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general description the max5051 evaluation kit (ev kit) is a fully assembled and tested circuit board that contains a high-efficiency, 50w, isolated, synchronously rectified forward convert- er in the industry-standard 1/8th brick pinout. the cir- cuit is configured for a +3.3v output voltage and pro- vides up to 15a of output current. the circuit can be powered from either a +36v to +72v or -36v to -72v dc source used in the telecom/datacom markets (48v modules), industrial environments, or in automotive 42v power systems. up to 91% high efficiency is achieved at 10a using a clamped, two-transistor power topology on the primary side and synchronous rectifiers on the secondary side. part of the efficiency improvement is due to the recov- ery of stored leakage and magnetizing inductance energy at the primary side. on the secondary side, high efficiency is achieved through synchronous rectifica- tion. up to 500v galvanic isolation is achieved by opto- couplers and a planar surface-mount transformer. operation at 250khz allows the use of small magnetics and output capacitors. the ev kit provides cycle-by cycle current-limit protection. integrating fault protec- tion provides additional steady-state fault protection that reduces average dissipated power during continu- ous short-circuit conditions. the max5051 also has a programmable undervoltage lockout (uvlo). warning: the max5051 ev kit is designed to operate with high voltages. dangerous voltages are present on this ev kit and on equipment connected to it. users who power up this ev kit or power the sources connect- ed to it must be careful to follow safety procedures appropriate to working with high-voltage electrical equipment. under severe fault or failure conditions, this ev kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of compo- nent debris at high velocity. operate this ev kit with care to avoid possible personal injury. features 50w, high-efficiency, isolated forward converter synchronous rectified 36v to 72v input range +3.3v output at 15a v out regulation better than 0.5% over line and load 91% efficiency at 3.3v/10a output cycle-by-cycle current-limit protection programmable integrating fault protection 1/8th brick module pinout 250khz switching frequency soft-start remote output voltage sense output voltage trim pin fully assembled and tested evaluates: max5051 max5051 evaluation kit ________________________________________________________________ maxim integrated products 1 19-2986; rev 0; 9/03 component list for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. ordering information part temp range ic package MAX5051EVKIT 0? to +50?* 28 tssop designation qty description c1 1 100pf 2%, 50v c0g ceramic capacitor (0603) murata grm1885c1h101ga01d c2 1 390pf 5%, 50v c0g ceramic capacitor (0603) taiyo yuden umk107ch391jz c3 1 4.7f 10%, 10v x5r ceramic capacitor (0805) tdk c2012x5r1a475k c4 1 4.7f 10%, 6.3v x5r ceramic capacitor (0805) tdk c2012x5r0j475k c5 1 4700pf 10%, 50v x7r ceramic capacitor (0603) tdk c1608x7r1h472k * with 100lfm airflow.
evaluates: max5051 max5051 evaluation kit 2 _______________________________________________________________________________________ component list (continued) designation qty description c6 1 0.1f 10%, 250v x7r ceramic capacitor (1206) tdk c3216x7r2e104k c7, c36 2 0.22f 10%, 10v x7r ceramic capacitors (0603) tdk c1608x7r1c224k c8 1 4.7f 10%, 16v x7r ceramic capacitor (1206) tdk c3216x7r1c475k c9 1 1f 10%, 16v x7r ceramic capacitor (0805) taiyo yuden emk212bj105kg c10, c11 2 0.47f 10%, 100v x7r ceramic capacitors (1206) tdk c3216x7r2a474k c12 1 1f 20%, 100v x7r ceramic capacitor (1210) tdk c3225x7r2a105m or avx12101c105kat9a c13, c14, c15 3 270f, 4v aluminum organic capacitors (x) kemet a700x277m004at c16 1 3.3f 10%, 6.3v x5r ceramic capacitor (0805) taiyo yuden jmk212bj335kg c17 1 0.33f 10%, 10v x5r ceramic capacitor (0603) tdk