Application Note 1790 ISL8225MEVAL3Z 30A, Single Output Evaluation Board Setup Procedure The ISL8225M is a complete, dual step-down switching mode DC/DC module. The dual outputs can easily be paralleled for single-output, high-current use. It is easy to apply this high-power, current-sharing DC/DC power module to power-hungry datacom, telecom, and FPGA applications. All that is needed in order to have a complete, 30A design ready for use are the ISL8225M, a few passive components, and VOUT setting resistors. Recommended Equipment The ease of use virtually eliminates design and manufacturing risks while dramatically improving time to market. Quick Start The simplicity of the ISL8225M is its off-the-shelf, unassisted implementation. Patented module structure allows for higher power density and better efficiency than competing solutions. Patented current sharing in multi-phase operation greatly reduces ripple currents, BOM costs, and complexity. The ISL8225MEVAL3Z evaluation board enables a single output by paralleling two phases to deliver 30A continuous load current. The ISL8225M supports input voltage from 4.5V to 20V and the output voltage ranges from 0.6V to 6V. With the single resistor modification, the output voltage can be easily adjusted to different voltages. Related Resources See how-to video at intersil.com/ evid01 + VIN • 0V to 20V power supply with at least 10A source current capability • Electronic load capable of sinking current up to 30A • Digital multimeters (DMMs) • 100MHz quad-trace oscilloscope The inputs are J1 (VIN) and J2 (GND). The outputs are J3 (VOUT) and J4 (GND). Refer to Figure 1 for connections. 1. Connect a power supply capable of sourcing at least 10A to the input (VIN J1 and GND J2) of the ISL8225MEVAL3Z evaluation board, with a voltage between 4.5V to 20V. Connect an electronic load or the device to be powered to the output (VOUT J3 and GND J4) of the board. All connections, especially the low voltage, high current VOUT lines, should be able to carry the desired load current and should be made as short as possible. 2. Turn on the power supply. Measure the output voltage, VOUT, which should be at 1.2V if the board is working properly. 3. The ISL8225MEVAL3Z is manufactured with a default VOUT value of 1.2V; if different output voltages are desired, board resistors can be exchanged to provide the desired VOUT. Please refer to the table printed on the backside of the evaluation board or Table 1 on page 2 for RVSET resistor values, which can be used to produce different output voltages. + + V - LOAD (0A~30A) 4.5V TO 20V - V VOUT - FIGURE 1. ISL8225MEVAL3Z BOARD IMAGE December 3, 2012 AN1790.0 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 1790 For 12V VIN, and VOUT more than 1.5V, the switching frequency will need to be adjusted, as shown in Table 1; no frequency adjustments are necessary for VOUT below 1.5V. For 5V VIN, the frequency does not need to be adjusted and the module default frequency can be used at any allowed VOUT. If the output voltage is set to more than 1.8V, the output current will need to be derated to allow for safe operation at elevated ambient temperatures. Please refer to the derating curves in the ISL8225M datasheet. For VIN < 5.5V, please tie VIN directly to VCC for best