View MP2305DS_8838773.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

mp2305 2a, 23v synchronous rectified step-down converter mp2305 rev. 1.83 www.monolithicpower.com 1 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. the future of analog ic technology description the mp2305 is a monolithic synchronous buck regulator. the device integrates 130m ? mosfets that provide 2a continuous load current over a wide operating input voltage of 4.75v to 23v. current mode control provides fast transient response and cycle-by-cycle current limit. an adjustable soft-start prevents inrush current at turn-on. shutdown mode drops the supply current to 1 a. this device, available in an 8-pin soic package, provides a very compact system solution with minimal reliance on external components. evaluation board reference board number dimensions ev2305ds-00a 2.0?x x 1.5?y x 0.5?z features ? 2a output current ? wide 4.75v to 23v operating input range ? integrated 130m ? power mosfet switches ? output adjustable from 0.923v to 20v ? up to 93% efficiency ? programmable soft-start ? stable with low esr ceramic output capacitors ? fixed 340khz frequency ? cycle-by-cycle over current protection ? input under voltage lockout applications ? distributed power systems ? networking systems ? fpga, dsp, asic power supplies ? green electronics/ appliances ? notebook computers all mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps website under products, quality assurance page. ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application c5 10nf mp2305 bs in fb sw ss gnd comp en 1 2 3 5 6 4 8 7 100 95 90 85 80 75 70 65 60 55 50 efficiency (%) 0 1.0 2.0 2.5 1.5 0.5 load current (a) mp2305-ec01 efficiency vs load current v out = 3.3v v out = 2.5v
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 2 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. ordering information part number* package top marking free air temperature (t a ) MP2305DS soic8 MP2305DS -40 c to +85 c * for tape & reel, add suffix ?z (e.g. MP2305DS?z); for rohs compliant packaging, add suffix ?lf (e.g. MP2305DS?lf?z) package reference bs in sw gnd ss en comp fb 1 2 3 4 8 7 6 5 top view mp2305_pd01 absolute maxi mum ratings (1) supply voltage v in .......................?0.3v to +26v switch voltage v sw ............................................. ?1v (-5v for <10ns) to 26.3v (28v for <10ns) boost voltage v bs ..........v sw ? 0.3v to v sw + 6v all other pins .................................?0.3v to +6v continuous power dissipation (t a = +25c) (2) ??????????????????.1.39w junction temperature ...............................150c lead temperature ....................................260c storage temperature ............. ?65c to +150c recommended operating conditions (3) input voltage v in ............................4.75v to 23v output voltage v out .....................0.923v to 20v operating junction temp. (t j ). -40c to +125c thermal resistance (4) ja jc soic8..................................... 90 ...... 45... 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.
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 3 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. electrical characteristics v in = 12v, t a = +25c, unless otherwise noted. parameter symbol condition min typ max units shutdown supply current v en = 0v 1 3.0 a supply current v en = 2.0v; v fb = 1.0v 1.3 1.5 ma feedback voltage v fb 4.75v v in 23v 0.900 0.923 0.946 v feedback overvoltage threshold 1.1 v error amplifier voltage gain (5) a ea 400 v/v error amplifier transconductance g ea i c = 10 a 800 a/v high-side switch on resistance (5) r ds(on)1 130 m ? low-side switch on resistance (5) r ds(on)2 130 m ? high-side switch leakage current v en = 0v, v sw = 0v 10 a upper switch current limit minimum duty cycle 2.4 3.4 5.3 a lower switch current limit from drain to source 1.1 a comp to current sense transconductance g cs 3.5 a/v oscillation frequency f osc1 340 khz short circuit oscillation frequency f osc2 v fb = 0v 100 khz maximum duty cycle d max v fb = 1.0v 90 % minimum on time (5) 220 ns en shutdown threshold voltage v en rising 1.1 1.5 2.0 v en shutdown threshold voltage hysteresis 210 mv en lockout threshold voltage 2.2 2.5 2.7 v en lockout hysterisis 210 mv input under voltage lockout threshold v in rising 3.80 4.10 4.40 v input under voltage lockout threshold hysteresis 210 mv soft-start current v ss = 0v 6 a soft-start period c ss = 0.1 f 15 ms thermal shutdown (5) 160 c note: 5) guaranteed by design, not tested.