c1608x5r1a334k c18, c24 2 1000pf 5%, 50v c0g ceramic capacitors (0603) tdk c1608c0g1h102j c19, c33 2 1f 10%, 10v x5r ceramic capacitors (0603) tdk c1608x5r1a105k c20 1 220pf 10%, 50v c0g ceramic capacitor (0603) tdk c1608c0g1h221k c21 1 4.7f, 80v electrolytic capacitor (d) cornell dubilier afk475m80d16b designation qty description c22 1 2200pf 10%, 2kv x7r ceramic capacitor (1812) tdk c4532x7r3d222k c23 1 1000pf, 250v x7r ceramic capacitor (0603) murata grm188r72e102kw07 c25 1 0.047f 10%, 100v x7r ceramic capacitor (0805) tdk c2012x7r2a473k c26, c29, c30, c31 4 0.1f 10%, 16v x7r ceramic capacitors (0603) tdk c1608x7r1c104k c27 1 0.15f 10%, 16v x7r ceramic capacitor (0603) taiyo yuden emk107bj154ka c28 1 0.047f 10%, 25v x7r ceramic capacitor (0603) tdk c1608x7r1e473k c32, c35 2 1f 10%, 25v x7r ceramic capacitors (0805) tdk c2012x7r1e105k c34 1 330pf 5%, 250v c0g ceramic capacitor (0603) tdk c1608c0g2e331j d1 1 150ma, 100v schottky diode (sod- 123) diodes incorporated bat46w d2, d3 2 2a, 100v schottky diodes (smb) diodes incorporated b2100 d4, d7 2 3a, 20v schottky diodes (sma) diodes incorporated b320a d5, d6, d8 3 250ma, 100v fast-switching diodes (sod-323) diodes incorporated 1n4448hws l1 1 2.4h, 20a inductor payton planar magnetics ltd. 50661 or pulse engineering pa1494-242 or coilcraft a9860-b*
quick start required equipment 36v to 72v power supply capable of providing up to 3a voltmeter a fan to provide at least 100lfm airflow for extend- ed operation at 15a 100f, 100v bulk storage capacitor to be connect- ed to the input terminals of the ev kit the max5051 ev kit is fully assembled and tested. follow these steps to verify board operation. do not turn on the power supply until all connections are completed. forward dc-dc converter no-load output 1) connect a jumper wire from the vout terminal to the sense(+) terminal. 2) connect a jumper wire from the sgnd terminal to the sense(-) terminal. 3) connect a voltmeter to the sense(+) and sense(-) terminals to measure the output voltage. evaluates: max5051 max5051 evaluation kit _______________________________________________________________________________________ 3 component list (continued) designation qty description n1, n2 2 100v, 7.3a n-channel mosfets (8-pin so) ir irf7495 or vishay siliconix si4486ey n3, n4 2 20v, 20a n-channel mosfets (8-pin so) ir irf7832 or vishay siliconix si4864dy n5 1 170ma, 100v n-channel mosfet (sot23) fairchild bss123 r1 1 11.5k ? 1% resistor (0603) r2 1 2.55k ? 1% resistor (0603) r3 1 2.2k ? 5% resistor (0603) r4 1 1m ? 1% resistor (0603) r5 1 38.3k ? 1% resistor (0603) r6 1 1m ? 1% resistor (0805) r7, r20 2 0 ? 5% resistors (0603) r8, r9 2 8.2 ? 5% resistors (0603) r10 1 20 ? 5% resistor (1206) r11 1 360 ? 5% resistor (0603) r12 1 100k ? 1% resistor (0603) r13 1 47 ? 5% resistor (1206) r14 1 270 ? 5% resistor (0603) r15 1 31.6k ? 1% resistor (0603) r16 1 10.5k ? 1% resistor (0603) r17 1 0.027 ? 1%, 0.5w resistor (1206) irc lr1206-01-r027-f r18 1 4.7 ? 5% resistor (1206) r19 1 475 ? 1% resistor (0805) r21 1 24.9k ? 1% resistor (0805) r22 1 15k ? 5% resistor (1206) designation qty description r23, r24 2 10 ? 5% resistors (0805) r25 1 100k ? 5% resistor (0805) r26 1 560 ? 5% resistor (0805) r27 1 10 ? 5% resistor (0603) r28 1 2k ? 5% resistor (0805) r29 1 1 ? 5% resistor (0603) t1 1 planar transformer pulse engineering pa0370 or payton planar magnetics ltd. 50659* u1 1 max5051aui (28-pin tssop) u2 1 high-speed, high-voltage photocoupler (ultra small flat lead) cel/nec ps2913-1-f3-m u3 1 0.6v 0.5% shunt regulator (5-pin sot23) maxim max8515aezk-t u4, u7 2 7.6a mosfet drivers (6-pin sot23) maxim max5048aaut-t u5 1 65v high-voltage linear regulator (8-pin so) maxim max5023masa u6 1 10mbps photocoupler (5-pin sop) cel/nec ps9715-f3 +vin, -vin, on/off, sense(+), sense(-), trim 6 0.040in pc pins vout, sgnd 2 0.062in pc pins none 1 max5051 pc board * modifications to the pc board traces are required to evaluate this component.
evaluates: max5051 4) connect a 100f, 100v bulk storage capacitor to the top of the +v in and -v in pins. 5) connect the positive terminal of a 36v to 72v power supply to the +vin terminal. connect the power sup- ply s ground to the -vin terminal. 6) turn on the power supply above 36v and verify that the voltmeter reads +3.3v. detailed description the max5051 ev kit is a 50w isolated forward convert- er that provides +3.3v at up to 15a output. the circuit can be powered from a 36v to 72v dc source. the user should supply an additional 100f bulk stor- age capacitor between the input terminals (+vin, -vin). this capacitor should be rated for 100v and be able to carry 1.5a of ripple current. lower ripple-cur- rent-rated capacitors should be fine for short-term operation. the 50w forward converter achieves high efficiency by using a clamped two-transistor power topology at the input power stage. the pc board footprint is minimized by using two external surface-mount, 8-pin so n-chan- nel, 100v-rated mosfets. cycle-by-cycle current limit- ing protects the converter against short circuits at the output. for a continuous short circuit at the output, the max5051 s fault integration feature provides hiccup fault protection, thus greatly minimizing destructive temperature rise. current-sense resistor r17 senses the current through the primary of transformer t1 and turns off both external transistors n1 and n2 when the trip level of 154mv (typ) is reached. the programmable integrating fault protection allows transient overload conditions to be ignored and is configured by resistor r4 and capacitor c7. the planar surface-mount transformer features a bias winding that (along with diode d5, current-limiting resis- tor r18, and reservoir capacitor c21) power the max5051 once the input voltage is stable. upon initial input voltage application, bootstrap resistor r22 and capacitor c21 enable the max5051 to start up within approximately 70ms. no reset windings are required on the transformer with a clamped two-transistor power topology simplifying transformer design and maximizing the available copper window in the transformer. when both external primary-side transistors turn off, schottky diodes d2 and d3 recover the magnetic energy stored in the core and feed it back to the input supply. the transformer provides galvanic isolation up to 500v. on the transformer s secondary side, a 0.6v shunt reg- ulator (max8515, u3) along with feedback resistors r1 and r2 provide voltage feedback to the primary side through optocoupler u2. remote output voltage sens- ing is provided by the sense(+) and sense(-) pins for accurate output voltage regulation across the load. the max5051 receives the voltage feedback signal on the primary side from biasing resistors r15, r16, and com- pensation resistor-capacitor network r11/c17 and c24 connected to optocoupler u2. optocoupler u6 receives the max5051 synchronous rectifier drive signal from the primary side and provides the max5048 secondary-side high-speed mosfet dri- vers, u4 and u7, with a galvanically isolated signal. mosfet n4 forms a synchronous rectifier for free- wheeling-diode d4 and mosfet n3 forms the synchro- nous rectifier for rectifier-diode d7. voltage regulation for u4, u6, and u7 is provided by a max5023 linear regulator on the secondary side. the max5051 controller switches at 250khz frequency set by resistor r21 and capacitor c1. the duty cycle is varied to control energy transfer to the output. the maximum duty cycle is 50% for the ev kit's forward converter design. the max5051 features output-voltage soft-start, thus eliminating any output-voltage overshoots. soft-start allows the output voltage to slowly ramp up in a con- trolled manner within approximately 3ms. capacitor c5 sets the soft-start time. the brownout uvlo threshold voltage is set by resis- tors r5 and r6. this prevents the power supply from operating below the programmed input supply voltage. the four-layer pc board layout and component place- ment have been designed to have an industry-standard 1/8th brick pinout. the actual pc board dimensions (58.42mm x 41.65mm) of the power-supply board are somewhat larger than that of 1/8th brick power supplies. evaluating other output voltages, current limits, soft-starts, and uvlos vout output voltage the max5051 ev kit s output (vout) is set to +3.3v by feedback resistors (r1, r2). to generate output volt- ages other than +3.3v (from +2.6v to +4.0v, limited by the output-capacitor voltage rating), select different voltage-divider resistors (r1, r2). resistor r1 is typical- ly chosen to be less than 25k ? . using the desired out- put voltage, resistor r2 is then found by the following equation: where v ref = 0.6v r r vout v ref 2 1 1 = ? () (/) max5051 evaluation kit 4 _______________________________________________________________________________________
