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march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 1 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? features ? ? input ? voltage ? range: ? 3v ? to ? 27v ?? ? output ? voltage ? range: ? 0.5v ? to ? 12v ? ? continuous ? 10a ? load ? capability ? ? constant ? on \ time ? control ? ? compensation ? loop ? not ? required ?? ? excellent ? efficiency ? at ? very ? low ? output ? currents ? ? programmable ? switching ? frequency ? and ? soft ? start ?? ? thermally ? compensated ? over ? current ? protection ? ? power ? good ? output ?? ? precision ? voltage ? reference ? (0.5v, ? +/ \ 1%) ? ? enable ? input ? with ? voltage ? monitoring ? capability ?? ? pre \ bias ? start ? up ? ? thermal ? shut ? down ?? ? under/over ? voltage ? fault ? protection ?? ? forced ? continuous ? conduction ? mode ? option ? ? very ? small, ? low ? profile ? 4mm ? x ? 5mm ? qfn ? package ? ? ? basic ? application ? ? figure ? 1: ? ir3475 ? basic ? application ? circuit ? description ? the ? ir3475 ? supirbuck tm ? is ? an ? easy \ to \ use, ? fully ? integrated ? and ? highly ? efficient ? dc/dc ? voltage ? regulator. ? the ? onboard ? constant ? on ? time ? hysteretic ? controller ? and ? mosfets ? make ? ir3475 ? a ? space \ efficient ? solution ? that ? delivers ? up ? to ? 10a ? of ? precisely ? controlled ? output ? voltage. ? programmable ? switching ? frequency, ? soft ? start, ? and ? thermally ? compensated ? over ? current ? protection ? allows ? for ? a ? very ? flexible ? solution ? suitable ? for ? many ? different ? applications ? and ? an ? ideal ? choice ? for ? battery ? powered ? applications. ? additional ? features ? include ? pre \ bias ? startup, ? very ? precise ? 0.5v ? reference, ? under/over ? voltage ? shutdown, ? thermal ? protection, ? power ? good ? output, ? and ? enable ? input ? with ? voltage ? monitoring ? capability. ? applications ? ? notebook ? and ? desktop ? computers ? ? consumer ? electronics ? ? ? stb, ? lcd, ? tv, ? printers ? ? 12v ? and ? 24v ? distributed ? power ? systems ? ? general ? purpose ? pol ? dc \ dc ? converters ? ? game ? consoles ? and ? graphics ? cards ? efficiency ? 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 95% 0.01 0.1 1 10 load current (a) efficiency vin = 12v vin = 8v vin = 19v ? figure ? 2: ? ir3475 ? efficiency ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 2 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? ordering ? information ? ?? ir3475 ?D ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? ??????? ? ? ? marking ? information ? package tape ? & ? reel ? qty ? part ? number m ? 750 ? ir3475mtr1pbf ? m ? 4000 ? IR3475MTRPBF ? pin ? diagram ? w c w c o pcb j o ja / 2 / 32 - = = pbf ? ? ? lead ? free ? tr ? ? ? tape ? and ? reel ? m ? ? ? package ? type ? 3475 ?yww? xxxxx site/date/marking ? code lot ? code pin ? 1 ? identifier
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 3 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? functional ? block ? diagram ? ? figure ? 3: ? ir3475 ? functional ? block ? diagram ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 4 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? typical ? application ? ? tp7 tp10 en vcc tp23 vouts tp24 pgnds c26 open c27 open vin r13 open c7 open c8 open c9 330uf c10 47uf c11 open c1 1uf r7 2.80k r8 2.55k c12 0.1uf pgood c24 open iset +3.3v vout vcc +3.3v vin tp6 pgnds tp14 +3.3v u1 ir3475 3vcbp 8 fccm 1 ss 6 pgood 3 ff 15 gnd1 4 fb 5 gnd 17 nc1 7 iset 2 boot 14 vin 13 vcc 10 nc2 9 pgnd 11 phase 12 en 16 c4 0.22uf vcc tp4 en sw1 en / fccm 1 2 4 3 tp17 pgnd c20 0.1uf tp26 agnd vsw c21 1uf tp11 pgood r9 open l1 1.5uh r6 open tp1 vins r4 13.7k r3 200k c13 open c2 22uf c16 open + c3 68uf tp2 vin tp5 pgnd c14 open c17 open c18 open tp16 vcc fb r5 10k c15 open r10 open c6 open tp18 voltage sense +vins 1 +vdd1s 2 +vdd2s 3 +vout1s 4 +vout2s 5 -vout2s 10 -vdd2s 8 -vout1s 9 -vins 6 -vdd1s 7 r1 10k fccm ir3475 +3.3v r11 20 c22 open tp25 b c25 1uf vout tp27 a +3.3v tp28 vid tp13 ss vsw r12 4.99 ohms ss r2 10k c19 open q1 open 2 1 3 pgnd vout c23 open ? figure ? 4: ? demoboard ? schematic ? for ? vout ? = ? 1.05v, ? f s ? = ? 300khz ? ? demoboard ? bill ? of ? materials ? qty ? reference ? designator ? value ? description ? manufacturer ? part ? number ? 3 ? c1, ? c21, ? c25 ? 1.00uf ? capacitor, ? x7r, ? 1.00uf, ? 25v, ? 0.1, ? 0603 ? murata ? grm188r71e105ka12d ? 1 ? c10 ? 47uf ? capacitor, ? 47uf, ? 6.3v, ? 805 ? tdk ? c2012x5r0j476m ? 2 ? c12, ? c20 ? 0.100uf ? capacitor, ? x7r, ? 0.100uf, ? 25v, ? 0.1, ? 603 ? tdk ? c1608x7r1e104k ? 1 ? c2 ? 22.0uf ? capacitor, ? x5r, ? 22.0uf, ? 16v, ? 20%, ? 1206 ? taiyo ? yuden ? emk316bj226ml \ t ? 1 ? c3 ? 68uf ? capacitor, ? electrolytic, ? 68uf, ? 25v, ? 0.2, ? smd ? panasonic ? eev \ fk1e680p ? 1 ? c4 ? 0.22uf ? capacitor, ? x5r, ? 0.22uf, ? 