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mp1496 high-efficiency, 2a, 16v, 500khz synchronous, step-down converter mp1496 rev. 1.05 www.monolithicpower.com 1 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. the future of analog ic technology description the mp1496 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 2a continuous output current with excellent load and line regulation over a wide input supply range. the mp1496 has synchronous mode operation for higher efficiency over the output-current?load range. current-mode operation provides a fast transient response and eases loop stabilization. protective features include over-current protection and thermal shut down and external ss control. the mp1496 requires a minimal number of readily-available standard external components, and is available in a space-saving 8-pin tsot23 package. features ? wide 4.5v to 16v operating input range ? 100m ? /40m ? low-r ds(on) internal power mosfets ? proprietary switching-loss?reduction technique ? high-efficiency synchronous mode operation ? fixed 500khz switching frequency ? can synchronize with a 200khz-to-2mhz external clock ? externally programmable soft-start ? ocp protection and hiccup ? thermal shutdown ? output adjustable starting from 0.8v ? available in an 8-pin tsot-23 package applications ? notebook computers and i/o power ? digital set-top boxes ? flat-panel television and monitors ? distributed power systems all mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps website under products, quality assurance page. ?mps? and ?the future of analog ic technology? are registered trademarks o f monolithic power systems, inc. typical application mp1496 in en/sync vcc ss gnd fb sw bst vin en c3 0.1 r r3 33k 1 40.2k r2 13k l1 c2 4.5v-16v c4 c1 22 2 6 7 1 5 3 8 4 3.3v/2a c5 22 f
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 2 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. ordering information part number* package top marking MP1496DJ tsot-23-8 act *for tape & reel, add suffix ?z (e.g. MP1496DJ?z); for rohs compliant packaging, add suffix ?lf (e.g. MP1496DJ?lf?z) package reference ss in sw gnd fb vcc en/sync bst 1 2 3 4 8 7 6 5 top view absolute maxi mum ratings (1) v in ..................................................-0.3v to 17v v sw ...-0.3v (-5v for <10ns) to 17v (19v for 5ns) v bs ......................................................... v sw +6v all other pins ................................ -0.3v to 6v (2) continuous power dissipation (t a = +25c) (3) ........................................................... 1.25w junction temperature ...............................150c lead temperature ....................................260c storage temperature................. -65c to 150c recommended operating conditions (4) supply voltage v in ...........................4.5v to 16v output voltage v out ..................... 0.8v to v in -3v operating junction temp. (t j ). -40c to +125c thermal resistance (5) ja jc tsot-23-8............................. 100 ..... 55... c/w notes: 1) exceeding these ratings may damage the device. 2) about the details of en pin?s abs max rating, please refer to page 9, enable 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 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. 4) the device is not guaranteed to function outside of its operating conditions. 5) measured on jesd51-7, 4-layer pcb.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 3 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 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 1 a supply current (quiescent) i q v en = 2v, v fb = 1v 0.7 1 ma hs-switch on resistance hs rds-on v bst-sw =5v 100 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 (6) i limit under 40% duty cycle 3 a oscillator frequency f sw v fb =750mv 440 500 580 khz fold-back frequency f fb v fb <400mv 0.25 f sw maximum duty cycle d max v fb =700mv 90 95 % minimum on time (6) on_min 60 ns sync frequency range f sync 0.2 2 mhz t a =25c 791 807 823 feedback voltage v fb -40c mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 4 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performanc e characteristics performance waveforms are tested on the evaluation board in the design example section. t a = 25c, unless otherwise noted.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 5 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performanc e characteristics (continued) performance waveforms are tested on the evaluation board in the design example section. t a = 25c, unless otherwise noted.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 6 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performanc e characteristics (continued) performance waveforms are tested on the evaluation board in the design example section. t a = 25c, unless otherwise noted.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 7 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions package pin # name description 1 ss soft-start. connect an external capacitor to pr ogram the soft start time for the switch mode regulator. 2 in supply voltage. the mp1496 operates from a 4.5v-to-16v input rail. c1 decouples the input rail. use wide pcb trace to make the connection. 