View MP38671DL_8201361.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

mp38671 10a, 25v, 600khz step-down converter with synchronizable gate driver mp38671 rev. 1.1 www.monolithicpower.com 1 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the mp38671 is a monolithic step-down switch mode converter with a built in internal power mosfet. it achieves 10a continuous output current over a wide input supply range with excellent load and line regulation. current mode operation provides fast transient response and eases loop stabilization. fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. the mp38671 requires a minimum number of readily available standard external components and is available in a space saving 3 x4mm 14-pin qfn package. features ? wide 4.5v to 25v operating input range ? 10a continuous output current ? 60m ? internal power mosfet switch ? power good indicator ? synchronous gate driver delivers up to 95% efficiency ? fixed 600khz frequency ? synchronizable to >1mhz external clock ? cycle-by-cycle over current protection ? thermal shutdown ? output adjustable from 0.8v to 15v ? stable with low esr output ceramic capacitor ? available in a 3x4mm 14-pin qfn package applications ? point of load regulator in distributed power system ? digital set top boxes ? personal video recorders ? broadband communications ? flat panel television and monitors for mps green status, please visit mps website under quality assurance. ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application mp38671 sw bg fb bst 8, 9, 10 13 1 14 11 gnd in vcc en/sync pg 4, 5, 6 12 3 2 off on 70 75 80 85 90 95 100 0246810
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 2 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. ordering information part number* package top marking free air temperature (t a ) MP38671DL 3x4 qfn14 3867 -40 c to +85 c * for tape & reel, add suffix ?z (e.g. MP38671DL?z); for rohs compliant packaging, add suffix ?lf (e.g. mp MP38671DL?lf?z) package reference top view fb pg en/sync in in in n/c 1 2 3 4 5 6 7 gnd bg vcc bst sw sw sw 14 13 12 11 10 9 8 exposed pad on backside connect to gnd absolute maxi mum ratings (1) supply voltage vin...................................... 28v vsw..................... -0.3v (-5v for < 10ns) to 29v vbs..................................................................... vsw + 6v all other pins .................................?0.3v to +6v junction temperature ...............................150 c lead temperature ....................................260 c storage temperature.............. ?65 c to +150 c recommended operating conditions (3) supply voltage vin..........................4.5v to 25v output voltage vout ......................0.8v to 15v maximum junction temp. (t j ) ................+125 c thermal resistance (4) ja jc 3x4 qfn14 .............................. 48....... 11.... 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 t a . 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 jesd5 1-7, 4-layer pcb.. the exposed pad must be thermally connected to a ground plane (or most negative supply plane in split-supply applications).
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 3 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. electrical characteristics v in = 12v, t a = +25 c, unless otherwise noted. parameters symbol condition min typ max units feedback voltage v fb 4.5v v in 25v 0.788 0.808 0.828 v feedback current i fb v fb = 0.8v 10 na switch on resistance (5) r ds(on) 60 m ? switch leakage v en = 0v, v sw = 0v 0 10 a current limit (5) 12 a oscillator frequency f sw v fb = 0.6v 400 600 800 khz fold-back frequency v fb = 0v 150 khz maximum duty cycle v fb = 0.6v 85 90 % minimum on time (5) t on 100 ns under voltage lockout threshold rising 3.9 4.1 4.3 v under voltage lockout threshold hysteresis 880 mv en input low voltage 0.4 v en input high voltage 1.2 v v en = 2v 2 en input current v en = 0v 0 a supply current (shutdown) v en = 0v 0 10 a supply current (quiescent) v en = 2v, v fb = 1v 1.1 ma thermal shutdown 150 c bg driver bias supply voltage v cc 4.5 5 v gate driver sink impedance (5) r sink 1 ? gate driver source impedance (5) r source 4 ? gate drive current sense trip threshold v sw 20 mv power good threshold 0.69 0.74 0.79 v power good threshold hysteresis 40 mv pg pin level v pg pg sink 4ma 0.4 v soft start time t ss 1 1.5 5 ms notes: 5) guaranteed by design.
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 4 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pin functions pin # name description 1 fb feedback. an external resistor divider from the output to gnd, tapped to the fb pin sets the output voltage. to prevent current limit r un away during a short circuit fault condition the frequency foldback comparator lowers the oscillator frequency when the fb voltage is below 250mv. 2 pg power good indicator. connect this pin to v cc or v out by a 100k ? pull-up resistor. the output of this pin is low if the output voltage is 10% less than the nominal voltage, otherwise it is an open drain. 3 en/sync on/off control and external frequency synchronization input. 4, 5, 6 in supply voltage. the mp38671 operates from a +4.5v to +25v unregulated input. c1 is needed to prevent large voltage spikes from appearing at the input. 7 n/c no connect. 8, 9, 10 sw switch output. 11 bst bootstrap. this capacitor is needed to dr ive the power switch?s gate above the supply voltage. it is connected between sw and bst pi ns to form a floating supply across the power switch driver. 12 vcc bg driver bias supply. decouple with a 1f ceramic capacitor. 13 bg gate driver output. connect this pin to the synchronous mosfet gate. 14 gnd, exposed pad ground. this pin is the voltage reference for the regulated output voltage. for this reason care must be taken in its layout. this node should be placed outside of the m2 to c1 ground path to prevent switching current spikes from inducing voltage noise into the part. the exposed pad and gnd pin must be connected to the same ground plane.
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 5 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics v in = 12v, v out = 3.3v, t a = +26oc, unless otherwise noted. v cc (v) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 3.5 4.0 4.5 5.0 5.5
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 6 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. typical performanc e characteristics v in = 12v, v out = 3.3v, t a = +26oc, unless otherwise noted. load transient response input ripple voltage i out =10a output ripple voltage i out =10a enable startup no load enable startup full load power up no load power up full load v out 2v/div v out 5v/div v in 2v/div v in 200mv/div v sw 10v/div v sw 10v/div i inductor 5a/div v out 20mv/div v out 100mv/div v sw 10v/div i inductor 10a/div i inductor 5a/div i inductor 5a/div v out 2v/div v en 10v/div v sw 10v/div i inductor 10a/div v out 2v/div v en 10v/div v sw 10v/div v sw 10v/div i inductor 10a/div v out 5v/div v in 2v/div v sw 10v/div i inductor 5a/div 2ms/div 1ms/div 1ms/div 400ns/div 2ms/div latch off with output short circuit
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 7 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation in en/sync fb sw vcc bg gnd pg bst regulator oscillator 600khz driver current sense amplifier x40 error amplifier current limit comparator pwm comparator driver d regulator reference -- + -- + -- + s r r q q -- + power good v bg v cc v cc v bg figure 1?functional block diagram the mp38671 is a fixed frequency, synchronous, step-down switching regulator with an integrated high-side power mosfet and a gate driver for a low-side external mosfet. it achieves 10a continuous output current over a wide input supply range with excellent load and line regulation. it provides a single highly efficient solution with current mode control for fast loop response and easy compensation. the mp38671 operates in a fixed frequency, peak current control mode to regulate the output voltage. a pwm cycle is initiated by the internal clock. the integrated high-side 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 until the next clock cycle starts. if, in 90% of one pwm period, the current in the power mosfet does not reach the comp set current value, the power mosfet will be forced to turn off. error amplifier the error amplifier compares the fb pin voltage with the internal 0.8v reference (ref) and outputs a current proportional to the difference between the two. this output current is then used to charge or discharge the internal compensation network to form the comp voltage, which is used to control the power mosfet current. the optimized internal compensation network minimizes the external component counts and simplifies the control loop design. internal regulator most of the internal circuitries are powered from the 5v internal regulator. this regulator takes the vin input and operates in the full vin range. when vin is greater than 5.0v, the output of the regulator is in full regulation. when vin is lower than 5.0v, the output decreases. since this internal regulator provides the bias current for the bottom gate driver that requires significant amount of current depending upon the external mosfet selection, a 1uf ceramic capacitor for decoupling purpose is required.
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 8 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. enable/synch control the mp38671 has a dedicated enable/synch control pin (en/sync). by pulling it high or low, the ic can be enabled and disabled by en. tie en to vin for automatic start up. to disable the part, en must be pulled low for at least 5s. the mp38671 can be synchronized to external clock range from 300khz up to 1.4mhz through the en/sync pin. the internal clock rising edge is synchronized to the external clock rising edge. under-voltage lockout (uvlo) under-voltage lockout (uvlo) is implemented to protect the chip from operating at insufficient supply voltage. the mp38671 uvlo comparator monitors the output voltage of the internal regulator, vcc. the uvlo rising threshold is about 4.0v while its falling threshold is a consistent 3.2v. internal soft-start the soft-start is implemented to prevent the converter output voltage from overshooting during startup. when the chip starts, the internal circuitry generates a soft-start voltage (ss) ramping up from 0v to 1.2v. 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. over-current-protection (ocp) the mp38671 has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current limit threshold. meanwhile, output voltage starts to drop until fb is below the under-voltage (uv) threshold, typically 30% below the reference. once a output uv is triggered, the mp38671 enters latch off mode. mode is especially useful to ensure system safety under fault condition. the mp38671 exits the latch off mode once the en or input power is re-cycled. thermal shutdown thermal shutdown is implemented to prevent the chip from operating at exceedingly high temperatures. when the silicon die temperature is higher than 150 c, it shuts down the whole chip. when the temperature is lower than its lower threshold, typically 140 c, the chip is enabled again. 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 uvlo?s rising threshold is 2.2v with a hysteresis of 150mv. the bootstrap capacitor voltage is regulated internally (figure 2). even at no load condition, as long as v in is 3v higher than v out , c4 will have enough voltage provided by v in through m2, m1, c4, l1 and c2. if (v in -v sw ) is more than 5v, u2 will regulate m1 to maintain a 5v bst voltage across c4. -- + -- + v in 5v u2 d1 m1 bst sw c4 c2 l1 v out figure 2 ? internal bootstrap charging circuit 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 is enabled. the regulator provides stable supply for the remaining circuitries. four events can shut down the chip: ocp, en low, vin low and thermal shutdown. in the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. the comp voltage and the internal supply rail are then pulled down. the floating driver is not subject to this shutdown command.
