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mp2459 0.5a, 55v, 480khz stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 1 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. the future of analog ic technology description the mp2459 is a monolithic, stepdown, switch mode converter with a builtin power mosfet. it achieves a 0.5a peakoutput current over a wide input supply range with excellent load and line regulation. currentmode operation provides a fast transient response and eases loop stabilization. fault condition protections include cyclebycycle current limiting and thermal shutdown. the mp2459 requires a minimal number of readilyavailable external components. the mp2459 is available in a tsot236 package. features ? 0.5a peak output current ? 1 internal power mosfet ? stable with lowesr ceramic output capacitors ? up to 90% efficiency ? 0.1a shutdown mode ? fixed 480khz frequency ? thermal shutdown ? cyclebycycle overcurrent protection ? wide 4.5vto55v operating input range ? output adjustable from 0.81v to 0.95*v in ? available in a tsot236 package applications ? power meters ? distributed power systems ? battery chargers ? preregulator for linear regulators ? wled drivers all mps parts are lead free and adhere to the rohs directive. for mps green status, please visit mps website under products, qu ality assurance page. mps and the future of analog ic technology are registered trademarks of monolithic power systems, inc. typical application vin gnd gnd vou t en en u1 l1 d1 mp2459 in bs t sw fb 30 40 50 60 70 80 90 100 0.0 0.1 0.2 0.3 0.4 0.5 0.6
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 2 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. ordering information part number * package top marking MP2459GJ tsot236 aeq * for tape & reel, add suffix Cz (eg. m2459gjCz); package reference bst gnd fb 12 3 65 4 swin en top view absolute maximum ratings (1) supply voltage v in ........................ ?0.3v to 60v v sw ........................................ ?0.3v to v in +0.3v v bs .................................................. .....v sw + 6v all other pins ................................ ?0. 3v to +6v continuous power dissipation (t a = +25c) (2) tsot236 .......................................... .... 0.568w junction temperature .............................. 150c lead temperature .................................. . 260c storage temperature .............. ?65c to +150c recommended operating conditions (3) supply voltage v in .......................... 4.5v to 55v output voltage v out ............... 0.81v to 0.95v in operating junction temp. ....... ?40c to +125c thermal resistance (4) ja jc tsot236 .............................. 220 ... 110 c/w notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a functi on of the maximum junction temperature t j (max), the junctionto ambient thermal resistance ja , and the ambient temperature t a . the maximum allowable continuous power dissipatio n at any ambient temperature is calculated by p d (max)=(t j (max) t a )/ ja . exceeding the maximum allowable power dissipation will caus e excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown ci rcuitry protects the device from permanent damage. 3) the device function is not guaranteed outside of th e recommended operating conditions. 4) measured on jesd517, 4layer pcb..
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 3 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. electrical characteristics v in = 12v, t a = +25c, unless otherwise noted. parameters symbol condition min typ max units feedback voltage v fb 4.5v v in 55v 0.792 0.812 0.832 v feedback current i fb v fb = 0.85v 0.1 a switchon resistance r ds(on) 1 switch leakage i sw_lkg v en = 0v, v sw = 0v 1 a current limit i lim 1.0 1.25 1.5 a oscillator frequency f sw v fb = 0.6v 380 480 580 khz foldback frequency f sw_f v fb = 0v 150 khz maximum duty cycle d max v fb = 0.6v 90 93.5 % minimum ontime on 100 ns undervoltage lockout threshold, rising v uvlo_r 2.9 3.3 3.7 v undervoltage lockout threshold, falling v uvlo_f 2.65 3.05 3.45 v undervoltage lockout threshold, hysteresis v uvlo_hys 250 mv en threshold, rising v en_r 1.35 v en threshold, falling v en_f 1.17 v en threshold, hysteresis v en_hys 180 mv en input current i en v en = 2v 3.1 a v en = 0v 0.1 supply current (shutdown) i s v en = 0v 0.1 1.0 a supply current (quiescent) i q v en = 2v, v fb = 1v 0.73 0.85 ma thermal shutdown t sd 165 c thermal shutdown hysteresis t sd_hys 20 c
