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MP1423 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 1 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. the future of analog ic technology tm tm description the MP1423 is a step-down regulator with a built in internal power mosfet. it achieves 3a 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. adjustable soft-start reduces the stress on the input source at turn-on. in shutdown mode the regulator draws 20a of supply current. the MP1423 requires a minimum number of readily available external components to complete a 3a step-down dc to dc converter solution. features ? 3a output current ? programmable soft-start ? 110m ? internal power mosfet switch ? stable with low esr output ceramic capacitors ? up to 94% efficiency ? 20a shutdown mode ? fixed 385khz frequency ? thermal shutdown ? cycle-by-cycle over current protection ? wide 6v to 23v operating input range ? output is adjustable from 1.22v to 21v ? under voltage lockout applications ? distributed power systems ? battery chargers ? pre-regulator for linear regulators ?mps? and ?the future of analog ic technology? are trademarks of monolithic power systems, inc. typical application input 6v to 23v output 2.5v 3a MP1423 bs in fb sw ss gnd comp en open open = automatic startup MP1423_tac01 10nf 5.6nf 10nf b330a 1 3 5 6 4 8 7 2 MP1423_ec01 efficiency vs load current 100 90 80 70 60 50 efficiency (%) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 load current (a) v out =5.0v v in = 10v v out =2.5v v out =3.3v http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 2 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm package reference part number* package temp MP1423dn soic8n ?40 c to +85 c MP1423dp pdip8 ?40 c to +85 c * for tape & reel, add suffix ?z (eg. MP1423dn?z) for lead free, add suffix ?lf (eg. MP1423dn?lf?z) absolute maxi mum ratings (1) supply voltage v in ....................... ?0.3v to +28v switch voltage v sw ................. ?1v to v in + 0.3v bootstrap voltage v bs ....v sw ? 0.3v to v sw + 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 (2) input voltage v in ................................. 6v to 23v ambient operating temp ..........?40 c to +85 c thermal resistance (3) ja jc soic8n .................................. 50 ...... 10... c/w pdip8 ..................................... 95 ...... 55... c/w notes: 1) exceeding these ratings may damage the device. 2) the device is not guaranteed to function outside of its operating conditions. 3) measured on approximately 1? square of 1 oz copper. electrical characteristics v in = 12v, t a = +25 c, unless otherwise noted. parameters symbol condition min typ max units shutdown supply current v en = 0v 20 30 a supply current v en = 2.8v, v fb =1.4v 1.0 1.2 ma feedback voltage v fb 6v v in 23v 1.194 1.222 1.250 v error amplifier voltage gain a vea 400 v/v error amplifier transconductance g ea ? i comp = 10a 500 800 1120 a/v high-side switch-on resistance r ds(on)1 0.11 ? low-side switch-on resistance r ds(on)2 10 ? high-side switch leakage current v en = 0v, v sw = 0v 0 10 a current limit 3.3 4.5 a current sense to comp transconductance g cs 3.8 a/v oscillation frequency f s 335 385 435 khz short circuit oscillation frequency d max v fb = 0v 25 40 55 khz maximum duty cycle v fb = 1.0v 90 % minimum duty cycle v fb = 1.5v 0 % en threshold voltage 0.9 1.2 1.5 v enable pull-up current v en = 0v 1.1 1.8 2.5 a under voltage lockout threshold v in rising 2.37 2.54 2.71 v under voltage lockout threshold hysteresis 210 mv soft-start period c ss = 0.1 f 10 ms thermal shutdown 160 c bs in sw gnd ss en comp fb 1 2 3 4 8 7 6 5 top view MP1423_pd01 exposed pad (soic8n only) connect to pin 4 http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 3 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm typical performanc e characteristics v en 5v/div. v out 2v/div. i l 1a/div. MP1423-tpc02 soft-start c ss open, v in = 10v, v out = 3.3v, 1.5a resistive load v en 5v/div. v out 2v/div. i l 1a/div. MP1423-tpc03 v en 5v/div. v out 2v/div. i l 1a/div. 1ms/div. MP1423-tpc04 MP1423-tpc01 100 90 80 70 60 50 efficiency (%) 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 load current (a) efficiency curve v in = 7v v in =5.0v v in =2.5v v in =3.3v pin functions pin # name description 1 bs high-side gate drive bootstrap input. bs s upplies the drive for the high-side n-channel mosfet switch. connect a 4.7nf or greater capacitor from sw to bs to power the high side switch. 