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LT3489 1 3489f a vdd load current (ma) 0 efficiency (%) 65 70 75 300 500 3489 ta01b 60 55 50 100 200 400 80 85 90 700 600 v on load = 10ma v off load = 20ma 2mhz boost dc/dc converter with 2.5a switch and soft-start the lt ? 3489 is a ? xed frequency step-up dc/dc converter containing an internal 2.5a, 40v switch. the LT3489 is ideal for large tft-lcd panel power supplies. the LT3489 switches at 2mhz, allowing the use of tiny, low pro? le inductors and low value ceramic capacitors. loop com- pensation can be either internal or external, giving the user ? exibility in setting loop compensation and allow- ing optimized transient response with low esr ceramic output capacitors. soft-start is controlled with an external capacitor, which determines the input current ramp rate during start-up. the 8-lead ms8e package and high switching frequency en- sure a low pro? le overall solution less than 1.1mm high. tft-lcd bias supplies gps receivers dsl modems local power supply 2.5a, 0.12 , 40v internal switch 2mhz switching frequency integrated soft-start function v in range: 2.6v to 16v adjustable output from v in to 40v low v cesat switch: 110mv at 1a (typical) 8v at 610ma from a 3.3v input internal or external loop compensation small 8-lead ms8e low pro? le, triple output tft supply (8v, C8v, 23v) applicatio s u features descriptio u typical applicatio u , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. v in v in 3.3v sw fb LT3489 2.2 h 5.23k 37.4k 28.7k 3489 ta01 20 f 220pf 0.1 f 0.1 f 0.1 f 2 f 2 f 4.7 f 100nf v off ?8v 20ma av dd 8v 610ma v on 23v 10ma 0.1 f v c gnd shdn ss comp + off on ef? ciency
LT3489 2 3489f v in voltage ................................................................16v sw voltage ................................................ C0.4v to 40v fb, v c , comp, ss voltages .........................................6v shdn voltage ...........................................................16v current into fb pin ................................................1ma maximum junction temperature .......................... 125c operating temperature range (note 2) ... C40c to 85c storage temperature range ................... C65c to 150c lead temperature (soldering, 10 sec) .................. 300c (note 1) the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v in = 3v, v shdn = v in unless otherwise noted. (note 2) note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the LT3489e is guaranteed to meet performance speci? cations from 0c to 70c. speci? cations over the 40c to 85c operating parameter conditions min typ max units minimum operating voltage 2.4 2.6 v maximum operating voltage 16 v feedback voltage 1.22 1.21 1.235 1.26 1.26 v v fb pin bias current v fb = 1.25v (note 3) 100 250 na error amp transconductance i = 10 a 100 mhos error amp voltage gain 80 v/v quiescent current v shdn = 2.5v, not switching 2 4 ma quiescent current in shutdown v shdn = 0v, v in = 3v 0 1 a reference line regulation 2.6v v in 16v 0.01 0.05 % switching frequency 1.8 2 2.2 mhz maximum switch duty cycle 85 90 % switch current limit (note 4) 2.5 3.5 5 a switch v cesat i sw = 2a 0.23 v switch leakage current v sw = 5v 0.01 1 a shdn pin current v shdn = 5v v shdn = 1.4v v shdn = 0v 100 20 2 a a a shdn pin threshold 0.3 1.5 2 v soft-start charging current v ss = 0.5v 5 10 20 a electrical characteristics absolute axi u rati gs w ww u package/order i for atio uu w 1 2 3 4 v c fb shdn gnd 8 7 6 5 ss comp v in sw top view ms8e package 8-lead plastic msop t jmax = 125c, ja = 40c/w, jc = 10c/w exposed pad (pin 9) is gnd (must be soldered to pcb) order part number ms8e part marking LT3489ems8e ltbyf order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/ consult ltc marketing for parts speci? ed with wider operating temperature ranges. temperature range are assured by design, characterization and correlation with statistical process controls. note 3: current ? ows out of the fb pin. note 4: current limit guaranteed by design and/or correlation to static test. current limit is independent of duty cycle and is guaranteed by design.