3 sw switch output. connect using a wide pcb trace. 4 gnd system ground. reference ground of the regu lated output voltage. use special care in pcb layout: connect to gnd with copper and vias. 5 bst bootstrap. connect a capacit or between sw and bst pins to form a floating supply across the high-side switch driver. a 10 ? resistor placed between sw and bst cap. is strongly recommended to reduce sw spike voltage. 6 en/sync enable/synchronize. en high to enable t he mp1496. apply an external clock to en/sync pin to change the switching frequency. 7 vcc bias supply. decouple with 0.1 f-to-0.22 f cap. the capacitance should not exceed 0.22 f. vcc capacitor should be put closely to vcc pin and gnd pin. 8 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 co mparator lowers the oscillator frequency when the fb voltage is below 400mv to pr event current-limit runaway during a short- circuit fault.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 8 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. block diagram 50pf 1meg bst rsen in oscillator vcc regulator bootstrap regulator vcc currrent sense amplifer vcc ss 6.5v current limit comparator error amplifier reference en fb + + - + - + - sw gnd ls driver hs driver comparator on time control logic control 1pf 400k figure 1: functional block diagram
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 9 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. operation the mp1496 is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in power mosfets. it offers a very compact solution to achieve 2a continuous output current with excellent load and line regulation over a wide input supply range, the mp1496 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 comp set current value within 95% of one pwm period, the power mosfet turns off. internal regulator the 5v internal regulator powers 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 is less than 5.0v, the output decreases and requires a 0.1f ceramic decoupling capacitor. error amplifier the error amplifier compares the fb pin voltage against the internal 0.8v reference (ref) and outputs a comp voltage, which controls the power mosfet current. the optimized internal compensation network minimizes the external component counts and simplifies the control loop design. enable/sync control en 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 1m ? resistor from en to gnd allows en to float to shut down the chip. a 6.5v-series zener diode clamps the en pin internally as shown in figure 2. the en input pin can then connect through a pullup resistor to any voltage connected to the in pin: the pullup resistor limits the en input current to less than 100a. for example, with v in =12v, r pullup [(12v ? 6.5v) 100a = 55k ? ]. directly connecting the en pin a voltage source without any pullup resistor requires limiting the voltage source amplitude to below 6.5v to prevent damaging the zener diode. en/sync en logic zener 6.5v-typ gnd figure 2: zener diode circuit for external clock synchronization, connect a clock with a frequency range between 200khz and 2mhz 2ms after setting the output voltage: the internal clock?s rising edge synchronizes with the external clock rising edge. select an external clock signal with a pulse width less than 1.7 s. under-voltage lockout under-voltage lockout (uvlo) protects the chip from operating at an insufficient supply voltage. the mp1496 uvlo comparator monitors the output voltage of the internal regulator, vcc. the uvlo rising threshold is about 3.9v while its falling threshold is 3.25v. external soft-start adjust the soft-start time by connecting a capacitor from ss pin to ground. when the soft- start begins, an internal 11a current source charges the external capacitor. during soft-start, the soft-start capacitor connects to the non- inverting input of the error amplifier. the soft-start period continues until the voltage on the soft-start capacitor exceeds the 0.8v reference. then the non-inverting amplifier uses the reference voltage takes as the input. use the following equation to calculate the soft-start time: ss 0.8v css(nf) t(ms) 11 a =
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 10 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. over-current protection and hiccup the mp1496 has a cycle-by-cycle over-current limit when the inductor current peak exceeds the set current-limit threshold. meanwhile, output voltage drops until fb falls below the under- voltage (uv) threshold?typically 50% below the reference. once uv triggers, the mp1496 enters hiccup mode to periodically restart the part. this protection mode is especially useful when the output is dead-shorted to ground. this greatly reduces the average short circuit current, alleviates thermal issues, and protects the regulator. the mp1496 exits 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 150c, the whole chip shuts down. when the temperature drops below its lower threshold? typically 130c?the chip is enabled again. floating driver and bootstrap charging an external bootstrap capacitor powers the floating power mosfet driver. this floating driver has its own uvlo protection with a rising threshold of 2.2v and a hysteresis of 150mv. the bootstrap capacitor voltage is regulated internally by v in through d1, m1, c4, l1 and c2 (see figure 3). if (v in -v sw ) exceeds 5v, u1 will regulate m1 to maintain a 5v bst voltage across c4. a 10 ? resistor placed between sw and bst cap. is strongly recommended to reduce sw spike voltage. figure 3: internal bootstrap startup and shutdown charging circuit if both v in and en exceed their appropriate thresholds, the chip starts. the reference block starts first, generating stable reference voltages 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 shutdown, 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.