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MP92325 24v, 3a, 500khz, high-efficiency, synchronous, step-down converter MP92325 rev. 1.0 www.monolithicpower.com 1 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. the future of analog ic technology description the MP92325 is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in, internal power mosfets. it offers a very compact solution that achieves 3a of continuous output current with excellent load and line regulation over a wide input supply range. the MP92325 uses synchronous mode operation for higher efficiency over the output current load range. current-mode operation provides a fast transient response and eases loop stabilization. full protection features include over-current protection (ocp) and thermal shutdown. the MP92325 requires a minimum number of readily available, standard, external components and is available in a space-saving, 8-pin tsot23 package. features ? wide 4.5v to 24v operating input range ? 90m ? /40m ? low r ds(on) internal power mosfets ? low quiescent current ? high-efficiency synchronous mode operation ? fixed 500khz switching frequency ? frequency sync from 200khz to 2mhz external clock ? power save mode at light load ? internal soft start ? power good indicator ? over-current protection (ocp) and hiccup ? thermal shutdown ? output adjustable from 0.8v ? available in an 8-pin tsot-23 package applications ? notebook systems and i/o power ? digital set-top boxes ? flat-panel televisions and monitors a ll mps parts are lead-free, halogen-free, and adhere to the rohs directive. fo r mps green status, please visit the mps website under quality assurance. ?mps? and ?the future of analog ic technology? are registered trademarks o f monolithic power systems, inc. typical application c3 0. 1f r1 40.2k r2 12.7k l1 4.9h c2 44f c4 0.1 f c1 22f 3.3v/3a rt 33 k r4 20 MP92325 r3 100k
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 2 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. ordering information part number* package top marking MP92325gj tsot23-8 ake * for tape & reel, add suffix ?z (e.g. MP92325gj?z) package reference pg in sw gnd fb vcc en/sync bst 1 2 3 4 8 7 6 5 top view tsot23-8 absolute maxi mum ratings (1) v in ................................................. -0.3v to +28v v sw ..... -0.3v (-5v < 10ns) to +28v (30v < 10ns) v bst ...................................................... v sw + 6v all other pins ................................... -0.3v to +6v continuous power dissipation (t a = +25c) (2) ................................................................. 1.25w junction temperature ................................ 150c lead temperature ..................................... 260c storage temperature .................. -65c to 150c recommended operating conditions (3) supply voltage (v in ) ........................... 4.5 to 24v output voltage (v out ) ................ 0.8v to v in *d max operating junction temp (t j ). ... -40c to +125c thermal resistance (4) ja jc tsot23-8????????...100....55....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 produces an excessive die temperature, causing the regulator to 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.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 3 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. electrical characteristics v in = 12v, t a = 25c, unless otherwise noted. parameter symbol condition min typ max units supply current (shutdown) i in v en = 0v 5.5 a supply current (quiescent) i q v en = 2v, v fb = 1v 130 180 240 a hs switch on resistance hs rds-on v bst-sw = 5v 90 m ? ls switch on resistance ls rds-on v cc = 5v 40 m ? switch leakage sw lkg v en = 0v, v sw = 12v 1 a current limit (5) i limit duty cycle = 40% 4.5 5.5 6.5 a oscillator frequency f sw v fb = 750mv 420 500 620 khz foldback frequency f fb v fb = 200mv 0.5 f sw maximum duty cycle d max v fb = 750mv 90 95 % minimum on time (5) t on min 60 ns sync frequency range f sync 0.2 2 mhz feedback voltage v fb t a = 25c 783 791 799 mv feedback current i fb v fb = 820mv 10 50 na en rising threshold v en rising 1.2 1.4 1.6 v en hysteresis v en hys 80 150 220 mv en input current i en v en = 2v 1.5 2 2.5 a v en = 0 0 50 na en turn off delay en td-off 6 10 14 s power good rising threshold pg vth-hi 0.9 v fb power good falling threshold pg vth-lo 0.85 v fb power good delay pg td 40 s power good sink current capability v pg sink 1ma 0.4 v power good leakage current i pg-leak 1 a vin under-voltage lockout threshold rising inuv vth 3.7 3.9 4.1 v vin under-voltage lockout threshold hysteresis inuv hys 550 650 750 mv vcc regulator v cc 4.65 4.9 5.15 v vcc load regulation i cc = 5ma 0 1 3 % soft-start period t ss 0.8 1.5 2.2 ms thermal shutdown (5) 150 c thermal hysteresis (5) 20 c note: 5) guaranteed by design.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 4 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. typical characteristics v in = 12v, v out = 3.3v, l = 4.9 h, t a = 25c, unless otherwise noted.