10v, ? 0.1, ? 0603 ? tdk ? c1608x5r1a224k ? 1 ? c9 ? 330uf ? capacitor, ? electrolytic, ? 330uf, ? 2.5v, ? 0.2, ? 7343 ? sanyo ? 2r5tpe330m9 ? 1 ? l1 ? 1.5uh ? inductor, ? ferrite, ? 1.5uh, ? 16.0a, ? 3.8mohm, ? smt ? cyntec ? pimb104t \ 1r5ms \ 39 ? 3 ? r1, ? r2, ? r5 ? 10.0k ? resistor, ? thick ? film, ? 10.0k, ? 1/10w, ? 0.01, ? 0603 ? koa ? rk73h1j1002f ? 1 ? r11 ? 20 ? resistor, ? thick ? film, ? 20, ? 1/10w, ? 0.01, ? 603 ? koa ? rk73h1jltd20r0f ? 1 ? r12 ? 4.99 ? resistor, ? thick ? film, ? 4.99, ? 1/10w, ? 0.01, ? 603 ? vishay/dale ? crcw06034r99fnea ? 1 ? r3 ? 200k ? resistor, ? thick ? film, ? 200k, ? 1/10w, ? 0.01, ? 603 ? koa ? rk73h1jltd2003f ? 1 ? r4 ? 13.7k ? resistor, ? thick ? film, ? 13.7k, ? 1/10w, ? 0.01, ? 603 ? koa ? rk73h1jltd1372f ? 1 ? r7 ? 2.80k ? resistor, ? thick ? film, ? 2.80k, ? 1/10w, ? 0.01, ? 603 ? koa ? rk73h1jltd2801f ? 1 ? r8 ? 2.55k ? resistor, ? thick ? film, ? 2.55k, ? 1/10w, ? 0.01, ? 0603 ? koa ? rk73h1j2551f ? 1 ? sw1 ? spst ? switch, ? dip, ? spst, ? 2 ? position, ? smt ? c&k ? components ? sd02h0sk ? 1 ? u1 ? ir3475 ? 4mm ? x ? 5mm ? qfn ? irf ? IR3475MTRPBF ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 5 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? pin ? descriptions ? pin # pin name i/o level pin description 1 ? fccm ? 3.3v ? forced ? continuous ? conduction ? mode ? (ccm). ? ground ? this ? pin ? to ? enable ? diode ? emulation ? mode ? or ? discontinuous ? conduction ? mode ? (dcm). ? pull ? this ? pin ? to ? 3.3v ? to ? operate ? in ? ccm ? under ? all ? load ? conditions. ? 2 ? iset ?? connecting ? resistor ? to ? phase ? pin ? sets ? over ? current ? trip ? point. ? 3 ? pgood ? 5v ? power ? good ? open ? drain ? output ? ? ? pull ? up ? with ? a ? resistor ? to ? 3.3v ? 4, ? 17 ? gnd ? reference ? bias ? return ? and ? signal ? reference. ? 5 ? fb ? 3.3v ? inverting ? input ? to ? pwm ? comparator, ? ovp ? / ? pgood ? sense. ? 6 ? ss ? 3.3v ? soft ? start/shutdown. ? this ? pin ? provides ? user ? programmable ? soft \ start ? function. ? connect ? an ? external ? capacitor ? from ? this ? pin ? to ? gnd ? to ? set ? the ? startup ? time ? of ? the ? output ? voltage. ? the ? converter ? can ? be ? shutdown ? by ? pulling ? this ? pin ? below ? 0.3v. ? 7 ? nc ? \? \? 8 ? 3vcbp ? 3.3v ? for ? internal ? ldo. ? bypass ? with ? a ? 1.0f ? capacitor ? to ? agnd. ? a ? resistor ? in ? series ? with ? the ? bypass ? capacitor ? may ? be ? required ? in ? single \ ground ? plane ? designs. ? refer ? to ? layout ? recommendation ? for ? details. ? 9 ? nc ? \? \? 10 ? vcc ? 5v ? vcc ? input. ? gate ? drive ? supply. ? a ? minimum ? of ? 1.0f ? ceramic ? capacitor ? is ? required. ? 11 ? pgnd ? reference ? power ? return. ? 12 ? phase ? vin ? phase ? node ? (or ? switching ? node) ? of ? mosfet ? half ? bridge. ? 13 ? vin ? vin ? input ? voltage ? for ? the ? system. ? 14 ? boot ? vin ? + ? vcc ? bootstrapped ? gate ? drive ? supply ? ? ? connect ? a ? capacitor ? to ? phase. ? 15 ? ff ? vin ? input ? voltage ? feed ? forward ? ? ? sets ? on \ time ? with ? a ? resistor ? to ? vin. ? 16 ? en ? 5v ? enable ? pin ? to ? turn ? on ? and ? off ? the ? device. ? use ? two ? external ? resistors ? to ? set ? the ? turn ? on ? threshold ? (see ? electrical ? specifications ) ? for ? input ? voltage ? monitoring. ?? ?? ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 6 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? absolute ? maximum ? ratings ? ? stresses ? beyond ? those ? listed ? under ? ?absolute ? maximum ? ratings? ? may ? cause ? permanent ? damage ? to ? the ? device. ? these ? are ? stress ? ratings ? only ? and ? functional ? operation ? of ? the ? device ? at ? these ? or ? any ? other ? conditions ? beyond ? those ? indicated ? in ? the ? operational ? sections ? of ? the ? specifications ? are ? not ? implied. ? ? vin, ? ff ? \ 0.3v ?? to ?? 30v ? vcc, ? pgood, ? en ?\ 0.3v ?? to ?? 8v ? boot ? \ 0.3v ?? to ?? 38v ? phase ?\ 0.3v ?? to ?? 30v ? (dc), ?\ 5v ? (100ns) ? boot ? to ? phase ? \ 0.3v ?? to ?? 8v ? iset ?\ 0.3v ?? to ?? 30v, ? 30ma ? pgnd ? to ? gnd ? \ 0.3v ?? to ?? +0.3v ? all ? other ? pins ?\ 0.3v ?? to ?? 3.9v ? storage ? temperature ? range ? \ 65c ?? to ?? 150c ? junction ? temperature ? range ?\ 40c ?? to ?? 150c ? esd ? classification ? jedec ? class ? 1c ? moisture ? sensitivity ? level ? jedec ? level ? 2 ? @ ? 260c ? (note ? 2) ? ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 7 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? electrical ? specifications ? recommended ? operating ? conditions ? for ? reliable ? operation ? with ? margin ? ? symbol ? min ? max ? units recommended ? vin ? range ? vin ? 3 ? 27* ? v ? recommended ? vcc ? range ? vcc ? 4.5 ? 5.5 ? recommended ? output ? voltage ? range ? v out ? 0.5 ? 12 ? recommended ? output ? current ? range ? i out ? 0 ? 