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mp q4560 - aec1 industrial - grade , 2a, 2mhz, 55v step - down converter available in aec - q100 mpq4560 rev. 1. 1 www.monolithicpower.com 1 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. description the mpq4560 is a high - frequency , step - down , switching regulator with an integrated , high - side , high - voltage , power mosfet. it provides a 2a output with current mode control for fast loop response and easy compensation. the wide 3.8 v - to - 55v inp ut 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 achieved by scaling down the switching frequency in light load condition s to reduce the switching and gate driving losses. frequency foldback prevent s inductor current runaway during startup and t hermal shutdown provides reliable, fault tolerant operation. by sw itching at 2 mhz, the mpq4560 can prevent electromagnetic interference problems, such as those found in am radio and adsl applications. the mpq4560 is available in small 3mm x 3mm qfn 10 and soic8 e packages . features ? guaranteed industrial automotive temp era ture 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 40 a quiescent current ? ceramic capacitor stable ? internal soft - start ? up to 95% efficiency ? output adjustable from 0.8v to 5 2 v ? av ailable in qfn 10 ( 3 mm x3 mm ) and soic8 e packages ? aec - q100 qualified 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 di rective. 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
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 2 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. ordering information pa rt number package top marking junction temperature (t j ) mpq4560dn * soic8e mp4560dn C 40 c to +125 c mpq4560dq ** qfn10 ( 3 3 mm) t8 mpq4560dn - aec1 soic8e mp4560dn mpq4560dq - aec1 qfn10 ( 3 3 mm) t8 * for tape & reel, add suffix C z (e.g. mpq4560d n - z ) for rohs compliant packaging, add suffix C lf , ( e.g. mpq4560d n - lf C z) ** for tape & reel, add suffix C z (e.g. mpq4560 dq - z) for rohs compliant packaging, add suffix C lf , ( e.g. mpq4560 dq - lf C z) package reference qfn10 ( 3x3 mm) soic8e absolut e maximum ratings (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) qfn10 ( 3 3 mm) ................................ ........ 2.5w soic8 e ................................ ..................... 2.5w junction temperature .............................. 150 c lea d 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 junct ion temp . (t j ) .............. + 125 c thermal resistance ( 4 ) ja jc qfn10 ( 3x3 mm) ..................... 50 ...... 12 ... c/w soic8e ................................ .. 50 ...... 10 ... 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 regulato r 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 .
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 3 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. electrical character istics v in = 12v, v en = 2.5v, v comp = 1.4v, t j = C 40 c to + 125 c , unless otherwise noted . typical values are at t j =25 c . parameter symbol condition min typ max units feedback voltage v fb 4.5v < v in < 55v t j =25 c 0.780 0. 797 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 limit i lim t j =25 c duty cycle 60% 2.6 3.2 4.5 a 2.2 4.7 comp to current sense transconductance ( 5 ) g cs 5.7 a/v error amp voltage gain ( 6 ) 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 swi t ching) 140 200 a thermal shutdown ( 5 ) hysteresis = 20 c 150 c minimum off time ( 5 ) t off 100 ns minimum on tim e ( 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) deriv ed from bench characterization . not tested in production. 6) guaranteed by design. not tested in production.
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 4 5/24/2016 mps proprietary information. 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 from 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 shut down 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 feed back. 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 out put capacitor and avoid the high - current switch paths. c onnect 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 inp ut supply. this 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. 10 8 bst bootstrap. positive power supply for the in ternal floating high - side mosfet driver. connect a bypass capacitor between this pin and sw pin.
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 5 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical characterist ics
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 6 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical characterist ics (continued)
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 7 5/24/2016 mps proprietary 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 = 10 h and t a = 25 c , unless otherwise noted.
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 8 5/24/2016 mps proprietary 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 a = 25 c , unless otherwise noted.