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 9 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. application information setting the output voltage the external resistor divider is used to set the output voltage (see the schematic on front page). the feedback resistor r1 also sets the feedback loop bandwidth with the internal compensation capacitor (see figure 1). choose r1 to be around 40.2k ? for optimal transient response. r2 is then given by: 1 v 8 . 0 v 1 r 2 r out ? = table 1?resistor selection for common output voltages v out (v) r1 (k ? ) r2 (k ? ) 1.2 40.2 (1%) 80.6 (1%) 1.8 40.2 (1%) 32.4 (1%) 2.5 40.2 (1%) 19.1 (1%) selecting the inductor a 1h to 10h inductor with a dc current rating of at least 25% higher than the maximum load current is recommended for most applications. for highest efficiency, the inductor dc resistance should be less than 10m ? . for most designs, the inductance value can be derived from the following equation. out in out in l osc v(vv) l1 vif ? = where i l is the inductor ripple current. choose inductor ripple current to be approximately 30% of the maximum load current, 10a. the maximum inductor peak current is: 2 i i i l load ) max ( l + = under light load conditions below 100ma, larger inductance is recommended for improving efficiency. synchronous mosfet the external synchronous mosfet is used to freewheel the inductor current when the internal high-side switch is off. it reduces the power loss significantly compared against a schottky rectifier. table 2 lists example synchronous mosfets and manufacturers. table 2?synchronous mosfet selection guide part no. manufacture si7114 vishay hat2165 renesas selecting the 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 with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 22f capacitor is sufficient. since the input capacitor (c1) absorbs the input switching current it requires an adequate ripple current rating. the rms current in the input capacitor can be estimated by: ? ? ? ? ? ? ? ? ? = in out in out load 1 c v v 1 v v i i the worse case condition occurs at v in = 2v out , where: 2 i i load 1 c = for simplification, choose the input capacitor whose rms current rating greater than half of the maximum load current.
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver mp38671 rev. 1.1 www.monolithicpower.com 10 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the input capacitor can be electrolytic, tantalum or ceramic. when using electrolytic or tantalum capacitors, a small, high quality ceramic capacitor, i.e. 0.1 f, 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. the input voltage ripple caused by capacitance can be estimated by: ? ? ? ? ? ? ? ? ? = in out in out s load in v v 1 v v 1 c f i v selecting the 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: out out out esr sin s vv 1 v1r fl1 v 8fc2 ?? ?? = ? + ?? ?? ?? ?? where l1 is the inductor value and r esr is the equivalent series resistance (esr) value of the output capacitor. in the 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: out out out 2 in s vv v1 v 8f l1c2 ?? =? ?? ?? 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: out out out esr in s vv v1r fl1 v ?? =? ?? ?? the characteristics of the output capacitor also affect the stability of the regulation system. the mp38671 can be optimized for a wide range of capacitance and esr values. pcb layout the high current paths (gnd, in and sw) should be placed very close to the device with short, direct and wide traces. the input capacitor needs to be as close as possible to the in and gnd pins. the external feedback resistors should be placed next to the fb pin. keep the switching node sw short and away from the feedback network. external bootstrap diode an external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external bst diode are: z v out =5v or 3.3v; and z duty cycle is high: d= in out v v >65% in these cases, an external bst diode is recommended from the output of the voltage regulator to bst pin, as shown in figure 3 mp38671 sw bst c l bst c 5v or 3.3v out external bst diode in4148 + figure 3?add optional external bootstrap diode to enhance efficiency the recommended external bst diode is in4148, and the bst cap is 0.1~1f.
mp38671 ? 10a, 25v, 600khz step-down with synchronous gate driver notice: the information in this document is subject to change wi thout notice. users should warra nt and guarantee that third party intellectual property rights are not infringed upon w hen integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp38671 rev. 1.1 www.monolithicpower.com 11 9/21/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information 3mm x 4mm qfn14 side view top view 1 14 87 bottom view 2. 90 3. 10 1.60 1.80 3.90 4.10 3.20 3.40 0.50 bsc 0.18 0.30 0.80 1.00 0.00 0.05 0.20 ref pin 1 id marking 1.70 0.50 0.25 recommended land pattern 2.90 note: 1) all dimensions are in millimeters . 2) exposed paddle size does not include mold flash . 3) lead coplanarity shall be 0.10 millimeter max. 4) jedec reference is mo-229, variation vged-3. 5) drawing is not to scale. pin 1 id see detail a 3.30 0.70 pin 1 id option b r0.20 typ. pin 1 id option a 0.30x45 o typ. detail a 0.30 0.50 pin 1 id index area

▲Up To Search▲

Price & Availability of MP38671DL

	To Download MP38671DL Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .