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mpq4559 - aec1 ind ustrial grade , 1.5a, 2mhz, 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 1 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. description the mpq4559 is a high frequency step - down switching regulator with integrated internal high - side high voltage power mosfet. it provides 1.5 a output with current mode control for fast loop response and easy compensation. the wide 3.8 v to 55v in put range accommodates a variety of step - down applications , in cluding those in automotive input environment. a 12 a shutdown mode supply current allows use in battery - powered applications. high power conversion efficiency over a wide load range is achieve d by scaling down the switching frequency at light load condition to reduce the switching and gate driving losses. the f requency foldback help s prevent inductor current runaway during startup and t hermal shutdown provides reliable, fault tolerant operatio n. by switching at 2 mhz, the mpq4559 is able to prevent emi (electromagnetic interference) noise problems, such as those found in am radio and adsl applications. the mpq4559 is available in small 3mm x 3mm qfn10 an d soic8 with exposed pad packages. . fe atures ? guaranteed industrial temp 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 ? ceramic capacitor stable ? internal soft - start ? up to 95% efficiency ? output a djustable from 0.8v to 5 2 v ? available in qfn (3mm x 3mm) and soic8 e with exposed pad package s ? aec - q100 qualified applications ? high voltage power conversion ? automotive systems ? industrial power systems ? distributed power systems ? battery powered systems all mp s parts are lead - free and adhere to the rohs directive. for mps green status, please visit mps website under quality assurance. mps and the future of analog ic technology are registered t rademarks of monolithic power systems, inc. typical applicat ion
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 2 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. ordering information part number package top marking MPQ4559DN * soic8e mp4559dn mpq4559dq** qfn10 (3x3mm) add mpq4559dq - aec1 qfn10 (3x3mm) add * for tape & reel, add suffix C z (e.g. mpq4559 dn C z) for rohs compliant packaging, add suffix C lf ( e .g. mpq4559 dn C lf C z) * for tape & reel, add suffix C z (e.g. mpq4559dq C z) for rohs compliant packaging, add suffix C lf ( e.g. mpq4559dq C lf C z) package reference qfn10 soic8 (exposed pad) absolute maximum rat ings (1) supply voltage (v in ) .................... C 0. 3 v to +60v sw itch 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 a = + 25 c) (2) soic8 e .2.5w qfn10 (3x3mm) .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 operating junct . temp (t j ) ..... C 40 ? c to + 125 ? c thermal resistance ( 4 ) ja jc soic8 (exposed pad) ............ 50 ...... 10 ... ? c/w qfn10 (3x3mm)5012 ? 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 r esistance 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 temperatur e, 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.
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 3 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. electric al characteristics v in = 12v, v en = 2.5v, v comp = 1.4v, t j = C 40 ? ? j =25 ? parameter symbol condition min typ max units feedback voltage v fb 4.5v < 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 curr ent limit i lim t j =25 ? c duty cycle 60% 1.9 2.3 4.5 a 1.8 4.7 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 3.0 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) 140 200 a thermal shutdown hysteresis = 20 ? c 150 ? c minimum off time t off 100 ns minimum on time ( 5 ) t on 100 ns en rising threshold t j =25 ? c 1.4 1.55 1.7 v 1.3 1.8 en threshold hysteresis 320 mv note: 5) derived from bench characterization. not tested in production.
