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MP2493 2a, 36v, low emi step-down converter with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 1 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. the future of analog ic technology description the MP2493 is a monolithic step-down switch mode converter with a programmable output current limit. it achieves 2a continuous output current over a wide input supply range with excellent load and line regulation. the maximum output current can be programmed by sensing current through the inductor dc resistance (dcr) or an accurate sense resistor. fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. the MP2493 requires a minimum number of readily available standard external components. the MP2493 is available in 8-pin soic, and 8- pin soice packages. features ? wide 4.5v to 36v operating input range ? programmable up to 2a output current ? output adjustable from 0.8v to 15v ? programmable output current limit without power loss ? 0.25 ? internal power mosfet switch ? stable with low esr output ceramic capacitors ? up to 95% efficiency ? fixed 130khz frequency with low emi ? thermal shutdown ? cycle-by-cycle over current protection ? available in 8-pin soic and 8-pin soic8e packages applications ? usb power supplies ? automotive cigarette lighter adapters ? power supply for linear chargers ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application c9 0.1uf c6 47nf l1 33uh dr1040-330-r r6 4.02k r9 20k r3 4.7k r8 0 u1 r7 200k c11 0.1uf 5v@2a r2 115k 1% c7 150pf r1 604k 1% r5 0 r4 1k d2 ns d1 3a/40v vin bst isn isp ss sw gnd fb tp1 sw tp2 1 4 2 3 8 6 5 7 5v 6v - 36v vin gnd vou t gnd MP2493 c10 4.7nf c5 0.1uf + + efficiency v out =5v output current (a) efficiency (%) 60 68 76 84 92 100 0 0.4 0.8 1.2 1.6 2 v in =12v
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 2 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. ordering information part number package top marking free air temperature (t a ) MP2493ds * soic8 MP2493ds ?40 c to +85 c MP2493dn ** soic8e MP2493dn ?40 c to +85 c * for tape & reel, add suffix ?z (e.g. MP2493ds?z); for rohs, compliant packaging, add suffix ?lf(e.g. MP2493ds?lf?z) ** for tape & reel, add suffix ?z (e.g. MP2493dn?z); for rohs, compliant packaging, add suffix ?lf(e.g. MP2493dn?lf?z) package reference vin gnd fb ss sw bst isp isn 1 2 3 4 8 7 6 5 top view vin gnd fb ss sw bst isp isn 1 2 3 4 8 7 6 5 top view exposed pad on backside connect to gnd soic8 soic8e absolute maxi mum ratings (1) supply voltage v in ....................................... 40v v sw ....................................... ?0.3v to v in + 0.3v v bst ................................................... v sw + 6.5v v isn, v isp ................................................0v to15v all other pins ..............................?0.3v to +6.5v continuous power dissipation (t a = +25c) (2) soic8???????????????...1.4w soic8e??????????????....2.5w 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 36v output voltage v out (v in >16.5v) .....0.8v to 15v output voltage v out (v in <=16.5v) ...................... ........................................0.8v to (v in ?1.5) v operating junction temperature (t j ) ................................................ ?40 c to +125 c thermal resistance (4) ja jc soic8 .....................................90 ...... 45 ... 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 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.
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 3 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 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 36v 0.78 0.8 0.82 v feedback bias current i bias(fb) v fb = 0.8v 10 na switch on resistance r ds(on) 0.25 ? switch leakage v en = 0v, v sw = 0v 0.1 10 a current limit (5) peak current limit 2.5 3.0 3.5 a oscillator frequency f sw v fb = 0.6v 100 130 160 khz switching frequency v fb = 0v 35 khz boot-strap voltage v bst - v sw 4.5 v minimum on time (5) t on v fb = 1v 100 ns sw rising edge (5) trise v in =12v, v o =5v, i o =1.5a 50 ns sw falling edge (5) tfall v in =12v, v o =5v, i o =1.5a 50 ns under voltage lockout threshold rising 3.0 3.3 3.6 v under voltage lockout threshold hysteresis 150 mv en input low voltage (6) 0.4 v en input high voltage (6) 1.8 v en input bias current (6) v en = 0-6v ?10 ?2 10 a supply current (shutdown) v en = 0v 4 10 a supply current (quiescent) v en = 2v, v fb = 1v 500 800 a thermal shutdown (5) 150 c current sense voltage v isp ?v isn v isp , v isn 0.4?15v 90 100 110 mv input bias current (isn, isp) i bias (isn,isp) v isp , v isn 0.4?15v ?1 0.1 +1 ua note: 5) guaranteed by design 6) enable function is only available for the MP2493dq
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 4 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. pin functions pin# name description 1 vin supply voltage. the MP2493 operates from a +4.5v to +36v unregulated input. c in is needed to prevent large voltage spikes from appearing at the input. put c in as close to the ic as possible. it is the drain of the internal power device and power supply for the whole chip. 2 gnd exposed pad ground. this pin is the voltage refere nce for the regulated output voltage. for this reason care must be taken in its layout. this node should be placed outside of the d1 to c in ground path to prevent switching current spikes from inducing voltage noise into the part. exposed pad must be connected with ground pin in soic8e package. 3 fb feedback. an external resistor divider from the output to gnd, tapped to the fb pin sets the output voltage. to prev ent current limit run away during a short circuit fault condition the freque ncy-fold-back comparator lowers the oscillator frequency when the fb voltage is below 250mv. 4 ss connect to an external capacitor used for soft-start and compensation for current limiting loop. 5 isn negative current sense input for load current limiting. 6 isp positive current sense 7 bst bootstrap. this capacitor is needed to drive the power switch?s gate above the supply voltage. it is connected between sw and bst pins to form a floating supply across the power switch driver. an on-chip regulator is used to charge up the external boot-strap capac itor. if the on-chip regulator is not strong enough, one optional diode can be connected from in or out to charge the external boot-strap capacitor. 8 sw switch output. it is the source of power device.
