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mpq4558 - aec1 1 a, 2mhz, 55v step - down converter aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 1 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. description the mpq4558 is a high - frequency , step - down switching regulator with an integrated internal high - side high - voltage power mosfet. it provides up to a 1 a output with current - mode control for fast loop response and easy compensation. the wide 3.8 v - to - 55v input range accommodates a variety of step - down applications , in cluding automotive input. a 12 a shutdown - mode supply current makes it suitable for battery - powered applications. a scaled - down switching frequency in light - load conditions provides h igh power - conversion efficiency over a wide load range while reducing switching and gate driv er losses. the f requency fold - back prevent s inductor current runaway during startup and t hermal shutdown provides reliable, fault - tolerant operation. by switchin g at 2 mhz, the mpq4558 can prevent emi ( electromagnetic interference ) noise problems, such as those found in am radio and adsl applications. the mpq4558 is available in an soic8 e and a 10 - pin 3mm x 3mm qfn package . features ? guaranteed industrial /automotiv e temp erature range l imits ? wide 3.8 v - to - 55v operating input range ? 2 50 m? internal power mosfet ? up to 2 mhz programmable switching frequency ? 1 4 0 a quiescent current ? stable with ceramic capacitor s ? internal soft - start ? up to 95% efficiency ? output adjustable from 0.8v to 5 2 v ? available i n soic8e and 3mm x 3mm qfn10 package s ? available in aec - q100 grade 1 applications ? high - voltage power conversion ? automotive systems ? industrial power systems ? distributed power systems ? battery powered systems all mps parts are lead - free and adhere to the rohs directive. for mps green status, please visit mps website under products, quality assurance page . mps and the future of analog ic technology are registered trademarks of monolithic power systems, inc. typical application
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 2 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. ordering information part number package top marking junction temperature (t j ) mpq4558dn * soic8e mp4558dn - 40 c to +12 5 c mpq4558d q * * qfn10 (3 x 3mm) abp mpq4558dq - aec1*** qfn10 (3 x 3mm) abp * for tape & reel, add suffix C z (e.g. mpq4558 dn C z) fo r rohs compliant packaging, add suffix C lf , ( e.g. mpq4558 dn C lf C z) * * for tape & reel, add suffix C z (e.g. mpq4558d q C z) for rohs compliant packaging, add suffix C lf , ( e.g. mpq4558d q C lf C z) ***available end sept. 2011 package reference soic8 e qfn10 (3mm x 3mm) absolute maximum rat ings ( 1 ) supply voltage (v in ) .................... C 0. 3 v to +60v switch voltage (v sw ) ......... C 0. 5 v to ( v in + 0. 5 v ) bst to sw ................................ .... C 0. 3 v to +5v all other pins ................................ C 0. 3 v to +5v continuous power dissipation (t j = + 25 c) ( 2 ) soic8 e . 2.5w qfn10 . 2.5w junction temperature .............................. 150 c lead temperature ................................ ... 260 c storage temperature .............. C 65c to +150 c recommended operating conditions ( 3 ) supply voltage v in .......................... 3.8 v to 55v output voltage v out ........................ 0.8v to 52 v maximum junction temp. (t j ) ............... 125c thermal resistance ( 4 ) ja jc soic8 e ................................ .. 50 ...... 10 ... c/w qfn10 (3mm x 3mm) .............. 50 ...... 12 ... c/w notes: 1) exceeding these ratings may damage the device 2) the maximum allowable power dissipation is a function of the maximum junction temperature t j (max), the junction - to - ambient thermal resistance ja , and the ambient temperature ta. the maximum allowable continuous power dissipation at any ambient temperature is calculated by p d (max)=(t j (max) - t a )/ ja . exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage . 3) the device is not guaranteed to function outside of its operating conditions. 4) measured on je s d51 - 7 4 - layer board .