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 4 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. pin functions qfn pin # soic8 pin # name description 1, 2 1 sw switch node. output fr om the high - side switch. a low v f schottky rectifier to ground is required. the rectifier must be close to the sw pins to reduce switching spikes. 3 2 en enable input. pull this pin below the specified threshold to shutdown the chip. pull it up above the specified threshold or leaving it floating to enable the chip. 4 3 comp compensation. output of the gm error amplifier. control loop frequency compensation is applied to this pin. 5 4 fb feedback. input to the error amplifier. sets the regulator voltage by comparing the tap of an external resistive divider connected between the output and gnd to the internal +0.8v reference. 6 5 gnd , exposed pad ground. connect as close as possible to the output capacitor and avoid the high - current switch paths. connect exposed pad to gnd plane for optimal thermal performance. 7 6 freq switching frequency program input. connect a resistor from this pin to ground to set the switching frequency. 8, 9 7 vin input supply. this supplies power to all the internal control circ uitry, both bs regulators, and the high - side switch. place a decoupling capacitor to ground close to this pin to minimize switching spikes. 10 8 bst bootstrap. positive power supply for the internal floating high - side mosfet driver. connect a bypass capac itor between this pin and sw pin.
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 5 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical performance characteristics v in = 12v, v out =3.3v, c1 = 4.7 f, c2 = 22f, l 1 = 10h and t a = +25 ?
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 6 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical performance characteristics v in = 12v, v out =3.3v, c1 = 4.7 f, c2 = 22f, l 1 = 10h and t a = +25 ?
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 7 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. block diagram figure 1 functional block diagram
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 8 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. operation the mpq4559 is a programmable frequency, non - synchronous, step - down switching regulator with an integrated high - side high voltage power mosfe t. 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 mpq4559 operates in a fixed frequency, peak current control mode to regulate the output voltage. a pwm cycle is initiated by the internal clock. the power mosfet is turned on and remains on until its current reaches the value set by the comp voltage. when the power switch is off, it remains off for at least 100ns before the next cycle starts. if, in one pwm period, the current in the power m osfet does not reach the comp set current value, the power mosfet remains on, saving a turn - off operation. pulse skipping mode under light load condition the switching frequency stretches down to zero to reduce the switching loss and driving loss . error a mplifier 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 is then used to charge the external compensation network to form the comp v oltage, which is used to control the power mosfet current. during 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. comp should not be pulled up beyond 2.6v. internal regulator most of the internal circuitries are powered from the 2.6v internal regulator. this regulator takes the vin input and operates in the full vin range. when vin is greater than 3.0v, the output of the regulator is in full regulation. when vin is lower than 3.0v, the output decreases. enable control the mpq4559 has a dedicated enable control pin (en). with high enough input voltage, the chip can be enabled and disabled by en which has positive logic. its falling threshold is a precision 1.2 v, and its rising threshold is 1. 8v ( 600mv higher). when floating, en is pulled up to about 3.0v by an internal 1a current source so it is enabled. to pull it down, 1a current capability is needed. when en is pulled down below 1.2v, the chip is put into the lowest shutdown current mode. when en is higher than zero but lower than its rising threshold, the chip is still in shutdown mode but the shutdown current increases slightly. under - voltage lockout (uvlo) under - voltage lockout (uvlo) is implemented to p rotect the chip from operating at 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 the soft - start is implemented to prevent the converter output voltage from overshoo ting during startup and short circuit recovery . when the chip starts, the internal circuitry generates a soft - start voltage (ss) ramping up from 0v to 2.6v. when it is lower than the internal reference (ref), ss overrides ref so the error amplifier uses ss as the reference. when ss is higher than ref, ref regains control. thermal shutdown thermal shutdown is implemented to prevent the chip from operating at exceedingly high temperatures. when the silicon die temperature is higher than its upper threshold, i t shuts down the whole chip. when the temperature is lower than its lower threshold, the chip is enabled again.