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 9 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. block diagram figure 1 : functional bloc k diagram
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 10 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. operation the mpq4560 is a n a synchronous, step - down , switching regulator with an integrated high - side , high - voltage , power mosfet and a programmable frequency . 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 precis e current limiting. its very low operational quiescent current makes it suitable for battery - powered applications. pwm control the mpq4560 o perates in a fixed - frequency, peak - current - control mode to regulate the output voltage at moderate - to - high output current . the internal clock initiates a pwm cycle. the power mosfet turn s on and remains on until its current reaches the value set by the com p voltage. when the power switch is off , it remains off for at least 100ns before the next cycle starts. if the current in the power mosfet does not reach the comp - set current value within one pwm period , the power mosfet remains on , saving a turn - off oper ation. pulse - skipping mode under light - load condition the switching frequency stretches the zero - voltage period to reduce the switching loss and driving loss . error amplifier the error amplifier compares the fb pin voltage (v fb ) to the internal reference ( v ref ) and outputs a current proportional to the difference. this output current charge s the external compensation network to form v comp , which control s the power mosfet current. during operation, the minimum v comp is clamped to 0.9v and its maximum is cl amped to 2.0v. comp is internally pulled down to gnd in shutdown mode. do not pull v comp above 2.6v. internal regulator an internal 2.6v regulator powers most of the internal circuits. this regulator takes the vin input and operates in the full v in range. when v in exceeds 3.0v, the output of the regulator is in full regulation. when v in is less than 3.0v, the output decreases. enable control the mpq4560 has a dedicated enable control pin (en) that can enable or disable the chip when the input voltage exceed s an upper threshold . its falling threshold (turn - off) is 1.2v, and its rising threshold (turn - on) is 1.5v (300mv higher). when floating, an internal 1a current source pulls en up to ~ 3.0v to enable the chip . pull - down requires a 1a current. when en is p ulled below 1.2v, the chip enters its lowest shutdown current mode. when en exceeds 0v but remains lower than its rising threshold, the chip remains in shutdown mode but the shutdown current increases slightly. under - voltage lockout under - voltage lockout (uvlo) protect s 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 soft - start prevent s the converter output voltage from overshooting during startup and short - circuit recovery . when the chip starts, the internal circuit generates a soft - start voltage (ss) ramping up from 0v to 2.6v. when it is less than the v ref , ss overrides v ref so the error amplifier uses ss as the reference. when ss exceeds v ref , v 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, the whole chip shuts down . when the temperature is less than 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 o wn uvlo protection. this uvlos rising threshold is 2.2v with a hyste resis of 150mv. the driver s uvlo is s oft - start related : when the bootstrap voltage hits its uvlo thre s hold , the soft - start circuit reset s . to prevent noise, there is 20 s delay before the reset action. when bootstrap uvlo is gone, the reset is off and the n the soft - start process resumes . the dedicated internal bootstrap regulator regulates and charges the bootstrap capacitor to
mpq4560 C 2a, 2 mh z , 55v step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 11 5/24/2016 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. ~ 5v. when the voltage between the bst and sw nodes is less than its regulation, a pmos pass transistor from vin to bst turn s on . t he charging current path is from vin, bst and then to sw. an external circuit must provide enough voltage headroom to facilitate charging. as long as v in is sufficiently higher than v sw , the bootstrap capacitor can charge. when the power mosfet is on, v in v sw so the bootstrap capacitor cannot charge. when the external diode is on , the difference between v in and v sw is at its largest, thus making it the best period to charge. when there is no current in the inductor, v sw = v out so the difference between v in a nd v out can charge the bootstrap capacitor. at higher duty cycle s , the time period available for bootstrap charging is shorter so the bootstrap capacitor may not sufficiently charge. if the internal circuit does not have sufficient voltage and the bootstra p capacitor is not charged, extra external circuitry can ensure the bootstrap voltage is with in the normal operational region. the dc quiescent current of the floating driver is about 20a. make sure the bleeding current at the sw node exceeds this value, such that: current comparator and current limit a current - sense mosfet accurately senses the power mosfet s current. the result goes to the high - speed current comparator for current - mode control .: when the power mosfet turn s on , th e comparator is first blanked till the end of the turn - on transition to avoid noise issues. the comparator then compares the power switch current to v comp . when the sensed current exceeds v comp , the comparator output is low , turning off the power mosfet. t he 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 fold s back and the current limit falls to lower the short - circuit current . when v fb is zero, the current limit drops to about 50% of its full current limit. when v fb exceeds 0.4v, c urrent limit reaches 100% . during a short circuit , the v fb voltage is low and pulls down v ss to ~ 100mv above v fb . removing the short circuit causes the ou tput voltage to recover with v ss . when v 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 respective thresholds, the chip starts. the reference block initiates to generat e a st able reference voltage and currents, and then the internal regulator is enabled. the regulator provides a 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 blan k the startup noise . when the internal soft - start block is enabled, it first holds its ss output low to ensure the remaining circuitries are ready and then slowly ramps up. three events can shut down the chip: v en low , v in low and thermal shutdown. during shutdown, the power mosfet turn s off first to avoid any fault triggering. the n v comp and the internal supply rail drop . programmable oscillator an external resistor (r freq ) from the freq pin to ground sets t he mpq4560 oscillating frequency. the value of r freq can be calculated from: for example, for f sw =500khz, r freq =195k ? . a 20 ) 2 r 1 r ( v i o o ? ? ? ? freq s 100000 r (k ) = - 5 f (khz)
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 12 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. application informat ion component selection setting the output voltage a resistive voltage divider from the output voltage to fb pin sets the output voltage. t he voltage divider divides the output voltage down to the feedback voltage by the ratio: thus the output voltage is: for example, the value for r2 can be 10k?. with this value, r1 is : so for a 3.3v output voltage, r2 is 10k?, and r1 is 31.6 k?. inductor the inductor provides constant current to the output load while being driven by the switched input voltage. a larger - value inductor will result in lower ripple current that wi ll lower the output ripple voltage . however, a larger inductor value will be physically larger, have higher series resistance, or lower saturation current. to determin e the inductance , allow the inductors peak - to - peak ripple current to approximately equa l 30% of the maximum switch current limit. make sure that the peak inductor current is less than 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 several suitable inductors from various manufacturers. the different inductor choices include price vs. size requirements and any emi requirement s . 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
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 13 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. table 1 : inductor selection guide part number inductance (h) max dcr ( ) current rating (a) dimensions l w h (mm3) wurth electronics 7447789004 4.7 0.033 2.9 7.3 7.3 3.2 744066100 10 0.035 3.6 10 10 3.8 744771115 15 0.025 3.75 12 12 6 744771122 22 0.031 3.37 12 12 6 tdk rlf7030t - 4r7 4.7 0.031 3.4 7.3 6.8 3.2 slf10145t - 100 10 0.0364 3 10.1 10.1 4.5 slf12565t - 150m4r2 15 0.0237 4.2 12.5 12.5 6.5 slf12565t - 220m3r5 22 0.0316 3.5 12.5 12.5 6.5 toko fdv0630 - 4r7m 4.7 0.049 3.3 7.7 7 3 919as - 100m 10 0.0265 4.3 10.3 10.3 4.5 919as - 160m 16 0.0492 3.3 10.3 10.3 4.5 919as - 220m 22 0.0776 3 10.3 10.3 4.5 output rectifier diode the output rectifier diode supplies the cu rrent to the inductor when the high - side switch is off . use a schottky diode to reduce losses from the diode forward voltage and recovery times. choose a diode whose maximum reverse voltage rating exceeds the maximum input voltage, and whose current rating exceeds 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
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 14 5/24/2016 mps proprietary 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 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 resistance s (esr) for the best performance. ceramic capacitors are best , but tanta lum 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 current. the input capacitor (c1) can be electrolytic, tantalum , or ceramic. when usi ng electrolytic or tantalum capacitors, place a small, high - quality , ceramic capacitor ( 0.1f ) 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 capacitance is approximately : output capacitor the output capacitor (c2) maintain s the dc output voltage. use ceramic , tantalum, or low - esr electrolytic capacitors. low - esr capacitors are preferred to keep the output voltage ripple low. the output voltage ripp le can be estimated as : where l is the inductor value and r esr is the esr value of the output capacitor. for ceramic capacitors, the capacitance dominates the impedance at the switching frequency and contributes the most to the out put voltage ripple. for simplification, the output voltage ripple can be estimated by: for tantalum or electrolytic capacitors, the esr dominates the impedance at the switching frequency. for simplification, the output ripple is app roximat ely : the characteristics of the output capacitor also affect the stability of the regulation system. the mpq4560 can be optimized for a wide range of capacitance s and esr values. compensation components mpq4560 employs curren t - 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 series capacitor - resistor combination sets a pole - zero combin ation to control the control systems characteristics. the dc gain of the voltage feedback loop is: where ? a vea is the error - amplifier voltage gain, 4 00v/v; ? g cs is the current - sense transconductance, 5.6 a/v; and ? r load is the load re sistor value. the system has two important poles : one from the c ompensation capacitor ( c 3 ) and the output resistor of error amplifier , and the other due to the output capacitor 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 important zero due to the compensation capacitor 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 ? ??
