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mpq4423 high efficiency 3a, 36v, synchronous step down converter aec-q100 qualified mpq4423 rev.1.0 www.monolithicpower.com 1 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. the future of analog ic technology description the mpq4423 is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in power mosfets. it offers a very compact solution to achieve a 3a continuous output current with excellent load and line regulation over a wide input supply range. the mpq4423 has synchronous mode operation for higher efficiency over the output current load range. current-mode operation provides fast transient response and eases loop stabilization. full protection features include over-current protection and thermal shut down. the mpq4423 requires a minimal number of readily-available standard external components, and is available in a space-saving qfn-8 (3mmx3mm) package. features ? wide 4v to 30v continuous operating input range ? 36v input transient tolerance for automotive load dump ? 85m ? /55m ? low r ds(on) internal power mosfets ? high-efficiency synchronous mode operation ? default 410khz switching frequency ? synchronizes to a 200khz to 2.2mhz external clock ? high duty cycle for automotive cold-crank ? power-save mode ? internal soft-start ? power good ? ocp protection and hiccup ? thermal shutdown ? output adjustable from 0.8v ? available in an qfn-8 (3mmx3mm) ? available in aec-q100 grade 1 applications ? automotive ? industrial control system ? distributed power systems a ll mps parts a r e lead-free and adhere to the rohs directive. for mps green status, please visit mps website under quality assurance. ?mps? and ?the future of analog ic technology? are registered trademarks of monolithi c power systems, inc. typical application mpq4423 bst sw fb en/sync in en/sync vin vout 47 f c2 l1 10 h r2 r1 41.2k 13k c1 22 f 3.3v/3a gnd vcc pg c3 0.1 f r3 51k c4 100nf r4 20
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 2 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. ordering information part number* package top marking MPQ4423GQ qfn-8 (3mmx3mm) see below MPQ4423GQ-aec1 qfn-8 (3mmx3mm) * for tape & reel, add suffix -z (e.g. MPQ4423GQ-z); top marking ajv: product code of MPQ4423GQ and MPQ4423GQ-aec1; y: year code; lll: lot number; package reference 1 2 3 45 6 7 8 top view qfn8 (3mmx3mm) fb vcc en/sync bst pg sw in gnd
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 3 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. absolute maximum ratings (1) v in ................................................ -0.3v to 40v v sw ................................................ -0.3v to 41v v bs ....................................................... v sw +6v all other pins ................................ -0.3v to 6v (2) continuous power dissipation (t a = +25c) (3) qfn-8 (3mmx3mm) ................................. 2.27w junction temper ature .............................. 150c lead temperat ure ................................... 260c storage temperature ................. -65c to 150c recommended operating conditions continuous supply voltage v in .......... 4v to 30v output voltage v out ................... 0.8v to 0.9xv in operating junction temp. (t j ). -40c to +125c thermal resistance (4) ja jc qfn-8 (3mmx3mm) .............. 55 ...... 13 ... c/w notes: 1) absolute maximum ratings are rated under room temperature unless otherwise noted. exceeding these ratings may damage the device. 2) about the details of en pin?s abs max rating, please refer to page 12, enable/sync control section. 3) 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 a t 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 permanen t damage. 4) measured on jesd51-7, 4-layer pcb.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 4 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. electrical characteristics v in = 12v, t j = -40c to +125c, unless otherwise noted. typical values are at t j =+25c. paramete r symbol condition min typ max units supply current (shutdown) i shdn v en = 0v 8 a supply current (quiescent) i q v en = 2v, v fb = 1v 0.5 0.7 ma hs switch-on resistance r on_hs v bst-sw =5v 85 150 m ? ls switch-on resistance r on_ls v cc =5v 55 105 m ? switch leakage i lkg sw v en = 0v, v sw =12v 1 a current limit i limit under 40% duty cycle 3.2 4.4 5.7 a oscillator frequency f sw v fb =750mv 320 410 500 khz fold-back frequency f fb v fb <400mv 70 100 130 khz maximum duty cycle d max v fb =750mv, 410khz 92 95 % minimum on time ( 5 ) t on _ min 70 ns sync frequency range f sync 0.2 2.4 mhz feedback voltage v fb t j =25c 780 792 804 mv 776 808 feedback current i fb v fb =820mv 10 100 na en rising threshold v en rising 1.15 1.4 1.65 v en falling threshold v en falling 1.05 1.25 1.45 v en threshold hysteresis v en_hys 150 mv en input current i en v en =2v 4 6 a v en =0 0 0.2 a vin under-voltage lockout threshold-rising inuv rising 3.3 3.5 3.7 v vin under-voltage lockout threshold-falling inuv falling 3.1 3.3 3.5 v vin under-voltage lockout threshold- hysteresis inuv hys 200 mv vcc regulator v cc i cc =0ma 4.6 4.9 5.2 v vcc load regulation i cc =5ma 1.5 4 % soft-start period t ss v out from 10% to 90% 0.45 1. 5 2.55 ms thermal shutdown ( 5 ) 150 170 c thermal hysteresis ( 5 ) 30 c pg rising threshold pg vth rising as percentage of v fb 86 90 94 % pg falling threshold pg vth falling as percentage of v fb 80 84 88 %
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 5 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. electrical characteristics (continued) v in = 12v, t j = -40c to +125c, unless otherwise noted. typical values are at t j =+25c. paramete r symbol condition min typ max units pg threshold hysteresis pg vth_hys as percentage of v fb 6 % pg rising delay pg td _ rising 40 90 160 s pg falling delay pg td _ falling 30 55 95 s pg sink current capability v pg sink 4ma 0.1 0.3 v pg leakage current i lkg_pg 10 100 na notes: 5) derived from bench characterization. not tested in production
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 6 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. pin functions package pin # name description 1 fb feedback. connect to the tap of an external resistor divider from the output to gnd, to set the output voltage. the frequency fold-back comparator lowers the oscillator frequency when the fb voltage is below 660mv to prevent current limit runaway during a short-circuit fault condition. 2 vcc bias supply. decouple with 0.1 f-to-0.22 f capacitor. select a capacitor that does not exceed 0.22 f. 3 en/sync enable/synchronize. en high to enable the mpq4423. apply an external clock to the en pin to change the switching frequency. 4 bst bootstrap. requires a capacitor connected between sw and bst pins to form a floating supply across the high-side switch driver. a 20 ? resistor placed between sw and bst cap is strongly recommended to reduce sw spike voltage. 5 gnd system ground. this pin is the reference ground of the regulated output voltage, and pcb layout requires special care. for best results, connect to gnd with copper traces and vias. 6 sw switch output. connect using a wide pcb trace. 7 in supply voltage. the mpq4423 operates from a 4v to 30v input rail. requires c1 to decouple the input rail. connect using a wide pcb trace. 8 pg power good. the output of this pin is an open drain and goes high if the output voltage exceeds 90% of the nominal voltage.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 7 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical performance characteristics v in = 12v, v out = 3.3v, l = 10h, r bst =20 ? , t a = +25c, unless otherwise noted.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 8 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical performance characteristics (continued) v in = 12v, v out = 3.3v, l = 10h, r bst =20 ? , t a = +25c, unless otherwise noted.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 9 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical performance characteristics (continued) v in = 12v, v out = 3.3v, l = 10h, r bst =20 ? , t a = +25c, unless otherwise noted.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 10 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical performance characteristics (continued) v in = 12v, v out = 3.3v, l = 10h, r bst =20 ? , t a = +25c, unless otherwise noted.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 11 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. block diagram figure 1: functional block diagram
