mp2360 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 1 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. the future of analog ic technology description the mp2360 is a monolithic step-down switch mode converter with a built-in internal power mosfet. it achieves 1.8a 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 mp2360 requires a minimum number of readily available standard external components. the mp2360 is available in a 2mm x 2mm qfn8 package. evaluation board reference board number dimensions ev2360dg-00b 1.8?x x 1.6?y x 0.4?z features ? 2.5a peak output current ? 1.8a continuous output current ? 0.3 ? internal power mosfet switch ? stable with low esr output ceramic capacitors ? 0.1a shutdown mode ? fixed 1.4mhz frequency ? thermal shutdown ? cycle-by-cycle over current protection ? wide 4.5v to 24v operating input range ? output adjustable from 0.81v to 15v ? available in 2x2 qfn8 packages applications ? broadband communications equipment ? digital entertainment systems ? distributed power systems ? battery charger ? pre-regulator for linear regulators ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application mp2360 sw fb bst 3 4 6 5 2 7 gnd in en v out 3.3v cb 10nf d1 b230a v in off on 100 90 80 70 60 50 efficiency (%) 0 0.5 1.0 1.5 2.0 load current (a) efficiency vs load current v out = 2.5v v out = 3.3v v in = 12v
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 2 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. package reference part number* package temperature MP2360DG 2x2 qfn8 ?40 c to +85 c * for tape & reel, add suffix ?z (eg. MP2360DG?z) for rohs compliant packaging, add suffix ?lf (eg. MP2360DG?lf?z) absolute maxi mum ratings (1) supply voltage v in ....................................... 26v v sw ....................................... ?0.3v to v in + 0.3v v bs ....................................................... 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) supply voltage v in ........................... 4.5v to 24v output voltage v out ...................... 0.81v to 15v operating temperature .............?40 c to +85 c thermal resistance (3) ja jc 2x2 qfn8 ............................... 80 ...... 16... 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 feedback voltage v fb 4.5v v in 24v 0.790 0.810 0.830 v feedback current i fb v fb = 0.8v 10 na switch on-resistance (4) r ds(on) 0.3 ? switch leakage v en = 0v, v sw = 0v 0 10 a current limit (4) duty cycle = 40% 2.0 2.5 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 87 % minimum on-time (4) t on 100 ns under-voltage lockout threshold rising 2.5 2.8 3.1 v under-voltage lockout threshold hysteresis 150 mv en input low voltage 0.4 v en input high voltage 1.2 v v en = 2v 2.1 en input current v en = 0v 0.01 a supply current (shutdown) v en = 0v 0.1 1.0 a supply current (quiescent) v en = 2v, v fb = 1v 0.8 1.0 ma thermal shutdown (4) 150 c note: 4) guaranteed by design. qfn8 (2mm x 2mm) top view nc sw in en 1 2 3 4 nc bst gnd fb 8 7 6 5
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 3 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. pin functions pin # name description 1, 8 nc no connect. 2 sw switch output. 3 in supply voltage. the mp2360 operates from a +4.5v to +24v unregulated input. c1 is needed to prevent large voltage spikes from appearing at the input. 4 en on/off control input. pull above 1.2v to turn the device on. 5 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. 6 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. 7 bst bootstrap. this capacitor is needed to drive t he 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. typical performanc e characteristics v in = 12v, v out = 3.3v, t a = +25 c, unless otherwise noted. efficiency vs load currents current limit vs duty cycle v out = 5v v out = 2.5v v out = 12v v in = 24v 100 90 80 70 60 50 40 load current (a) efficiency (%) current limit (a) 100 90 80 70 60 50 40 efficiency (%) 0 1.0 0.5 1.5 2.0 2.5 load current (a) efficiency vs load current v out = 5v v out = 2.5v v in = 12v 0 1.0 0.5 1.5 2.0 2.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 duty cycle (%) 040 20 60 80 100
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 4 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. typical performanc e characteristics (continued) v in = 12v, v out = 3.3v, t a = +25 c, unless otherwise noted. v sw 10v/div. v en 5v/div. v out 2v/div. i l 2a/div. start-up through enable v in = 12v, v out = 3.3v, i out = 2a resistive load v out 2v/div. v sw 10v/div. v en 5v/div. start-up through enable v in = 12v, v out = 3.3v, no load v out 2v/div. v sw 10v/div. v en 5v/div. i l 2a/div. shut-down through enable v in = 12v, v out = 3.3v, i out = 2a resistive load short circuit entry v in = 12v, v out = 3.3v i l 2a/div. v out 2v/div. i l 2a/div. v sw 10v/div. v en 5v/div. v out 2v/div. i l 2a/div. shut-down through enable v in = 12v, v out = 3.3v, no load short circuit recovery v in = 12v, v out = 3.3v v out 2v/div. i l 2a/div. 400ns/div. steady state test v in = 12v, v out = 3.3v, i out = 0.5a v out 20mv/div. v sw 10v/div. i l 500ma/div. v out ac coupled 200mv/div. i l 1a/div. i load 1a/div. load transient test v in = 12v, v out = 3.3v
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 5 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. operation the mp2360 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 comparator?s output is low. the rising edge of the 1.4 mhz clk 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 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 the 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 0.81v 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 also increases current delivered to the output. in en fb gnd sw bst regulator oscillator 1.4mhz driver current sense amplifier error amplifier current limit comparator pwm comparator d x20 m1 regulator reference ea -- + -- + -- + s r r q -- + 27pf 1pf figure 1?functional block diagram
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 6 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. application information setting 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 1 h to 10 h 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?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 of approximately 30% higher than the maximum load current if the maximum load current is 1.8a. the maximum inductor peak current is calculated from: 2 i i i l load ) max ( l ? + = under light load conditions below 100ma, a larger inductance is recommended for improved efficiency. see table 2 for suggested inductors. selecting the input capacitor the input capacitor 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 10 f capacitor is sufficient. selecting the output capacitor the output capacitor 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. for most applications, a 22 f ceramic capacitor will be sufficient. 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.
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 7 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. top layer bottom layer 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 mp2360 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 0.1~1 f. table 2?suggested surface mount inductors manufacturer part number inductance(h) max dcr( ? ) current rating (a) dimensions l x w x h (mm 3 ) wurth electronics 7447785004 4. 7 0.060 2.5 5.9 x 6.2 x 3.3 toko a916cy-4r7m 4.7 0.026 2.5 6.2 x 6.3 x 3.5 coiltronics dr73-4r7 4.7 0.03 3 6.0 x 7.6 x 3.5
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter mp2360 rev. 0.91 www.monolithicpower.com 8 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. typical application circuit v in v out 3.3v c4 10nf d1 b230a mp2360 fb sw bst 5 6 2 7 4 3 gnd en in off on figure 4?1.4mhz, 3.3v output step-down converter
mp2360 ? 1.8a, 24v, 1.4mhz step-down converter 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. mp2360 rev. 0.91 www.monolithicpower.com 9 5/19/2008 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2008 mps. all rights reserved. package information 2mm x 2mm qfn8 top view 1 8 54 bottom view 1.90 2.10 0.45 0.65 1.90 2.10 1.05 1.25 0.50 bsc 0.18 0.30 pin 1 id marking 0.60 0.50 0.25 recommended land pattern 1.90 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) drawing conforms to jedec mo-229, variation vccd-3. 5) drawing is not to scale. pin 1 id see detail a 0.70 pin 1 id option a r0.20 typ. pin 1 id option b r0.20 typ. detail a 0.25 0.45 pin 1 id index area side view 0.00 0.05 0.80 1.00 0.20 ref 1.20
|