mpq4560 C 2a, 2 mh z , 55v step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 15 5/24/2016 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. the system may have another significant zero if the output capacitor has a large capacitance or a high esr value. th is zero is located at: i n this case, a third pole set by the compensation capacitor ( c 5 ) and the compensation resistor can compensate for the effect of the esr zero. this pole is located at: the goal of compensation design is to shape the converter transfer function for a desired loop gain. the system crossover frequency where the feedback loop has unity gain is important : lower crossover frequencies result in slower line and load transient responses, while higher crossover frequencies lead to system instability . generally, set the crossover frequency to ~0.1f sw . 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, follow these steps : 1. choo se r 3 to set the d esired crossover frequency: where f c is the desired crossover frequency. 2. choose c 3 to achieve the desired phase margin. for applications with typical inductor values, set the compensation zero ( f z1 ) <0.25 f c to provide sufficie nt phase margin. c 3 is then : 3. c 5 is required if the esr zero of the output capacitor is located at <0.5 f sw , or the following relationship is valid: if this is the case, use c 5 to set the pole ( f p3 ) at th e location of the esr zero. determine the c 5 : high - frequency operation the switching frequency of mpq4560 can be programmed up to 2 mhz by an external resistor. the minimum on time of mpq4560 is about 100 ns (typ). pulse - skipping occ urs more readily at higher switching frequenc ies due to the minimum on time. since the internal bootstrap circuitry has higher impedance, which may not sufficiently charge the bootstrap capacitor during each (1 ? d) s charging period, add an external boots trap charging diode if the switching frequency is abo ut 2mhz (see external bootstrap diode section for detailed implementation information). with higher switching frequencies, the capacitors inductive reactance s (xl) dominate so that the esl of input/outp ut capacito r s determine the input/output ripple voltage s at higher switching frequenc ies . as a result, use high - frequency ceramic capacitor s as input decoupling capacitor s and output filtering capacitor s for high - frequency operation. external bootstrap dio de a n external bootstrap diode from the 5v rail to the bst pin may enhance the efficiency under the following conditions : ? there is a 5v rail available in the system; ? v in 5v; ? 3.3v < v out < 5v; and 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 ? ?
mpq4560 C 2a, 2 mh z , 55v step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 16 5/24/2016 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. ? for high duty - cycle operation (when v out / v in > 65%). the boot strap diode can be a low cost one such as in4148 or bat54. figure 2 : external bootstrap diode at no - load or light - load, the converter may operate in pulse - skipping mode in order to maintain output - voltage regulation. thus there i s less time to refresh the bs voltage. for sufficient gate voltage during pulse - skipping , v in C v out > 3v. for example, if the v out = 3.3v, v in must be exceed 3.3v+3v=6.3v to maintain 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.
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 17 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. typical application circuits figure 3 : typical application, 1.8v output figure 4 : typical application, 5v output
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 18 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. pcb layout guide pcb layout is very important for stable operation. try to duplicate the evb layout for optimum performance. for change s , please follow these guidelines and use f igure 5 as reference. 1) p l ace the input decoupling capacitor and the catch diode as close to the mpq4560 ( vin pin, sw pin and pgnd) as possible, with traces that are very short and fairly wide. this can help to greatly reduce the voltage spike on sw node, and the emi noise. 2) ensure all feedback connections are short and direct. place the feedback resistors and compensation components as close to the chip as possible. try to run the feedback trace as far from the inductor and noisy power traces as possible. run the feedback trace on the side of the pcb opposite of the inductor with a ground plane separating the t wo. 3) rout e sw away from sensitive analog areas such as fb. 4) connect in, sw, and especially gnd to large copper surfaces to cool the chip to improve thermal performance and long - term reliability. 5) place t h e compensation components close to the mpq4560 . avoid plac ing the compensation components close to or under high dv/dt sw node , or inside the high di/dt power loop. if necessary , add a ground plane to isolate the loops . 6) switching loss increase s at high er frequencies . to improve thermal conduction, a dd a grid of thermal vias under the exposed pad. use small vias (15mil barrel diameter) so that the hole fills during the plating process : larger vias can cause solder - wicking during the reflow process. the pitch (distance between the centers) between these thermal vias is typically 40mil. mpq4560 typical application circuit
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 19 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. top layer bottom layer mpq4560 dn layout guide top layer bottom layer mpq4560 dq layout guide figure 5 : mpq4560 typical application circuit and pcb 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 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
mpq4560 C 2a, 2mh z , 55v, step - down converter mpq4560 rev. 1. 1 www.monolithicpower.com 20 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. p ackage informati on 3 mm 3mm qfn10 (exposed pad)
mpq4560 C 2a, 2mh z , 55v, step - down converter 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 n ot assume any legal responsibility for any said applications. mpq4560 rev. 1 . 1 www.monolithicpower.com 21 5/24/2016 mps proprietary information. patent protected . unauthorized photocopy and duplication prohibited. ? 2016 mps . all rights reserved. soic8 e

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