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 4 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. pin functions pin # name description 1 bs high-side gate drive boost input. bs supplies the drive for the high-side n-channel mosfet switch. connect a 0.01 f 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 4.75v to 23v power source. by pass 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 c apacitor is required from sw to bs to power the high-side switch. 4 gnd ground. 5 fb feedback input. fb senses the output voltage to regulate that voltage. drive fb with a resistive voltage divider from the output vo ltage. the feedback threshold is 0.923v. see setting the output voltage. 6 comp compensation node. comp is used to compensate the regulation control loop. connect a series rc network from comp to gnd to co mpensate the regulation control loop. in some cases, an additional capacitor from comp to gnd is required. see compensation components. 7 en enable input. en is a digital input that turns the regulator on or off. drive en high to turn on the regulator, drive it low to turn it off. pull up with 100k ? resistor for automatic startup. 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 0.1 f capacitor sets the soft-start period to 15ms. to disable the soft-start feature, leave ss unconnected.
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 5 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. typical performanc e characteristics v in = 12v, v o = 3.3v, l = 10h, c1 = 10f, c2 = 22f, t a = +25c, unless otherwise noted. startup through enable v in = 12v, v out = 3.3v i out = 1a (resistance load) shutdown through enable v in = 12v, v out = 3.3v i out = 1a (resistance load) light load operation medium load operation load transient steady state test v in = 12v, v out = 3.3v i out = 0a, i in = 8.2ma heavy load operation short circuit recovery short circuit protection v en 5v/div. v out 1v/div. v sw 10v/div. i l 1a/div. v en 5v/div. v out 2v/div. v sw 10v/div. i l 1a/div. v in 20mv/div. v out 20mv/div. v sw 10v/div. i l 1a/div. v out 2v/div. i l 2a/div. v out 2v/div. i l 2a/div. v out 200mv/div. i load 1a/div. i l 1a/div. v in, ac 200mv/div. v o, ac 20mv/div. v sw 10v/div. i l 1a/div. v in, ac 200mv/div. v o, ac 20mv/div. v sw 10v/div. i l 1a/div. v in, ac 20mv/div. v o, ac 20mv/div. v sw 10v/div. i l 1a/div. 2a load 1a load no load
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 6 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. operation functional description the mp2305 is a synchronous rectified, current-mode, step-down regulator. it regulates input voltages from 4.75v to 23v down to an output voltage as low as 0.923v, and supplies up to 2a of load current. the mp2305 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 transconductance error amplifier. the voltage at the comp pin is compared to the switch current measured internally to control the output voltage. the converter uses internal n-channel mosfet switches to step-down the input voltage to the regulated output voltage. since the high side mosfet requires a gate voltage greater than the input voltage, a boost capacitor connected between sw and bs is needed to drive the high side gate. the boost capacitor is charged from the internal 5v rail when sw is low. when the mp2305 fb pin exceeds 20% of the nominal regulation voltage of 0.923v, the over voltage comparator is tripped and the comp pin and the ss pin are discharged to gnd, forcing the high-side switch off. lockout comparator internal regulators in en + error amplifier 1.2v ovp ramp clk 0.923v 0.3v current comparator current sense amplifier 1.1v shutdown comparator comp ss fb gnd oscillator 340khz s r q sw bs in 5v ovp in < 4.1v en ok + q + + 1.5v + + 2.5v 7v zener + + -- -- -- -- -- -- -- figure 1?functional block diagram
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 7 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. applications 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: 2r1r 2r vv out fb + = where v fb is the feedback voltage and v out is the output voltage. thus the output voltage is: 2r 2r1r 923.0v out + = r2 can be as high as 100k ? , but a typical value is 10k ? . using the typical value for r2, r1 is determined by: )923.0v(83.101r out ?= (k ? ) for example, for a 3.3v output voltage, r2 is 10k ? , and r1 is 26.1k ? . 