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| MP3421 5.5a, 600khz high-efficiency, synchronous step-up converter with tr ue output disconnect in a 2mmx2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 1 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. the future of analog ic technology description the MP3421 is a high-efficiency, synchronous, current?mode, step-up converter with true output disconnect. the MP3421 starts up from low input voltage (as low as 1.9v) while providing in-rush current limiting and output short-circuit protection. the integrated, p-channel synchronous rectifier improves efficiency and eliminates the need for an external schottky diode; the p-channel disconnects the output load from the input during shutdown. the MP3421 has 600khz switching frequency, which accommodates small external components. in addition, its internal compensation and soft-start functions minimize external component count. the MP3421 provides a compact solution for a 5v output, 2.1a load requirement, using a supply voltage as low as 2.8v. the MP3421 is available in a 14-pin qfn 2mmx2mm package. features ? support 5v/2.1a output at 2.8v input ? up to 98% efficiency ? 1.9v to 5.5v input range ? 2.5v to 5.5v output range ? internal synchronous rectifier ? 600khz fixed-switching frequency ? >5.5a switch-current limit capability ? 43ua quiescent current ? high-efficiency over full-load range ? internal soft-start and compensation ? output-load disconnect from input ? ocp, scp, ovp and otp protection ? small 2x2mm qfn14 package applications ? battery-powered products ? power banks, juice packs, battery back-up units ? usb power supply ? consumer electronic accessories ? tablets all mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps website unde r products, quality assurance page. ?mps? and ?the future of analog ic technology? are registered trademarks o f monolithic power systems, inc. typical application 84 86 88 90 92 94 96 98 100 00.511.522.5 load current (a) efficiency vs. load current v out =5v v in =2.8v v in =4.2v v in =3.3v
MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 2 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. ordering information part number* package top marking MP3421gg qfn-14 (2mmx2mm) see below * for tape & reel, add suffix ?z (e.g. MP3421gg?z) top marking dk: product code of MP3421gg; y: year code; lll: lot number; package reference top view MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 3 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. absolute maxi mum ratings (1) sw .. ......................-0.3v to +6.5v (9v for <5ns) all other pins................................-0.3v to +6.5v continuous power dissipation (t a = +25c) (2) ........................................................... 1.56w junction temperature ...............................150 c lead temperature ....................................260 c storage temperature............... -65 c to +150 c recommended operating conditions (3) supply voltage v in ..........................1.9v to 5.5v v out .................................................2.5v to 5.5v operating junction temp. (t j ). -40c to +125c thermal resistance (4) ja jc qfn-14 (2mmx2mm)............. 80....... 16 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 powe r 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. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 4 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. electrical characteristics v in = v en = 3.3v, v out = 5v, t j = -40c to125c, typical values are tested at t j =25c, unless otherwise noted. parameters symbol condition min typ max units voltage range start-operating input voltage v in 1.9 5.5 v v en =v in =3.3v, v out =5v, no load measured on out, t j =25c 43 57 a quiescent current i q_ns v en =v in =3.3v, v out =5v, no load measured on in 0.3 a shutdown current i sd v en =v out =0v, measured on in, t j =25c 0.1 1 a in uvlo rising threshold v uvlo_in-r v in rising t j =25c 1 1.3 1.6 v in uvlo falling threshold v uvlo_in-f v in falling, v out =5v 650 mv vout start-switching rising threshold v uvlo_out_r t j =25c 1.7 1.79 v step-up converter t j =25c 500 600 700 operation frequency f sw -40c t j 125c 440 600 760 khz t j =25c 795 807 819 feedback voltage v fb -40c t j 125c 791 807 823 mv feedback input current i fb v fb =850mv 1 50 na nmos on-resistance r nds_on 15 m ? nmos leakage current i n_lk v sw =5v 100 na pmos on-resistance r pds_on 20 m ? pmos leakage current i p_lk v sw =5v, v out =0v 0.1 a maximum duty cycle d max 90 95 % v out =1.7v 0.7 a linear-charge current limit (5) i ch_limit v out =0v 0.2 a i sw_limit1 v in =5v, v out =3.3v 4 a nmos current limit (5) i sw_limit2 duty=44%, v in =2.8v, v out =5v 5.5 a logic interface en high-level voltage v en _h 1.2 v en low-level voltage v en _l 0.4 v en input current i en connect to v in 10 na protection thermal shutdown (5) 150 c over temperature hysteresis (5) 20 c notes: 5) guaranteed by characterization, not production tested. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 5 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical characteristics v in = v en = 3.3v, v out = 5v, l = 1.5h, t a = 25c, unless otherwise noted. en threshold(v) vin uvlo threshold(v) output voltage(v) quiescent current vs. output voltage v in MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 6 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical characteristics (continued) v in = v en = 3.3v, v out = 5v, l = 1.5h, t a = 25c, unless otherwise noted. linear charging limit(ma) linear-charging current limit vs. temperature v in =3.3v linear charging limit(ma) linear-charging current limit vs. temperature v in =1.9v 0 200 400 600 800 -40 -20 0 20 40 60 80 100120140 v out =0v v out =1.6v 0 200 400 600 800 -40 -20 0 20 40 60 80 100120140 v out =0v v out =1.6v MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 7 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical performanc e characteristics v in = 3.3v, v out = 5v, l=1.5uh, t a = 25c, tested on standard evb, unless otherwise noted. 84 86 88 90 92 94 96 98 100 00.511.522.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 1.5 2 2.5 3 3.5 4 4.5 5 5.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 0 0.5 1 1.5 2 2.5 00.511.522.5 0 5 10 15 20 25 30 0 100 200 300 400 500 1.5 2 2.5 3 3.5 4 4.5 5 v out /ac 100mv/div. sw 2v/div. i l 2a/div. v out /ac 50mv/div. sw 2v/div. i l 5a/div. v out 2v/div. v in 2v/div. sw 2v/div. i l 1a/div. v out /ac 100mv/div. sw 2v/div. i l 2a/div. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 8 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical performanc e characteristics (continued) v in = 3.3v, v out = 5v, l=1.5uh, t a = 25c, tested on standard evb, unless otherwise noted. v out 2v/div. v en 5v/div. v sw 5v/div. i l 500ma/div. v out 2v/div. v en 5v/div. v sw 5v/div. i l 2a/div. v out 2v/div. i l 2a/div. v out 2v/div. v in 2v/div. sw 2v/div. i l 2a/div. v out 2v/div. en 5v/div. sw 5v/div. i l 2a/div. v out 2v/div. en 5v/div. sw 5v/div. i l 2a/div. v out /ac 200mv/div. i load 500ma/div. v out 2v/div. i l 5a/div. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 9 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. pin functions pin # name pin function 1, 2, 13 pgnd power ground. 3, 14 sw power-switch output. sw is the internal nm os switch and synchronous switch connection node . connect the power inductor between sw and input power. keep these pcb trace lengths as short and wide as possible to reduce emi and voltage spikes. 4, 5, 6 out output. out is the internal synchronous rectif ier mosfet drain. bias is derived from out when v out is higher than v in . pcb trace length from out to the output filter capacitor(s) should be as short and wide as possible. due to the output disconnect feature, out is completely disconnected from in when en is low. 7 nc no connect. reserved for factory use only. fl oat or connect nc to gnd in the application. 8 en enable control input. 9 in power-supply input. the startup bias is derived from in. it must be locally bypassed. once out exceeds in, bias comes from out. once started, operation is completely independent from in. 10 ina power-supply input (for factory use only). in a must be connected to in in the application. 11 agnd analog signal ground. 12 fb feedback input to error amplifie r. connect resistor divider t ap to fb. the output voltage can be adjusted from 2.5v to 5.5v MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 10 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. function diagram cout voutgood 1.7v pwm control slope comp sync drive control enable control 0.8v ref body control vin startup b c ea cp r1 r2 rc cc enable osc 600khz cin l1 pwm comparator undervoltage lockout vref in en fb pgnd out sw agnd current limit scp/ovp a rt ina figure 1: functional block diagram MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 11 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. operation the MP3421 is a 600khz, synchronous step-up converter with true output disconnect offered in a compact qfn 2x2-14 lead package. it features fixed-frequency current mode pwm controls for excellent line and load regulation. internal soft-start and loop compensation simplifies the design process and minimizes external components. the internal, r ds(on) low mosfets, combined with frequency-stretching operation, allows the device to maintain high efficiency over a wide-load current range. start-up when the ic is enabled and in voltage exceeds v uvlo_in-r , the MP3421 starts up in the linear charge period. during this period, the pmos rectifier turns on until the output capacitor is charged to 1.7v. the pmos current is limited to 0.2a when v out is 0v to avoid an inrush current. while the output ramps, the pmos current limit increases and ramps to 0.7a at 1.7v output. this circuit helps to limit the output current under short-circuit conditions. once the output is charged to 1.7v, the linear charge period elapses and the MP3421 starts switching in normal closed-loop operation. in normal operation, with vo lower than v in +0.3v, the MP3421 operates in step-down mode with 4a typical peak-current limit. also it works in boost mode when vo is higher than v in +0.3v with more than 5.5a current limit (see table 1). table 1: work mode during startup v out <1.7v linear charge mode v out 1.7v & v out < v in + 0.3v down mode v out 1.7v & v out v in + 0.3v boost mode in down mode (if hs-fet is on), the hs-fet gate is pulled to vin and works with high impedance. in down mode, power loss is high and regulation is poor. down mode is designed to work in startup and scp conditions; do not set MP3421 in down mode for normal operation (unless the thermal temperature and regulation do not affect system performance). once the output voltage exceeds the input voltage, the MP3421 powers its internal circuits from v out instead of v in. soft-start (ss) the MP3421 provides soft-start by charging an internal capacitor with a current source. during the linear-charge period, the soft-start voltage rises, following the fb voltage. once the linear charge period elapses and the voltage on the capacitor is charged, the reference voltage slowly ramps. the reference soft-start time is typically 2ms from 0v to 0.807v. the soft-start capacitor is discharged completely at output in the event of a commanded shutdown, thermal shutdown, or short circuit. enable (en) operation is enabled when en is switched high; it enters shutdown mode when en is switched low. in shutdown mode, the regulator stops switching and all internal control circuitry is turned off; the load is isolated from the input. power-save mode (psm) the MP3421 automatically enters power-save mode (psm) when the load decreases; it resumes pwm mode when the load increases. when the device goes into psm, it lowers the switching frequency. this prevents switching and driver losses and switches to pulse-skip mode if the load continues to decrease. error amplifier (ea) the error amplifier (ea) is an internally- compensated amplifier. the ea compares the internal 0.807v reference voltage against v fb to generate an error signal. the output voltage of the MP3421 is adjusted by an external resistor divider. a voltage divider from v out to ground programs the output voltage via the fb from 2.5v to 5.5v using the equation: v out =0.807v x (1+r1/r2) set the value of r1 and r2 to achieve low- quiescent current. r1 values larger than 600k MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 12 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. are recommended for good stability and transient balance. current sensing lossless-current sensing converts the nmos switch current signal to voltage, which is summed with the internal slope compensation. the summed signal is compared to the error amplifier output to provide a peak-current control command for the pwm. the minimum peak-switch current limit is 5.5a. internally, the switch-current signal is blanked for about 60ns to enhance noise rejection. output disconnect the MP3421 has true output disconnect by eliminating body diode conduction from the internal pmos rectifier. this allows v out to go to 0v during shutdown or isolate and maintain an external bias on v out . also, it allows for inrush-current limit at startup, minimizing surge current from the input supply. to efficiently utilize output disconnect, eliminate (if necessary) the external schottky diode connection between the switch and v out . over-load (olp)and short-circuit (scp) protection if an overload or short circuit occurs, the output voltage drops. if v out drops below v in +0.3 v, MP3421 converts to step-down mode. if v out drops below 1.7v, the device enters linear charge mode. if v out drops below 70% of the nominal output voltage, the MP3421 immediately shuts down and re-starts in a power-on cycle after 40 s. over-voltage protection (ovp) if v out is higher than 7v, boost switching stops. this prevents overvoltage from damaging the internal power mosfet. when the output drops below 7v, the device resumes switching automatically. thermal shutdown (tsd) the device contains an internal temperature monitor. the switches turn off if the die temperature exceeds 150c. the device resumes normal operation below 130c. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 13 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. application information component selection input capacitor selection low esr input capacitors reduce input- switching noise and reduce the peak current drawn from the battery. ceramic capacitors are recommended for input decoupling and should be located as close to the device as possible. a ceramic capacitor larger than 22 f is recommended to restrain the v in ripple. output capacitor selection to ensure stability over the full-operating range, the output capacitor requires a minimum capacitance value of 22 f at the programmed output voltage. a higher capacitance value may be required to lower both the output ripple and the transient ripple. low esr capacitors, such as x5r or x7r type ceramic capacitors are recommended. supposing that esr is zero, the minimum output capacitor to support the ripple in the pwm mode can be calculated by: o out(max) in(min) o sout(max) i(v v ) c fv v ? where, v out(max) = maximum output voltage v in(min) = minimum input voltage i o =output current f s = switching frequency v= acceptable output ripple a 1 f ceramic capacitor is recommended between the out and pgnd. this reduces spikes on the sw node and improves emi performance. inductor selection due to the 600khz switching frequency, the MP3421 utilizes small surface mount-chip inductors, inductor values run between 1 h and 2.2 h, and they are suitable for most applications. larger inductance values allow slightly greater output-current capability by reducing the inductor-ripple current. however, larger inductance values also increase component size. the minimum inductance value is given by: in(min) out(max) in(min) out(max) l s v(v v) l vif ? (3) where i l =acceptable inductor-current ripple. the inductor-current ripple is typically set at 30% to 40% of the maximum inductor current. the inductor should have low dcr (inductor current series resistance without saturating windings) to reduce the resistive power loss. the saturated current (i sat ) should be large enough to support the peak current. pcb layout considerations proper pcb layout for high-frequency switching power supplies is critical. poor layout results in weak performance, excessive emi, resistive loss and system instability. the steps below ensure a good layout design: 1. the output capacitor must be placed as close as possible to the out, with minimal distance from pgnd. a small decoupling capacitor should be parallel with the bulk output capacitor and placed as close as possible to the out. this is critical for reducing spikes on the sw and improving emi performance. 2. the input capacitor and inductor should be as close as possible to the in and sw. the trace between the inductor and the sw should be as wide and short as possible. 3. the feedback loop should be far from any noise sources, such as the sw. the feedback divider resistors should be as close as possible to the fb and agnd. 4. the ground return of the input/output capacitors should be tied as close as possible to the pgnd with a large copper gnd area. vias around the gnd are recommended to lower the die temperature. 5. ina must be connected to in. nc can either float or be connected to gnd. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 14 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. figure 2 shows recommended component placement for the MP3421. en in ina nc pgnd out fb agnd sw top layer bottom layer via vout vin pgnd pgnd pgnd pgnd sw out sw out MP3421 l1 c2a c2b c1 r1 r2 vias for heat sink figure 2: layout recommendation design example table 2 shows a design example (using the application guidelines) for the following specifications: table 2: design example v in 2.8v-4.2v v out 5v i out 0a-2.1a see figure 3 for the detailed application schematic. the typical application circuit for v out = 5v is the basis for the typical performance waveforms. for details on additional device applications, please refer to the related evaluation board datasheets. MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package MP3421 rev. 1.0 www.monolithicpower.com 15 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical application circuits figure 3: typical boost application circuit, v in =2.8v to 4.2v, v out =5v, i out =0a-2.1a MP3421?5.5a, 600khz high efficiency, synchronous, step-up converter with output disconnect in 2x2mm qfn package 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. MP3421 rev. 1.0 www.monolithicpower.com 16 11/13/2014 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. package information qfn-14 (2mmx2mm) |
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