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 9 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. floating driver and bootstrap charging the floating power mosfet driver is powered by an external bootstrap capacitor. this floating driver has its own uvlo protection. this uvlos rising threshold is 2.2v with a hysteresis of 150mv. the driver s uvlo is s oft - start related . in case the bootstrap voltage hits its uvlo, the soft - start circuit is reset. to prevent noise, there is 20 s delay before t he reset action. when bootstrap uvlo is gone, the reset is off and then soft - start process resumes . the bootstrap capacitor is charged and regulated to about 5v by the dedicated internal bootstrap regulator. when the voltage between the bst and sw nodes is lower than its regulation, a pmos pass transistor connected from vin to bst is turned on. the charging current path is from vin, bst and then to sw. external circuit should provide enough voltage headroom to facilitate the charging. as long as vin is suff iciently higher than sw, the bootstrap capacitor can be charged. when the power mosfet is on, vin is about equal to sw so the bootstrap capacitor cannot be charged. when the external diode is on, the difference between vin and sw is 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 be used to charge the bootstrap capacitor. at higher duty cycle operation condition, the time period availabl e to the bootstrap charging is less so the bootstrap capacitor may not be sufficiently charged. in case the internal circuit does not have sufficient voltage and the bootstrap capacitor is not charged, extra external circuitry can be used to ensure the boo tstrap voltage is in the normal operational region. refer to 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: current comparator and current limit the power mosfet current is accurately sensed via a current sense mosfet. it is then fed to the high speed current comparator for the current mode control purpose. the current comparator takes this sensed current as one of its inputs. when the power mosfet is turned on, the comparator is first blanked till the end of the turn - on transition to avoid noise issues. the comparator then compares the power switch current with the comp voltage. when th e sensed current is higher than the comp voltage, the comparator output is low, turning off the power mosfet. the cycle - by - cycle maximum current of the internal power mosfet is internally limited. short circuit protection when the output is shorted to the ground, the switching frequency is fold ed back and the current limit is reduced to lower the short circuit current . when the voltage of fb is at zero, the current limit is reduced to about 50% of its full current limit. when fb voltage is higher than 0.4v, c urrent limit reaches 100% . i n short circuit fb voltage is low, the ss is pulled down by fb and ss is about 100mv above fb. in case the short circuit is removed, the output voltage will recover at the ss pace. when fb is high enough, the frequency and cur rent limit return to normal values. startup and shutdown if both vin and en are higher than their appropriate thresholds, the chip starts. the reference block starts first, generating stable reference voltage and currents, and then the internal regulator i s enabled. the regulator provides stable supply for the remaining circuitries. while the internal supply rail is up, an internal timer holds the power mosfet off for about 50s to blank the startup glitches. when the internal soft - start block is enabled, i t first holds its ss output low to ensure the remaining circuitries are ready and then slowly ramps up. a 20 ) 2 r 1 r ( v i o o ? ? ? ?
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 10 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. three events can shut down the chip: en low, vin low and thermal shutdown. in the shutdown procedure, power mosfet is turned off first to avoid any fau lt triggering. the comp voltage and the internal supply rail are then pulled down. programmable oscillator the mpq4559 oscillating frequency is set by an external resistor, r freq from the freq pin to ground. the value of r freq can be calculated from: to get f sw =500khz, r freq =195k ? . freq s 100000 r (k ) = - 5 f (khz)
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 11 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. application informat ion component selection setting the output voltage the output voltage is set using a resistive voltage divider from the output voltage to fb pin. the voltage divider divides the output voltage down to the feedback voltage by the ra tio: thus the output voltage is: for example, the value for r2 can be 10k?. with this value, r1 can be determined by: for example, for a 3.3v output voltage, r2 is 10k?, an d r1 is 31.6 k?. inductor the inductor is required to supply 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 result in lower output ripple voltage. ho wever, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. a good rule for determining the inductance to use is to allow the peak - to - peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. also, make sure that the peak inductor current is below the maximum switch current limit. the inductance value can be calculated by: where v out is the output voltage, v in is the input vol tage, f s is the switching frequency, and ?i l is the peak - to - peak inductor ripple current. choose an inductor that will not saturate under the maximum inductor peak current. the peak inductor current can be calculated by: where i load is the load current. table 1 lists a number of suitable inductors from various manufacturers. the choice of which style inductor to use 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 ? out r1=12.5 (v -0.8)(k ) ? 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
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 12 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. table 1 inductor selection guide part num ber inductance (h) max dcr ( ) current rating (a) dimensions l x w x h (mm3) wurth electronics 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 22 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 cu rrent to the inductor when the high - side switch is off. to reduce losses due to the diode forward 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 cur rent 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 , 2 a diodes inc. b380 - 13 - f 80v, 3a diodes inc. cmsh2 - 100 m 100v, 2 a central semi cmsh3 - 100m a 100v, 3a central semi
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 13 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. input capacitor the input current to the step - down converter is discontinuous, therefore a capacitor is required to supply the ac current to the step - down converter while maintaining the dc input voltage. use low esr capacitors 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 rms current rating greater than half of the maximum load current. the input capacitor (c1) can be electrolytic, tantalum or ceramic. when using elect rolytic or tantalum capacitor s, a small, high quality ceramic capacitor, i.e. 0.1f, should be 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 input. t he input voltage ripple caused by capacitance can be estimated by: output capacitor the output capacitor (c2) is required to maintain the dc output voltage. ceramic, tantalum, or low esr electrolytic capacitors are recommended. low esr capacitors are preferred to keep the output voltage ripple low. the output voltage ripple can be estimated by: where l is the inductor value and r esr is the equivalent series resistance (esr) value of the output capacitor. in t he case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. the output voltage ripple is mainly caused by the capacitance. for simplification, the output voltage ripple can be estimated by: in the case of tantalum or electrolytic capacitors, the esr dominates the impedance at the switching frequency. for simplification, the output ripple can be approximated to: the characteristics of the output capacitor also affect the stability of the regulation system. the mpq4559 can be optimized for a wide range of capacitance and esr values. compensation components mpq4559 employs current mode control for easy compensation and fast transient response. the system stability and t ransient response are controlled through the comp pin. comp pin is the output of the internal error amplifier. a series capacitor - resistor combination sets a pole - zero combination to control the characteristics of the control system. the dc gain of the vol tage feedback loop is given by: where a vea is the error amplifier voltage gain, 4 00v/v; g cs is the current sense transconductance, 5.6 a/v; r load is the load resistor value. the system has two poles of importance. one is due to the c ompensation capacitor ( c 3 ), the output resistor of error amplifier. the other is due to the output capacitor and the load resistor. these poles are located at: where, g ea is the erro r amplifier transconducta nce, 120 a/v. the system has one zero of importance, due to the compensation capacitor ( 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
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 14 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. the system may have another zero of importance, if the output capacitor has a large capacitance and/or a high esr value. the zero, due to the esr and capacitance of the output capacitor, is located at: i n this case, a third pole set by the compensation capacitor ( c 5 ) and the compensation resistor (r3) is used to compensate the effect of the esr zero on the loop gain. this pole is located at: the goal of compensation design is to shape the converter transfer function to get a desired loop gain. the system crossover frequency where the fe edback loop has the unity gain is important. lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies could cause system unstable. a good rule of thumb is to set the crossover frequency to approxima tely one - tenth of the switching frequency. table 3 compensation values for typical output voltage/capacitor combinations v out (v) l (h) c2 (f) r3 (k?) c3 (pf) c 6 (pf) 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, the following procedu re can be used. 1. choo se the compensation resistor ( r 3 ) to set the desired crossover frequency. determine the r3 value by the following equation: where f c is the desired crossover frequency. 2. choose the compensation capacitor ( c 3 ) to achieve the desired phase margin. for applications with typical inductor values, setting the compensation zero, f z1 , below one forth of the crossover frequency provides sufficient phase margin. determine the c 3 value by the following equation: 3. determine if the second compensation capacitor ( c 5 ) is required. it is required if the esr zero of the output capacitor is located at less than half of the switching frequency, or the following relationship is valid: if this is the case, then add the second compensation capacitor ( 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 switching frequency of mpq4559 can be programmed up to 2 mhz by an external resistor. the minimum on time of mpq4559 is about 100 ns (typ). pulse skipping operation can be seen more easily at higher switching frequency due to the minimum on time. since the internal bootstrap circuitry has h igher impedance, which may not be adequate to charge the bootstrap capacitor during each (1 - d)ts charging period, an external bootstrap charging diode is strongly recommended if the switching frequency is abo ut 2mhz (see external bootstrap diode section for detailed implementation information). ? ?? 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