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 ls out v v 1 if v l where v out is the output voltage, v in is the input voltage, f s is the 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 lf2 v ii where i load is the load current. the choice of which style inductor to use mainly depends on the price vs. size requirements and any emi requirements. optional schottky diode during the transition between high-side switch and low-side switch, the body diode of the low- side power mosfet conducts the inductor current. the forward voltage of this body diode is high. an optional schottky diode may be paralleled between the sw pin and gnd pin to improve overall efficiency. table 1 lists example schottky diodes and their manufacturers. table 1?diode selection guide part number voltage/current rating vendor b130 30v, 1a diodes, inc. sk13 30v, 1a diodes, inc. mbrs130 30v, 1a international rectifier 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. choose x5r or x7r dielectrics when using ceramic capacitors. 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 1c v v 1 v v ii
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 8 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. the worst-case condition occurs at v in = 2v out , where i c1 = i load /2. 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. 0.1 f, 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 for low esr capacitors can be estimated by: ? ? ? ? ? ? ? ? ? = in out in out s load in v v 1 v v f1c i v where c1 is the input capacitance value. 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: ? ? ? ? ? ? ? ? + ? ? ? ? ? ? ? ? ? = 2cf8 1 r v v 1 lf v v s esr in out s out out where 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 2clf8 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 lf v v ? ? ? ? ? ? ? ? ? = the characteristics of the output capacitor also affect the stability of the regulation system. the mp2305 can be optimized for a wide range of capacitance and esr values. compensation components mp2305 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 ea cs load vdc v v agra = where a vea is the error amplifier voltage gain; g cs is the current sense transconductance and 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 the error amplifier, and the other is due to the output capacitor and the load resistor. these poles are located at: vea ea 1p a3c2 g f = load 2p r2c2 1 f = where g ea is the error amplifier transconductance. the system has one zero of importance, due to the compensation capacitor (c3) and the compensation resistor (r3). this zero is located at: 3r3c2 1 f 1z = 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 r2c2 1 f =
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 9 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. in this case (as shown in figure 2), 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: 3r6c2 1 f 3p = 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 instability. a good rule of thumb is to set the crossover frequency below one-tenth of the switching frequency. to optimize the compensation components, 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 s fb out cs ea c v v gg f1.02c2 v v gg f2c2 3r < = where f c is the desired crossover frequency which is typically below one tenth of the switching frequency. 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 f3r2 4 3c > where r3 is the compensation resistor. 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 switching frequency, or the following relationship is valid: 2 f r2c2 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: 3r r2c 6c esr = external bootstrap diode an external bootstrap diode may enhance the efficiency of the regulator, and it will be a must if the applicable condition is: z v out =5v or 3.3v; and 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 figure 2 mp2305 sw bst c l bst c 5v or 3.3v out external bst diode in4148 + figure 2?add optional external bootstrap diode to enhance efficiency the recommended external bst diode is in4148, and the bst cap is 0.1~1f.
mp2305 ? 2a, 23v synchronous rect ified, step-down converter mp2305 rev. 1.83 www.monolithicpower.com 10 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 mps. all rights reserved. typical application circuit input 4.75v to 23v mp2305 bs in fb sw ss gnd comp en 1 2 3 5 6 4 8 7 figure 3?mp2305 with 3.3v output, 22f/6.3v ceramic output capacitor
mp2305 ? 2a, 23v synchronous rect ified, 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. mp2305 rev. 1.83 www.monolithicpower.com 11 12/24/2013 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2013 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

▲Up To Search▲

Price & Availability of MP2305DS

	To Download MP2305DS Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .