mp2259 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 1 9/15/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. the future of analog ic technology description the mp2259 is a monolithic integrated step- down switch mode converter with an internal power mosfet. it achieves 1a 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 mp2259 requires a minimum number of readily available standard external components. the mp2259 is available in tsot23-6 and sot23-6 packages. features ? 1a output current ? 0.5 ? internal power mosfet switch ? stable with low esr output ceramic capacitors ? up to 92% efficiency ? 0.1 a shutdown mode ? fixed 1.4mhz frequency ? thermal shutdown ? cycle-by-cycle over current protection ? wide 4.5v to 16v operating input range ? output adjustable from 0.81v to 14v ? available in tsot23-6 and sot23-6 packages applications ? hand disk drive ? xdsl modems cable ? set-top box 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 mp2259 sw fb bst gnd in en 1 6 3 2 4 5 v out 3.3v @ 1a cb 10nf d1 b230a v in 12v off on 100 95 90 85 80 75 70 65 60 55 50 efficiency (%) 10 100 1000 load current (ma) mp2259-ec01 efficiency vs load current v out = 3.3v v out = 5v v in = 12v
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 2 9/15/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. ordering information part number package top marking temperature mp2259dt ** sot23-6 k1 ?40 c to +85 c * for tape & reel, add suffix ?z (eg. MP2259DJ?z); for rohs compliant packaging, add suffix ?lf. (eg. MP2259DJ?lf?z) * * for tape & reel, add suffix ?z (eg. mp2259dt?z); for rohs compliant packaging, add suffix ?lf (eg. mp2259dt?lf?z) package reference bst gnd fb 1 2 3 6 5 4 sw in en mp2259_pd01_tsot23 top view bst gnd fb 1 2 3 6 5 4 sw in en mp2259_pd02_sot23 top view tsot23-6 sot23-6 absolute maxi mum ratings (1) supply voltage v in ....................................... 20v v sw ............................................................... 21v v bs ....................................................... v sw + 6v all other pins .................................?0.3v to +6v continuous power dissipation (t a = +25c) (2) tsot23-6 ................................................ 0.57w sot23-6 .................................................. 0.57w junction temperature ...............................150 c lead temperature ....................................260 c storage temperature.............. ?65 c to +150 c recommended operating conditions (3) supply voltage v in ...........................4.5v to 16v output voltage v out ......................... 0.81 to 14v maximum junction temp. (t j ) .............. +125c thermal resistance (4) ja jc tsot23-6.............................. 220 .... 110.. c/w sot23-6 ................................ 220 .... 110.. 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 jesd51-7 4-layer pcb. part number package top marking temperature MP2259DJ * tsot23-6 j9 ?40 c to +85 c
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 3 9/15/2011 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 16v 0.790 0.810 0.830 v v fb = 0.8v 10 na feedback current i fb v fb = 2v 2 a switch-on resistance r ds(on) 0.5 ? switch leakage v en = 0v, v sw = 0v 10 a current limit (5) 1.8 a oscillator frequency f sw v fb = 0.6v 1.4 mhz fold-back frequency v fb = 0v 460 khz maximum duty cycle v fb = 0.6v 85 % minimum on-time t on 100 ns under voltage lockout threshold rising 2.5 2.8 3.1 v under voltage lockout threshold hysteresis 200 mv en input low voltage 0.4 v en input high voltage 1.2 v v en = 5v 3 7 en input current v en = 0v -1 1 a supply current (shutdown) v en = 0v 0.1 a supply current (quiescent) v en = 2v, v fb = 1v 1.0 ma thermal shutdown 150 c note: 5) slope compensation changes curr ent limit above 40% duty cycle. pin functions pin # name description 1 bst bootstrap. this capacitor is needed to drive t he power switch?s gate above the supply voltage. it is connected between sw and bs pins to form a fl oating supply across the power switch driver. 2 gnd ground. this pin is the voltage reference for t he regulated output voltage. for this reason care must be taken in its layout. this node should be pl aced outside of the d1 to c1 ground path to prevent switching current spikes from inducing voltage noise into the part. 3 fb feedback. an external resistor divider from t he output to gnd, tapped to the fb pin sets the output voltage. to prevent current limit run aw ay during a short circuit fault condition the frequency foldback comparator lowers the osc illator frequency when the fb voltage is below 250mv. 4 en on/off control input. pull above 1.2v to turn the device on. 5 in supply voltage. the mp2259 operates from a +4.5v to +16v unregulated input. c1 is needed to prevent large voltage spikes from appearing at the input. 6 sw switch output.
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 4 9/15/2011 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, l = 4.7h, c1 = 10f, c2 = 22f, t a = +25oc, unless otherwise noted. v sw 10v/div. v en 5v/div. v out 1v/div. i l 1a/div. start-up through enable i out = 1a resistive load v out 1v/div. v sw 10v/div. v en 5v/div. start-up through enable no load v out 2v/div. v sw 10v/div. v en 5v/div. i l 1a/div. shut-down through enable no load shut-down through enable i out = 1a resistive load i l 500ma/div. v out 2v/div. v sw 10v/div. v en 5v/div. i l 1a/div. v out 1v/div. i l 1a/div. short circuit entry short circuit recovery v out 1v/div. i l 1a/div. 400ns/div. steady state test i out = 0.5a v out ac coupled 50mv/div. i l 1a/div. i load 1a/div. v out 20mv/div. v sw 10v/div. i l 500ma/div. current limit vs duty cycle current limit (a) 3.0 2.5 2.0 1.5 1.0 0.5 0 duty cycle (%) 0 20 40 60 80 100
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 5 9/15/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. operation the mp2259 is a current mode buck regulator. with ea output voltage proportional to the peak inductor current. at the beginning of a cycle, m1 is off. the ea output voltage is higher than the current sense amplifier output, and the current comparator?s output is low. the rising edge of the 1.4mhz clk signal sets the rs flip-flop. its output turns on m1 then connects the sw pin and inductor to the input supply. the increasing inductor current is sensed and amplified by the current sense amplifier. ramp compensation is summed to current sense amplifier output and compared to the error amplifier output by the pwm comparator. when the sum of the current sense amplifier output and the slope compensation signal exceeds the ea output voltage, the rs flip- flop is reset and m1 is turned off. the external schottky rectifier diode (d1) conducts the inductor current. if the sum of the current sense amplifier output and the slope compensation signal does not exceed the ea output for a whole cycle, then the falling edge of the clk resets the flip-flop. the output of the error amplifier integrates the voltage difference between the feedback and the 0.8v bandgap reference. the polarity is such that a fb pin voltage lower than 0.8v increases the ea output voltage. since the ea output voltage is proportional to the peak inductor current, an increase in its voltage increases current delivered to the output. 5 in en fb gnd sw bst 4 3 2 1 6 regulator oscillator 1.4mhz driver current sense amplifier error amplifier current limit comparator pwm comparator mp2259_f01_bd01 x20 m1 regulator reference ea -- + -- + -- + s r r q -- + 27pf 1pf figure 1?functional block diagram
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 6 9/15/2011 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). r2 can be determined by: 1 v 81 . 0 v 1 r 2 r out ? = table 1?resistor selection for common output voltages v out (v) r1 (k ? ) r2 (k ? ) 1.8 80.6 (1%) 64.9 (1%) 2.5 49.9 (1%) 23.7 (1%) 3.3 49.9 (1%) 16.2 (1%) 5 49.9 (1%) 9.53 (1%) selecting the inductor a 1h to 10h inductor is recommended for most applications. for highest efficiency, the inductor?s dc resistance should be less than 200m ? . for most designs, the required inductance value can be derived from the following equation: osc l in out in out f i v ) v v ( v l ? = where i l is the inductor ripple current. choose an inductor with a rating current higher than the maximum load current. the maximum inductor peak current can be calculated from: 2 i i i l load ) max ( l + = under light load conditions below 100ma, a larger inductance is recommended for improved efficiency. selecting the input capacitor the input capacitor (c1) reduces the surge current drawn from the input and the switching noise from the device. the input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from passing through the input. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 4.7f capacitor is sufficient. selecting the output capacitor the output capacitor (c2) keeps output voltage ripple small and ensures loop stability. the output capacitor impedance should be low at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended for their low esr characteristics. a 10f~ 22f capacitor is good for most applications. pcb layout guide pcb layout is very important to achieve stable operation. please follow these guidelines and take figure2 for references. 1) keep the path of switching current short and minimize the loop area formed by input cap, high-side mosfet and schottky diode. 2) keep the connection of schottky diode between sw pin and input power ground as short and wide as possible. 3) ensure all feedback connections are short and direct. place the feedback resistors and compensation components as close to the chip as possible. 4) route 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. for single layer, do not solder exposed pad of the ic.
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 7 9/15/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. pgnd 1 2 3 6 5 4 en in sw bst gnd fb c1 l1 d1 c3 r1 r2 r3 c2 sgnd figure2 D pcb layout 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 fig.3 mp2259 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.
mp2259 ? 1a, 16v, 1.4mhz step-down converter mp2259 rev. 0.92 www.monolithicpower.com 8 9/15/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. package information tsot23-6 0.30 0.50 seating plane 0.95 bsc 0.84 0.90 1.00 max 0.00 0.10 top view front view side view recommended land pattern 2.80 3.00 1.50 1.70 2.60 3.00 13 4 6 0.09 0.20 note: 1) all dimensions are in millimeters . 2) package length does not include mold flash , protrusion or gate burr . 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming ) shall be 0.10 millimeters max. 5) drawing conforms to jedec mo-193, variation ab. 6) drawing is not to scale. 7) pin 1 is lower left pin when reading top mark from left to right, (see example top mark) 0.30 0.50 0 o -8 o 0.25 bsc gauge plane 2.60 typ 1.20 typ 0.95 bsc 0.60 typ see detail "a" detail A aaaa pin 1 see note 7 example top mark
mp2259 ? 1a, 16v, 1.4mhz step-down converter notice: the information in this document is subject to change wi thout notice. please contact m ps 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. mp2259 rev. 0.92 www.monolithicpower.com 9 9/15/2011 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2011 mps. all rights reserved. sot23-6 0.30 0.50 seating plane 0.95 bsc 0.90 1.30 1.45 max 0.00 0.15 top view front view side view recommended land pattern 2.80 3.00 1.50 1.70 2.60 3.00 13 4 6 0.09 0.20 0.30 0.55 0 o -8 o 0.25 bsc gauge plane 2.60 typ 1.20 typ 0.95 bsc 0.60 typ see detail "a" detail A aaaa pin 1 see note 7 example top mark note: 1) all dimensions are in millimeters . 2) package length does not include mold flash , protrusion or gate burr . 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming ) shall be 0.10 millimeters max. 5) drawing conforms to jedec mo-193, variation ab. 6) drawing is not to scale. 7) pin 1 is lower left pin when reading top mark from left to right , (see example top mark)
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