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 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 ha ve a complete, 30a design ready for use are the isl8225m, a few passive components, and v out setting resistors. the ease of use virtually eliminates design and manufacturing risks while dramatically im proving time to market. 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, bo m costs, and complexity. the isl8225meval3z evaluation board enables a single output by paralleling two phas es to deliver 30a continuous load current. the isl8225m supports input voltage from 4.5v to 20v and the output voltage rang es from 0.6v to 6v. with the single resistor modification, th e output voltage can be easily adjusted to different voltages. related resources recommended equipment ? 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 quick start 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 lo w voltage, high current v out 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, v out , which should be at 1.2v if the board is working properly. 3. the isl8225meval3z is manufactured with a default v out value of 1.2v; if different output voltages are desired, board resistors can be exchanged to provide the desired v out . please refer to the table printed on the backside of the evaluation board or table 1 on page 2 for r vset resistor values, which can be used to produce different output voltages. see how-to video at intersil.com/ evid01 figure 1. isl8225meval3z board image load (0a~30a) v out 4.5v to 20v v + - v in + - v + - december 3, 2012 an1790.0
application note 1790 2 an1790.0 december 3, 2012 for 12v v in , and v out more than 1.5v, the switching frequency will need to be adjusted, as shown in table 1; no frequency adjustments are necessary for v out below 1.5v. for 5v v in , the frequency does not need to be adjusted and the module default frequency can be used at any allowed v out . if the output voltage is set to more than 1.8v, the output current will need to be derated to allow for safe op eration at elevated ambient temperatures. please refer to the derating curves in the isl8225m datasheet . for v in < 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. 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 th e ?layout? section beginning on page 4. the board is made up of fr4 material and all components, including the solder attachment, are lead-free. 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. this evaluation board is design ed for running 30a @ 1.2v at room temperature without additi onal 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 ). table 1. resistance setting for different output voltages and operating frequency (r3 = 1k) v out (v) r vset ( ) frequency (khz) r fset ( ) (v in = 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
application note 1790 3 an1790.0 december 3, 2012 isl8225meval3z board schematic figure 2. isl8225meval3z board schematic sgnd 4.5v to 20v sgnd gnd isl8225m single output dual phase 30a 1.2v @ 30a gnd sgnd gnd_s1 egnd phase1 phase2 vin en vcc pgood vout vcc dnp 4.7uf ISL8225MIRZ 470pf 1000pf 2.05k 6.04k 22uf 22uf 22uf 22uf 470uf 10/18/2012 tim klemann schematic isl8225m evaluation board jian yin 3.3k 330uf 100uf 100uf 100uf dnp 47uf open 1k 1k 470pf sync vsen2- vsen1- vsen2+ vsen1+ pgood in en/ff1 en/ff2 clkout vmon1 ishare comp1 vout2 1 10 11 12 21 22 23 24 25 26 pgnd vin1 n/c mode sgnd sync vmon2 comp2 vout1 vcc tp4 tp3 j2 tp8 tp9 tp1 j1 tp2 j3 j4 tp6 tp7 tp10 tp5 released by: drawn by: date: date: date: date: engineer: title: updated by: e pgnd vin2 s1 e e s1 s1 s1 s1 e e e c1 2 3 4 5 6 7 8 913 14 15 16 17 18 19 20 phase1 phase2 rfset c8 c7 r2 r1 c5 c4 c3 c2 r4 c16 c6 c9 r3 rvset c15 c14 c13 c12 c11 c10 m1
application note 1790 4 an1790.0 december 3, 2012 layout figure 3. top components figure 4. top layer figure 5. layer 2 figure 6. layer 3
application note 1790 5 an1790.0 december 3, 2012 figure 7. bottom layer figure 8. bottom components layout (continued)
application note 1790 6 an1790.0 december 3, 2012 bill of materials part number ref des qty. value tol. voltage power package type jedec type manufacturer description 108-0740-001 j1-j4 4 conn ban-jack johnson components standard type banana jack 10tpb330m c15 1 330f 20% 10v smd cap_7343_149 sanyo-poscap st andard solid electrolytic chip tantalum smd capacitor 5002 tp1-tp10 10 thole mtp500x keystone miniature white test point 0.100 pad 0.040 thole eee1ea471p c1 1 470f 20% 25v smd capae_393x402 panasonic alumi num electrolytic s series type v capacitor (rohs compliant) grm32er71e226ke15l c2-c5 4 22f 10% 25v 1210 ca p_1210 murata ceramic chip capacitor h1045-00102-50v10-t c7 1 1000pf 10% 50v 603 cap_0603 generic multilayer capacitor h1045-00471-50v10 c8, c16 2 470pf 10% 50v 603 cap_0603 generic multilayer capacitor h1045-00475-6r3v10-t c6 1 4.7f 10% 6.3v 603 cap_0603 generic multilayer capacitor h1045-open c9 1 open 5% open 603 cap_0 603 generic multilayer capacitor h1046-00476-6r3v20-t c10 1 47f 20% 6.3v 805 cap_0805 generic multilayer capacitor h1065-00107-6r3v20-t c12-c14 3 100f 20% 6.3v 1206 cap_1206 generic multilayer capacitor h1065-open c11 1 open 5% open 1206 cap_1 206 generic multilayer capacitor h2505-dnp-dnp-1 rfset 1 dnp 1% dnp 603 res_0603 generic met al film chip resistor (do not populate) h2511-02051-1/10w1-t r2 1 2.05k ? 1% 1/10w 603 res_0603 generic t hick filmchip resistor h2511-01001-1/16w1 r3, rvset 2 1k ? 1% 1/16w 603 res_0603 generic t hick filmchip resistor h2511-03301-1/16w5 r4 1 3.3k ? 5% 1/16w 603 res_0603 generic t hick filmchip resistor h2511-06041-1/16w1 r1 1 6.04k ? 1% 1/10w 603 res_0603 generic t hick filmchip resistor ISL8225MIRZ m1 1 qfn qfn26_670x 670_isl8225m intersil dual 15a dc/dc power module note: resistance accuracy of feedback resistor divider r1/r2 can affect the output accuracy. plea se use high accuracy resistance (i.e. 0.5% or 0.1%) to meet the output accuracy requirement.
application note 1790 7 intersil corporation reserves the right to make changes in circuit design, software and/or specifications at any time without n otice. 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 an1790.0 december 3, 2012 isl8225meval3z efficiency curves test conditions at +25c and no air flow. figure 9. efficiency curves for 12v input f igure 10. efficiency curves for 5v input 60 65 70 75 80 85 90 95 0 5 10 15 20 25 30 load current (a) efficiency (%) 1.2v out 1.5v out 2.5v out 1.8v out 1v out 70 75 80 85 90 95 100 0 5 10 15 20 25 30 load current (a) efficiency (%) 1.2v out 1.5v out 2.5v out 1.8v out 1v out
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