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 12 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. operation the mpq4423 is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in power mosfets. it offers a very compact solution to achieve 3a continuous output current with excellent load and line regulation over a wide input supply range. the mpq4423 operates in a fixed-frequency, peak-current?control mode to regulate the output voltage. an internal clock initiates a pwm cycle. the integrated high-side power mosfet turns on and remains on until its current reaches the value set by the comp voltage. when the power switch is off, it remains off until the next clock cycle starts. if the current in the power mosfet does not reach the current value set by comp within 95% of one pwm period, the power mosfet will be forced to turn off. internal regulator the 5v internal regulator power most of the internal circuitries. this regulator takes the v in input and operates in the full v in range: when v in exceeds 5.0v, the output of the regulator is in full regulation; when v in falls below 5.0v, the output of the regulator decreases following the vin. a 0.1uf decoupling ceramic capacitor is needed at the pin. error amplifier the error amplifier compares the fb pin voltage against the internal 0.8v reference (ref) and outputs a comp voltage?this comp voltage controls the power mosfet current. the optimized internal compensation network minimizes the external component count and simplifies the control loop design. enable/sync control en/sync is a digital control pin that turns the regulator on and off: drive en high to turn on the regulator, drive it low to turn it off. an internal 500k ? resistor from en/sync to gnd allows en/sync to be floated to shut down the chip. the en pin is clamped internally using a 6.5v series zener diode, as shown in figure 2. connect the en input pin through a pullup resistor to any voltage connected to the v in pin? the pullup resistor limits the en input current to less than 150a. for example, with 12v connected to v in , r pullup (12v ? 6.5v) 150a = 36.7k ? . connecting the en pin directly to a voltage source without any pullup resistor requires limiting voltage amplitude to 6v to prevent damage to the zener diode. figure 2: 6.5v-type zener diode connect an external clock with a range of 200khz to 2.2mhz 2ms after output voltage is set to synchronize the internal clock rising edge to the external clock rising edge. the pulse width of external clock signal should be less than 1.7 s. under-voltage lockout under-voltage lockout (uvlo) protects the chip from operating at an insufficient supply voltage. the mpq4423 uvlo comparator monitors the output voltage of the internal regulator, vcc. the uvlo rising threshold is about 3.5v while its falling threshold is 3.3v. internal soft-start the soft-start prevents the converter output voltage from overshooting during startup. w hen the chip starts, the internal circuitry generates a soft-start voltage (ss) that ramps up from 0v to 1.2v. when ss is lower than ref, ss overrides ref so the error amplifier uses ss as the reference. when ss exceeds ref, the error amplifier uses ref as the reference. the ss time is internally set to 1.5ms. over-current protection and hiccup the mpq4423 has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current limit threshold. if the output voltage starts to drop until fb is below the under-voltage (uv) threshold?typically 84% below the reference?the mpq4423 enters hiccup mode to periodically restart the part. this protection
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 13 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. mode is especially useful when the output is dead-shorted to ground. the average short- circuit current is greatly reduced to alleviate the thermal issue and to protect the regulator. the mpq4423 exits the hiccup mode once the over- current condition is removed. thermal shutdown thermal shutdown prevents the chip from operating at exceedingly high temperatures. when the silicon die temperature exceeds 170c, it shuts down the whole chip. when the temperature drops below its lower threshold (typically 140c) the chip is enabled again. floating driver and bootstrap charging an external bootstrap capacitor power the floating-power-mosfet driver. a dedicated internal regulator (see figure 3) charges and regulates the bootstrap capacitor voltage to ~5v. when the voltage between the bst and sw nodes drops below regulation, a pmos pass transistor connected from v in to bst turns on. the charging current path is from v in , bst and then to sw. the external circuit should provide enough voltage headroom to facilitate charging. as long as v in is significantly higher than sw, the bootstrap capacitor remains charged. when the hs-fet is on, v in v sw so the bootstrap capacitor cannot charge. when the ls-fet is on, v in ? v sw reaches its maximum for fast charging. when there is no inductor current, v sw =v out so the difference between v in and v out can charge the bootstrap capacitor. the floating driver has its own uvlo protection, with a rising threshold of 2.2v and hysteresis of 150mv. a 20 ? resistor placed between sw and bst cap is strongly recommended to reduce sw spike voltage. figure 3: internal bootstrap charging circuit startup and shutdown if both v in and en exceed their appropriate thresholds, the chip starts: the reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. the regulator provides stable supply for the remaining circuitries. three events can shut down the chip: en low, v in low, and thermal shutdown. in the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. the comp voltage and the internal supply rail are then pulled down. the floating driver is not subject to this shutdown command. power good the mpq4423 has power good (pg) output. the pg pin is the open drain of a mosfet. it should be connected to vcc or some other voltage source through a resistor (e.g. 100k ? ). in the presence of an input voltage, the mosfet turns on so that the pg pin is pulled to low before ss is ready. after v fb reaches 90%ref, the pg pin is pulled high after a delay, typically 90 s. when v fb drops to 84%ref, the pg pin is pulled low. also, pg is pulled low if thermal shutdown or en is pulled low.
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 14 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. application information setting the output voltage the external resistor divider sets the output voltage (see typical application on page 1). the feedback resistor r1 also sets the feedback loop bandwidth with the internal compensation capacitor. choose r1 around 40k ? . r2 is then given by: 1 0.792v v r1 r2 out ? = the t-type network?as shown in figure 4?is highly recommended when v out is low. r2 r1 rt fb v out figure 4: t-type network rt+r1 is used to set the loop bandwidth. basically, higher rt+r1, lower bandwidth. to ensure the loop stability, it is strongly recommended to limit the bandwidth lower than 40khz based on the 410khz default fsw. table 1 lists the recommended t-type resistors value for common output voltages. table 1: resistor selection for common output voltages v out (v) r1 (k ? ) r2 (k ? ) rt (k ? ) 3.3 41.2 (1%) 13 (1%) 51 (1%) 5 41.2 (1%) 7.68 (1%) 51 (1%) selecting the inductor use a1h-to-10h inductor with a dc current rating of at least 25% percent higher than the maximum load current for most applications. for highest efficiency, an inductor with small dc resistance is recommended. for most designs, the inductance value can be derived from the following equation. out in out 1 in l osc v(vv) l vif ? = where i l is the inductor ripple current. choose the inductor ripple current to be approximately 30% of the maximum load current. the maximum inductor peak current is: 2 i i i l load ) max ( l + = use a larger inductor for improved efficiency under light-load conditions?below 100ma. vin uvlo setting mpq4423 has internal fix under voltage lock out (uvlo) threshold: rising threshold is 3.5v while falling threshold is about 3.3v. for the application needs higher uvlo point, external resistor divider between en and in as shown in figure 4 can be used to get higher equivalent uvlo threshold. vin en in r5 500 k r6 figure 5: adjustable uvlo using en divider the uvlo threshold can be computed from below two equations: en_rising rising v 500k//r6 r5 (1 inuv + = ) en_falling falling v 500k//r6 r5 (1 inuv + = ) where v en_rising =1.4v, v en_falling =1.25v. when choose r5, make sure it is big enough to limit the current flows into en pin lower than 150ua. selecting the input capacitor the input current to the step-down converter is discontinuous, therefore requires a capacitor is to supply the ac current to the step-down converter while maintaining the dc input voltage. use low esr capacitors for the best performance. use ceramic capacitors with x5r or x7r dielectrics
