Application Note 1732 Author: Steve Schulte ISL70002SEH 12A Synchronous Buck Regulator Evaluation Board User Guide Circuit Comments Schematic and BOM The ISL70002SEHEVAL1Z evaluation board is designed to demonstrate the features of the ISL70002SEH, a TID and SEE hardened 12A synchronous buck regulator IC with integrated MOSFETs intended for Space applications. For more detailed information about the ISL70002SEH, please refer to the ISL70002SEH datasheet (FN8264). A schematic and BOM of the ISL70002SEHEVAL1Z evaluation board are shown in Figure 1 and Table 1, respectively. The schematic indicates the test points, which allow many nodes of the evaluation circuit to be monitored directly. The BOM shows components that are representative of the types needed for a design, but these components are not spacequalified. Equivalent space-qualified components would be required for flight applications. A 1µH inductor is recommended for 500kHz and a 500µH inductor is recommended for 1MHz. The ISL70002SEHEVAL1Z evaluation board accepts a nominal 3V to 5.5V input voltage and provides a regulated output voltage ranging from 0.8V to 85% of the input voltage at output currents ranging from 0A to 12A. The output can be quickly set to a preset voltage of 1.0V, or adjusted to an alternate voltage using the onboard potentiometer. A PGOOD (Power Good) signal goes high and lights a red LED to indicate that the output voltage is within a ±11% typical regulation window. A toggle switch is provided to conveniently enable or disable the output voltage. The ISL70002SEHEVAL1Z evaluation board can be set to run from the nominal 500kHz or 1MHz internal oscillator of the ISL70002SEH or synchronized to a 500kHz to 1MHz ±20% external clock. Two ISL70002SEHEVAL1Z evaluation boards can be synchronized to each other in a Master/Slave configuration, providing nearly twice the output current while switching 180° out-of-phase with respect to each other. See AN1751, “ISL70002SEH 2-Phase Buck Regulator User Guide.” Recommended Test Equipment • A 0V to 6V power supply with at least 20A current capability • An electronic load capable of sinking current up to 12A • Two digital multimeters (DMMs) • A 500MHz dual-trace oscilloscope Quick Start 1. Toggle S1 to the down (OFF) position. 2. Turn on the power supply. Set the output voltage to 3.3V and set the output current limit to 20A. Turn off the power supply. 3. Connect the positive lead of the power supply to J1 and the negative lead of the power supply to J2. 4. Turn on the electronic load and set the output current to 6A. 5. Connect the positive lead of the electronic load to J39 and connect the negative lead of the electronic load to J40. 6. Configure one DMM to monitor the input voltage from TP7 to TP11. FIGURE 1. PHOTOGRAPH OF ISL70002SEHEVAL1Z April 12, 2012 AN1732.0 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 1732 7. Configure another DMM to monitor the output voltage from TP13 to TP11. 8. Connect Channel 1 of the oscilloscope to J6 (or from TP33 to TP28) to monitor the rectangular waveform on the LXx pins. 9. Connect Channel 2 of the oscilloscope to J14 (or from TP36 to TP37) to monitor the output voltage. Ripple voltage is customarily measured with 20MHz bandwidth limiting 10. Toggle S1 to the up (ON) position. 