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 5 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical performanc e characteristics c1=68uf, c2=10uf, c3=100uf, c4=22uf, c8=c7=0.1uf, l=33uh, t a =25oc, unless otherwise noted. load regulation load regulation v out =5v load regulation v out =3.3v output current (a) v out =1.8v 60 68 76 84 92 100 0 0.4 0.8 1.2 1.6 2 output current ( a ) efficiency ( % ) v in =18v v in =12v v in =8v efficiency vs. load current v out =5v efficiency vs . load current v out =3.3v efficiency vs . load current v out =1.8v 40 50 60 70 80 90 100 0 0.4 0.8 1.2 1.6 2 o utput current ( a ) output current ( a ) efficiency ( % ) efficiency ( % ) v in =8v v in =12v v in =18v v in =24v 40 50 60 70 80 90 100 0 0.4 0.8 1.2 1.6 2 v in =12v v in =8v v in =18v v in =24v 4.96 4.98 5.00 5.02 5.04 5.06 0 0.4 0.8 1.2 1.6 2 o utput current ( a ) o utput current ( a ) output voltage ( v ) v in =12v v in =8v v in =18v 3.26 3.27 3.28 3.29 3.30 3.31 0 0.4 0.8 1.2 1.6 2 output voltage ( v ) output voltage ( v ) v in =12v v in =18v v in =8v 1.785 1.790 1.795 1.800 1.805 1.810 0 0.4 0.8 1.2 1.6 2 v in =8v v in =18v v in =12v 2.6 2.8 3.0 3.2 3.4 3.6 30 39 48 57 66 75 duty cycle ( % ) i l current (a) maximum i out vs. duty cycle v out =5v -60 -40 -20 0 20 40 60 100 1000 10000 100000 frequency ( hz ) gain ( db ) -180 -120 -60 0 60 120 180 phase ( o ) loop gain with phase margin 0.4 1.4 2.4 3.4 4.4 5.4 0.0 0.5 1.0 1.5 2.0 2.5 load current ( a ) v out (v) current regulation v in =12v
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 6 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical performanc e characteristics (continued) c1=68uf, c2=10uf, c3=100uf, c4=22uf, c8=c7=0.1uf, l=33uh, t a =25oc, unless otherwise noted. v in 10v/div. v sw 10v/div. v out 10mv/div. v out 5v/div. v out 5v/div. i l 2a/div. 10us/div. v in 10v/div. v sw 10v/div. i l 2a/div. i l 2a/div. 4 s/div. v in 10v/div. v sw 10v/div. 10 s/div. v in 10v/div. v sw 10v/div. v out 20mv/div. i l 2a/div. 10us/div. vfb vs. temperature v in 20v/div. v sw 20v/div. v out 20mv/div. v out 2v/div. v out 2v/div. i l 2a/div. i l 2a/div. i l 2a/div. 10us/div. 10 s/div. short circuit 4 s/div. short circuit recovery 30 0 5 10 15 20 25 30 35 40 45 50 55 60 60 100 200 400 1000 frequency (mhz) noise level (dbv/m) 0.790 0.792 0.794 0.796 0.798 0.800 -50 -20 10 40 70 100 tempertaure ( o c) v fb voltage(v)
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 7 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. operation main control loop the MP2493 is a current mode buck regulator. that is, the error amplifier (ea) output voltage is proportional to the peak inductor current. at the beginning of a cycle, the integrated high side power switch m1 (fig.1) 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 130khz clock signal sets the rs flip-flop. 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 added to current sense amplifier output and compared to the error amplifier output by the pwm comparator. when the current sense amplifier plus slope compensation signal exceeds the ea output voltage, the rs flip-flop is reset and the MP2493 reverts to its initial m1 off state. if the current sense amplifier plus slope compensation signal does not exceed the comp voltage, 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. an external schottky diode (d1) carries the inductor current when m1 is off. load current limiting loop the output current information is sensed via the isp and isn pins. the regulation threshold is set at 100mv. if v sense , the difference of v isp and v isn , is less than 100mv, the output voltage of the power supply will be set by the fb pin. if v sense reaches 100mv, the current limit loop will pull down ss and regulate the output at a constant current determined by the external sense resistor. the external capacitor on ss pin is the dominant compensation capacitor for load current regulation loop. the capacitor has normal value of 100nf, which will put the bandwidth of load current regulation loop to be less than 1 khz. when v sense is higher than 100mv, ss will not drop down to the final regulation level immediately. it will cause the load current to be higher than the programmed level for a short period. a fast comparator is added to shut down power switch when the average load current is higher than 120% of the programmed current limit level. an inductor dc resistance (dcr) or accurate sense resistor can be used for load current sensing.
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 8 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. isp isn 4.0v ss vin ss fb sw x13.5 bst regulator 100mv driver pwm comparator current limit comparator rsen 25m m1 1pf 3398k 33pf er gnd enable regulator en oscillator 150khz reference current sense amplifier ramp generator por regulator s r r q d + + -- + -- -- + + -- + -- figure 1?functional block diagram
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 9 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 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 300k ? 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 ? ) 1.8 604 (1%) 475 (1%) 2.5 604 (1%) 280 (1%) 3.3 604 (1%) 191 (1%) 5 604 (1%) 115 (1%) selecting the inductor a 1h to 15h inductor with a dc current rating of at least 25% percent higher than the maximum load current is recommended for most applications. for highest efficiency, the inductor dc resistance should be less than 200m ? . for most designs, the 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 inductor current ripple to be approximately 30% of the maximum load current,. 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 improved efficiency. selecting the input capacitor the input capacitor reduces the surge current drawn from the input and also 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 pass to 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 10f capacitor is sufficient. selecting the output capacitor the output capacitor keeps output voltage small and ensures regulation loop stability. the output capacitor impedance should be low at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended. selecting soft start capacitor MP2493 has external soft start function. this external function reduces the start up current surge into the output capacitor. this allows the gradual built up of output voltage to its final set value. the soft start time is decided by following equation; ss ss 6 c t0.7 39 10 ? = pc board 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. isn, isp are sensitive nodes. put the sensing components as close to the device as possible and keep them away from the high current and noisy paths such as gnd, in, sw). match the trace and components on isn, isp paths as good as possible.
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 10 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. output current sensing the output current can be sensed through the dc resistance (dcr) of the inductor, as shown in figure 2a. in figure 2a, the output current limit is set as: ab out b rr 100mv i dcr r + = where dcr is the dc resistance of the inductor winding. in figure 2a, it is desirable to keep ab s ab rr l1 c r r dcr ? = + if, there is no rb: = as l1 rc dcr for more accurate sensing, use a more accurate sense resistor, as in figure 2b, where the output current limit is set as: out sense 100mv i r = figure 2?current sensing methods
MP2493 ? 2a, 36v, low emi step-down with programmable output current limit MP2493 rev. 0.9 www.monolithicpower.com 11 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. package information soic8 0.016(0.41) 0.050(1.27) 0 o -8 o detail "a" 0.010(0.25) 0.020(0.50) x 45 o see detail "a" 0.0075(0.19) 0.0098(0.25) 0.150(3.80) 0.157(4.00) pin 1 id 0.050(1.27) bsc 0.013(0.33) 0.020(0.51) seating plane 0.004(0.10) 0.010(0.25) 0.189(4.80) 0.197(5.00) 0.053(1.35) 0.069(1.75) top view front view 0.228(5.80) 0.244(6.20) side view 14 85 recommended land pattern 0.213(5.40) 0.063(1.60) 0.050(1.27) 0.024(0.61) note: 1) control dimension is in inches. dimension in bracket is in millimeters. 2) package length does not include mold flash, protrusions or gate burrs. 3) package width does not include interlead flash or protrusions. 4) lead coplanarity (bottom of leads after forming) shall be 0.004" inches max. 5) drawing conforms to jedec ms-012, variation aa. 6) drawing is not to scale. 0.010(0.25) bsc gauge plane
MP2493 ? 2a, 36v, 130khz step-down with programmable output current limit 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. MP2493 rev. 0.9 www.monolithicpower.com 12 4/23/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. soic8e

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