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 3 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. electrical characte ristics v in = 12v, v en = 2.5v, v comp = 1.4v, t j = C 40 c to + 12 5 c . typical values are at t j =25 c , unless otherwise noted . parameter symbol condition min typ max units feedback voltage v fb 4.5 v < v in < 55v t j =25 c 0.780 0.8 00 0.820 v - 40 c t j 85 c 0.772 0.829 - 40 c t j 125 c 0.766 0.829 feedback leakage current i fb 0.1 1.0 a upper switch on resistance ( 5 ) r ds(on) v bst C v sw = 5v t j =25 c 175 2 50 330 m 160 400 upper switch leakage i sw v en = 0v, v sw = 0v 1 a current li mit i lim t j =25 c duty cycle 60% 1.3 1.9 3.5 a 1.1 3.7 comp to current sense transconductance g cs 5.7 a/v error amp voltage gain 400 v/v error amp transconductance i comp = 3 a 120 a/v error amp min source current v fb = 0.7v 10 a error amp min sink current v fb = 0.9v - 10 a vin uvlo threshold t j =25 c 2.7 3.0 3.3 v 2.4 3.6 vin uvlo hysteresis 0.35 v soft - start time ( 5 ) 0v < v fb < 0.8v 0. 19 0.5 ms oscillator frequency f sw r freq = 95k? t j =25 c 0.8 1 1.2 mhz 0 .7 1.3 shutdown supply current i s v en < 0.3v 12 20 a quiescent supply current i q no load, v fb = 0.9v (no switching) 1 40 200 a thermal shutdown hysteresis = 20 c 150 c minimum off time t off 100 ns minimum on time ( 5 ) t on 100 ns en risi ng threshold t j =25 c 1.4 1.55 1.7 v 1.3 1.8 en threshold hysteresis 320 mv note s : 5) derived from bench characterization. not tested in production..
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 4 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. pin functions soic8 pin # qfn10 pin# name description 1 1, 2 sw switch node. output of the hig h - side switch. requires a low v f schottky rectifier to ground. place the rectifier close to the sw pins to reduce switching spikes. 2 3 en enable input. pul l this pin below the specified threshold to shut the chip down. pull it above the specified thresho ld or leaving it floating to enable the chip. 3 4 comp compensation. gm error amplifier output. apply control - loop frequency compensation to this pin. 4 5 fb feedback. input to the error amplifier. connect an external resistive divider between the outpu t and gnd : compare to the internal +0.8v reference to set the regulation voltage. 5 6 gnd , exposed pad ground. connect as close as possible to the output capacitor and avoid high - current switch ing paths. c onnect the exposed pad to gnd plane for optimal th ermal performance. 6 7 freq switching frequency program input. connect a resistor from this pin to ground to set the switching frequency. 7 8, 9 vin input supply. supplies power to all the internal control circuitry , both bs regulators , and the high - side switch. place a decoupling capacitor to ground close to this pin to minimize switching spikes. 8 10 bst bootstrap. positive power supply for the internal floating high - side mosfet driver. connect a bypass capacitor between this pin and the sw pin.
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 5 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typ ical characteristics
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 6 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical characterist ics (continued)
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 7 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical performance characteristics v in = 12 v, v out =3.3v, c1 = 4.7 f, c2 = 22f, l 1 = 10h and t j = 25 c , unless otherwise noted.
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 8 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical performance characteristics (continued) v in = 12 v, v out =3.3v, c1 = 4.7 f, c2 = 22f, l 1 = 10h and t j = 25 c , unless otherwise noted.
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 9 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. block diagram figure 1 : functional block diagram operation the mpq4558 is a programmable - frequency, non - synchronous, step - down , switching regulator with an integrated high - side , high - voltage power mosfet. it provides a single , highly efficient solution with current - mode control for fast loop response and easy compensation. it features a wide input voltage range, internal soft - start control , and precision current limiting. its very low operational quiescent current makes it suitable for battery - powered applications. pwm control mode at moderate - to - high output current, the mpq4558 operates in a fixed - frequency, peak - current C control mode to regu late the output voltage. the internal clock initiates a pwm cycle. the power mosfet turns on and remains on until its current reaches the value set by the comp voltage. when the power mosfet is off, it remains off for at least 100ns before the next cycle s tarts. if, in one pwm period, the power mosfet current does not reach the comp set current value, the power mosfet remains on to saves on a turn - off operation. pulse - skipping mode under light - load condition , the switching frequency drops to zero to reduc e switching and driving loss es . error amplifier the error amplifier compares the fb pin voltage with the internal reference (ref) and outputs a current proportional to the difference between the two. this output current then charge s the external compensat ion network to form the comp voltage, which control s the power mosfet current. while in operation, the minimum comp voltage is clamped to 0.9v and its maximum is clamped to 2.0v. comp is internally pulled down to gnd in shutdown mode. avoid pulling comp u p beyond 2.6v.