2 in power input. in supplies the power to the ic, as well as the step-down converter switches. drive in with a 6v to 23v power source. bypass in to gnd with a suitably large capacitor to eliminate noise on the input to the ic. see input capacitor 3 sw power switching output. sw is the switching node that supplies power to the output. connect the output lc filter from sw to the output load. note that a capacitor is required from sw to bs to power the high-side switch. 4 gnd ground. (note: for the soic8n package, connect the exposed pad on backside to pin 4). 5 fb feedback input. fb senses the output voltage to regulate said voltage. drive fb with a resistive voltage divider from the output volt age. the feedback threshold is 1.222v. see setting the output voltage http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 4 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm pin functions (continued) pin # name description 6 comp compensation node. comp is used to compensate the regulation control loop. connect a series rc network from comp to gnd to compensate the regulation control loop. in some cases, an additional capacitor from comp to gnd is required. see compensation 7 en enable input. en is a digital input that turns the regulator on or o ff. drive en high to turn on the regulator, low to turn it off. for aut omatic startup, leave en unconnected. 8 ss soft start control input. ss controls the soft star t period. connect a capacitor from ss to gnd to set the soft-start period. a 0.1f capacitor se ts the soft-start period to 10ms. to disable the soft-start feature, leave ss unconnected. operation the MP1423 is a current-mode step-down regulator. it regulates input voltages from 6v to 23v down to an output voltage as low as 1.222v, and is able to supply up to 3a of load current. the MP1423 uses current-mode control to regulate the output voltage. the output voltage is measured at fb through a resistive voltage divider and amplified through the internal error amplifier. the output current of the transconductance error amplifier is presented at comp where a network compensates the regulation control system. the voltage at comp is compared to the switch current measured internally to control the output voltage. the converter uses an internal n-channel mosfet switch to step-down the input voltage to the regulated output voltage. since the mosfet requires a gate voltage greater than the input voltage, a boost capacitor connected between sw and bs drives the gate. the capacitor is internally charged while sw is low. an internal 10 ? switch from sw to gnd is used to insure that sw is pulled to gnd when sw is low to fully charge the bs . capacitor. MP1423_bd01 lockout comparator error amplifier frequency foldback comparator internal regulators 1.8v slope comp clk current comparator current sense amplifier shutdown comparator ss 8 comp 6 in 2 en 7 gnd 4 oscillator 40/385khz s r q sw 3 bs 1 5v + q 0.7v + + 2.37v/ 2.71v + 1.222v 0.7v + + fb 5 -- -- -- -- -- -- figure 1?functional block diagram http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 5 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm application information 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 ratio: 2 r 1 r 2 r v v out fb + = where v fb is the feedback voltage and v out is the output voltage. thus the output voltage is: 2 r 2 r 1 r 22 . 1 v out + = a typical value for r2 can be as high as 100k ? , but a typical value is 10k ? . using that value, r1 is determined by: ) k )( 22 . 1 v ( 18 . 8 1 r out ? ? = for example, for a 3.3v output voltage, r2 is 10k ? , and r1 is 17k ? . 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. however, 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: ? ? ? ? ? ? ? ? ? = in out l s out v v 1 ? i f v l where v in is the input voltage, f s is the 385khz 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: ? ? ? ? ? ? ? ? ? + = in out s out load lp v v 1 l f 2 v i i 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. table 1?inductor selection guide package dimensions (mm) vendor/ model core type core material w l h sumida cr75 open ferrite 7.0 7.8 5.5 cdh74 open ferrite 7.3 8.0 5.2 cdrh5d28 shielded ferrite 5.5 5.7 5.5 cdrh5d28 shielded ferrite 5.5 5.7 5.5 cdrh6d28 shielded ferrite 6.7 6.7 3.0 cdrh104r shielded ferrite 10.1 10.0 3.0 toko d53lc type a shielded ferrite 5.0 5.0 3.0 d75c shielded ferrite 7.6 7.6 5.1 d104c shielded ferrite 10.0 10.0 4.3 d10fl open ferrite 9.7 1.5 4.0 coilcraft do3308 open ferrite 9.4 13.0 3.0 do3316 open ferrite 9.4 13.0 5.1 http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 6 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm output rectifier diode the output rectifier diode supplies the current 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 current rating is greater than the maximum load current. table 2 lists example schottky diodes and manufacturers. table 2?diode selection guide diode v oltage/current rating manufacture sk33 30v, 3a diodes inc. sk34 40v, 3a diodes inc. b330 30v, 3a diodes inc. b340 40v, 3a diodes inc. mbrs330 30v, 3a on semiconductor mbrs340 40v, 3a on semiconductor 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. 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 worst-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. the input capacitor can be electrolytic, tantalum or ceramic. when using electrolytic or tantalum capacitors, 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. 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 output capacitor the output capacitor 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: ? ? ? ? ? ? ? ? + ? ? ? ? ? ? ? ? ? = ? 2 c f 8 1 r v v 1 l f v v s esr in out s out out where l is the inductor value, c2 is the output capacitance 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: ? ? ? ? ? ? ? ? ? = in out 2 s out out v v 1 2 c l f 8 v ? v 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: esr in out s out out r v v 1 l f v ? v ? ? ? ? ? ? ? ? ? = the characteristics of the output capacitor also affect the stability of the regulation system. the MP1423 can be optimized for a wide range of capacitance and esr values. http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 7 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm compensation components MP1423 employs current mode control for easy compensation and fast transient response. the system stability and transient response are controlled through the comp pin. comp pin is the output of the internal transconductance 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 voltage feedback loop is given by: out fb vea cs load vdc v v a g r a = where a vea is the error amplifier voltage gain, 400v/v; g cs is the current sense transconductance, 3.8a/v; r load is the load resistor value. the system has two poles of importance. one is due to the compensation capacitor (c3) and the output resistor of error amplifier, and the other is due to the output capacitor and the load resistor. these poles are located at: vea ea 1 p a 3 c 2 g f = load 2 p r 2 c 2 1 f = where g ea is the error amplifier transconductance, 800a/v. the system has one zero of importance, due to the compensation capacitor (c3) and the compensation resistor (r3). this zero is located at: 3 r 3 c 2 1 f 1 z = 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: esr esr r 2 c 2 1 f = in this case, a third pole set by the compensation capacitor (c6) and the compensation resistor (r3) is used to compensate the effect of the esr zero on the loop gain. this pole is located at: 3 r 6 c 2 1 f 3 p = the goal of compensation design is to shape the converter transfer function to get a desired loop gain. the system crossover frequency where the feedback 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 approximately one-tenth of the switching frequency. switching frequency for the MP1423 is 385khz, so the desired crossover frequency is around 38khz. table 3 lists the typical values of compensation components for some standard output voltages with various output capacitors and inductors. the values of the compensation components have been optimized for fast transient responses and good stability at given conditions. table 3?compensation values for typical output voltage/capacitor combinations v out c2 r3 c3 c6 2.5v 22f ceramic 3.9k ? 5.6nf none 3.3v 22f ceramic 4.7k ? 4.7nf none 5v 22f ceramic 7.5k ? 4.7nf none 12v 22f ceramic 16.9k ? 1.5nf none 2.5v 560f al. 30m ? esr 91k ? 1nf 150pf 3.3v 560f al 30m ? esr 120k ? 1nf 120pf 5v 470f al. 30m ? esr 100k ? 1nf 120pf 12v 220f al. 30m ? esr 169k ? 1nf 39pf http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 8 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm to optimize the compensation components for conditions not listed in table 2, the following procedure can be used. 1. choose the compensation resistor (r3) to set the desired crossover frequency. determine the r3 value by the following equation: fb out cs ea c v v g g f 2 c 2 3 r = where f c is the desired crossover frequency (which typically has a value no higher than 38khz). 2. choose the compensation capacitor (c3) 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 c3 value by the following equation: c f 3 r 2 4 3 c > where r3 is the compensation resistor value. 3. determine if the second compensation capacitor (c6) is required. it is required if the esr zero of the output capacitor is located at less than half of the 385khz switching frequency, or the following relationship is valid: 2 f r 2 c 2 1 s esr < if this is the case, then add the second compensation capacitor (c6) to set the pole f p3 at the location of the esr zero. determine the c6 value by the equation: 3 r r 2 c 6 c esr = external bootstrap diode it is recommended that an external bootstrap diode be added when the system has a 5v fixed input or the power supply generates a 5v output. this helps improve the efficiency of the regulator. the bootstrap diode can be a low cost one such as in4148 or bat54. MP1423 sw bs 3 1 10nf 5v boost diode MP1423_f02 figure 2?external bootstrap diode this diode is also recommended for high duty cycle operation (when in out v v >65%) and high output voltage (v out >12v) applications. http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 9 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm typical application circuits input 6v to 23v output 2.5v 3a c3 3.3nf c4 10nf c6 47pf d1 c5 10nf MP1423 bs in fb sw ss gnd comp en 1 3 5 6 4 8 7 2 MP1423_f03 open = automatic startup figure 3?MP1423 with murata 22f, 10v ceramic output capacitor input 6v to 23v output 2.5v 3a c3 3.3nf c4 10nf c6 47pf d1 c5 10nf MP1423 bs in fb sw ss gnd comp en MP1423_f04 open = automatic startup 1 3 5 6 4 8 7 2 figure 4?MP1423 with panasonic 47f, 6.3v special polymer output capacitor http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter MP1423 rev. 1.1 www.monolithicpower.com 10 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm package information soic8n (exposed pad) note: 1) control dimension is in inches. dimension in bracket is millimeters. 2) exposed pad option (n-package) ; 2.31mm -2.79mm x 2.79mm - 3.81mm. recommend solder board area: 2.80mm x 3.82mm = 10.7mm 2 (16.6 mil 2 ) 3) the length of the package does not include mold flas h. mold flash shall not exceed 0.006in. (0.15mm) per side. with the mold flash included, over-a ll length of the package is 0.2087in. (5.3mm) max. 4) the width of the package does not include mold flash . mold flash shall not exceed 0.10in. (0.25mm) per side. with the mold flash included, over-a ll width of the package is 0.177in. (4.5mm) max. 0.016(0.410) 0.050(1.270) 0 o -8 o detail "a" 0.011(0.280) 0.020(0.508) x 45 o see detail "a" 0.0075(0.191) 0.0098(0.249) 0.229(5.820) 0.244(6.200) land pattern .028 .050 0.140 (3.55mm) 0.200 (5.07 mm) 0.060 0.150(3.810) 0.157(4.000) pin 1 ident. 0.050(1.270)bsc 0.013(0.330) 0.020(0.508) note 2 note 4 seating plane 0.001(0.030) 0.004(0.101) 0.189(4.800) 0.197(5.000) 0.053(1.350) 0.068(1.730) 0.049(1.250) 0.060(1.524) note 3 http://www..net/ datasheet pdf - http://www..net/
MP1423 ? 3a, 23v, 385khz step-down converter notice: the information in this document is subject to change wi thout notice. please contact mps for current specifications. users should warrant and guarantee that third party intellectual property rights ar e not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. MP1423 rev. 1.1 www.monolithicpower.com 11 1/6/2006 mps proprietary information. unauthorized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. tm pdip8 note: 1) control dimension is in inches. dimension in bracket is millimeters. 0.021(0.533) 0.015(0.381) 0.100 bsc(2.540) 0.145(3.683) 0.134(3.404) 0.140(3.556) 0.120(3.048) 0.035 (0.889) 0.015 (0.381) 0.260 (6.604) 0.240 (6.096) 0.387 (9.830) 0.367 (9.322) pin 1 ident. 0.040 (1.016) 0.020 (0.508) 0.065 (1.650) 0.050 (1.270) 0.014 (0.356) 0.008 (0.200) 0.325(8.255) 0.300(7.620) 0.392(9.957) 0.332(8.433) 3 ~ 11 lead bend http://www..net/ datasheet pdf - http://www..net/

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