10 ? a ? recommended ? switching ? frequency ? f s ? n/a ? 750 ? khz ? recommended ? operating ? junction ? temperature ? t j ?\ 40 ? 125 ? c ? * ? phase ? pin ? must ? not ? exceed ? 30v. ? electrical ? characteristics ? unless ? otherwise ? specified, ? these ? specifications ? apply ? over ? vin ? = ? 12v, ? 4.5v ? < ? vcc ? < ? 5.5v, ? 0c ?? t j ?? 125c. ? parameter ? symbol ? conditions ? min ? typ ? max ? unit ? control ? loop ? reference ? accuracy ? v ref ? v fb ? = ? 0.5v ? 0.495 ? 0.5 ? 0.505 ? v ? on \ time ? accuracy ??? r ff ? = ? 180k, ? t j ? = ? 65c ? 280 ? 300 ? 320 ? ns ? min. ? off ? time ????? ?? 500 ? 580 ?? ns ? soft \ start ? current ??? en ? = ? high ? 8 ? 10 ? 12 ? a ? dcm ? comparator ? offset ??? measure ? at ? v phase ?\ 4.5 ?\ 2.5 ? 0 ? mv ?? feedback ? input ? current ?? v fb ? = ? 0.5v, ? t a ? = ? 25c, ? note ? 1 ?? 0.01 ? 0.2 ? a ? supply ? current ? vcc ? supply ? current ? (standby) ??? en ? = ? low, ? no ? switching ??? 23 ??? a ? vcc ? supply ? current ? (dynamic) ?? en ? = ? high, ? f s ? = ? 300khz ??? 7 ??? ma ? ff ? shutdown ? current ?? ? en ? = ? low, ? r ff ? = ? 180k ?? 2 ? ? ? a ? forced ? continuous ? conduction ? mode ? (fccm) ? fccm ? start ? threshold ? ? ? ?? 2 ? ? ? ? ? v ? fccm ? stop ? threshold ? ? ? ?? ?? ?? 0.6 ? v ? gate ? drive ? deadtime ??? monitor ? body ? diode ? conduction ? on ? phase ? pin, ? note ? 1 ? 5 ?? 30 ? ns ? bootstrap ? pfet ? forward ? voltage ? ? i(boot) ? = ? 10ma ?? 300 ?? mv ? upper ? mosfet ? static ? drain \ to \ source ? on \ resistance ?? ? vcc ? = ? 5v, ? i d ? = ? 10a, ? t j ? = ? 25c ?? 25 ? 32 ? m ? lower ? mosfet ? ? static ? drain \ to \ source ? on \ resistance ?? ? vcc ? = ? 5v, ? i d ? = ? 10a, ? t j ? = ? 25c ? ? 13 ? 17 ? m ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 8 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? parameter ? symbol ? conditions ? min ? typ ? max ? unit ? fault ? protection ? iset ? pin ? output ? current ?? ? on ? the ? basis ? of ? 25c ? 17 ? 19 ? 21 ? a ? iset ? pin ? output ? current ?? temperature ? coefficient ? ? ? on ? the ? basis ? of ? 25c, ? note ? 1 ??? 4400 ??? ppm/ ? c ? under ? voltage ? threshold ?? ? falling ? v fb ? & ? monitor ? pgood ? 0.37 ? 0.4 ? 0.43 ? v ? under ? voltage ? hysteresis ?? ? rising ? v fb , ? note ? 1 ??? 7.5 ??? mv ? over ? voltage ? threshold ?? ? rising ? v fb ? & ? monitor ? pgood ? 0.586 ? 0.625 ? 0.655 ? v ? over ? voltage ? hysteresis ?? ? falling ? v fb , ? note ? 1 ??? 7.5 ??? mv ? vcc ? turn \ on ? threshold ?? ? ?\ 40c ? to ? 125c ? 3.9 ? 4.2 ? 4.5 ?? v ? vcc ? turn \ off ? threshold ?? ? ?? 3.6 ? 3.9 ? 4.2 ? v ? vcc ? threshold ? hysteresis ????? ?? 300 ??? mv ? en ? rising ? threshold ???\ 40c ? to ? 125c ? 1.1 ? 1.25 ? 1.45 ? v ? en ? hysteresis ???? ? 400 ?? mv ? en ? input ? current ?? en ? = ? 3.3v ??? 15 ? a ? pgood ? pull ? down ? resistance ?? ? ? 25 ? 50 ?? pgood ? delay ? threshold ? v ss ?? ? 1 ?? v ? thermal ? shutdown ? threshold ?? note ? 1 ? 125 ? 140 ?? c ? thermal ? shutdown ? threshold ? hysteresis ? ? note ? 1 ?? 20 ?? c ? note: ?? 1. guaranteed ? by ? design ? but ? not ? tested ? in ? production ? 2. upgrade ? to ? industrial/msl2 ? level ? applies ? from ? date ? codes ? 1227 ? (marking ? explained ? on ? application ? note ? an1132 ? page ? 2). ? products ? with ? prior ? date ? code ? of ? 1227 ? are ? qualified ? with ? msl3 ? for ? consumer ? market. ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 9 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? typical ? operating ? data ? ? tested ? with ? demoboard ? shown ? in ? figure ? 4, ? vin ? = ? 12v, ? vcc ? = ? 5v, ? vout ? = ? 1.05v, ? fs ? = ? 300khz, ? t a ? = ? 25 o c, ? no ? airflow, ?? unless ? otherwise ? specified. 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 95% 0.01 0.1 1 10 load current (a) efficiency vin = 12v vin = 8v vin = 19v ? figure ? 5: ? efficiency ? vs. ? load ? current ? for ? vout ? = ? 1.05v ? 0 50 100 150 200 250 300 350 0246810 load current (a) switching frequency (khz) ? figure ? 7: ? switching ? frequency ? vs. ? load ? current ? 1.054 1.056 1.058 1.060 1.062 1.064 0246810 load current (a) output voltage (v) 12vin 8vin 19vin ? figure ? 9: ? load ? regulation ? 45% 50% 55% 60% 65% 70% 75% 80% 85% 90% 95% 0.01 0.1 1 10 load current (a) efficiency vout = 1.05v; l = 1.5h, 3.8m ? vout = 1.5v; l = 2.2h, 6m ? vout = 3.3v; l = 3.3h, 10.8m ? ? figure ? 6: ? efficiency ? vs. ? load ? current ? for ? vin ? = ? 12v ? 0 200 400 600 800 1000 1200 1400 200 250 300 350 400 450 500 550 600 650 700 750 switching frequency (khz) rff (kohm) 5.0 vout 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 ? figure ? 8: ? r ff ? vs. ? switching ? frequency ?? 1.054 1.056 1.058 1.060 1.062 1.064 8 9 10 11 12 13 14 15 16 17 18 19 input voltage (v) output voltage (v) ? figure ? 10: ? line ? regulation ? at ? i out ? = ? 10a ??
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 10 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? typical ? operating ? data ?? tested ? with ? demoboard ? shown ? in ? figure ? 4, ? vin ? = ? 12v, ? vcc ? = ? 5v, ? vout ? = ? 1.05v, ? fs ? = ? 300khz, ? t a ? = ? 25 o c, ? no ? airflow, ? unless ? otherwise ? specified. ? figure ? 11: ? startup ? ? figure ? 13: ? dcm ? (i out ? = ? 0.1a) ? ? ? ? figure ? 15: ? over ? current ? protection ?? (tested ? by ? shorting ? vout ? to ? pgnd) ? ? figure ? 12: ? shutdown ? ? figure ? 14: ? ccm ? (i out ? = ? 10a) ? ? ? figure ? 16: ? over ? voltage ? protection ?? (tested ? by ? shorting ? fb ? to ? vout) en pgood ss vout 2v/div 5v/div 1v/div 500mv/div 5ms/div en pgood ss v out 2v/div 5v/div 1v/div 500mv/div 1ms/div v out phase il 20mv/div 5v/div 1a/div 20s/div v out phase il 20mv/div 5v/div 5a/div 2s/div pgood ss vout il 5v/div 1v/div 1v/div 10a/div 5ms/div pgood fb v out il 5v/div 1v/div 500mv/div 2a/div 50s/div
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 11 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? typical ? operating ? data ?? tested ? with ? demoboard ? shown ? in ? figure ? 4, ? vin ? = ? 12v, ? vcc ? = ? 5v, ? vout ? = ? 1.05v, ? fs ? = ? 300khz, ? t a ? = ? 25 o c, ? no ? airflow, ? unless ? otherwise ? specified. ? ? figure ? 17: ? load ? transient ? 0 \ 4a ? ? figure ? 19: ? dcm/fccm ? transition ? ? figure ? 21: ? thermal ? image ? at ? vin ? = ? 12v, ? i out ? = ? 10a ?? (ir3475: ? 95 o c, ? inductor: ? 57 o c, ? pcb: ? 44 o c) ? figure ? 18: ? load ? transient ? 6 \ 10a ? ? figure ? 20: ? fccm/dcm ? transition ? ? figure ? 22: ? thermal ? image ? at ? vin ? = ? 19v, ? i out ? = ? 10a ?? (ir3475: ? 97 o c, ? inductor: ? 58 o c, ? pcb: ? 44 o c) ? v out phase il 20mv/div 5v/div 2a/div 50s/div v out phase il 20mv/div 5v/div 5a/div 50s/div fccm phase vout il 5v/div 10v/div 500mv/div 5a/div 10s/div fccm phase v out il 2v/div 10v/div 500mv/div 5a/div 5s/div
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 12 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? theory ? of ? operation ? ? pwm ? comparator ? the ? pwm ? comparator ? initiates ? a ? set ? signal ? (pwm ? pulse) ? when ? the ? fb ? pin ? falls ? below ? the ? reference ? (vref) ? or ? the ? soft ? start ? (ss) ? voltage. ?? on \ time ? generator ? the ? pwm ? on \ time ? duration ? is ? programmed ? with ? an ? external ? resistor ? (r ff ) ? from ? the ? input ? supply ? (vin) ? to ? the ? ff ? pin. ? the ? simplified ? equation ? for ? r ff ? is ? shown ? in ? equation ? 1. ?? the ? ff ? pin ? is ? held ? to ? an ? internal ? reference ? after ? en ? goes ? high. ? a ? copy ? of ? the ? current ? in ? r ff ? charges ? a ? timing ? capacitor, ? which ? sets ? the ? on \ time ? duration, ? as ? shown ? in ? equation ? 2. ? ? ? ? control ? logic ? the ? control ? logic ? monitors ? input ? power ? sources, ? sequences ? the ? converter ? through ? the ? soft \ start ? and ? protective ? modes, ? and ? initiates ? an ? internal ? run ? signal ? when ? all ? conditions ? are ? met. ?? vcc ? and ? 3vcbp ? pins ? are ? continuously ? monitored, ? and ? the ? ir3475 ? will ? be ? disabled ? if ? the ? voltage ? of ? either ? pin ? drops ? below ? the ? falling ? thresholds. ? en_delay ? will ? become ? high ? when ? vcc ? and ? 3vcbp ? are ? in ? the ? normal ? operating ? range ? and ? the ? en ? pin ? = ? high. ?? soft ? start ? with ? en ? = ? high, ? an ? internal ? 10a ? current ? source ? charges ? the ? external ? capacitor ? (c ss ) ? on ? the ? ss ? pin ? to ? set ? the ? output ? voltage ? slew ? rate ? during ? the ? soft ? start ? interval. ? the ? soft ? start ? time ? (t ss ) ? can ? be ? calculated ? from ? equation ? 3. ? ? ? the ? feedback ? voltage ? tracks ? the ? ss ? pin ? until ? ss ? reaches ? the ? 0.5v ? reference ? voltage ? (vref), ? then ? feedback ? is ? regulated ? to ? vref. ? c ss ? will ? continue ? to ? be ? charged, ? and ? when ? ss ? pin ? reaches ? v ss ? (see ? electrical ? specification ), ? ss_delay ? goes ? high. ? with ? en_delay ? = ? low, ? the ? capacitor ? voltage ? and ? ss ? pin ? is ? held ? to ? the ? fb ? pin ? voltage. ? a ? normal ? startup ? sequence ? is ? shown ? in ? figure ? 23. ? pgood ? the ? pgood ? pin ? is ? open ? drain ? and ? it ? needs ? to ? be ? externally ? pulled ? high. ? high ? state ? indicates ? that ? output ? is ? in ? regulation. ? the ? pgood ? logic ? monitors ? en_delay, ? ss_delay, ? and ? under/over ? voltage ? fault ? signals. ? pgood ? is ? released ? only ? when ? en_delay ? and ? ss_delay ? = ? high ? and ? output ? voltage ? is ? within ? the ? ov ? and ? uv ? thresholds. ? pre \ bias ? startup ? ir3475 ? is ? able ? to ? start ? up ? into ? pre \ charged ? output, ? which ? prevents ? oscillation ? and ? disturbances ? of ? the ? output ? voltage. ? with ? constant ? on \ time ? control, ? the ? output ? voltage ? is ? compared ? with ? the ? soft ? start ? voltage ? (ss) ? or ? vref, ? depending ? on ? which ? one ? is ? lower, ? and ? will ? not ? start ? switching ? unless ? the ? output ? voltage ? drops ? below ? the ? reference. ? this ? scheme ? prevents ? discharge ? of ? a ? pre \ biased ? output ? voltage. ? shutdown ? the ? ir3475 ? will ? shutdown ? if ? vcc ? is ? below ? its ? uvlo ? limit. ? the ? ir3475 ? can ? be ? shutdown ? by ? pulling ? the ? en ? pin ? below ? its ? lower ? threshold. ? alternatively, ? the ? output ? can ? be ? shutdown ? by ? pulling ? the ? soft ? start ? pin ? below ? 0.3v. ?? ? ? figure ? 23: ? normal ? startup ? (1) f 20 1 v r sw out ff ? ? = pf v (2) v 20 1 r t in ff on pf v ? ? = (3) a 10 5 . 0 v c t ss ss ? =