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 10 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. internal regulator the 2.6v internal regulator powers most of the internal circuit s . this regulator takes the vin input and operates in the full vin range. when v in exceeds 3.0v, the output of the regulator is in full regulation : when v in i s less than 3.0v, the output drops to 0v . enable control the mpq4558 has a dedicated enable control pin (en) : an input voltage that exceeds an upper threshold enables the chip , while a voltage the drops below a lower threshold disables the chip . its fallin g threshold is precisely 1.2v, and its rising threshold is 300mv higher , or 1.5v . when floating, en is pulled up to about 3.0v by an internal 1a current source to enable the chip . pulling it down requires a 1a current. when en drops below 1.2v, the chip enters the lowest shutdown current mode. when en exceeds 0v but remains below its rising threshold, the chip is still in shutdown mode but with a slightly higher shutdown current. under - voltage lockout under - voltage lockout (uvlo) protect s the chip from op erating at an insufficient supply voltage. the uvlo rising threshold is about 3.0v while its falling threshold is a consist e nt 2.6v. i nternal soft - start soft - start prevent s the converter output voltage from overshooting during start - up and short - circuit re covery . when the chip starts, the internal circuitry generates a soft - start (ss) voltage that ramp s up from 0v to 2.6v. when this voltage is less than the internal reference (ref), ss overrides ref so the error amplifier uses ss as the reference. when ss e xceeds ref, ref regains control. thermal shutdown thermal shutdown prevent s the chip from operating at exceedingly high temperatures. when the silicon die temperature exceeds its upper threshold, it shuts down the whole chip. when the temperature falls bel ow its lower threshold, the chip is enabled again. floating driver and bootstrap charging an external bootstrap capacitor powers the floating power mosfet driver. this floating driver has its own uvlo protection with a rising threshold of 2.2v and a hyste resis of 150mv. the driver s uvlo is connected to the ss: if the bootstrap voltage hits its uvlo, the soft - start circuit reset s . to prevent noise, there is 20 s delay before the reset action. when the device exits the bootstrap uvlo condition , the reset tu rns off and then soft - start process resumes . the dedicated internal bootstrap regulator charges and regulates the bootstrap capacitor to about 5v. when the voltage between the bst and sw nodes falls below regulation, a pmos pass transistor connected from v in to bst turn s on. the charging current path goes from vin, to bst and then to sw. the external circuit must provide enough voltage headroom to facilitate charging. as long as v in is sufficiently higher than sw, the bootstrap capacitor will charge. when t he power mosfet is on, v in is about equal to sw so the bootstrap capacitor cannot charge. when the external diode is on, the difference between vin and sw is at its largest, thus making it the best period to charge. when there is no current in the inductor , sw equals the output voltage v out so the difference between v in and v out can charge the bootstrap capacitor. under higher duty - cycle operation condition s , the time period available for bootstrap charging is smaller so the bootstrap capacitor may not suff iciently charge. in case the internal circuit does not have sufficient voltage and the bootstrap capacitor is not charged, extra external circuitry can ensure the bootstrap voltage is in the normal operational region. refer to the external bootstrap diode in application section. the dc quiescent current of the floating driver is about 20a. make sure the bleeding current at the sw node is higher than this value, such that: a 20 ) 2 r 1 r ( v i o o ? ? ? ?