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 5 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. typical performanc e characteristics v in = 12v, v out = 3.3v, l = 4.9 h, t a = 25c, unless otherwise noted. v out /ac 10mv/div. v in /ac 200mv/div. v sw 5v/div. i l 1a/div. v out /ac 20mv/div. v in /ac 200mv/div. v sw 5v/div. i l 2a/div. v out 2v/div. v in 5v/div. v sw 5v/div. i l 1a/div. v out 2v/div. v in 5v/div. v sw 5v/div. i l 2a/div. v out 2v/div. v en 5v/div. v sw 5v/div. i l 1a/div. v out 2v/div. v en 5v/div. v sw 5v/div. i l 2a/div. v out 2v/div. v en 5v/div. v sw 5v/div. i l 2a/div. v out 2v/div. v in 5v/div. v sw 5v/div. i l 2a/div. v out 2v/div. v in 5v/div. v sw 5v/div. i l 2a/div.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 6 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. typical performanc e characteristics (continued) v in = 12v, v out = 3.3v, l = 4.9h, t a = 25c, unless otherwise noted. v out 2v/div. v pg 5v/div. v sw 5v/div. i l 5a/div. v out 2v/div. v pg 5v/div. v sw 5v/div. i l 5a/div. v out 2v/div. v pg 5v/div. v sw 5v/div. i l 5a/div. v out 2v/div. v en 5v/div. v pg 5v/div. i l 1a/div. v out 2v/div. v en 5v/div. v pg 5v/div. i l 2a/div. v out 2v/div. v en 5v/div. v pg 5v/div. i l 2a/div. v out 2v/div. v en 5v/div. v pg 5v/div. i l 2a/div. v out /ac 200mv/div. i out 1a/div. v out 2v/div. v en 5v/div. v sw 5v/div. i l 2a/div.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 7 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. pin functions package pin # name description 1 pg power good output. the output of pg is an open drain. pg is pulled up to vcc by an external resistor when the out put voltage exceeds 90% of the normal voltage. there is a 40s delay between the detection that fb 90% and pg going high. 2 in supply voltage. in supplies power to the internal mosfet and regulator. the MP92325 operates from a +4.5v to +24v input rail. requires a low esr, low-inductance capacitor (c1) to decouple the input rail. place the input capacitor very close to in and connect it with wide pcb traces and multiple vias. 3 sw switch output. connect sw to the inductor and bootstrap capacitor. sw is driven up to v in by the high-side switch during the pwm dut y cycle on time. the inductor current drives sw negative during the off time. the on resistan ce of the low-side switch and the internal body diode fixes the negative voltage. connect using wide pcb traces and multiple vias. 4 gnd system ground. gnd is the reference ground of the regulated output voltage and requires careful consideration during pcb layout. connect gnd to pcb ground with coppers and vias. 5 bst bootstrap. a capacitor and a 20 ? resistor connected between sw and bst are required to form a floating supply across the high-side switch driver. 6 en/sync set en/sync = 1 to enable the MP92325. an external clock can be applied to en/sync to change the switching frequency. for automat ic start-up, connect en to vin with a 100k ? resistor. 7 vcc bias supply. decouple with a 0.1 f-0.22 f capacitor. the capacitance should be no more than 0.22 f. 8 fb feedback. a n external resistor divider from t he output to gnd tapped to fb sets the output voltage. to prevent a current-limit runaway during a short-circuit fault condition, the frequency foldback comparator lowers the oscillator frequency when the fb voltage is below 400mv.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 8 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. block diagram 50pf 1meg 6.5v bst rsen in oscillator vcc regulator bootstrap regulator vcc currrent sense amplifer vcc current limit comparator error amplifier ref reference en/sync fb + + + - - + - + - pg sw gnd ls driver hs driver comparator on time control logic control 1pf 400k figure 1: functional block diagram
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 9 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. operation the MP92325 is a high-frequency, synchronous, rectified, step-down, switch mode converter with built-in, internal power mosfets. it offers a very compact solution that achieves 3a of continuous output current with excellent load and line regulation over a wide input supply range. the MP92325 operates in a fixed-frequency, peak-current control mode to regulate the output voltage. a pwm cycle is initiated by the internal clock. the integrated high-side power mosfet is turned 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 comp-set current value within 95% of one pwm period, the power mosfet is forced off. internal regulator most of the internal circuitries are powered from the 5v internal regulator. this regulator takes the v in input and operates in the full v in range. when v in is greater than 5.0v, the output of the regulator is in full regulation. when v in is lower than 5.0v, the output decreases. a 0.1f ceramic capacitor is required for decoupling. error amplifier (ea) the error amplifier compares the fb voltage with the internal 0.8v reference (ref) and outputs a comp voltage (v comp ), which is used to control the power mosfet current. the optimized internal compensation network minimizes the external component counts and simplifies the control loop design. power-save mode for light-load condition the MP92325 uses advanced asynchronous modulation (aam) power-save mode in light load. under heavy-load conditions, v comp is higher than v aam . when the clock goes high, the high-side power mosfet turns on and remains on until v ilsense reaches the value set by v comp . the internal clock resets whenever v comp is higher than v aam . under light-load conditions, v comp is low. when v comp is less than v aam and v fb is less than v ref , v comp ramps up until it exceeds v aam . during this time, the internal clock is blocked, and the MP92325 skips some pulses for pulse frequency modulation (pfm) mode to achieve a light-load power save. figure 2: simplified aam control logic for v in = 12v, v out = 3.3v, l = 4.9 h, the inductor peak current is set to about 500ma internally at light load. the internal aam voltage varies with the duty cycle to keep the inductor peak current constant. figure 3: aam selection for common output voltages (v in = 4.5v - 24v) enable/sync control en/sync is a digital control pin that turns the regulator on and off. drive en/sync high to turn on the regulator; drive en/sync low to turn off the regulator. there is an internal 1m ? resistor from en/sync to gnd that enables en/sync to be floated to shut down the chip. the en/sync voltage is clamped at around 6.5v by an internal zener diode. be sure to use a pull-up resistor that is large enough to connect v in and en/sync to limit the en/sync input current to below 100a. generally, a resistor around 100k should be sufficient. the MP92325 can be synchronized to the external clock range from 200khz up to 2mhz through en/sync 2ms after the output voltage is set with the internal clock rising edge synchronized to the external clock rising edge.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 10 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. the en/sync logic high voltage should be higher than 2v. the en/sync logic low voltage should be lower than 400mv. the en/sync logic high pulse width must be less than 1.6s; otherwise, the internal clock may turn on the high-side mosfet again. the en/sync logic low pulse width must be less than 6s; otherwise the MP92325 may shut down. power good indicator the MP92325 uses an open drain for the power good indicator. when fb is higher than 90% of the regulation voltage, pg is pulled up to vcc by the external resistor. if the fb voltage drops down to 85% of the regulation voltage, pg is pulled down to ground by an internal mosfet. under-voltage lockout (uvlo) under-voltage lockout (uvlo) is implemented to protect the chip from operating at an insufficient supply voltage. the MP92325?s uvlo comparator monitors the output voltage of the internal regulator (vcc). the uvlo rising threshold is about 3.9v, while its falling threshold is consistent at 3.25v. internal soft start (ss) the soft start is implemented to prevent the converter output voltage from overshooting during start-up. when the chip starts, the internal circuitry generates a soft-start (ss) voltage that ramps up from 0v. the soft-start period lasts until the voltage on the soft-start capacitor exceeds the reference voltage of 0.8v. at this point, the reference voltage takes over. the soft-start time is set to around 1.5ms internally. over-current protection (ocp) and hiccup the MP92325 uses a cycle-by-cycle over- current limit when the inductor current peak value exceeds the set current limit threshold. the output voltage begins to drop until fb is below the under-voltage (uv) threshold, typically 50% below the reference. once uv is triggered, the MP92325 enters hiccup mode to restart the part periodically. this protection mode is especially useful when the output is dead-shorted to ground. the average short- circuit current is greatly reduced to alleviate thermal issues and protect the regulator. the MP92325 exits hiccup mode once the over- current condition is removed. thermal shutdown thermal shutdown is implemented to prevent the chip from operating at exceedingly high temperatures. when the silicon die temperature is higher than 150c, the entire chip shuts down. when the temperature is below its lower threshold (typically 130c), the chip is enabled again. floating driver and bootstrap charging the floating power mosfet driver is powered by an external bootstrap capacitor. this floating driver has its own uvlo protection. the uvlo rising threshold is 2.2v with a hysteresis of 150mv. the bootstrap capacitor voltage is regulated internally by v in through d1, r5, c5, l1, and c2 (see figure 4). if v in -v sw is more than 5v, u1 regulates m1 to maintain a 5v bst voltage across c5. figure 4: internal bootstrap charging circuit start-up and shutdown if both v in and en/sync are higher than their appropriate thresholds, the chip starts. the reference block starts first, generating a stable reference voltage and current, and then the internal regulator is enabled. the regulator provides a stable supply for the remaining circuitries. three events can shut down the chip: en/sync low, v in low, and thermal shutdown. in the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. v comp and the internal supply rail are then pulled down. the floating driver is not subject to this shutdown command.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 11 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. application information setting the output voltage the external resistor divider is used to set the output voltage (see the typical application on page 1). the feedback resistor (r1) also sets the feedback loop bandwidth with the internal compensation capacitor. r2 can then be calculated with equation (1): out r1 r2 v 1 0.8v ? ? (1) the t-type network (see figure 5) is highly recommended. rt fb 8 r2 r1 cf vout figure 5: t-type network table 1 lists the recommended t-type resistor values for common output voltages. table 1: resistor selection for common output voltages v out (v) r1 (k ? ) r2 (k ? ) rt (k ? ) l (h) cf (f) 1 20.5 76.8 100 1.8 15 1.2 20.5 39.2 100 1.8 15 1.8 40.2 31.6 56 3.3 15 2.5 40.2 18.7 56 3.3 15 3.3 40.2 12.7 33 4.9 15 5 40.2 7.5 33 4.9 15 selecting the inductor a 1h-to-22h inductor with a dc current rating at least 25% percent higher than the maximum load current is recommended for most applications. for the highest efficiency, the inductor?s dc resistance should be less than 15m ? . for most designs, the inductance value can be derived from equation (2): out in out 1 in l osc v(vv) l vif ?? ? ?? ? (2) where ? i l is the inductor ripple current. choose the inductor current to be approximately 30% of the maximum load current. the maximum inductor peak current can be calculated with equation (3): 2 i i i l load ) max ( l ? ? ? (3) under light-load conditions below 100ma, a larger inductance is recommended for improved efficiency. selecting the input capacitor the input current to the step-down converter is discontinuous and therefore requires a capacitor to supply ac current to the step-down converter while maintaining the dc input voltage. use low esr capacitors for the best performance. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 22f capacitor is sufficient. 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 with equation (4): ? ? ? ? ? ? ? ? ? ? ? ? in out in out load 1 c v v 1 v v i i (4) the worse case condition occurs at v in = 2v out , shown in equation (5): 2 i i load 1 c ? (5) 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, 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, ensure that they have enough capacitance to provide a sufficient charge to prevent excessive voltage ripple at the input. the input voltage ripple caused by capacitance can be estimated with equation (6): load out out in in sin iv v v1 fc1v v ?? ?? ? ?? ?? ? ?? (6)
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 12 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. selecting the output capacitor the output capacitor (c2) is required to maintain the dc output voltage. ceramic, tantalum, or low esr electrolytic capacitors are recommended. low esr capacitors are preferred for keeping the output voltage ripple low. the output voltage ripple can be estimated with equation (7): out out out esr s1 in s vv 1 v1r fl v 8fc2 ?? ?? ?? ?? ? ? ?? ?? ??? ?? ?? (7) 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 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 with equation (8): out out out 2 in s1 vv ? v1 v 8f l c2 ?? ??? ?? ??? ?? (8) 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 with equation (9): out out out esr in s1 vv ? v1r fl v ?? ???? ?? ? ?? (9) the characteristics of the output capacitor also affect the stability of the regulation system. the MP92325 can be optimized for a wide range of capacitance and esr values. external bootstrap diode an external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of the external bst diode are: ? v out is 5v or 3.3v ? duty cycle is high: d = in out v v > 65% in these cases, an external bst diode is recommended to be placed between vcc and bst (see figure 6). figure 6: optional external bootstrap diode added to enhance efficiency the recommended external bst diode is in4148, and the bst cap is recommended to be 0.1 f - 1 f.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 13 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. pcb layout guidelines (6) efficient pcb layout is critical for stable operation. for best results, refer to figure 7 and follow the guidelines below. 1. keep the connection of the input ground and gnd as short and wide as possible. 2. keep the connection of the input capacitor and in as short and wide as possible. 3. ensure that all feedback connections are short and direct. 4. place the feedback resistors and compensation components as close to the chip as possible. 5. route sw away from sensitive analog areas such as fb. note: 6) the recommended layout is based on figure 8: typical application circuit on page 14. figure 7: sample board layout design example table 2 is a design example following the application guidelines for the specifications below. table 2: design example v in 19v v out 5v i o 3a the detailed application schematics are shown in figure 8 through figure 13. the typical performance and circuit waveforms are shown in the typical performance characteristics section. for more device applications, please refer to the related evaluation board datasheets.
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 14 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. typical application circuits figure 8: vo = 5v, io = 3a figure 9: vo = 3.3v, io = 3a figure 10: vo = 2.5v, io = 3a
MP92325 ? 24v, 3a, synchronous , step-down converter MP92325 rev. 1.0 www.monolithicpower.com 15 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. typical application circuits (continued) figure 11: vo = 1.8v, io = 3a figure 12: vo = 1.2v, io = 3a figure 13: vo = 1v, io = 3a
MP92325 ? 24v, 3a, synchronous , 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. MP92325 rev. 1.0 www.monolithicpower.com 16 3/24/2016 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2016 mps. all rights reserved. package information tsot23-8

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