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 13 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? under/over ? voltage ? monitor ? the ? ir3475 ? monitors ? the ? voltage ? at ? the ? fb ? node ? through ? a ? 350ns ? filter. ? if ? the ? fb ? voltage ? is ? below ? the ? under ? voltage ? threshold, ? uv# ? is ? set ? to ? low ? holding ? pgood ? to ? be ? low. ? if ? the ? fb ? voltage ? is ? above ? the ? over ? voltage ? threshold, ? ov# ? is ? set ? to ? low, ? the ? shutdown ? signal ? (sd) ? is ? set ? to ? high, ? mosfet ? gates ? are ? turned ? off, ? and ? pgood ? signal ? is ? pulled ? low. ? toggling ? vcc ? or ? en ? will ? allow ? the ? next ? start ? up. ? figure ? 24 ? and ? 25 ? show ? pgood ? status ? change ? when ? uv/ov ? is ? detected. ? the ? over ? voltage ? and ? under ? voltage ? thresholds ? can ? be ? found ? in ? the ? electrical ? specification ? section. ?? ? ? ? ? ? ? ? ? * ? typical ? filter ? delay ? figure ? 24: ? under/over ? voltage ? monitor ? ? ? ? ? ? ? * ? typical ? filter ? delay ? figure ? 25: ? over ? voltage ? protection ? ? over ? current ? monitor ? the ? over \ current ? circuitry ? monitors ? the ? output ? current ? during ? each ? switching ? cycle. ? the ? voltage ? across ? the ? lower ? mosfet, ? vphase, ? is ? monitored ? for ? over ? current ? and ? zero ? crossing. ? the ? ocp ? circuit ? evaluates ? vphase ? for ? an ? over ? current ? condition ? typically ? 270ns ? after ? the ? lower ? mosfet ? is ? gated ? on. ? this ? delay ? functions ? to ? filter ? out ? switching ? noise. ? the ? minimum ? lower ? gate ? interval ? allows ? time ? to ? sample ? vphase. ? the ? over ? current ? trip ? point ? is ? programmed ? with ? a ? resistor ? from ? the ? iset ? pin ? to ? phase ? pin, ? as ? shown ? in ? equation ? 4. ?? when ? over ? current ? is ? detected, ? the ? mosfet ? gates ? are ? tri \ state ? and ? ss ? voltage ? is ? pulled ? to ? 0v. ?? this ? initiates ? a ? new ? soft ? start ? cycle. ? if ? there ? is ? a ? total ? of ? four ? oc ? events, ? the ? ir3475 ? will ? disable ? switching. ? toggling ? vcc ? or ? en ? will ? allow ? the ? next ? start ? up. ? ? ? ? ? ? ? ? ? ? ? ? figure ? 26: ? over ? current ? protection ? under ? voltage ? lock \ out ? the ? ir3475 ? has ? vcc ? and ? en ? under ? voltage ? lock \ out ? (uvlo) ? protection. ? when ? either ? vcc ? or ? en ? is ? below ? their ? uvlo ? threshold, ? ir3475 ? is ? disabled. ? ir3475 ? will ? restart ? when ? both ? vcc ? and ? en ? are ? above ? their ? uvlo ? thresholds. ? over ? temperature ? protection ?? when ? the ? ir3475 ? exceeds ? its ? over ? temperature ? threshold, ? the ? mosfet ? gates ? are ? tri \ state ? and ? pgood ? is ? pulled ? low. ? switching ? resumes ? once ? temperature ? drops ? below ? the ? over ? temperature ? hysteresis ? level. ? (4) 19 i r r oc dson set a ? =
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 14 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? gate ? drive ? logic ? the ? gate ? drive ? logic ? features ? adaptive ? dead ? time, ?? diode ? emulation, ? and ? a ? minimum ? lower ? gate ? interval. ?? an ? adaptive ? dead ? time ? prevents ? the ? simultaneous ? conduction ? of ? the ? upper ? and ? lower ? mosfets. ? the ? lower ? gate ? voltage ? must ? be ? below ? approximately ? 1v ? after ? pwm ? goes ? high ? before ? the ? upper ? mosfet ? can ? be ? gated ? on. ? also, ? the ? differential ? voltage ? between ? the ? upper ? gate ? and ? phase ? must ? be ? below ? approximately ? 1v ? after ? pwm ? goes ? low ? before ? the ? lower ? mosfet ? can ? be ? gated ? on. ? the ? upper ? mosfet ? is ? gated ? on ? after ? the ? adaptive ? delay ?? for ? pwm ? = ? high ? and ? the ? lower ? mosfet ? is ? gated ? on ? after ? the ? adaptive ? delay ? for ? pwm ? = ? low. ? when ? fccm ? = ? low, ? the ? lower ? mosfet ? is ? driven ? ?off? ? when ? the ? zcross ? signal ? indicates ? that ? the ? inductor ? current ? is ? about ? to ? reverse ? direction. ? the ? zcross ? comparator ? monitors ? the ? phase ? voltage ? to ? determine ? when ? to ? turn ? off ? the ? lower ? mosfet. ? the ? lower ? mosfet ? stays ? ?off? ? until ? the ? next ? pwm ? falling ? edge. ? when ? the ? lower ? peak ? of ? the ? inductor ? current ? is ? above ? zero, ? ir3475 ? operates ? in ? continuous ? conduction ? mode. ? the ? continuous ? conduction ? mode ? can ? also ? be ? selected ? for ? all ? load ? current ? levels ? by ? pulling ? fccm ? to ? high. ? whenever ? the ? upper ? mosfet ? is ? turned ? ?off?, ? it ? stays ?? ?off? ? for ? the ? min ? off ? time ? denoted ? in ? the ? electrical ? specifications . ? this ? minimum ? duration ? allows ? time ? to ? recharge ? the ? bootstrap ? capacitor ? and ? allows ? the ? over ? current ? monitor ? to ? sample ? the ? phase ? voltage. ? ? component ? selection ? ? selection ? of ? components ? for ? the ? converter ? is ? an ? iterative ? process ? which ? involves ? meeting ? the ? specifications ? and ? tradeoffs ? between ? performance ? and ? cost. ? the ? following ? sections ? will ? guide ? one ? through ? the ? process. ? inductor ? selection ?? inductor ? selection ? involves ? meeting ? the ? steady ? state ? output ? ripple ? requirement, ? minimizing ? the ? switching ? loss ?? of ? the ? upper ? mosfet, ? meeting ? transient ? response ? specifications ? and ? minimizing ? the ? output ? capacitance. ?? the ? output ? voltage ? includes ? a ? dc ? voltage ? and ? a ? small ? ac ? ripple ? component ? due ? to ? the ? low ? pass ? filter ? which ? has ? incomplete ? attenuation ? of ? the ? switching ? harmonics. ? neglecting ? the ? inductance ? in ? series ? with ? the ? output ? capacitor, ? the ? magnitude ? of ? the ? ac ? voltage ? ripple ? is ? determined ? by ? the ? total ? inductor ? ripple ? current ? flowing ? through ? the ? total ? equivalent ? series ? resistance ? (esr) ? of ? the ? output ? capacitor ? bank. ? ? one ? can ? use ? equation ? 5 ? to ? find ? the ? required ? inductance. ?? i ? is ? defined ? as ? shown ? in ? figure ? 27. ? the ? main ? advantage ?? of ? small ? inductance ? is ? increased ? inductor ? current ? slew ? rate ? during ? a ? load ? transient, ? which ? leads ? to ? a ? smaller ? output ? capacitance ? requirement ? as ? discussed ? in ? the ? output ? capacitor ? selection ? section. ? the ? drawback ? of ? using ? smaller ? inductances ? is ? increased ? switching ? power ? loss ? in ? the ? upper ? mosfet, ? which ? reduces ? the ? system ? efficiency ? and ? increases ? the ? thermal ? dissipation. ? ? figure ? 27: ? typical ? input ? current ? waveform ? input ? capacitor ? selection ?? the ? main ? function ? of ? the ? input ? capacitor ? bank ? is ? to ? provide ? the ? input ? ripple ? current ? and ? fast ? slew ? rate ? current ? during ? the ? load ? current ? step ? up. ? the ? input ? capacitor ? bank ? must ? have ? adequate ? ripple ? current ? carrying ? capability ? to ? handle ? the ? total ? rms ? current. ? figure ? 27 ? shows ? a ? typical ? input ? current. ? equation ? 6 ? shows ? the ? rms ? input ? current. ??? the ? rms ? input ? current ? contains ? the ? dc ? load ? current ? and ? the ? inductor ? ripple ? current. ? as ? shown ? in ? equation ? 5, ? the ? inductor ? ripple ? current ? is ? unrelated ? to ? the ? load ? current. ? the ? maximum ? rms ? input ? current ? occurs ? at ? the ? maximum ? output ? current. ?? the ? maximum ? power ? dissipation ? in ? the ? input ? capacitor ? equals ? the ? square ? of ? the ? maximum ? rms ? input ? current ? times ? the ? input ? capacitor?s ? total ? esr. ?? ? ? ? the ? voltage ? rating ? of ? the ? input ? capacitor ? needs ? to ? be ? greater ? than ? the ? maximum ? input ? voltage ? because ? of ? high ? frequency ? ringing ? at ? the ? phase ? node. ? the ? typical ? percentage ? is ? 25%. ? () (6) i i 3 1 1 fs t i dt t f ts 1 i 2 out on out ts 0 2 in_rms ? ? ? ? ? ? ? + ? ? ? = ? ? = ( ) (5) l 2 v v t i out in on ? ? = ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 15 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? output ? capacitor ? selection ?? selection ? of ? the ? output ? capacitor ? requires ? meeting ?? voltage ? overshoot ? requirements ? during ? load ? removal, ? and ? meeting ? steady ? state ? output ? ripple ? voltage ? requirements. ?? the ? output ? capacitor ? is ? the ? most ? expensive ? converter ? component ? and ? increases ? the ? overall ? system ? cost. ?? the ? output ? capacitor ? decoupling ? in ? the ? converter ? typically ? includes ? the ? low ? frequency ? capacitor, ? such ? as ? specialty ? polymer ? aluminum, ? and ? mid ? frequency ? ceramic ? capacitors. ?? the ? first ? purpose ? of ? output ? capacitors ? is ? to ? provide ? current ? when ? the ? load ? demand ? exceeds ? the ? inductor ? current, ?? as ? shown ? in ? figure ? 28. ? equation ? 7 ? shows ? the ? charge ? requirement ? for ? a ? certain ? load ? step. ? the ? advantage ? provided ? by ? the ? ir3475 ? at ? a ? load ? step ? is ? the ? reduced ? delay ? compared ? to ? a ? fixed ? frequency ? control ? method. ? if ? the ?? load ? increases ? right ? after ? the ? pwm ? signal ? goes ? low, ? the ? longest ? delay ? will ? be ? equal ? to ? the ? minimum ? lower ? gate ?? on \ time ? as ? shown ? in ? the ? electrical ? specifications ? section. ?? the ? ir3475 ? also ? reduces ? the ? inductor ? current ? slew ? time, ? the ? time ? it ? takes ? for ? the ? inductor ? current ? to ? reach ? equality ? with ? the ? output ? current, ? by ? increasing ? the ? switching ? frequency ? up ? to ? 1/( t on ? + ? min ? off ? time ). ? this ? results ? in ? reduced ? recovery ? time. ?? ? figure ? 28: ? charge ? requirement ? during ? load ? step ?? ? the ? output ? voltage ? drop, ? v drop , ? initially ? depends ? on ? the ? characteristic ? of ? the ? output ? capacitor. ? v drop ? is ? the ? sum ? of ? the ? equivalent ? series ? inductance ? (esl) ? of ? the ? output ? capacitor ? times ? the ? rate ? of ? change ? of ? the ? output ? current ? and ? the ? esr ? times ? the ? change ? of ? the ? output ? current. ??? vesr ? is ? usually ? much ? greater ? than ? vesl. ? the ? ir3475 ? requires ? a ? total ? esr ? such ? that ? the ? ripple ? voltage ? at ? the ?? fb ? pin ? is ? greater ? than ? 7mv. ? the ? second ? purpose ? of ? the ? output ? capacitor ? is ? to ? minimize ? the ? overshoot ? of ? the ? output ? voltage ? when ? the ? load ? decreases ? as ? shown ? in ? figure ? 29. ? by ? using ? the ? law ? of ? energy ? before ? and ? after ? the ? load ? removal, ? equation ? 8 ? shows ? the ? output ? capacitance ? requirement ? for ? a ? load ?? step ? down. ?? ? ? ? ? figure ? 29: ? typical ? output ? voltage ? response ? waveform ? ? ? boot ? capacitor ? selection ?? the ? boot ? capacitor ? starts ? the ? cycle ? fully ? charged ? to ? a ? voltage ? of ? vb(0). ? cg ? equals ? 0.58nf ? in ? ir3475. ? choose ? a ? sufficiently ? small ? v ? such ? that ? vb(0) \ v ? exceeds ? the ? maximum ? gate ? threshold ? voltage ? to ? turn ? on ? the ? upper ? mosfet. ?? ? ? choose ? a ? boot ? capacitor ? value ? larger ? than ? the ? calculated ? c boot ? in ? equation ? 9. ? equation ? 9 ? is ? based ? on ? charge ? balance ? at ? ccm ? operation. ? usually ? the ? boot ? capacitor ? will ? be ? discharged ? to ? a ? much ? lower ? voltage ? when ? the ? circuit ? is ? operating ? in ? dcm ? mode ? at ? light ? load, ? due ? to ? much ? longer ? lower ? mosfet ? off ? time ? and ? the ? bias ? current ? drawn ? by ? the ? ic. ? boot ? capacitance ? needs ? to ? be ? increased ? if ? insufficient ? turn \ on ? of ? the ? upper ? mosfet ? is ? observed ? at ? light ? load, ? typically ? larger ? than ? 0.1f ? is ? needed. ?? the ? voltage ? rating ? of ? this ? part ? needs ? to ? be ? larger ? than ? vb(0) ? plus ? the ? desired ? derating ? voltage. ? it?s ? esr ? and ? esl ? needs ? to ? be ? low ? in ? order ? to ? allow ? it ? to ? deliver ? the ? large ? current ? and ? di/dt?s ? which ? drive ? mosfets ? most ? efficiently. ? in ? support ? of ? these ? requirements ? a ? ceramic ? capacitor ? should ? be ? chosen. i out i step v out v l v esr v os v drop (8) v v i l c 2 out 2 os 2 step out ? ? = (9) 1 v (0) v c c b g boot ? ? ? ? ? ? ? ? = t load current i step inductor slew rate output charge t () (7b) v v i l 2 1 v 1 c (7a) t i 0.5 v c q out in 2 step drop out step ? ? ? ? ? ? ? ? = ? ? = ? = ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 16 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? design ? example ? ? design ? criteria ?? ? input ? voltage, ? vin ? = ? 