efficiency. Also, it is preferred that the EN/FF voltage be over 1.5V in order to achieve better stability. TABLE 1. RESISTANCE SETTING FOR DIFFERENT OUTPUT VOLTAGES AND OPERATING FREQUENCY (R3 = 1k) VOUT (V) RVSET (Ω) FREQUENCY (kHz) RFSET (Ω) (VIN = 12V) 1.0 1500 Default Default 1.2 Default Default Default 1.5 665 Default Default 2.5 316 650 249k 3.3 221 800 124k 5.0 137 950 82.5k 5.5 121 950 82.5k Evaluation Board Information The evaluation board size is 3 inch x 3 inch. It is a 4-layer board, containing 2-ounce copper on the top and bottom layers and 1-ounce copper on all internal layers. The board can be used as a 30A reference design. Refer to the “Layout” section beginning on page 4. The board is made up of FR4 material and all components, including the solder attachment, are lead-free. This evaluation board is designed for running 30A @ 1.2V at room temperature without additional cooling systems needed. However, if the output voltage is increased or the board is operated at elevated temperatures, then the available current is derated. Refer to the derated current curves in the datasheet to determine the output current available. For layout of designs using the ISL8225M, the thermal performance can be improved by adhering to the following design tips: 1. Use the top and bottom layers to carry the large current. VOUT1, VOUT2, Phase 1, Phase 2, PGND, VIN1 and VIN2 should have large, solid planes. Place enough thermal vias to connect the power planes in different layers under and around the module. 2. Phase 1 and Phase 2 pads are switching nodes that generate switching noise. Keep these pads under the module. For noise-sensitive applications, it is recommended to keep phase pads only on the top and inner layers of the PCB; do not place phase pads exposed to the outside on the bottom layer of the PCB. To improve the thermal performance, the phase pads can be extended in the inner layer, as shown in Phase 1 and Phase 2 pads on layer 3 (Figure 6) for this 30A evaluation board. Make sure that layer 2 and layer 4 have the GND layers to cover the extended areas of phase pads at layer 3 to avoid noise coupling. 3. To avoid noise coupling, we recommend adding 470pF capacitors on all COMP pins of each module for multiple module operations. 4. If the ambient temperature is high or the board space is limited, airflow is needed to dissipate more heat from the modules. A heat sink can also be applied to the top side of the module to further improve the thermal performance (heat sink recommendation: Aavid Thermalloy, part number 375424B00034G, www.aavid.com). Thermal Considerations and Current Derating For high current applications, board layout is very critical in order to make the module operate safely and deliver maximum allowable power. To carry large currents, the board layout needs to be carefully designed to maximize thermal performance. To achieve this, select enough trace width, copper weight and the proper connectors. 2 AN1790.0 December 3, 2012 ISL8225MEVAL3Z Board Schematic VCC C6 S1 C16 VIN 470PF J1 E TP1 SINGLE OUTPUT DUAL PHASE 30A DNP RFSET TP4 4.7UF 4.5V TO 20V ISL8225M SYNC TP3 SGND C5 22UF C4 22UF C3 22UF C2 22UF 23 C15 330UF C14 100UF C13 100UF RVSET C12 1K 21 100UF OPEN R3 22 COMP1 VMON1 ISHARE CLKOUT EN/FF2 EN/FF1 SGND C9 C11 VSEN1- VIN1 PGND E 1.2V @ 30A VOUT J3 24 DNP VSEN1+ TP6 TP10 25 C10 VOUT1 12 PGOOD PGOOD 47UF ISL8225MIRZ N/C 1 26 1K 19 20 18 17 16 15 14 13 GND J4 EN C8 TP7 470PF 6.04K R1 E E S1 R2 2.05K C7 1000PF TP8 SGND TP9 S1 DRAWN BY: DATE: ENGINEER: RELEASED BY: DATE: TITLE: UPDATED BY: DATE: FIGURE 2. ISL8225MEVAL3Z BOARD SCHEMATIC TIM KLEMANN 10/18/2012 JIAN YIN DATE: ISL8225M EVALUATION BOARD SCHEMATIC Application Note 1790 VOUT2 M1 R4 PHASE2 VSEN2+ PHASE1 PHASE1 COMP2 VMON2 MODE SYNC 10 11 EGND SGND E IN VSEN2- PHASE2 TP2 VCC J2 VIN2 3.3K C1 2 3 4 5 6 PGND S1 S1 VCC GND GND_S1 7 E 8 9 470UF 3 TP5 AN1790.0 December 3, 2012 Application Note 1790 Layout FIGURE 3. TOP COMPONENTS FIGURE 4. TOP LAYER FIGURE 5. LAYER 2 FIGURE 6. LAYER 3 4 AN1790.0 December 3, 2012 Application Note 1790 Layout (Continued) FIGURE 7. BOTTOM LAYER 5 FIGURE 8. BOTTOM COMPONENTS AN1790.0 December 3, 2012 Bill of Materials PART NUMBER QTY. VALUE TOL. VOLTAGE POWER 108-0740-001 J1-J4 4 10TPB330M C15 1 TP1-TP10 10 C1 1 470µF 20% 25V C2-C5 4 22µF 10% C7 1 1000pF 10% C8, C16 2 470pF H1045-00475-6R3V10-T C6 1 H1045-OPEN C9 H1046-00476-6R3V20-T H1065-00107-6R3V20-T PACKAGE TYPE JEDEC TYPE MANUFACTURER DESCRIPTION CONN BAN-JACK Johnson Components Standard type banana jack SMD CAP_7343_149 SANYO-POSCAP Standard solid electrolytic chip tantalum SMD capacitor MTP500X Keystone Miniature white test point 0.100 pad 0.040 Thole SMD CAPAE_393X402 Panasonic Aluminum electrolytic S series type V capacitor (RoHS compliant) 25V 1210 CAP_1210 Murata Ceramic chip capacitor 50V 603 CAP_0603 Generic Multilayer capacitor 10% 50V 603 CAP_0603 Generic Multilayer capacitor 4.7µF 10% 6.3V 603 CAP_0603 Generic Multilayer capacitor 1 OPEN 5% OPEN 603 CAP_0603 Generic Multilayer capacitor C10 1 47µF 20% 6.3V 805 CAP_0805 Generic Multilayer capacitor C12-C14 3 100µF 20% 6.3V 1206 CAP_1206 Generic Multilayer capacitor C11 1 OPEN 5% OPEN 1206 CAP_1206 Generic Multilayer capacitor RFSET 1 DNP 1% DNP 603 RES_0603 Generic Metal film chip resistor (do not populate) R2 1 2.05kΩ 1% 1/10W 603 RES_0603 Generic Thick filmchip resistor H2511-01001-1/16W1 R3, RVSET 2 1kΩ 1% 1/16W 603 RES_0603 Generic Thick filmchip resistor H2511-03301-1/16W5 R4 1 3.3kΩ 5% 1/16W 603 RES_0603 Generic Thick filmchip resistor H2511-06041-1/16W1 R1 1 6.04kΩ 1% 1/10W 603 RES_0603 Generic Thick filmchip resistor ISL8225MIRZ M1 1 QFN QFN26_670X670_ISL8225M Intersil 5002 6 EEE1EA471P GRM32ER71E226KE15L H1045-00102-50V10-T H1045-00471-50V10 H1065-OPEN H2505-DNP-DNP-1 H2511-02051-1/10W1-T 330µF 20% 10V THOLE Dual 15A DC/DC power module NOTE: Resistance accuracy of feedback resistor divider R1/R2 can affect the output accuracy. Please use high accuracy resistance (i.e. 0.5% or 0.1%) to meet the output accuracy requirement. Application Note 1790 REF DES AN1790.0 December 3, 2012 Application Note 1790 ISL8225MEVAL3Z Efficiency Curves 95 Test conditions at +25°C and no air flow. 100 1.8VOUT 2.5VOUT 90 1.5VOUT EFFICIENCY (%) EFFICIENCY (%) 1.8VOUT 95 85 1.2VOUT 80 1VOUT 75 70 90 1.2VOUT 85 1.5VOUT 1VOUT 80 75 65 60 2.5VOUT 0 5 10 15 20 25 LOAD CURRENT (A) FIGURE 9. EFFICIENCY CURVES FOR 12V INPUT 30 70 0 5 10 15 20 25 30 LOAD CURRENT (A) FIGURE 10. EFFICIENCY CURVES FOR 5V INPUT 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 7 AN1790.0 December 3, 2012