABLE 4. VOUT DYNAMIC RESPONSE; CH3: 500mV/DIV; TIME: 4ms/DIV 25%-50%-25% (for every 5ms) 50%-75%-50% (for every 5ms) VIN = 18V VIN = 24V VIN = 36V 5 AN1717.0 February 2, 2012 Application Note 1717 Figure 16 and 17 show the soft-start and soft-stop waveforms. The active load is set to constant-current (CC) mode. FIGURE 16. VOUT DURING START-UP FIGURE 17. VOUT DURING SHUT-DOWN 6 AN1717.0 February 2, 2012 Schematic Q3 IPP072N10N3 G 3 2 1 P20 R12 17.4k C7 4.7n C4 100p 6.49k 3 R11 4 EN 30k 5 R14 6 330p C6 C0G 7 8 9 10 SS SY NC DCLIM UV MODE DELAY EN VREF RTC CT GND OUTM ISET VERR FB VDD OUTAC SLOPE CS IOUT ISL6726AAZ 2 DNP 1u C15 R21 4.99 VREF 100n C11 R22 4.99 1 D7 BAV99 C16 3 4 1 3 1u 1 C14 VREF R20 4.99k 470n PA0185 6 T3 4 PA0185 6 T4 1 R32 1.33k D6 R33 2k 1N4148X 2 12 11 R18 40.2k R49 511k PS2701-1 150p C9 C0G DNP P19 P18 VR2 D16 1N4148X 1 C45 Q12 0.47u MMBT3906TT1 0 R48 R17 34k C40 22u C39 22u R41 P24 0 Note: 1) Unless otherwise specified, all capacitors are ceramic X7R, all resistor are 5%. 2) DNP: Do Not Populate (although there is a placeholder on the PCB) 3)T1 can be one of below three transformer: (1)Kaschke 095549-a (the original design,T11); (2) Wurth750340993; (3)Pulse PG1031NL (footprint is different, need 6 pcs of wire, T12). Vo C43 DNP R34 22.1k R46 DNP C19 220p 15 14 VDD 2.2u C10 13 2 R28 200 2 D8 BAV99 C17 470n R30 4.99 R29 4.99 R31 U2 1.5k 1 4 DNP Q7 1 R10 40.2k 1.0V 2 20 C12 330n 19 R47 0 R50 18 DNP 51k R19 17 VREF 5V 16 P10 C99 3 UV UVP=13.5V 1.0Vth C5 1n VREF 1 U1 R7 4.99 Q6 R27 200 P4 P14 R26 10k DNP 3 R15 10k R8 61.9k R16 10k VREF R9 20.5k DNP 1.64V P21 VIN+ 3.74k 1N4148X D12 R40 0 R23 499 C13 3 1 Q1 PHT6N06LT R99 P11 10k C3 100n 1N4148X P12 VR1 BZX84-C12 R13 D4 1N4148X 12V VDD D1 3 P17 3.3n/Y 2 Q5 R35 8.2k C20 47n 2 2.5V LM431-BIM U3 R36 5.76k 1001 Murphy Ranch Rd., Milpitas, CA, 95035 Title 18~36Vin,[email protected] (90W) Activ e Clamp Forward Conv erter AN1717.0 February 2, 2012 Size A Date: FIGURE 18. SCHEMATIC ISL6726EVAL2Z Document Number ISL6726EVAL2Z Thursday , October 27, 2011 Rev B Sheet 1 of 1 Application Note 1717 1 VIN+ 4 2 R1 10k C22 330u IPP072N10N3 G R25 10k C98 DNP 4 ES1B D3 301 1n C18 C32 10n 1n PZT651T1 2 C96 2.2u IRF6217 5 R39 10k R43 240 470 R24 P3 1 C31 Q4 C95 2.2u 3 3 D2 1N4148X 470 R37 1 3 VDD L2 Vo 12V L1 1 2.2mH DNP 5 6 7 8 R2 P9 1 R42 240 2 7 VDD R3 5.11k US1B 2 D11 P16 750340993 2 2 D5 6 BAV70 11uH 3 C2 7 IPP072N10N3 G 100n 3 Q2 6 PA1005.100 1 P13 D10 US1B C37 22u C38DNP 5 P22 2 2 10.0 10.0 DNP C21DNP C24DNP C25 DNP C26 22u 3 P15 1 8 P5 DNP P23 VR3 BZX84-B6V2 R98 0 2 4 5 1 1 7 PZT651T1 T2 P8 R38 0 3 R5 P6 15 10 8 9 13 11 12 5 1 2 4 +5.7V L3 100uH C23 10u D9 BAV70 2 2 3 100u 3 14 T1 2 R4 C1 10u 10u 10u 10u DNP DNPDNP DNP P2 2 P7 DNP 1 C36 C35 C34 C33 C30 C29 C28 C27 L4 Shorted 1 VIN+ 2 P1 Application Note 1717 Bill of Materials TABLE 5. BOM FOR ISL6726EVAL2Z REV. B QTY REFERENCE DESIGNATOR TYPE/MOUNT/PACKAGE/VOL/TOL/MAT MANUFACTURER MANUFACTURER PART # 1 C1 Cap, TH, DiaxL = 10x12.5mm, 100µ, 50V, 20%, ELECT, Aluminum Nichicon UBT1H101MPD 1 C2 Cap, SM, 1206, 100n, 250V, 20%, X7R 2 C3, C11 Cap, SM, 0603, 100n, 25V, 20%, X7R 1 C4 Cap, SM, 0603, 100p, 25V, 20%, X7R 1 C5 Cap, SM, 0603, 1n, 25V, 20%, X7R 1 C6 Cap, SM, 0603, 330p, 25V, 20%, C0G 1 C7 Cap, SM, 0603, 4.7n, 25V, 20%, X7R 0 C8, C43 Cap, SM, 0603, DNP, 25V, 20%, X7R 1 C9 Cap, SM, 0603, 150p, 25V, 20%, C0G 3 C10, C95, C96 Cap, SM, 0805, 2.2µ, 16V, 20%, X7R 1 C12 Cap, SM, 0603, 330n, 10V, 20%, X7R 1 C13 Cap, SM, 2220, 3.3n/Y2, 20%, Monolithic Ceramic Murata GA355QR7GF332KW01L 2 C14, C15 Cap, SM, 0603, 1µ, 16V, 20%, X7R 2 C16, C17 Cap, SM, 0603, 470n, 16V, 20%, X7R 1 C18 Cap, SM, 1210, 10n, 100V, 20%, X7R 1 C19 Cap, SM, 0603, 220p, 25V, 20%, X7R 1 C20 Cap, SM, 0603, 47n, 25V, 20%, X7R 0 C21, C24, C25, C38 Cap, SM, 1210, DNP, 16V, 20%, X7R Murata GRM43ER61C226KE01L 1 C22 Cap, TH, DiaxL = 10x12.5 mm, 330µ, 16V, 20%, ELECT, Aluminum Nichicon UBT1C331MPD 1 C23 Cap, SM, 1206, 10µ, 16V, 20%, X7R 4 C26, C37, C39, C40 Cap, SM, 1210, 22µ, 16V, 20%, X7R Murata GRM43ER61C226KE01L 0 C27, C28, C29, C30 Cap, SM, 1210, DNP, 50V, 20%, X7R 2 C31, C32 Cap, SM, 1206, 1n, 100V, 20%, X7R Murata GRM21AR72E102KW01D 4 C33, C34, C35, C36 Cap, SM, 1210, 10µ, 50V, 20%, X7R 1 C45 Cap, SM, 0805, 0.47µ, 16V, 20%, X7R 0 C98, C99 Cap, SM, 0603, DNP, 16V, 20%, X7R 6 D1, D2, D4, D6, D12, D16 Diode, SM, SOD523, 1N4148, 75V, 250mA, SWITCH MCC 1N4148X 1 D3 Diode, SM, SMA, ES1B, Fast Recovery Fairchild 2 D5, D9 Diode, SM, SOT-23, BAV70, Fast Recovery Diodes Inc 2 D7, D8 Diode, SM, SOT-23, BAV99, Fast Recovery Diodes Inc 2 D10, D11 Diode, SM, SMA, US1B, Ultra Fast Recovery Diodes Inc 1 L1 11µH Pulse PG0936.113NL 2nd source of L1 Wurth 74435561100 1 L2 Inductor, SM, 2.2mH CoilCraft LPS4018-225MLD 1 L3 Inductor, SM, 100µH Sunlord SDWL3225F101JTF 0 L4 Bare wire 5 P1, P2, P3, P4, P5 Terminal, TH, 1514-2 KeyStone 1562-4 8 AN1717.0 February 2, 2012 Application Note 1717 TABLE 5. BOM FOR ISL6726EVAL2Z REV. B QTY 12 REFERENCE DESIGNATOR TYPE/MOUNT/PACKAGE/VOL/TOL/MAT MANUFACTURER MANUFACTURER PART # P6, P8, P11~13, P15~20, P24 5002 KEYSTONE 5002 0 P7, P9, P10, P14, P21, P22, P23 DNP KEYSTONE 5002 1 Q1 MOSFET, SM, SOT-223, PHT6N06LT, N-Chan NXP 2 Q2, Q5 MOSFET, TH, TO-220F, IPP072N10N3 G Infineon 1 Q3 MOSFET, SM, SO-8, IRF6217, P-Chan IR 1 Q4 MOSFET, SM, TO-220F, IPP072N10N3 G Infineon 2 Q6, Q7 