6v ? to ? 21v ? ? output ? voltage, ? vout ? = ? 1.25v ? ? switching ? frequency, ? fs ? = ? 400khz ? ? inductor ? ripple ? current, ?? 2 i ? = ? 2.5a ? ? maximum ? output ? current, ? iout ? = ? 10a ? ? over ? current ? trip, ? ioc ? = ? 15a ? ? current ? transient ? step ? size ? = ? 4a ? ? overshoot ? allowance, ? vos ? = ? vout ? + ? 50mv ? ? undershoot ? allowance, ? vdrop ? = ? 50mv ? find ? r ff : ? pick ? a ? standard ? value ? 158 ? k , ? 1% ? resistor. ? find ? rset: ? pick ? a ? 10.5k , ? 1% ? standard ? resistor. ?? find ? a ? resistive ? voltage ? divider ? for ? v out ? = ? 1.25v: ? r 2 ? = ? 1.33k , ? r 1 ? = ? 1.96 ? k , ? both ? 1% ? standard ? resistors. ?? choose ? the ? soft ? start ? capacitor: ? once ? the ? soft ? start ? time ? has ? chosen, ? such ? as ? 1000s ? to ? reach ? to ? the ? reference ? voltage, ? a ? 22nf ? for ? c ss ? is ? used ? to ? meet ? 1000s. ? choose ? an ? inductor ? to ? meet ? the ? design ? specification: ? ? ? ? choose ? the ? inductor ? with ? the ? lowest ? dcr ? and ? ac ? power ? loss ? as ? possible ? to ? increase ? the ? overall ? system ? efficiency. ?? for ? instance, ? choose ? a ? pimb104t \ 1r5ms \ 39 ? manufactured ? by ? cyntec. ? the ? inductance ? of ? this ? part ? is ? 1.5h ? and ? has ? 3.8m ? dcr. ? ripple ? current ? needs ? to ? be ? recalculated ? using ? the ? chosen ? inductor. ? choose ? an ? input ? capacitor: ? ? ? ? a ? panasonic ? 10f ? (ecj3yb1e106m) ? accommodates ? 6 ? arms ? of ? ripple ? current ? at ? 300khz. ? due ? to ? the ? chemistry ? of ? multilayer ? ceramic ? capacitors, ? the ? capacitance ? varies ? over ? temperature ? and ? operating ? voltage, ? both ? ac ? and ? dc. ? one ? 10f ? capacitor ? is ? recommended. ?? in ? a ? practical ? solution, ? one ? 1f ? capacitor ? is ? required ? along ? with ? 10f. ? the ? purpose ? of ? the ? 1f ? capacitor ? is ? to ? suppress ? the ? switching ? noise ? and ? deliver ? high ? frequency ? current. ?? choose ? an ? output ? capacitor: ? to ? meet ? the ? undershoot ? and ? overshoot ? specification, ? equations ? 7b ? and ? 8 ? will ? be ? used ? to ? calculate ? the ? minimum ? output ? capacitance. ? as ? a ? result, ? 190 f ? will ? be ? needed ? for ? 4a ? load ? removal. ? to ? meet ? the ? stability ? requirement, ? choose ? an ? output ? capacitor ? with ? esr ? larger ? than ? 9m . ? combine ? those ? two ? requirements, ? one ? can ? choose ? a ? set ? of ? output ? capacitors ? from ? manufactures ? such ? as ? sp \ cap ? (specialty ? polymer ? capacitor) ? from ? panasonic ? or ? poscap ? from ? sanyo. ? a ? 220 f ? (4tpe220mic2) ? from ? sanyo ? with ? 18m ? esr ? will ? meet ? both ? requirements. ? if ? an ? all ? ceramic ? output ? capacitor ? solution ? is ? desired, ? the ? external ? slope ? injection ? circuit ? composed ? of ? r6, ? c13, ? and ? c14 ? is ? required ? as ? explained ? in ? the ? stability ? considerations ? section. ? in ? this ? design ? example, ? we ? can ? choose ? c14 ? = ? 1nf ? and ? c13 ? = ? 100nf. ? to ? calculate ? the ? value ? of ? r6 ? with ? pimb104t \ 1r5ms \ 39 ? as ? our ? inductor: ? ? ? ? ? ? pick ? a ? standard ? value ? for ? r6 ? = ? 3.92k . ? k 156 400k 20 1 1.25 r ff = ? ? = hz pf v v = = ? .3k 0 1 9 1 15 13m r set a a v 0.5 v r r r v out 1 2 2 fb = ? + = () () h hz a v v v v 1.18 400k 2.5 21 1.25 - 21 1.25 f i 2 v v v v l s in out in out = ? ? ? = ? ? = ? ? ( ) a hz h v v v v i 2 400k 1.5 21 1.25 - 21 1.25 2 = ? ? ? = a a a v v a 4 . 2 10 1 3 1 1 21 1.25 10 i 2 in_rms = ? ? ? ? ? ? ? + ? ? = = ? = ? = k nf m h c dcr l 95 . 3 100 8 . 3 5 . 1 r 13 6
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 17 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? stability ? considerations ?? constant \ on \ time ? control ? is ? a ? fast, ? ripple ? based ? control ? scheme. ? unstable ? operation ? can ? occur ? if ? certain ? conditions ? are ? not ? met. ? the ? system ? instability ? is ? usually ? caused ? by: ? switching ? noise ? coupled ? to ? fb ? input: ?? this ? causes ? the ? pwm ? comparator ? to ? trigger ? prematurely ? after ? the ? 500ns ? minimum ? on \ time ? for ? lower ? mosfet. ?? it ? will ? result ? in ? double ? or ? multiple ? pulses ? every ? switching ? cycle ? instead ? of ? the ? expected ? single ? pulse. ? double ? pulsing ? can ? causes ? higher ? output ? voltage ? ripple, ? but ? in ? most ? application ? it ? will ? not ? affect ? operation. ? this ? can ? usually ? be ? prevented ? by ? careful ? layout ? of ? the ? ground ? plane ? and ? the ?? fb ? sensing ? trace. ? steady ? state ? ripple ? on ? fb ? pin ? being ? too ? small: ?? the ? pwm ? comparator ? in ? ir3475 ? requires ? minimum ?? 7mvp \ p ? ripple ? voltage ? to ? operate ? stably. ? not ? enough ? ripple ? will ? result ? in ? similar ? double ? pulsing ? issue ? described ? above. ? solving ? this ? may ? require ? using ? output ? capacitors ? with ? higher ? esr. ?? esr ? loop ? instability: ?? the ? stability ? criteria ? of ? constant ? on \ time ? is: ?? ? ? if ? esr ? is ? too ? small ? that ? this ? criteria ? is ? violated ? then ? sub \ harmonic ? oscillation ? will ? occur. ? this ? is ? similar ? to ? the ? instability ? problem ? of ? peak \ current \ mode ? control ? with ? d>0.5. ? increasing ? esr ? is ? the ? most ? effective ? way ? to ? stabilize ? the ? system, ? but ? the ? tradeoff ? is ? the ? larger ? output ? voltage ? ripple. ?? system ? with ? all ? ceramic ? output ? capacitors: ?? for ? applications ? with ? all ? ceramic ? output ? capacitors, ? the ? esr ? is ? usually ? too ? small ? to ? meet ? the ? stability ? criteria. ? in ? these ? applications, ? external ? slope ? compensation ? is ? necessary ? to ? make ? the ? loop ? stable. ? the ? ramp ? injection ? circuit, ? composed ? of ? r6, ? c13, ? and ? c14, ? shown ? in ? figure ? 4 ? is ? required. ?? the ? inductor ? current ? ripple ? sensed ? by ? r6 ? and ? c13 ? is ? ac ? coupled ? to ? the ? fb ? pin ? through ? c14. ? c14 ? is ? usually ? chosen ? between ? 1 ? to ? 10nf, ? and ? c13 ? between ? 10 ? to ? 100nf. ? r6 ? should ? then ? be ? chosen ? such ? that ? l/dcr ? = ? c13*r6. ?? layout ? recommendations ? bypass ? capacitor: ?? as ? vcc ? bypass ? capacitor, ? a ? 1f ? high ? quality ? ceramic ? capacitor ? should ? be ? placed ? on ? the ? same ? side ? as ? the ? ir3475 ? and ? connected ? to ? vcc ? and ? pgnd ? pins ? directly. ? a ? 1f ? ceramic ? capacitor ? should ? be ? connected ? from ? 3vcbp ? to ? gnd ? to ? avoid ? noise ? coupling ? into ? controller ? circuits. ? for ? single \ ground ? designs, ? a ? resistor ? (r12) ? in ? the ? range ? of ? 5 ? to ? 10 ? in ? series ? with ? the ? 1f ? capacitor ? as ? shown ? in ? figure ? 4 ? is ? recommended. ?? boot ? circuit: ?? c boot ? should ? be ? placed ? near ? the ? boot ? and ? phase ? pins ? to ? reduce ? the ? impedance ? when ? the ? upper ? mosfet ? turns ? on. ?? power ? stage: ?? figure ? 30 ? shows ? the ? current ? paths ? and ? their ? directions ?? for ? the ? on ? and ? off ? periods. ? the ? on ? time ? path ? has ? low ? average ? dc ? current ? and ? high ? ac ? current. ?? therefore, ? it ? is ? recommended ? to ? place ? the ? input ? ceramic ? capacitor, ? upper, ? and ? lower ? mosfet ? in ? a ? tight ? loop ? as ? shown ? in ? figure ? 30. ?? the ? purpose ? of ? the ? tight ? loop ? from ? the ? input ? ceramic ? capacitor ? is ? to ? suppress ? the ? high ? frequency ? (10mhz ? range) ? switching ? noise ? and ? reduce ? electromagnetic ? interference ? (emi). ?? if ? this ? path ? has ? high ? inductance, ? the ? circuit ? will ? cause ? voltage ? spikes ? and ? ringing, ? and ? increase ? the ? switching ? loss. ? the ? off ? time ? path ? has ? low ? ac ? and ? high ? average ? dc ? current. ? therefore, ? it ? should ? be ? laid ? out ? with ?? a ? tight ? loop ? and ? wide ? trace ? at ? both ? ends ? of ? the ? inductor. ? lowering ? the ? loop ? resistance ? reduces ? the ? power ? loss. ? the ? typical ? resistance ? value ? of ? 1 \ ounce ? copper ? thickness ? is ? 0.5m ? per ? square ? inch. ? ? figure ? 30: ? current ? path ? of ? power ? stage ? 2 on out t c esr > ? q1 q2
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 18 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? pcb ? metal ? and ? component ? placement ? ? lead ? lands ? (the ? 13 ? ic ? pins) ? width ? should ? be ? equal ? to ? nominal ? part ? lead ? width. ? the ? minimum ? lead ? to ? lead ? spacing ? should ? be ?? 0.2mm ? to ? minimize ? shorting. ?? ? lead ? land ? length ? should ? be ? equal ? to ? maximum ? part ? lead ? length ? + ? 0.3 ? mm ? outboard ? extension. ? the ? outboard ? extension ? ensures ? a ? large ? toe ? fillet ? that ? can ? be ? easily ? inspected. ? ? pad ? lands ? (the ? 4 ? big ? pads) ? length ? and ? width ? should ? be ? equal ? to ? maximum ? part ? pad ? length ? and ? width. ? however, ? the ? minimum ? metal ? to ? metal ? spacing ? should ? be ? no ? less ? than; ? 0.17mm ? for ? 2 ? oz. ? copper ? or ? no ? less ? than ? 0.1mm ? for ? 1 ? oz. ? copper ? or ? no ? less ? than ? 0.23mm ? for ? 3 ? oz. ? copper. ? ? ? ? figure ? 31: ? metal ? and ? component ? placement ?
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 19 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? * ? contact ? international ? rectifier ? to ? receive ? an ? electronic ? pcb ? library ? file ? in ? your ? preferred ? format
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 20 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? solder ? resist ? ? it ? is ? recommended ? that ? the ? lead ? lands ? are ? non ? solder ? mask ? defined ? (nsmd). ? the ? solder ? resist ? should ? be ? pulled ? away ? from ? the ? metal ? lead ? lands ? by ? a ? minimum ? of ? 0.025mm ? to ? ensure ? nsmd ? pads. ?? ? the ? land ? pad ? should ? be ? solder ? mask ? defined ? (smd), ? with ? a ? minimum ? overlap ? of ? the ? solder ? resist ? onto ? the ? copper ? of ? 0.05mm ? to ? accommodate ? solder ? resist ? misalignment. ? ? ensure ? that ? the ? solder ? resist ? in ? between ? the ? lead ? lands ? and ? the ? pad ? land ? is ?? 0.15mm ? due ? to ? the ? high ? aspect ? ratio ? of ? the ? solder ? resist ? strip ? separating ? the ? lead ? lands ? from ? the ? pad ? land. ? figure ? 32: ? solder ? resist ? ? ? ? ? ? ? ? ? ? ? * ? contact ? international ? rectifier ? to ? receive ? an ? electronic ? pcb ? library ? file ? in ? your ? preferred ? format
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 21 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? stencil ? design ? ? the ? stencil ? apertures ? for ? the ? lead ? lands ? should ? be ? approximately ? 80% ? of ? the ? area ? of ? the ? lead ? lads. ? reducing ? the ? amount ? of ? solder ? deposited ? will ? minimize ? the ? occurrences ? of ? lead ? shorts. ? if ? too ? much ? solder ? is ? deposited ? on ? the ? center ? pad ? the ? part ? will ? float ? and ? the ? lead ? lands ? will ? open. ? ? the ? maximum ? length ? and ? width ? of ? the ? land ? pad ? stencil ? aperture ? should ? be ? equal ? to ? the ? solder ? resist ? opening ? minus ? an ? annular ? 0.2mm ? pull ? back ? in ? order ? to ? decrease ? the ? risk ? of ? shorting ? the ? center ? land ? to ? the ? lead ? lands ? when ? the ? part ? is ? pushed ? into ? the ? solder ? paste. ? figure ? 33: ? stencil ? design ? * ? contact ? international ? rectifier ? to ? receive ? an ? electronic ? pcb ? library ? file ? in ? your ? preferred ? format
march ? 27, ? 2013 ?? | ?? v2.2 ?? | ?? pd97602 22 ir3475 ? 10a ? highly ? integrated ? supirbuck tm ? package ? information ? ? figure ? 34: ? package ? dimensions ? data ? and ? specifications ? subject ? to ? change ? without ? notice. ? this ? product ? has ? been ? designed ? and ? qualified ? for ? the ? industrial ? market ? (note2). ? qualification ? standards ? can ? be ? found ? on ? ir?s ? web ? site. ? ir world headquarters: 233 kansas st., el segundo, california 90245, usa tel: (310) 252-7105 tac fax: (310) 252-7903 visit us at www.irf.com for sales contact information . www.irf.com

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