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 11 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. application information setting the output voltage the external resistor divider sets the output voltage (see the typical application on page 1). the feedback resistor r1?in conjunction with the internal compensation capacitor?also sets the feedback loop bandwidth. r2 is then given by: out r1 r2 v 1 0.807v = ? the t-type network shown in figure 4 is highly recommended. fb 8 rt r2 r1 vout figure 4: 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 ? ) 1.0 20.5 82 82 1.2 30.1 60.4 82 1.8 40.2 32.4 56 2.5 40.2 19.1 33 3.3 40.2 13 33 5 40.2 7.68 33 selecting the inductor use a 1h-to-10h inductor with a dc current rating of at least 25% percent higher than the maximum load current for most applications. select an inductor with a dc resistance less than 15m ? for highest efficiency. 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 an 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 inductance for improved light-load efficiency. selecting the input capacitor the input current to the step-down converter is discontinuous, and therefore requires a capacitor to supply the ac current to the step- down converter while maintaining the dc-input voltage. use low-esr capacitors for best performance, especially ceramic capacitors with x5r or x7r dielectrics for their low esr and small temperature coefficients. for most applications, use a 22f capacitor. since the input capacitor (c1) absorbs the input switching current, it requires an adequate ripple current rating. estimate the rms current in the input capacitor with: ? ? ? ? ? ? ? ? ? = 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 the maximum load current. the input capacitor can be electrolytic, tantalum or ceramic. when using electrolytic or tantalum capacitors, place a small, high quality ceramic capacitor?e.g. 0.1 f?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 ?? = ? ?? ??
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 12 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. 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 esr value of the output capacitor. for ceramic capacitors, the capacitance dominates the impedance at the switching frequency, and causes most 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 mp1496 can be optimized for a wide range of capacitance and esr values. external bootstrap diode an external bootstrap diode can improve the regulator efficiency, given the following applicable conditions: z v out is 5v or 3.3v; and z duty cycle is high: d= in out v v >65% in these cases, use an external bst diode from the vcc pin to bst pin, as shown in figure 5. figure 5: optional external bootstrap diode to enhance efficiency the recommended external bst diode is in4148, and the bst capacitor value is 0.1f to 1 f. pc board layout (8) pcb layout is very important to achieve stable operation especially for vcc capacitor and input capacitor placement. for best results, follow these guidelines: 1) use large ground plane directly connect to gnd pin. add vias near the gnd pin if bottom layer is ground plane. 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) place the ceramic input capacitor close to in and gnd pins. keep the connection of input capacitor and in pin as short and wide as possible. 4) route sw, bst away from sensitive analog areas such as fb. it?s not recommended to route sw, bst trace under chip?s bottom side. 5) place the t-type feedback resistor r9 close to chip to ensure the trace which connects to fb pin as short as possible notes: 8) the recommended layout is based on the figure 6 typical application circuit on the last page.
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 13 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. 8 7 6 5 l1 c2 c2a c1 c1a r5 r6 r9 r1 r2 r3 r4 c3 c4 c5 c6 1 2 3 4 vin gnd vout sw gnd gnd sw gnd en/sync bst
mp1496 ? synchronous, step-down co nverter with internal mosfets mp1496 rev. 1.05 www.monolithicpower.com 14 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical application circuits en/sync ss gnd fb sw bst in vcc c3 15pf c1a ns c5 22nf r3 0 3.3v r1 40.2k r2 13k r9 33k r6 11k r5 28.7k v in 4.5-16v r4 10 5 3 8 4 6 1 7 2 mp1496 figure 6: 12v in , 3.3v/2a
mp1496 ? synchronous, step-down co nverter with internal mosfets 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. mp1496 rev. 1.05 www.monolithicpower.com 15 12/26/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. package information tsot23-8

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