BJT, SM, SOT-223, PZT651T1, NPN ON Semi 0 Q8 SOT-26, DNP, Dual PNP Diodes Inc 0 Q11 MOSFET, SM, SOT-23, DNP, N-Chan ON Semi 1 Q12 BJT, SM, SOT-23, MMBT3906TT1, PNP ON Semi 1 R1 Res, SM, 1206, 10k, 1%, Thick Film 1 R2 Res, SM, 0603, 301, 1%, Thick Film 1 R3 Res, SM, 0603, 5.11k, 1%, Thick Film 2 R4, R5 Res, SM, 0603, 10.0, 1%, Thick Film 5 R7, R21, R22, R29, R30 Res, SM, 0603, 4.99, 1%, Thick Film 1 R8 Res, SM, 0603, 61.9k, 1%, Thick Film 1 R9 Res, SM, 0603, 20.5k, 1%, Thick Film 2 R10, R18 Res, SM, 0603, 40.2k, 1%, Thick Film 1 R11 Res, SM, 0603, 6.49k, 1%, Thick Film 1 R12 Res, SM, 0603, 17.4k, 1%, Thick Film 1 R13 Res, SM, 0603, 3.74k, 1%, Thick Film 1 R14 Res, SM, 0603, 30k, 1%, Thick Film 6 R15, R16, R25, R26, R39, R99 Res, SM, 0603, 10k, 1%, Thick Film 1 R17 Res, SM, 0603, 34k, 1%, Thick Film 1 R19 Res, SM, 0603, 51k, 1%, Thick Film 1 R20 Res, SM, 0603, 4.99k, 1% ,Thick Film 1 R23 Res, SM, 0603, 499, 1%, Thick Film 2 R24, R37 Res, SM, 2512, 470, 1%, Thick Film 2 R27, R28 Res, SM, 0603, 200, 1%, Thick Film 1 R31 Res, SM, 0603, 1.5k, 1%, Thick Film 1 R32 Res, SM, 0603, 1.33k, 1% ,Thick Film 1 R33 Res, SM, 0603, 2k, 1%, Thick Film 1 R34 Res, SM, 0603, 22.1k, 1%, Thick Film 1 R35 Res, SM, 0603, 8.2k, 1%, Thick Film 1 R36 Res, SM, 0603, 5.76k, 1%, Thick Film 6 R38, R40, R41, R47, R48, R98 Res, SM, 0603, 0, 1%, Thick Film 2 R42, R43 Res, SM, 2512, 240, 5%, Thick Film 9 AN1717.0 February 2, 2012 Application Note 1717 TABLE 5. BOM FOR ISL6726EVAL2Z REV. B QTY REFERENCE DESIGNATOR TYPE/MOUNT/PACKAGE/VOL/TOL/MAT MANUFACTURER MANUFACTURER PART # 0 R45, R52, R53 Res, SM, 0603, DNP, 1%, Thick Film 0 R46, R50 Res, SM, 0603, DNP, 1%, Thick Film 1 R49 Res, SM, 0603, 511k, 1%, Thick Film 1 T1 Txfmr, SM, 750340993, Transformer Wurth Midcom 750340993 2nd source of T1 Pulse PG1031NL 2nd source of T1 Kaschke Components 095549-a Txfmr, SM, PA1005.100, Current Transformer Pulse PA1005.100NL 2nd source of T2 Wurth Midcom 31333R-LF1 1 T2 2 T3, T4 Txfmr, SM, PA0185, Gate driver Pulse PA0185 1 U1 IC, SM, SSOP20, ISL6726, PWM controller Intersil ISL6726AAZ 1 U2 IC, SM, SSOP4, PS2701-1, Photo Coupler NEC 1 U3 IC, SM, SOT-23, LM431-BIM, Shunt Regulator National 1 VR1 Diode, SM, SOT-23, BZX84-C12, Zener NXP 1 VR2 DNP 10 AN1717.0 February 2, 2012 Application Note 1717 Assembly Drawing FIGURE 19. ASSEMBLY ON TOP FIGURE 20. ASSEMBLY ON BOTTOM 11 AN1717.0 February 2, 2012 Application Note 1717 PCB Layout FIGURE 21. LAYER 1 (TOP LAYER) FIGURE 22. LAYER 2 12 AN1717.0 February 2, 2012 Application Note 1717 PCB Layout (Continued) FIGURE 23. LAYER 3 FIGURE 24. LAYER 4 (BOTTOM LAYER) Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 13 AN1717.0 February 2, 2012