11. Verify the output voltage is 1.0V ±3% and the frequency of the LXx waveform is 1MHz ±10%. Layout Guidelines 1. Use an eight layer PCB with 2 ounce (70µm) copper or equivalent in thinner layers. 2. 2 layers should be dedicated for ground plane. 3. Top and bottom layers should be used primarily for signals, but can also be used to increase the VIN, VOUT and ground planes as required. 4. Connect all AGND, DGND and PGNDx pins directly to the ground plane. Connect all PVINx pins directly to the VIN portion of the power plane. 6. Locate the output voltage resistive divider as close as possible to the FB pin of the IC. The top leg of the divider should connect directly to the load and the bottom leg of the resistive divider should connect directly to AGND. The junction of the resistive divider should connect directly to the FB pin. 7. Use a small island of copper to connect the LXx pins of U1 to the inductor(s), L1 and L2, to minimize the routing capacitance that degrades efficiency. Separate the island from ground and power planes as much as possible. 8. Keep all signal traces as short as possible. 9. A small series snubber (R25 and C20) connected from the LXx pins to the PGNDx pins may be used to dampen ringing on the LXx pins if desired. 10. For optimum thermal performance, place a pattern of vias on the top layer of the PCB directly underneath U1. Connect the vias to the ground planes which serves as a heatsink. Thermal interface material such as a Sil-Pad should be used to fill the gap between the vias and the bottom of U1 to insure good thermal contact. Using a Sil-Pad has the added benefit of raising the bottom of U1 from the PCB surface so that a slight bend can be added to the leads for strain relief. 5. Locate ceramic bypass capacitors as close as possible to U1. Prioritize the placement of the bypass capacitors on the pins of U1 in the order shown: PVINx, REF, AVDD, DVDD, SS, EN, PGOOD. 2 AN1732.0 April 12, 2012 3 ISL70002SEH Application Note 1732 FIGURE 2. ISL70002SEHEVAL1Z BOARD SCHEMATIC AN1732.0 April 12, 2012 TABLE 1. ISL70002SEHEVAL1Z BILL OF MATERIALS PART NUMBER REF DES QTY VALUE TOL. C0805C103K2RAC C12, C14 2 0.01µF 10% H1082-OPEN C16 1 OPEN C1812C472F2GAC C17 1 H1045-00471-25V20 C1-C3 C0805C102K2RAC 4 JEDEC TYPE MANUFACTURER 200V 805 CAP_0805 KEMET Ceramic Chip Cap 10% OPEN 1210 CAP_1210 GENERIC Ceramic Chip Cap 4700pF 1% 200V 1812 CAP_1812 KEMET Multilayer Cap 3 470pF 20% 25V 603 CAP_0603 GENERIC Multilayer Cap C20 1 1000pF 10% 200V 805 CAP_0805 KEMET H1045-OPEN C28, C29, C32, C33, C35 5 OPEN 5% OPEN 603 CAP_0603 GENERIC C1825C224K2RAC C31 1 0.22µF 10% 200V 1825 CAP_1825 KEMET Ceramic Chip Cap C1210C104K2RAC C36 1 0.1µF 10% 200V 1210 CAP_1210 KEMET Ceramic Chip Cap T530D157M010AHE006 C4, C5, C11, C1, C19, C21-C26 11 150µF 20% 10V SMD CAP_7343_31 KEMET High Capacitance Ultra-Low ESR Tantalum SMD Cap C2225C105K2RAC C6, C7, C10, C13, C18, C27, C30, C34 8 1µF 10% 200V 2225 CAP_2225 KEMET Multilayer Cap C0805C682K2RAC C8, C9 2 6800pF 10% 200V 805 CAP_0805 KEMET Multilayer Cap LTST-C170CKT D1 1 SMD LTST_C170CKT LITEON AlGaAs on GaAs Red LED 1N5822US D2 0 SMD2 DIO_CASE_D-5B MICROSEMI 3A 40V SCHOTTKY BARRIER RECTIFIER 575-4 J1, J2, J39, J40 4 CONN CON_BAN_575 KEYSTONE SOLDER MOUNT BANANA PLUG JUMPER-3-100 J13, J18, J23, J26-J29 7 THOLE JUMPER-3 GENERIC Three Pin Jumper JUMPER2_100 J30-J32 3 THOLE JUMPER-1 GENERIC Two Pin Jumper 131-4353-00 J33, J36 2 CONN TEK131-4353-00 TEKTRONIX IHLP-2525CZ-ER-1R0-M-01 L1, L2 2 SMD IND_IHLP-2525CZ-01 VISHAY 2N7002-7-F Q1 1 SOT23 SOT23 FAIRCHILD H2505-DNP-DNP-1 R12, R18 2 DNP 1% DNP 603 RES_0603 GENERIC Metal Film Chip Resistor (Do Not Populate) S0603CPZ1R00F10 R13, R14 2 1 1% 1/10W 603 RES_0603 State of the Art 100ppm Thick Film Chip Resistor S0603CA1002BEZ R15 1 10k 0.10% 1/10W 603 RES_0603 State of the Art 25ppm Thin Film Chip Resistor MCR03EZPFX1001 R16 1 1k 1% 1/10W 603 RES_0603 ROHM 20% 11A DESCRIPTION Ceramic Chip Cap Multilayer Cap Scope Probe Test Point PCB Mount LOW PROFILE HIGH CURRENT INDUCTOR (RoHS COMPLIANT) N-Channel EMF Effect Transistor (Pb-Free) Metal Film Chip Resistor Application Note 1732 AN1732.0 April 12, 2012 PACKAGE TYPE 1µH VOLTAGE POWER TABLE 1. ISL70002SEHEVAL1Z BILL OF MATERIALS (Continued) PART NUMBER REF DES QTY VALUE TOL. VOLTAGE POWER 5 JEDEC TYPE MANUFACTURER S0603CPZ1001F10 R17 1 1k 1% H2511-00R00-1/16W1 R19 1 0 ERJ3GEY0R00V R1-R7 7 S0603CA1501BEZ R20 S0603CA1001BEZ 1/10W 603 RES_0603 State of the Art 100ppm Thick Film Chip Resistor 1% 1/16W 603 RES_0603 GENERIC Thick Film Chip Resistor 0 0% 1/10W 603 RES_0603 PANASONIC Thick Film Chip Resistor 1 1.5k 0.10% 1/10W 603 RES_0603 State of the Art 25ppm Thin Film Chip Resistor R21 1 1k 0.10% 1/10W 603 RES_0603 State of the Art 25ppm Thin Film Chip Resistor S0603CPZ1000F10 R22 1 100 1% 1/10W 603 RES_0603 State of the Art 100ppm Thick Film Chip Resistor 3299W-1-502-LF R23 1 5k 10% 1/2W RADIAL RES_POT_3299W BOURNS TRIMMER POTENTIOMETER (RoHS COMPLIANT) H2511-01001-1/16W1 R24 1 1k 1% 1/16W 603 RES_0603 GENERIC Thick Film Chip Resistor H2513-001R8-1/8W1 R25 1 1.8 1% 1/8W 1206 RES_1206 GENERIC Thick Film Chip Resistor S0603CA1962BEZ R8, R10 2 19.6k 0.10% 1/10W 603 RES_0603 State of the Art 25ppm Thin Film Chip Resistor S0603CA4021BEZ R9, R11 2 4.02k 0.10% 1/10W 603 RES_0603 State of the Art 25ppm Thin Film Chip Resistor GT11MSCBE-T S1 1 SMT GT13MSCKE C&K 1514-2 TP1, TP2, TP6, TP10, TP12 5 THOLE TP-150C100P KEYSTONE Test Point Turret 0.150 Pad 0.100 Thole 5002 TP3-TP5, TP7-TP9, TP11, TP13 8 THOLE MTP500X KEYSTONE Miniature White Test Point 0.100 Pad 0.040 Thole ISL70002SEHVF U1 1 CQFP CQFP64_555X555_635 INTERSIL 12A SYNCHRONOUS BUCK REGULATOR W/MOSFET Bergquist Thermal Interface Material, Sil-Pad, 12inx12inx0.020in, with adhesive, cut to 0.4inx0.4in and placed on underside of U1 SP2000-0.020-AC-1212 1 DESCRIPTION SPDT On-None-On SMT Ultraminiature Toggle Switch (RoHS compliant) Application Note 1732 PACKAGE TYPE AN1732.0 April 12, 2012 Application Note 1732 FIGURE 3. TOP SIDE ASSEMBLY DRAWING FIGURE 4. TOP LAYER 6 AN1732.0 April 12, 2012 Application Note 1732 FIGURE 5. LAYER 2 FIGURE 6. LAYER 3 7 AN1732.0 April 12, 2012 Application Note 1732 FIGURE 7. LAYER 4 FIGURE 8. LAYER 5 8 AN1732.0 April 12, 2012 Application Note 1732 FIGURE 9. LAYER 6 FIGURE 10. LAYER 7 9 AN1732.0 April 12, 2012 Application Note 1732 FIGURE 11. BOTTOM LAYER FIGURE 12. BOTTOM SIDE ASSEMBLY DRAWING 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 10 AN1732.0 April 12, 2012