View MP1497_7309396.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

MP1497 high-efficiency, 3a, 16v, 500khz synchronous, step-down converter MP1497 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 MP1497 is a high-frequency, synchronous, rectified, step-down switch mode converter with built in internal 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 MP1497 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, thermal shutdown, and external ss control. the MP1497 requires a minimal number of readily-available external components and is available in a space-saving 8-pin tsot23 package. features ? wide 4.5v-to-16v operating input range ? 80m ? /30m ? low r ds(on) internal power mosfets ? proprietary switching-loss?reduction technique ? high-efficiency synchronous mode operation ? fixed 500khz switching frequency ? can synchronize to a 200khz-to-2mhz external clock ? externally-programmable soft-start ? 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 ? 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 MP1497 in en/sync vcc ss gnd fb sw bst vin en c3 0.1 r1 r3 33k 40.2k r 2 13k l1 c2 c4 c1 22 2 6 7 1 5 3 8 4 3.3 4.5v-16v v/3a c5 22
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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 MP1497dj tsot-23-8 acq for tape & reel, add suffix ?z (e.g. MP1497dj?z); for rohs, compliant packaging, add suffix ?lf (e.g. MP1497dj?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 the 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.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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 80 m ? ls-switch on resistance ls rds-on v cc =5v 30 m ? switch leakage sw lkg v en = 0v, v sw =12v 1 a current limit (6) i limit under 40% duty cycle 4.2 5 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 MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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 program the soft start time for the switch- mode regulator. 2 in supply voltage. the MP1497 operates from a 4. 5v-to-16v input rail. use c1 to decouple the input rail. connect using a wide pcb trace. 3 sw switch output. connect using a wide pcb trace. 4 gnd system ground. the regulated output voltage reference ground. 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 the mp 1497. apply an external clock to change the switching frequency. 7 vcc bias supply. decouple with a 0.1 f-to-0.22 f capacitor. avoid a capacitance that exceeds 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 comparator lowers the oscillator frequency when the fb voltage drops below 400mv to prevent current-limit run-away during a short-circuit fault.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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 MP1497 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 MP1497 operates in a fixed-frequency, peak-current?control mode to regulate the output voltage. the 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 will be forced to turn 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 below 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 that 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. the en pin is clamped internally using a 6.5v series-zener-diode as shown in figure 2. connecting the en pin through a pullup resistor to any voltage connected to v in limits the en input current to less than 100a. for example, when connecting v in to a 12v source, r pullup [(12v ? 6.5v) 100a = 55k ? ]. connecting the en pin directly to a voltage source without any pullup resistor requires limiting the amplitude of the voltage source 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 of 200khz and 2mhz 2ms after the output voltage is set: the internal clock rising edge will synchronize 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 MP1497 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 the ss pin to ground. when the soft-start period starts, an internal 11a current source charges the external capacitor. the soft- start capacitor connects to the non-inverting input of the error amplifier. the soft-start period lasts until the voltage on the soft-start capacitor exceeds the reference voltage of 0.8v. at this point, the non-inverting amplifier uses the reference voltage. the soft-start time can be calculated as: ss ss 0.8v c (nf) t(ms) 11 a = over-current-protection and hiccup the MP1497 has a cycle-by-cycle over-current limit that protects against the inductor current peak value exceeding the set current limit threshold. under-voltage protection (uvp) triggers if the fb voltage drops below the
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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. under-voltage (uv) threshold?typically 50% below the reference. once uvp triggers, the MP1497 enters hiccup mode to periodically restart the part. this protection mode is especially useful when the output is dead- shorted to ground. the average short-circuit current falls to alleviate thermal issues and to protect the regulator. the MP1497 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, it shuts down the whole chip. 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 (figure 3). if (v in -v sw ) exceed 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 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. for 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.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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 typical application on page 1). the feedback resistor (r1) sets the feedback loop bandwidth in conjunction with the internal compensation capacitor. r2 is then: 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 resistors value for common output voltages. table 1: resistor values 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. for highest efficiency, select an inductor with a dc resistance less than 15m ? . for most designs, calculate the inductance value with: 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, therefore requires a capacitor supply the ac current to the step-down converter while maintaining the dc input voltage. use low-esr capacitors for the best performance, such as ceramic capacitors with x5r or x7r dielectrics that have low esr and small temperature coefficients. for most applications, use a 22f capacitor. the input capacitor (c1) requires an adequate ripple current rating because it absorbs the input switching current. estimate the rms current in the input capacitor as: ? ? ? ? ? ? ? ? ? = in out in out load 1 c v v 1 v v i i the worst-case condition occurs at v in =2v out , where: 2 i i load 1 c = for simplification, choose the 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, include 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 prevent excessive input voltage ripple. estimate the input voltage ripple caused by the capacitance as: 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. low esr capacitors are preferred to keep the output
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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. 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 of the output capacitor. for ceramic capacitors, the capacitance dominates the impedance at the switching frequency. the capacitance also causes the majority of the output voltage ripple. for simplification, estimate the output voltage ripple with: 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 mp1495 can be optimized for a wide range of capacitance and esr values. external bootstrap diode an external bootstrap diode can enhance the efficiency of the regulator, given the following conditions: z v out is 5v or 3.3v; and z duty cycle is high: d= in out v v >65% in these cases, connect 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 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 next page.
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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
MP1497 ? synchronous, step-down co nverter with internal mosfets MP1497 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 MP1497 in vcc ss en/sync bst sw gnd fb c1a ns 2 7 1 6 4 8 3 5 v in 4.5-16v r4 10 r9 33k r1 40.2k r2 13k c3 15pf 3.3v r3 0 c5 22nf r5 28.7k r6 11k figure 6: 12v in , 3.3v/3a
MP1497 ? 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. MP1497 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 front view note: 1) all dimensions are in millimeters. 2) package length does not include mold flash, protrusion or gate burr. 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bot tom of leads after forming) shall be 0.10 millimeters max. 5) jedec reference is mo-193, variation ba. 6) drawing is not to scale. 7) pin 1 is lower left pin when reading top mark from left to right, (see example top mark) top view recommended land pattern seating plane side view detail ''a'' see detail ''a'' pin 1 id see note 7 example top mark

▲Up To Search▲

Price & Availability of MP1497

	To Download MP1497 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .