mp3213 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 1 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. the future of analog ic technology description the mp3213 is a current mode step-up converter with a 3.5a, 0.18 ? internal switch to provide a highly efficient regulator with fast response. the mp3213 operates at 700khz or 1.3mhz allowing for easy filtering and low noise. an external compensation pin gives the user flexibility in setting loop dynamics, which allows the use of small, low-esr ceramic output capacitors. soft-start results in small inrush current and can be programmed with an external capacitor. the mp3213 operates from an input voltage as low as 2.5v and can generate 12v at up to 500ma from a 5v supply. the mp3213 includes under-voltage lockout, current limiting and thermal overload protection to prevent damage in the event of an output overload. the mp3213 is available in a low profile 8-pin msop package with exposed pad. evaluation board reference board number dimensions EV3213DH-00A 2.1?x x 2.1?y x 0.5?z features ? 3.5a, 0.18 ? , 25v power mosfet ? uses tiny capacitors and inductors ? pin selectable 700khz or 1.3mhz fixed switching frequency ? programmable soft-start ? operates with input voltage as low as 2.5v and output voltage as high as 22v ? 12v at 500ma from 5v input ? uvlo, thermal shutdown ? internal current limit ? available in an 8-pin msop package with exposed pad applications ? lcd displays ? portable applications ? handheld computers and pdas ? digital still and video cameras ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application v in 5v v out 12v mp3213 sw in fb comp ss gnd en fsel 65 2 1 4 8 3 7 off on d1 c4 10nf c3 2.2nf efficiency vs load current 100 95 90 85 80 75 70 65 60 55 50 efficiency (%) load current (ma) 1 10 100 1000 v in = 5v v out = 12v
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 2 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. package reference comp fb en gnd 1 2 3 4 8 7 6 5 ss fsel in sw top view part number* package temperature mp3213dh msop8 (exposed pad) ?40 c to +85 c * for tape & reel, add suffix ?z (eg. mp3213dh?z) for rohs compliant packaging, add suffix ?lf (eg. mp3213dh?lf?z) absolute maxi mum ratings (1) sw ............................................... ?0.5v to +25v in ............................................... ?0.5v to +25v all other pins.............................. ?0.3v to +6.5v junction temperature...............................150 c lead temperature ....................................260 c storage temperature ..............?65 c to +150 c recommended operating conditions (2) supply voltage v in ........................... 2.5v to 22v output voltage v out ........................... 3v to 22v operating temperature .............?40 c to +85 c thermal resistance ja jc msop8 ................................... 80 ...... 12... c/w notes: 1) exceeding these ratings may damage the device. 2) the device is not guaranteed to function outside of its operating conditions. electrical characteristics v in = v en = 5v, t a = +25 c, unless otherwise noted. parameter symbol condition min typ max units operating input voltage v in 2.5 22 v undervoltage lockout v in rising 2.15 2.45 v undervoltage lockout hysteresis 100 mv supply current (shutdown) v en = 0v 0.1 1 a supply current (quiescent) v fb = 1.35v 700 900 a v fsel = v in 1.1 1.3 1.5 mhz switching frequency f sw v fsel = gnd 560 700 840 khz fsel high threshold v fsel rising 1.5 v fsel low threshold 0.5 v v fb = 0v, v fsel = v in 85 90 % maximum duty cycle v fb = 0v, v fsel = gnd 92 95 en high threshold v en rising 1.5 v en low threshold 0.5 v en input bias current v en = 0v, 5v 1 a soft-start current 6 a fb voltage 1.225 1.25 1.275 v fb input bias current ?200 ?100 na error amp voltage gain a vea 1000 v/v error amp transconductance g ea 350 mho error amp output current 35 a sw on-resistance (3) r on 0.18 ? sw current limit (3) duty cycle = 0% 3.5 a sw current limit (3) duty cycle = 50% 2.7 a sw leakage v sw = 20v 1 a thermal shutdown (3) 160 c note: 3) guaranteed by design.
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 3 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. typical performanc e characteristics circuit on front page, v in = 5v, v out = 12v, t a = +25 c, c2 = 4.7f, c4 = 10nf, unless otherwise noted. v in = 3.3v v out = 12v -45 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 current limit (a) 0 10 20 30 40 50 60 70 80 90 duty cycle (%) current limit vs duty cycle 1.28 1.26 1.24 1.22 1.20 1.18 1.16 1.14 frequency (mhz) temperature ( c) frequency (1.3mhz) vs temperature 690 680 670 660 650 640 630 620 frequency (khz) temperature ( c) frequency (700khz) vs temperature 1.259 1.258 1.257 1.256 1.255 1.254 1.253 1.252 1.251 1.250 feedback voltage (v) temperature ( c) feedback voltage vs temperature 690 680 670 660 650 640 630 620 -45 -25 0 25 45 65 85 105125145 -25 0 25 45 65 85 105125145 -45 -25 0 25 45 65 85 105125145 temperature ( c) quiescent current vs temperature -45 -25 0 25 45 65 85 105125145 efficiency vs load current 95 90 85 80 75 70 65 60 55 50 efficiency (%) 1 10 100 1000 load current (ma) efficiency vs load current 100 95 90 85 80 75 70 65 60 55 50 efficiency (%) load current (ma) 1 10 100 1000 v in = 5v v out = 18v v in = 3.3v v out = 8v 100 95 90 85 80 75 70 65 60 55 50 efficiency (%) 1 10 100 1000 load current (ma) efficiency vs load current efficiency vs load current 100 95 90 85 80 75 70 65 60 55 50 efficiency (%) load current (ma) 1 10 100 1000 v in = 5v v out = 12v
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 4 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. typical performanc e characteristics (continued) circuit on front page, v in = 5v, v out = 12v, t a = +25 c, c2 = 4.7f, c4 = 10nf, unless otherwise noted. v sw 5v/div. i inductor 0.5a/div. 400ns/div. v sw 5v/div. i inductor 0.5a/div. v out ac coupled 0.2v/div. i out 0.2a/div. v out ac coupled 0.2v/div. i out 0.2a/div. v en 2v/div. v out 5v/div. i inductor 0.5a/div. v en 2v/div. v out 5v/div. i inductor 0.5a/div.
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 5 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. pin functions pin # name description 1 comp compensation pin. connect a capacitor and resistor in series to ground for loop stability. 2 fb feedback input. reference voltage is 1.25v. connect a resistor divider to this pin. 3 en regulator on/off control input. a high input at en turns on the converter, and a low input turns it off. when not used, connect en to the input source (through a 100k ? pull-up resistor if v in > 6v) for automatic startup. en cannot be left floating. 4 gnd ground. the exposed pad is connected to gnd. 5 sw power switch output. sw is the drain of t he internal mosfet switch. connect the power inductor and output rectifier to sw . sw can swing between gnd and 25v. 6 in input supply pin. in must be locally bypassed. 7 fsel frequency select pin. tie to in (through a 100k ? resistor if v in > 6v) for 1.3mhz operation or to gnd for 700khz operation. 8 ss soft-start control pin. connect a soft-start capaci tor to this pin. the soft-start capacitor is charged with a constant current of 6a. leave ss disconnected if the soft-start is not used. operation the mp3213 uses a constant frequency, peak current mode boost regulation architecture to regulate the feedback voltage. the operation of the mp3213 can be understood by referring to the block diagram of figure 1. pwm control logic current sense amp oscillator internal regulator and enable circuitry -- + gm + -- gnd fb comp ss 1.25v sw in -- + fsel en figure 1?functional block diagram
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 6 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. at the beginning of each cycle, the n-channel mosfet switch is turned on, forcing the inductor current to rise. the current at the source of the switch is internally measured and converted to a voltage by the current sense amplifier. that voltage is compared to the error voltage at comp. the voltage at the output of the error amplifier is an amplified version of the difference between the 1.25v reference voltage and the feedback voltage. when these two voltages are equal, the pwm comparator turns off the switch forcing the inductor current to the output capacitor through the external rectifier. this causes the inductor current to decrease. the peak inductor current is controlled by the voltage at comp, which in turn is controlled by the output voltage. thus the output voltage is regulated by the inductor current to satisfy the load. the use of current mode regulation improves transient response and control loop stability. application information components referenced below apply to typical application circuit on page 1. selecting the soft-start capacitor the mp3213 includes a soft-start timer that limits the voltage at comp during startup to prevent excessive current at the input. this prevents fault tripping of the input voltage at startup due to input current overshoot. when power is applied to the mp3213, and enable is asserted, a 6a internal current source charges the external capacitor at ss. as the ss capacitor is charged, the voltage at ss rises. the mp3213 internally clamps the voltage at comp to 700mv above the voltage at ss. the soft-start ends when the voltage at ss reaches 0.45v. this limits the inductor current at startup, forcing the input current to rise slowly to the current required to regulate the output voltage. the soft-start period is determined by the equation: ss ss c 5 7 t = where c ss (in nf) is the soft-start capacitor from ss to gnd, and t ss (in s) is the soft-start period. determine the capacitor required for a given soft-start period by the equation: ss ss t 0133 . 0 c = setting the output voltage set the output voltage by selecting the resistive voltage divider ratio. use 10k ? for the low-side resistor r2 of the voltage divider. determine the high-side resistor r1 by the equation: fb fb out v ) v v ( 2 r 1 r ? = where v out is the output voltage. for r2 = 10k ? and v fb = 1.25v, then r1 (k ? ) = 8k ? (v out ? 1.25v). selecting the input capacitor an input capacitor (c1) is required to supply the ac ripple current to the inductor, while limiting noise at the input source. a low esr capacitor is required to keep the noise at the ic to a minimum. ceramic capacitors are preferred, but tantalum or low-esr electrolytic capacitors may also suffice. use an input capacitor value greater than 4.7f. the capacitor can be electrolytic, tantalum or ceramic. however since it absorbs the input switching current it requires an adequate ripple current rating. use a capacitor with rms current rating greater than the inductor ripple current (see selecting the inductor to determine the inductor ripple current). to ensure stable operation, place the input capacitor as close to the ic as possible. alternately a smaller high quality ceramic 0.1f capacitor may be placed closer to the ic with the larger capacitor placed further away. if using this technique, the larger capacitor can be a tantalum or electrolytic type. all ceramic capacitors should be placed close to the mp3213.
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 7 5/12/2006 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. selecting the output capacitor the output capacitor is required to maintain the dc output voltage. low esr capacitors are preferred to keep the output voltage ripple to a minimum. the characteristic of the output capacitor also affects the stability of the regulation control system. ceramic, tantalum, or low esr electrolytic capacitors are recommended. in the case of ceramic capacitors, the impedance of the capacitor at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the esr. the output voltage ripple is estimated to be: sw load out in ripple f 2 c i v v - 1 v ? ? ? ? ? ? ? ? where v ripple is the output ripple voltage, v in and v out are the dc input and output voltages respectively, i load is the load current, f sw is the switching frequency, and c2 is the capacitance of the output capacitor. in the case of tantalum or low-esr electrolytic capacitors, the esr dominates the impedance at the switching frequency, and so the output ripple is calculated as: in out esr load sw load out in ripple v v r i f 2 c i ) v v 1 ( v + ? where r esr is the equivalent series resistance of the output capacitors. choose an output capacitor to satisfy the output ripple and load transient requirements of the design. a 4.7f-22f ceramic capacitor is suitable for most applications. selecting the inductor the inductor is required to force the higher output voltage while being driven by the input voltage. a larger value inductor results in less ripple current that results in lower peak inductor current, reducing stress on the internal n-channel . switch. however, the larger value inductor has a larger physical size, higher series resistance, and/or lower saturation current. a 4.7 h inductor is recommended for most 1.3mhz applications and a 10 h inductor is recommended for most 700khz applications. however, a more exact inductance value can be calculated. a good rule of thumb is to allow the peak-to-peak ripple current to be approximately 30-50% of the maximum input current. make sure that the peak inductor current is below 75% of the current limit at the operating duty cycle to prevent loss of regulation due to the current limit. also make sure that the inductor does not saturate under the worst-case load transient and startup conditions. calculate the required inductance value by the equation: i f v ) v - (v v l sw out in out in ? = = in ) max ( load out ) max ( in v i v i ( ) ) max ( in i % 50 % 30 i ? = ? where i load(max) is the maximum load current, ? i is the peak-to-peak inductor ripple current, and is efficiency. selecting the diode the output rectifier diode supplies current to the inductor when the intern al mosfet is off. to reduce losses due to diode forward voltage and recovery time, use a schottky diode with the mp3213. the diode should be rated for a reverse voltage equal to or greater than the output voltage used. the average current rating must be greater than the maximum load current expected, and the peak current rating must be greater than the peak inductor current.
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 8 5/12/2006 mps proprietary information. unauth orized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. compensation the output of the transconductance error amplifier (comp) is used to compensate the regulation control system . the system uses two poles and one zero to stabilize the control loop. the poles are f p1 set by the output capacitor c2 and load resistance and f p2 set by the compensation capacitor c3. the zero f z1 is set by the compensation capacitor c3 and the compensation resistor r3. these are determined by the equations: load 1 p r c2 1 f = vea ea 2 p a c3 2 g f = r3 c3 2 1 f 1 z = where r load is the load resistance, g ea is the error amplifier transconductance, and a vea is the error amplifier voltage gain. the dc loop gain is: 2 load out fb in vea vdc v v r v a 5 . 1 a = where v fb is the feedback regulation threshold. there is also a right-half-plane zero (f rhpz ) that exists in continuous conduction mode (inductor current does not drop to zero on each cycle) step-up converters. the frequency of the right half plane zero is: 2 2 out load in rhpz v l 2 r v f = table 1 lists generally recommended compensation components for different input voltage, output voltage and capacitance of most frequently used output ceramic capacitors. ceramic capacitors have extremely low esr, therefore the second compensation capacitor (from comp to gnd) is not required. table 1?component selection v in (v) v out (v) c2 (f) r3 (k ? ) c3 (nf) 3.3 8 4.7 10 2.2 3.3 8 10 10 2.2 3.3 8 22 10 2.2 3.3 12 4.7 15 1 3.3 12 10 15 1 3.3 12 22 15 2.2 3.3 18 4.7 20 1 3.3 18 10 20 1 3.3 18 22 30 2.2 5 8 4.7 10 4.7 5 8 10 10 4.7 5 8 22 15 1 5 12 4.7 15 2.2 5 12 10 15 2.2 5 12 22 20 1 5 18 4.7 20 1 5 18 10 20 1 5 18 22 30 1 12 15 4.7 10 2.2 12 15 10 10 2.2 12 15 22 15 1 12 18 4.7 5.1 2.2 12 18 10 5.1 2.2 12 18 22 15 1 for faster control loop and better transient response, set the capacitor c3 to the recommended value in table 1. then slowly increase the resistor r3 and check the load step response on a bench to make sure the ringing and overshoot on the output voltage at the edge of the load steps is minimal. finally, the compensation needs to be checked by calculating the dc loop gain and the crossover frequency. the crossover frequency where the loop gain drops to 0db or a gain of 1 can be obtained visually by placing a ?20db/decade slope at each pole, and a +20db/decade slope at each zero. the crossover frequency should be at least one decade below the frequency of the right-half-plane zero at maximum output load current to obtain high enough phase margin for stability.
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch mp3213 rev. 1.1 www.monolithicpower.com 9 5/12/2006 mps proprietary information. unauth orized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. layout consideration high frequency switching regulators require very careful layout for stable operation and low noise. all components must be placed as close to the ic as possible. keep the path between the sw pin, output diode, output capacitor and gnd pin extremely short for minimal noise and ringing. the input capacitor must be placed close to the in pin for best decoupling. all feedback components must be kept close to the fb pin to prevent noise injection on the fb pin trace. the ground return of the input and output capacitors should be tied close to the gnd pin. see the mp3213 demo board layout for reference. typical application circuit v in 5v v out 12v mp3213 sw in fb comp ss gnd en fsel 5 2 1 4 8 3 7 6 off on d1 c4 10nf c3 2.2nf figure 2?typical application circuit
mp3213 ? 700khz/1.3mhz boost converter with a 3.5a switch notice: the information in this document is subject to change wi thout notice. please contact mps 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. mp3213 rev. 1.1 www.monolithicpower.com 10 5/12/2006 mps proprietary information. unauth orized photocopy and duplication prohibited. ? 2006 mps. all rights reserved. package information msop8
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