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 15 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. with higher switching frequencies, the inductive reactance (xl) of capacitor comes to dominate, so that the esl of input/output capacitor determines the input/output ripple voltage at higher switching frequency. a s a result of that, high frequency ceramic capacitor is strongly recommended as input decoupling capacitor and output filtering capacitor for such high frequency operation. layout becomes more important when the device switches at higher frequency. it is e ssential to place the input decoupling capacitor, catch diode and the mpq4559 (vin pin, sw pin and pgnd) as close as possible, with traces that are very short and fairly wide. this can help to greatly reduce the voltage spike on sw node, and lower the emi noise level as well. try to run the feedback trace as far from the inductor and noisy power traces as possible. it is often a good idea to run the feedback trace on the side of the pcb opposite of the inductor with a ground plane separating the two. the co mpensation components should be placed closed to the mpq4559 . do not place the compensation components close to or under high dv/dt sw node, or inside the high di/dt power loop. if you have to do so, the proper ground plane must be in place to isolate thos e. switching loss is expected to be increased at high switching frequency. to help to improve the thermal conduction, a grid of thermal vias can be created right under the exposed pad. it is recommended that they be small (15mil barrel diameter) so that th e hole is essentially filled up during the plating process, thus aiding conduction to the other side. too large a hole can cause solder wicking problems during the reflow soldering process. the pitch (distance between the centers) of several such thermal vias in an area is typically 40mil. external bootstrap diode a n external bootstrap diode may enhance the efficiency of the regulator. in below cases, an external bst diode is recommended from the 5v to 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 diode is also recommended for high duty 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 dio de at no load or light load, the converter may operate in pulse skipping mode in order to maintain the output voltage in regulation. thus there is less time to refresh the bs voltage. in order to have enough gate voltage under such operating conditions, th e difference of ( v in C v out should be greater than 3v. for example, if the v out is set to 3.3v, the v in needs to be higher than 3.3v+3v=6.3v to maintain enough bs t voltage at no load or light load. to meet this requirement, en pin can be used to program the input uvlo voltage to v out +3v.
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 16 5/24/2016 mps proprietary informa tion. 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
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 17 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. pcb layout guide pcb layout is very important to achieve stable operation. it is hig hly recommended to duplicate evb layout for optimum performance. if change is necessary, please follow these guidelines and take f igure 5 for reference. 1) keep the path of switching current short and minimize the loop area formed by input cap, high - side mos fet and external switching diode . 2) bypass ceramic capacitors are suggested to be put close to the v in pin. 3) ensure all feedback connections are short and direct. place the feedback resistors and compensation components as close to the chip as possible. 4) ro ut e sw away from sensitive analog areas such as fb. 5) connect in, sw, and especially gnd respectively to a large copper area to cool the chip to improve thermal performance and long - term reliability. mpq4559 typical application circuit top layer bott om layer mpq4559 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
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified mpq4559 rev. 1.01 www.monolithicpower.com 18 5/24/2016 mps proprietary informa tion. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. p ackage informati on soic8 (exposed pad)
mpq4559 C 1.5a, 2mh z , 55v step - down converter aec - q100 qualified notice: the information in this document is subject to change without notice. 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. mpq4559 rev. 1.01 www.monolithicpower.com 19 5/24/2016 mps proprietary information. patent protected . unauthorized phot ocopy and duplication prohibited. ? 2016 mps . all rights reserved. package information qfn10 ( 3 mm x 3mm ) (exposed pad)

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