the maximum output current should be limited to less than 15a. the usable output voltage range for the ev kit is +2.6v to +4.0v. additionally, u3, u2, and resistor r19 limit the minimum output voltage (vout) to +2.6v. current limiting the ev kit features cycle-by-cycle current limiting of the transformer primary current. the max5051 turns off both external switching transistors (n1, n2) when the voltage at the cs pin of the max5051 reaches 154mv (typ). current-sense resistor r17 (= 0.027 ? ) limits the peak primary current to approximately 5.7a (154mv/0.027 ? 5.7a). this limits short-circuit current on the secondary output (vout) to 20.3a peak typical- ly. under short-circuit conditions, the average output current is only 473ma typically due to hiccup-mode fault protection. to evaluate lower current limits, cur- rent-sense resistor r17 must be replaced with a differ- ent value surface-mount resistor (1206 size) as deter- mined by the following equation: where v sense = 0.154v, n s = 2, n p = 8 and i outmax = maximum dc output current (15a or less). note that some fine tuning may be required when selecting the current-limit resistor. there are errors introduced as a result of the presence of the transformer and output inductor ripple current. soft-start the max5051 ev kit limits the output voltage rate of rise with a soft-start feature. capacitor c5 sets the ramp time to 91ms. to evaluate other soft-start ramp times, replace capacitor c5 with another surface-mount capacitor (0603 size) as determined by the following equation: where softstart_time is the desired soft-start time in seconds. undervoltage lockout (uvlo) the max5051 ev kit features a uvlo circuit that pre- vents operation below the programmed input supply start voltage. resistors r5 and r6 set the input voltage brownout uvlo of the ev kit. to evaluate other input uvlo voltages, replace resistor r6 with another sur- face-mount resistor (0805 size). using the desired start- up voltage, resistor r6 is then found by using the fol- lowing equation: where vin startup is the desired startup voltage at which the ev kit starts and resistor r5 is typically 38.3k ? . r vin v v r startup 6 124 124 5 = ? () ? ? ? ? ? ? . . c a softstart time v 5 65 124 = (_) . r v nn i sense s p outmax 17 12 = () (/) (. ) evaluates: max5051 max5051 evaluation kit _______________________________________________________________________________________ 5 component suppliers supplier phone fax website avx 843-946-0238 843-626-3123 www.avxcorp.com cel/nec; california eastern laboratories 800-997-5227 408-588-2213 www.cel.com coilcraft 847-639-6400 847-639-1469 www.coilcraft.com cornell dubilier 508-996-8564 508-336-3830 www.cornell-dubilier.com diodes inc 805-446-4800 805-446-4850 www.diodes.com fairchild 888-522-5372 local representative only www.fairchildsemi.com international rectifier 310-322-3331 310-726-8721 www.irf.com irc 361-992-7900 361-992-3377 www.irctt.com kemet 864-963-6300 864-963-6322 www.kemet.com murata 770-436-1300 770-436-3030 www.murata.com payton planar magnetics ltd. 561-969-9585 561-989-9587 www.paytongroup.com pulse engineering 858-674-8100 858-674-8262 www.pulseeng.com taiyo yuden 800-348-2496 847-925-0899 www.t-yuden.com tdk 847-803-6100 847-390-4405 www.component.tdk.com vishay www.vishay.com
evaluates: max5051 max5051 evaluation kit 6 _______________________________________________________________________________________ 60 65 75 70 85 90 80 95 efficiency vs. output current load current (a) efficiency (%) 36v 48v 72v 046 2 8 10 12 14 figure 1. efficiency vs. output current 0 1 3 2 5 6 4 7 046 2 8 10 12 14 power dissipation vs. load current load current (a) power dissipation (w) 72v 48v 36v figure 2. power dissipation vs. load current 4ms/div i out 5a/div v out 1v/div v in = 48v 0 0 figure 3. turn-on transient at full load (resistive load) 4ms/div v out 1v/div i out 0 0 v in = 48v figure 4. turn-on transient at zero load synchronous rectified forward dc-to-dc converter waveforms
evaluates: max5051 max5051 evaluation kit _______________________________________________________________________________________ 7 1ms/div v out 100mv/div i out 5a/div load capacitor: no external capacitor required for transient response. figure 5. output voltage response to step change in load current (50%-75%-50% of i out (max), di/dt = 5a/ms, 7.5a to 11.25a to 7.5a) 2 s/div v out 50mv/div load capacitance: 0.1 f ceramic capacitor scope bandwidth: 20mhz. figure 6. output voltage ripple at nominal input voltage and rated load current 0 1 3 2 4 5 load current (a) output voltage (v) 010 hiccup point 51520 output voltage vs. load current figure 7. output voltage vs. load current showing typical limit curves and converter shutdown points ( note: hiccup current limiting provides current foldback mechanism that helps to minimize power-supply power dissipation during fault conditions) a: 1ms/div b: 20ms/div i out 10a/div i out 10a/div a b figure 8. load current (10a/div) as a function of time when converter attempts to turn on into a 0.050 ? short circuit (also acts as current-sense resistor)
evaluates: max5051 max5051 evaluation kit 8 _______________________________________________________________________________________ 0 0.5 3.0 1.5 3.5 4.0 input voltage (v) output voltage (v) 20 30 25 35 40 1.0 2.0 2.5 output voltage vs. input voltage figure 9. output voltage vs. input voltage (point device comes out of programmed uvlo and goes into uvlo) 85 88 87 86 89 90 91 92 93 94 95 35 45 55 65 75 efficiency vs. input voltage input voltage (v) efficiency (%) figure 10. efficiency vs. input voltage, i out = 15a 2 s/div 25v/div 0 figure 11. waveform across primary-side transformer (t1), input = 48v
evaluates: max5051 max5051 evaluation kit _______________________________________________________________________________________ 9 -vin c25 0.047 f 100v c35 1 f c32 1 f 1 2 in out wdi n.c. hold u5 en gnd reset 1 2 d6 3 45 5 6 4 2 1 1 2 3 6 5 4 3 u4 u7 gnd gnd n_out n_out p_out p_out v+ v+ in- in- in+ in+ 6 +vin +vin n1 3 27 8 6 5 4 1 1 2 d2 xfrmrh xfrmrh r29 1 ? drvb 1 2 3 n5 5v c16 3.3 f c33 1 f 10v c15 270 f 4v vout l1 2.4 h vout sgnd c12 1 f 100v c11 0.47 f 100v c10 0.47 f 100v reg9 28 r4 1m ? 1% c7 0.22 f c8 4.7 f c9 1 f c34 330pf d3 12 4 1 5 7 2 3 n2 68 2 8 2t 10 d7 1 8 7 3 21 4 n3 5 6 2 5 8t t1 r13 47 ? xfrmrh r10 20 ? c23 1000pf c20 220pf c19 1 f r27 10 ? r16 10.5k ? 1% r21 24.9k ? 1% r15 31.6k ? 1% c18 1000pf 14 13 12 11 +vin +vin r6 1m ? 1% r5 38.3k ? 1% r7 0 ? r8 8.2 ? r9 8.2 ? r14 270 ? d1 xfrmrh drvb 2 1 27 26 25 24 23 22 21 20 19 18 17 16 15 29 tp3 lxh +vin pvin r22 15k ? r18 4.7 ? 1 1 2 6 4t d5 r17 0.027 ? 1% c21 4.7 f 80v reg9 +vin 7 8 c14 270 f 4v c13 270 f 4v 5v c29 0.1 f c30 0.1 f 5v 5v 51 2 4 3 u6 v cc out an lxh r26 560 ? r28 2k ? ca gnd c31 0.1 f 5v reg9 c26 0.1 f c22 2200pf 2kv r24 10 ? r23 10 ? vout u3 4 1 3 1 4 3 2 c28 0.047 f c27 0.15 f r12 100k ? 1% r19 475 ? r20 0? r3 2.2k ? r11 360 ? c17 0.33 f c24 1000pf c36 0.22 f out in pgnd gnd fb sense (+) sense (-) 5 trim r2 2.55k ? 1% r1 11.5k ? 1% 2 vout vout reg5 u2 reg5 pvin c3 4.7 f 9 8 7 6 5 4 3 2 1 rcosc on/off syncout rcff con css comp fb reg5 reg9 pvin stt lxvdd lxh lxl ic_paddle cs drvl pgnd drvdd drvb xfrmrh drvh bst avin gnd uvlo startup fltint syncin c6 0.1 f 10 c4 4.7 f c5 4700pf c2 390pf tp1 d8 21 reg9 reg5 reg5 r25 100k ? +vin c1 100pf u1 max5051 d4 1 8 7 1 2 3 n4 4 5 6 2 figure 12. max5051 ev kit schematic
evaluates: max5051 max5051 evaluation kit 10 ______________________________________________________________________________________ figure 15. max5051 ev kit pc board layout?nner layer, gnd plane figure 16. max5051 ev kit pc board layout?nner layer, v cc plane figure 13. max5051 ev kit component placement guide component side figure 14. max5051 ev kit pc board layout?omponent side
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 11 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. evaluates: max5051 max5051 evaluation kit figure 17. max5051 ev kit pc board layout?older side figure 18. max5051 ev kit component placement guide solder side

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