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 4 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. typical characteristics v in =12v, v out =5v, i out =0.5a, l=15h, t a =25c, unless otherwise noted. -80 -60 -40 -20 0 20 40 60 80 100 1000 10000 1000001000000 -180 -120 -60 0 60 120 180 -80 -60 -40 -20 0 20 40 60 80 100 1000 10000 1000001000000 -180 -120 -60 0 60 120 180 0.3 0.5 0.7 0.9 1.1 1.3 5 15 25 35 45 55 65 radiation emi conduction emi 0 10 20 30 40 50 60 70 80 150k 300 8001m 2m 3m 5m 810m 20m 30m en 55022 voltage on m ains q p en 55022 voltage on m ains av 0 5 10 15 20 25 30 35 40 45 50 55 60 30m 5060 80100m 200 300 400500 8001g en 55022 electric field strength 3 m q p
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 5 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. typical performance characteristics v in =12v, v out =5v, l=22h, t a =25c, unless otherwise noted. 750 770 790 810 830 850 400 440 480 520 560 600 -2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 6 16 26 36 46 56 -2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 0.00.10.20.30.40.50.60.70.8 30 40 50 60 70 80 90 100 0.0 0.2 0.4 0.6 0.8 1.0 load current ( a ) load current ( a ) -2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 6 16 26 36 46 56 input voltag ( v )input voltag ( v ) line regulation ( % ) -2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 0.00.10.20.30.40.50.60.70.8 30 40 50 60 70 80 90 100 0.0 0.2 0.4 0.6 0.8 1.0 load current ( a ) load current ( a ) load regulation line regulation i out =0.5a load regulation v out =3.3v efficiency vs. load 0.5 0.8 1.1 1.4 1.7 2.0 -40 -10 20 50 80 110 140 -40 -10 20 50 80 110 140 -40 -10 20 50 80 110 140
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 6 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. typical performance characteristics (continued) v in =12v, v out =5v, l=22h, t a =25c, unless otherwise noted. steady state v in =8v, i out =0.8a steady state i out =0.15a load transient i out =0.2a to 0.7 a steady state v in =6v, v out =3.3v, i out =0.1a steady state v in =60v, v out =3.3v, i out =0.9a v in 10v/div. v sw 10v/div. v ou t 200mv/div. i l 500ma/div. v in 50v/div. v sw 50v/div. v ou t 2v/div. i l 1a/div. v in 5v/div. v sw 5v/div. v ou t 2v/div. i l 200ma/div. v in 5v/div. v sw 5v/div. v ou t 5v/div. i l 500ma/div. v in 10v/div. v sw 10v/div. v ou t 5v/div. i l 1a/div. v in 10v/div. v sw 10v/div. v ou t 200mv/div. i l 500ma/div. load transient v out =3.3v, i out =0.2a to 0.7 a power ramp up v in =60v, i out =0.5a power ramp down v in =60v, i out =0.5a short output i out =0.65a v in 50v/div. v sw 50v/div. v ou t 5v/div. i ou t 500ma/div. v in 50v/div. v sw 50v/div. v ou t 5v/div. v ou t 5v/div. i ou t 500ma/div. v in 10v/div. v sw 10v/div. i l 1a/div.
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 7 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. typical performance characteristics (continued) v in =12v, v out =5v, l=22h, t a =25c, unless otherwise noted. enable oni out =0.5a enable offi out =0.5a short output recoveri out =0.65a v ou t 5v/div. v en 2v/div. v sw 10v/div. i l 500ma/div. v ou t 5v/div. v en 2v/div. v sw 10v/div. i l 500ma/div. v ou t 5v/div. v in 10v/div. v sw 10v/div. i l 1a/div.
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 8 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. pin functions pin # name description 1 bst bootstrap. connect a capacitor between the sw and bs pins to form a floating supply across the power switch driver. this capacitor drives the power switchs gate above the supply voltage. 2 gnd ground. voltage reference for the regulated output voltage. requires special layout considerations. isolate this node from the d1 to c1 ground path to prevent switching curre nt spikes from inducing. 3 fb feedback. sets the output voltage. connect to the t ap of an external resistor divider from the output to gnd. the frequency foldback comparator lowers the oscill ator frequency when the fb voltage is below 250mv to prevent currentlimit run away during a shortcircuit fault. 4 en on/off. pull en above 1.2v to turn the device on. f or automatic enable, connect to v in using a 100k resistor. 5 in supply voltage. the mp2459 operates from a 4.5vto 55v unregulated input. requires c1 to prevent large voltage spikes from appearing at the input. 6 sw switch output.