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 15 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. for best results because of their low esr and small temperature coefficients. for most application, a 22f ceramic capacitor is sufficient to maintain the dc input voltage. and it is strongly recommended to use another lower value capacitor (e.g. 1f) with small package size (0603) to absorb high frequency switching noise. make sure place the small size capacitor as close to in and gnd pins as possible (see pcb layout section). since 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 1 c v v 1 v v i i the worse case condition occurs at v in = 2v out , where: 2 i i load 1 c = for simplification, choose an input capacitor with an 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, add a small, high quality ceramic capacitor (e.g. 1 f) 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 caused by capacitance can be estimated by: load out out in in sin iv v v1 fc1v v ?? = ? ?? ?? selecting the output capacitor the output capacitor (c2) maintains the dc output voltage. use ceramic, tantalum, or low- esr electrolytic capacitors. for best results, use low esr capacitors to keep the output voltage ripple low. the output voltage ripple can be estimated by: out out out esr s1 in s vv 1 v1r fl v 8fc2 ?? ?? = ? + ?? ?? ??? ? where l 1 is the inductor value and r esr is the equivalent series resistance (esr) value of the output capacitor. for ceramic capacitors, the capacitance dominates the impedance at the switching frequency, and the capacitance causes the majority of the output voltage ripple. for simplification, the output voltage ripple can be estimated by: out out out 2 in s1 vv v1 v 8f l c2 ?? =? ?? ?? for tantalum or electrolytic capacitors, the esr dominates the impedance at the switching frequency. for simplification, the output ripple can be approximated to: out out out esr in s1 vv v1r fl v ?? =? ?? ?? the characteristics of the output capacitor also affect the stability of the regulation system. the mpq4423 can be optimized for a wide range of capacitance and esr values. bst resistor and external bst diode a 20ohm resistor in series with bst capacitor is recommended to reduce the sw spike voltage. higher resistance is better for sw spike reduction, but will compromise the efficiency on the other hand. an external bst diode can enhance the efficiency of the regulator when the duty cycle is high (>65%). a power supply between 2.5v and 5v can be used to power the external bootstrap diode and vcc or vout is the good choice of this power supply in the circuit as shown in figure 6. c bst c out l bst sw external bst diode 1n4148 vcc/v out vcc v out r bst figure 6: optional external bootstrap diode to enhance efficiency
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 16 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. the recommended external bst diode is in4148, and the bst capacitor value is 0.1f to 1 f. pcb layout pcb layout, especially the input capacitor and vcc capacitor placement, is very important to achieve stable operation. for the best results, follow these guidelines: 1) place the ceramics input capacitor as close to in and gnd pins as possible, especially the small package size (0603) input bypass capacitor. keep the connection of input capacitor and in pin as short and wide as possible. 2) place the vcc capacitor to vcc pin and gnd pin as close as possible. make the trace length of vcc pin-vcc capacitor anode-vcc capacitor cathode-chip gnd pin as short as possible. 3) use large ground plane directly connect to gnd pin. add vias near the gnd pin if bottom layer is ground plane. 4) route sw, bst away from sensitive analog areas such as fb. 5) place the t-type feedback resistor close to chip to ensure the trace which connects to fb pin as the short as possible. top layer bottom layer figure 7: recommended pcb layout
mpq4423 ? 36v, 3a synchronous step-down converter mpq4423 rev.1.0 www.monolithicpower.com 17 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. typical application circuits mpq4423 bst sw fb en/sync in vin vout c4 100nf 22 f c2a l1 10 h r2 r1 41.2k 13k c1c 1 f 3.3v/3a gnd 7 3 5 1 6 4 vcc pg c3 0.1 f r3 51k 8 2 c1b 10 f 10 f c1a 1m r5 r4 20 22 f c2b r6 100 k figure 8: 3.3v output typical application circuit
mpq4423 ? 36v, 3a synchronous step-down converter notice: the information in this document is subject to change without notice. users should warrant 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. mpq4423 rev.1.0 www.monolithicpower.com 18 8/18/2014 mps proprietary information. patent protected. unauthorized photocopy and duplication prohibited. ? 2014 mps. all rights reserved. package information qfn-8 (3mm x 3mm)

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