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 11 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. current comparator and current limit a current - sense mosfet accurately senses the current in the power mosfet. this signal is then fed to the high speed current comparator for current - mode C control purpose s , which uses it as one of its inputs with the comp voltage . when the power mosfet turn s on, the comparator is f irst blanked until the end of the turn - on transition to avoid noise issues. when the sensed current exceeds the comp voltage, the comparator output is low and the power mosfet turns off . the cycle - by - cycle maximum current of the internal power mosfet is in ternally limited. short - circuit protection when the output is shorted to the ground, the switching frequency fold s back and the current limit falls to reduce the short circuit current . when the fb voltage equals 0v , the current limit falls to about 50% of its full current limit. the fb voltage reaches its 100% of its current limit when it exceeds 0.4v when the short - circuit fb voltage is low, the ss drops by v fb and ss v fb + 100mv. if the short circuit is removed, the output voltage recover s at the ss rate . when fb is high enough, the frequency and current limit return to normal values. startup and shutdown if both v in and v en exceed their appropriate thresholds, the chip starts. the reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. the regulator provides stable supply for the remaining circuitries. while the internal supply rail is up, an intern al timer blanks the power mosfet off for about 50s to avoid start - up glitches. when the internal soft - start block is enabled, it first holds its ss output low to ensure the other circuits are ready and then slowly ramps up. three events can shut down the chip: en low, v in low and thermal shutdown. in shutdown, the power mosfet turn s off first to avoid any fault triggering. the comp voltage and the internal supply rail are then pulled down. programmable oscillator an external resistor r freq connected from the freq pin to gnd sets t he mpq4558 oscillating frequency. calculate the value of r freq from: for f sw =500khz, r freq =195k ? . freq s 100000 r (k ) = - 5 f (khz)
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 12 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. application informat ion component selection setting the output voltage set the output voltage with a resistor divider between the output voltage and the fb pin. the voltage divider drops the output voltage down to the feedback voltage by the ratio: thus the output voltage is: for example, for r2 = 10k?, r1 can be determined by: for example, for a 3.3v output voltage, r2 is 10k?, and r1 is 31.6 k?. inductor the inductor suppl ies constant current to the output load while being driven by the switched input voltage. a larger value inductor will result in less ripple current that will lower the output ripple voltage. however, a larger - value d inductor is physical ly larger , has a hi gher series resistance, or lower saturation current. generally, determin e an appropriate inductance value by selecting the peak - to - peak inductor ripple current equal to approximately 30% of the maximum switch current limit. also, make sure that the peak inductor current is below the maximum switch current limit. calculate the inductance value with : where : ? v out is the output voltage , ? v in is the input voltage , ? f s is the switching frequency, and ? ? i l is the peak - to - peak inductor r ipple current. choose an inductor that will not saturate under the maximum inductor peak current. calculate the peak inductor current with : where i load is the load current. table 1 lists a number of suitabl e inductors from various manufacturers. the choice the inductor style mainly depends on the price vs. size requirements and any emi requirement. fb out r2 v =v r1+r2 ? out fb r1+r2 v =v r2 ? ) )( 8 . 0 ? ? ? ? k (v 12.5 r1 out out out s l in vv l1= (1- ) f i v ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? in out s out load lp v v 1 1 l f 2 v i i
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 13 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. table 1 : inductor selection guide part number inductance (h) max dcr ( ) 7447789004 4.7 0.033 2.9 7.3x7.3x3.2 744066100 10 0.035 3.6 10x10x3.8 744771115 15 0.025 3.75 12x12x6 744771122 22 0.031 3.37 12x12x6 tdk rlf7030t - 4r7 4.7 0.031 3.4 7.3x6.8x3.2 slf10145t - 100 10 0.0364 3 10.1x10.1x4.5 slf12565t - 150m4r2 15 0.0237 4.2 12.5x12.5x6.5 slf12565t - 220m3r5 2 2 0.0316 3.5 12.5x12.5x6.5 toko fdv0630 - 4r7m 4.7 0.049 3.3 7.7x7x3 919as - 100m 10 0.0265 4.3 10.3x10.3x4.5 919as - 160m 16 0.0492 3.3 10.3x10.3x4.5 919as - 220m 22 0.0776 3 10.3x10.3x4.5 output rectifier diode the output rectifier diode supplies the cur rent to the inductor when the high - side switch is off. to reduce losses due to the forward diode voltage and recovery times, use a schottky diode. choose a diode whose maximum reverse voltage rating is greater than the maximum input voltage, and whose cu rrent rating is greater than the maximum load current. table 2 lists example schottky diodes and manufacturers. table 2 : diode selection guide diodes voltage/ current rating manufacturer b2 9 0 - 13 - f 9 0v , 2a diodes inc. b380 - 13 - f 80v, 3a diodes inc. cmsh2 - 100 m 100v, 2a central semi cmsh3 - 100m a 100v, 3a central semi
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 14 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. input capacitor the input current to the step - down converter is discontinuous and therefore requires a capacitor to supply the ac current to the step - down converter while maintaining the dc input voltage. use capacitors with low equivalent series re sistance (esr) for the best performance. ceramic capacitors are preferred, but tantalum or low - esr electrolytic capacitors may also suffice. for simplification, choose the input capacitor with an rms current rating greater than half of the maximum load cu rrent. the input capacitor (c1) can be electrolytic, tantalum or ceramic. when using electrolytic or tantalum capacitors, include a small, high - quality ceramic capacito r i.e. 0.1f placed as close to the ic as possible. when using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at the input. the input voltage ripple caused by the capacitance can b e estimated by: output capacitor the output capacitor (c2) maintain s the dc output voltage. use ceramic , tantalum, or low - esr electrolytic capacitors for best results . low esr capacitors are preferred to keep the output voltage ripp le low. the output voltage ripple can be estimated by: where l is the inductor value and r esr is the esr value of the output capacitor. for ceramic capacitors, the impedance at the switching frequency is dominated by the capacitanc e. the output voltage ripple is mainly caused by the capacitance. for simplification, the output voltage ripple can be estimated by: for tantalum or electrolytic capacitors, the esr dominates the impedance at the switching frequen cy. for simplification, the output ripple can be approximated as : the characteristics of the output capacitor also affect the stability of the regulation system. the mpq4558 can be optimized for a wide range of capacitance s and esr values. compensation components mpq4558 employs current - mode control for easy compensation and fast transient response. the comp pin controls the system stability and transient response the comp pin is the output of the internal error amplifier. a capacito r - resistor combination in series sets a pole - zero combination to control the characteristics of the control system. the dc gain of the voltage feedback loop is given by: where ? a vea is the error amplifier voltage gain, 4 00v/v , ? g cs i s the current sense transconductance, 5.6 a/v , and ? r load is the load resistor value. the system has two poles of importance : one is caused by the c ompensation capacitor ( c 3 ) and the output resistor of error amplifier ; the other is caused by the output capac itor and the load resistor. these poles are located at: where, g ea is the erro r amplifier transconductance, 120 a/v. the system has one zero of importance from c 3 and the compensation resistor ( r 3 ). this zero is located at: ? ? ? ? ? ? ? ? ? ? ? ? ? ? in out in out s load in v v 1 v v 1 c f i v ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 2 c f 8 1 r v v 1 l f v v s esr in out s out out ? ? ? ? ? ? ? ? ? ? ? ? ? ? in out 2 s out out v v 1 2 c l f 8 v v esr in out s out out r v v 1 l f v v ? ? ? ? ? ? ? ? ? ? ? ? ? out fb vea cs load vdc v v a g r a ? ? ? ? ? ?? ea p1 vea g f 2 c3 a ? ?? p2 load 1 f 2 c2 r ? ?? z1 1 f 2 c3 r3
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 15 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. the system may have another important zero if the output capacitor has a large capacitance or a high esr value. the ze ro, due to the esr and the output capacitor value , is located at: i n this case, a third pole set by the compensation capacitor ( c 5 ) and r3 compensate s for the effect of the esr zero on the loop gain. this pole is located at: the compensation network shape s the converter transfer function for a desired loop gain. the feedback - loop unity gain at the system crossover frequency is important : lower crossover frequencies result in slower line and load transient resp onses, while higher crossover frequencies can destabilize the system. generally, set the crossover frequency to approximately 1/10 of the switching frequency. table 3 : compensation values for typical output voltage/capacitor combina tions v out (v) l (h) c2 (f) r3 (k?) 1.8 4.7 33 32.4 680 none 2.5 4.7 - 6.8 22 26.1 680 none 3.3 6.8 - 10 22 68.1 220 none 5 15 - 22 33 47.5 330 none 12 10 22 16 470 2 to optimize the compensation components for conditions not listed in table 3 , use the following procedure. 1. choo se r 3 to set the desired crossover frequency. determine the r3 value from the following equation: where f c is the desired crossover frequency. 2. choose c 3 to achieve the desired phase marg in. for applications with typical inductor values, set the compensation zero f z1 below ? the crossover frequency to provide sufficient phase margin. determine c 3 from the following equation: 3. determine if c 5 is required if the esr zero of the output capacitor is located at less than 1/2 f s , or if the following relationship is valid: if this is the case, then add c 5 to set the pole f p3 at the location of the esr zero. determine the c 5 value by the equation: high - frequency operation the mpq4558 switching frequency can be programmed up to 2 mhz by an external resistor. the minimum mpq4558 on - time is typically about 100 ns . pulse - skipping operation can be seen more easily at higher switchin g frequenc ies due to the minimum on - time. since the internal bootstrap circuitry has higher impedance that may not be adequate to charge the bootstrap capacitor during each (1 - d) t s charging period, add an external bootstrap charging diode if the switchi ng frequency is abo ut 2mhz (see external bootstrap diode section for detailed implementation information). wi th higher switching frequencies, the inductive reactance (xl) of the capacitor dominate s so that the esl of the input/output capacitor determines t he input/output ripple voltage at higher switching frequenc ies . because of this ripple , use high - frequency ceramic capacitor s for the input decoupling capacitor and output the filtering capacitor for high - frequency operation. layout becomes more important when the device switches at higher frequenc ies . for best results, ? ?? esr esr 1 f 2 c2 r ? ?? p3 1 f 2 c5 r3 ?? ?? ? c out ea cs fb 2 c2 f v r3 g g v ? ?? c 4 c3 2 r3 f ? ?? s esr f 1 2 c2 r 2 ? ? esr c2 r c5 r3
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 16 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. place the input decoupling capacitor and the catch diode as close to the mpq4558 (vin pin, sw pin and pgnd) as close as possible with short and wide traces. this can help to greatly reduce the voltage spike s on the sw node, and lower the emi noise level. route the feedback trace as far from the inductor and noisy power traces as possible. if possible, run the feedback trace on the opposite side of the pcb opposite from the inductor with a gr ound plane separating the two. p lacing the compensation components close to the mpq4558 . avoid p lac ing the compensation components close to or under the high - dv/dt sw node, or inside the high - di/dt power loop. if this is not possible, route a ground plane to isolate the circuit . switching loss is expected to increase at high switching frequenc ies . to help to improve the thermal conduction, a dd grid of thermal vias under the exposed pad. use small vias (15mil barrel diameter) so that the plating process fill s the hole s , thus aiding conduction to the other side. excessively large hole s can cause solder wicking during the reflow soldering process. the typical pitch (distance between the centers) between thermal vias is typically 40mil. external bootstrap diode a n external bootstrap diode may enhance the regulator efficiency. for the cases described below , add an external bst diode from 5v to the bst pin: ? there is a 5v rail available in the system; ? v in is no greater than 5v; ? v out is between 3.3v and 5v; this d iode is also recommended for high - duty C cycle operation (when v out / v in > 65%) applications. the bootstrap diode can be a low - cost one such as in4148 or bat54. figure 2 : external bootstrap diode at no load or light load, the conver ter may operate in pulse - skipping mode to maintain the output voltage in regulation : there is less time to refresh the bs voltage. for sufficient gate voltage under such operating conditions, chose v in C v out > 3v. for example, if v out = 3.3v, v in needs to be greater than 3.3v+3v=6.3v for sufficient bs t voltage at no load or light load. to meet this requirement, the en pin can program the input uvlo voltage to v out +3v.
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 17 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical application circuits figure 3 1.8v output typical application schematic figure 4 5v output typical application schematic
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 18 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. pcb layout guide pcb layout is very important to achieve stable operation. duplicate the evb layout below for optim al performance. for changes , please follow these guidelines and use figure 3 for reference. 1) keep the switching - current path short and minimize the loop area formed by the input cap acitor , high - side mosfet and external switching diode . 2) place the bypass ceramic capacitors close to the v in pin . 3) use short and direct fe edback connections. place the feedback resistors and compensation components as close to the chip as possible. 4) rout e the sw path away from sensitive analog areas such as the fb path . 5) connect in, sw, and gnd , respectively , to a large copper area to cool the chip to improve thermal performance and long - term reliability. mpq4558 typical application circuit top layer bottom layer mpq4558 dn layout guide r 6 f r e q 1 2 3 4 8 7 6 5 f b c o m p e n s w b s t v i n g n d c 4 c 1 r 2 r 3 c 3 r 1 r 5 r 4 gnd gnd vin vo sw l 1 c 2 d 1 gnd
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 19 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. top layer bottom layer mpq4558 dq layout guide figure 3 : mpq4558 typi cal application circuit and pcb layout guide c 4 c 1 r 2 r 3 c 3 r 1 r 5 r 4 gnd gnd vin vo sw l 1 c 2 s w e n f b d 1 s w c o m p r 6 g n d v i n f r e q b s t 6 7 8 1 2 3 4 5 1 0 9 v i n gnd
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified mpq4558 rev. 1. 01 www.monolithicpower.com 20 5/24/2016 mps pr oprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. package information soic8 (exposed pad)
mpq4558 C 1 a, 2mh z , 55v step - down converter , aec - q100 qualified notice: the information in this document is subject to change without notic e. users should warrant and guarantee that third party intellectual property rights are not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mpq4558 rev. 1. 01 www.mo nolithicpower.com 21 5/24/2016 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. qfn10 (3mm x 3mm)

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