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 9 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. operation the mp2459 is a current mode buck regulator. that is, the ea output voltage is 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 comparators output is low. the rising edge of the 480khz clk signal sets the rs flipflop. its output turns on m1 thus connecting 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 the 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 flipflop. the output of the error amplifier integrates the voltage difference between the feedback and the 0.81v bandgap reference. the polarity is such that lower than 0.81v fb pin voltage increases the ea output voltage. since the ea output voltage is proportional to the peak inductor current, an increase in its voltage also increases current delivered to the output. figure 1: functional block diagram
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 10 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. application information setting output voltage the external resistor divider sets the output voltage (see the typical application schematic). table 1 lists resistors for common output voltages. the feedback resistor (r1) also sets the feedback loop bandwidth with the internal compensation capacitor (see figure 1). r2 is: 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 use an inductor with a dc current rating at least 25% percent higher than the maximum load current for most applications. for best efficiency, the inductors dc resistance should be less than 200m . refer to table 2 for suggested surfacemount inductors. for most designs, the required inductance value can be derived from the following equation. sw l in out in out f i v ) v v ( v l ? = where i l is the inductor ripple current. choose the inductor ripple current to be 30% of the maximum load current. the maximum inductor peak current is: 2 i i i l load ) max (l + = under lightload conditions (below 100ma), use a larger inductance to improve efficiency. selecting the input capacitor the input capacitor reduces the surge current drawn from the input supply 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 highfrequencyswitching current from passing through the input. use ceramic capacitors with x5r or x7r dielectrics for their low esrs and small temperature coefficients. for most applications, a 4.7f capacitor will sufficient. selecting the output capacitor the output capacitor keeps the output voltage ripple small and ensures feedback loop stability. the output capacitor impedance should be low at the switching frequency. use ceramic capacitors with x5r or x7r dielectrics for their low esr characteristics. for most applications, a 22f ceramic capacitor will sufficient. pcb layout guide pcb layout is very important to stability. please follow these guidelines and use figure 2 as reference. 1) keep the path of switching current short and minimize the loop area formed by the input capacitor, highside mosfet, and schottky diode. 2) keep the connection from the power ground schottky diode sw pin 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 to large copper areas to cool the chip for improved thermal performance and long term reliability. for single layer pcbs, avoid soldering the exposed pad .
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 11 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 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 figure 2: pcb layout external bootstrap diode an external bootstrap diode may enhance regulator efficiency under the following conditions: v out =5v or 3.3v; and high duty cycle: d= in out v v >65% in these cases, add an external bst diode from the output of the voltage regulator to the bst pin, as shown in figure 3. mp2459 figure 3: optional bootstrap diode for enhanced efficiency the recommended external bst diode is in4148, and the bst capacitor is 0.1f1f.
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 mp2459 rev. 1.0 www.monolithicpower.com 12 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. typical application circuit vin in 5 4 2 3 6 1 r60 c3100nf d1dfls160 r3 ns c6 ns fb10805 d2ns 3.3v/0.5 a gnd gnd fb sw bs t en en vou t gnd mp2459 u1
mp2459 C 0.5a, 55v, 480khz, stepdown converter in a tsot236 notice: the information in this document is subject to cha nge without notice. users should warrant and guaran tee that third party intellectual property rights are not infringe d upon when integrating mps products into any appli cation. mps will not assume any legal responsibility for any said applic ations. mp2459 rev. 1.0 www.monolithicpower.com 13 3/4/2013 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibi ted. ? 2013 mps. all rights reserved. package information tsot236 0.30 0.50 se a ting pla ne 0.95 b sc 0.84 0.90 1.00 m a x 0.00 0.10 to p view fr o n t view sid e view r ec o mm en d ed lan d pa tter n 2.80 3.00 1.50 1.70 2.60 3.00 1 3 4 6 0.09 0.20 n o te: 1) a ll d im en sio n s a r e in m illim eters. 2) pa c ka g e len g th d o es n o t in c lu d e m o ld fla sh, pr o tru sio n o r g a te bur r. 3) pa c ka g e w id th d o es n o t inc lu d e inter lea d fla sh o r pr o tr u sio n. 4) lea d co pla na rity (b o tto m o f lea d s a fter fo r m in g ) sh a ll be 0.10 m illim eter s m a x. 5) dr a w in g co n fo r m s to jed ec m o-193, va r ia tio n a b. 6) dr a w in g is no t to sc a le. 7) pin 1 is lo we r left pin w h en rea din g to p m a r k fr o m left to r ig ht, (se e ex a m ple to p m a r k) 0.30 0.50 0 o -8 o 0.25 b sc g a u g e pla n e 2.60 typ 1.20 typ 0.95 b sc 0.60 typ see d eta il "a" aaaa pin 1 see n ote 7 exa m ple to p m a rk

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