LT3489 3 3489f temperature (?c) ?50 feedback voltage (v) 1.25 1.26 1.27 25 75 3489 g01 1.24 1.23 ?25 0 50 100 125 1.22 1.21 temperature ( c) ?50 1.6 oscillator frequency (mhz) 1.8 2.0 2.2 2.4 ?25 0 25 50 3489 g02 75 100 125 temperature ( c) ?50 current limit (a) 1.5 2.0 2.5 25 75 3489 03 1.0 0.5 0 ?25 0 50 3.0 3.5 4.0 100 switch current (a) 1 0 v ce(sat) (mv) 100 200 300 400 500 600 0.5 1.0 1.5 2.0 3489 g04 2.5 ?50 c 25 c 125 c temperature (?c) ?50 quiescent current (ma) 3.0 3.5 4.0 25 75 3489 g05 2.5 2.0 ?25 0 50 100 125 1.5 1.0 v out 100mv/div ac coupled i l 1a/div v sw 10v/div 200ns/div v in = 3.3v a vdd = 8v i load , a vdd = 400ma v on = 23v, 10ma v off = ?8v, 20ma 3489 g06 feedback pin voltage oscillator frequency current limit switch v ce(sat) voltage quiescent current switching waveform for the cover page circuit typical perfor a ce characteristics uw t a = 25c unless otherwise noted.
LT3489 4 3489f pi fu ctio s uuu block diagra w v c (pin 1): error ampli? er output pin. tie external compen- sation network to this pin, or use the internal compensation network by shorting the v c pin to the comp pin. fb (pin 2): feedback pin. reference voltage is 1.235v. connect resistive divider tap here. minimize the trace area at fb. set v out according to v out = 1.235 ? (1 + r1/r2). shdn (pin 3): shutdown pin. tie to 2v or more to enable device. ground to shut down. do not ? oat this pin. gnd (pin 4): ground. tie directly to local ground plane. sw (pin 5): switch pin. this is the collector of the internal npn power switch. minimize the metal trace area connected to this pin to minimize emi. v in (pin 6): input supply pin. must be locally bypassed. comp (pin 7): internal compensation pin. provides an internal compensation network. tie directly to the v c pin for internal compensation. tie to gnd if not in use. ss (pin 8): soft-start pin. place a soft-start capacitor here. upon start-up, 10 a of current charges the capacitor to 1.8v. use a larger capacitor for slower start-up. leave ? oating if not in use. exposed pad (pin 9): ground. must be soldered to pcb. ? + ? + a2 fb shdn shutdown v in driver q1 0.01 ? 100k 125pf sw gnd comparator 5 v c 1 comp 4 s rq ramp generator 2mhz oscillator ? + 2 3 1.235v reference 6 ss + 8 7 r1 (external) fb v out r2 (external) a1 gnd 9 3489 f01 figure 1. block diagram
LT3489 5 3489f operatio u the LT3489 uses a constant frequency, current mode con- trol scheme to provide excellent line and load regulation. please refer to figure 1 for the following description of the parts operation. at the start of the oscillator cycle, the sr latch is set, turning on the power switch, q1. the switch current ? ows through the internal current sense resistor generating a voltage. this voltage is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the pwm comparator, a2. when this voltage exceeds the level at the negative input of a2, the sr latch is reset, turning off the power switch. the level at the negative input of a2 (v c pin) is set by the error ampli? er (g m ) and is simply an ampli? ed version of the difference between the feedback voltage and the reference voltage of 1.235v. in this manner, the error ampli? er sets the correct peak current level to keep the output in regulation. a soft-start function is provided to enable a clean start-up for the LT3489. when the part is brought out of shut- down, 10a of current is sourced out of the ss pin. by connecting an external capacitor to the ss pin, the rate of voltage rise on the pin can be set. typical values for the soft-start capacitor range from 10nf to 200nf. the ss pin indirectly limits the rate of rise on the v c pin, which in turn limits the peak switch current. current limit is not shown in figure 1. the switch current is constantly monitored and not allowed to exceed the nominal value of 2.5a. if the switch current reaches 2.5a, the sr latch is reset regardless of the output of comparator a2. this current limit helps protect the power switch as well as the external components connected to the LT3489.
LT3489 6 3489f inductor selection several inductors that work well with the LT3489 are listed in table 1. this table is not exclusive; there are many other manufacturers and inductors that can be used. consult each manufacturer for more detailed information and for their entire selection of related parts, as many different sizes and shapes are available. ferrite core inductors should be used to obtain the best ef? ciency, as core losses at 2mhz are much lower for ferrite cores than for the cheaper powdered-iron ones. choose an inductor that can handle at least 2.5a without saturating, and ensure that the inductor has a low dcr (copper wire resistance) to minimize i 2 r power losses. a 2.2 h to 5 h inductor will be the best choice for most LT3489 designs. note that in some applications, the current handling require- ments of the inductor can be lower, such as in the sepic topology where each inductor only carries one-half of the total switch current. the inductors shown in table 1 were chosen for small size. for better ef? ciency, use similar valued inductors with a larger volume. capacitor selection low esr (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. multilayer ceramic capacitors are an excellent choice, as they have an extremely low esr and are available in very small packages. x5r or x7r dielectrics are preferred, as these materials retain the capacitance over wide voltage and temperature ranges. a 4.7f to 20f output capacitor is suf? cient for most applications, but systems with very low output currents may need only a 1f or 2.2f output capacitor. solid tantalum or os-con capacitors can be used, but they will occupy more board area than a ceramic and will have a higher esr. always use a capacitor with a suf? cient voltage rating. ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to the LT3489. a 2.2 f to 4.7 f input capacitor is suf? cient for most applications. table 2 shows a list of several ceramic capacitor manufacturers. consult the manufacturers for detailed information on their entire selection of ceramic parts. applicatio s i for atio wu u u table 1. recommended inductors part l ( h) typical dcr (m ) size l w h (mm) vendor sd25-2r2 sd25-3r3 sd25-4r7 2.2 3.3 4.7 31 38 47 5.45 5.45 2.7 cooperbussmann (888) 414-2645 www.cooperet.com a916cy-2r7m a916cy-3r3m a916cy-4r7m 2.7 3.3 4.7 18.3 21.4 26.3 6 6 3.5 toko www.toko.com lqh55dn2r2m03 lqh55dn3r3m03 lqh55dn4r7m03 2.2 3.3 4.7 29 36 41 5.7 5 4.7 murata (770) 436-1300 www.murata.com table 2. ceramic capacitor manufacturers taiyo yuden (408) 573-4150 www.t-yuden.com avx (843) 448-9411 www.avxcorp.com murata (770) 436-1300 www.murata.com
LT3489 7 3489f diode selection schottky diodes, with their low forward voltage drop and fast switching speed, are ideal for LT3489 applications. table 3 lists several schottky diodes that work well with the LT3489. the diodes average current rating must exceed the average output current. the diodes maximum reverse voltage must exceed the output voltage. the diode conducts current only when the power switch is turned off (typically less than 50% duty cycle), so a 3a diode is suf? cient for most designs. the companies below also offer schottky diodes with high voltage and current ratings. applicatio s i for atio wu u u frequency compensation to compensate the feedback loop of the LT3489, a series resistor-capacitor network should be connected from the comp pin to gnd. for most applications, a capacitor in the range of 220pf to 680pf will suf? ce. a good starting value for the compensation capacitor, c c , is 470pf. the compensation resistor, r c , is usually in the range of 20k to 100k. a thorough analysis of the switching regulator control loop is not within the scope of this data sheet and will not be presented here, but values of 20k and 680pf will be a good choice for many designs. table 3. suggested diodes manufacturer part number maximum current (a) maximum reverse voltage (v) manufacturer ups340 ups315 3 3 40 15 microsemi www.microsemi.com b220 b230 b240 b320 b330 b340 sbm340 2 2 2 3 3 3 3 20 30 40 20 30 40 40 diodes, inc www.diodes.com setting output voltage to set the output voltage, select the values of r1 and r2 (see figure 1) according to the following equation: rr v v out 12 1 235 1 =? ? ? ? ? ? ? . a good range for r2 is from 5k to 30k. board layout the high speed operation of the LT3489 demands care- ful attention to board layout. for high-current switching regulators like the LT3489, the board layout must have good thermal performance. vias located underneath the part should be connected to an internal ground plane to improve heat transfer from the LT3489 to the pcb board. you will not get advertised performance with careless lay- out. thermal and noise consideration must be taken into account. figure 2 shows the recommended component placement for a boost converter. 1 2 8 7 3 4 6 5 l1 c2 LT3489 v out v in gnd shutdown r1 r2 multiple vias ground plane 3489 f02 c1 c ss c c r c + figure 2. recommended component placement for boost converter. note direct high current paths using wide pc traces. minimize trace area at pin 1 (v c ) and pin 2 (fb). use multiple vias to tie pin 4 copper to ground plane. use vias at one location only to avoid introducing switching currents into the ground plane
LT3489 8 3489f load current (a) 0 efficiency (%) 75 80 85 1.1 3489 ta09 65 50 0.2 0.3 0.1 0.4 0.6 0.5 0.8 0.7 1.0 0.9 90 70 60 55 v in = 3.3v v in = 5v v in v in 3.3v to 5v sw fb 3 8 7 14 2 65 LT3489 l1 2.2 h d1 r2 5.23k r1 28.7k r c 35.7k 3489 ta02 c2 20 f c1 4.7 f c c 330pf c ss 100nf v out 650ma, v in = 3.3v 1.1a, v in = 5v v c gnd shdn ss comp c1: avx 08056d475kat c2: 2 10 f, taiyo yuden lmk3168bj106ml d1: diodes inc. dfls220l l1: cooper bussmann sd25-2r2 *exposed pad must also be grounded + off on typical applicatio s u 8v output boost converter ef? ciency transient response v out 100mv/div ac coupled i l1 1a/div 400ma i out 200ma 50 s/div v in = 3.3v 3489 g10
LT3489 9 3489f v in v in 3.3v to 5v sw fb LT3489 l1 3.3 h d1 c ss 100nf c c 680pf r c 16.5k v out 12v 625ma, v in = 5v 410ma, v in = 3.3v 3489 ta03 c2 10 f c1 4.7 f v c gnd comp ss shdn 3 65 4 7 8 2 1 c1: taiyo yuden jmk212bj475mg, 4.7 f, 6.3v c2: taiyo yuden gmk316bj106ml, 10 f, 35v d1: diodes, inc. dfls220 l1: toko a916cy-3r3m (type d63cb) r1 84.5k r2 9.76k off on 12v output boost converter typical applicatio s u ef? ciency transient response load current (a) 0 40 efficiency (%) 45 55 60 65 90 75 0.2 0.4 0.5 3489 ta05 50 80 85 70 0.1 0.3 0.6 0.7 v in = 3.3v v in = 5v v out 500mv/div ac coupled i l1 1a/div 300ma i out 100ma 50 s/div v in = 3.3v 3489 ta06
LT3489 10 3489f a vdd load current (ma) 0 efficiency (%) 65 70 75 300 500 3489 ta01b 60 55 50 100 200 400 80 85 90 700 600 v on load = 10ma v off load = 20ma typical applicatio u v in v in 3.3v sw fb LT3489 l1 2.2 h d1 r3 5.23k r2 28.7k 3489 ta04 c2 20 f c5 0.1 f c6 0.1 f c7 0.1 f c4 2 f c3 2 f c1 4.7 f c ss 100nf d7 d2 d3 v off ?8v 20ma av dd 8v 610ma v on 23v 10ma d6 c8 0.1 f v c gnd* shdn 3 8 7 14 2 5 6 ss comp + d4 d5 c1 to c8: x5r or x7r c1: avx 08056d475kat c2: 2 10 f, taiyo yuden lmk316bj106ml c3: 2 10 f, 10v c4: 2 1 f, avx08053d105kat c5, c6, c7: 0.1 f, 10v c8: 0.1 f, 16v d1: diodes inc. dfls220l d2 to d7: zetex bat54s or equivalent l1: cooper bussmann sd25-2r2 * exposed pad must also be grounded off on 10ma 37.4k 220pf transient response start-up waveforms a vdd 100mv/div ac coupled i l1 1a/div 400ma i load 200ma 5 s/div 3489 ta07 a vdd 5v/div v on 20v/div v off 5v/div i in 0.5a/div 5ms/div 3489 ta08 effciency
LT3489 11 3489f information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package descriptio u ms8e package 8-lead plastic msop (reference ltc dwg # 05-08-1662) msop (ms8e) 0603 0.53 0.152 (.021 .006) seating plane note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.18 (.007) 0.254 (.010) 1.10 (.043) max 0.22 ? 0.38 (.009 ? .015) typ 0.127 0.076 (.005 .003) 0.86 (.034) ref 0.65 (.0256) bsc 0 ? 6 typ detail ?a? detail ?a? gauge plane 12 3 4 4.90 0.152 (.193 .006) 8 8 1 bottom view of exposed pad option 7 6 5 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) 0.52 (.0205) ref 1.83 0.102 (.072 .004) 2.06 0.102 (.081 .004) 5.23 (.206) min 3.20 ? 3.45 (.126 ? .136) 2.083 0.102 (.082 .004) 2.794 0.102 (.110 .004) 0.889 0.127 (.035 .005) recommended solder pad layout 0.42 0.038 (.0165 .0015) typ 0.65 (.0256) bsc
LT3489 12 3489f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2006 lt 0606 ? printed in usa part number description comments lt1613 550ma (i sw ), 1.4mhz, high ef? ciency step-up dc/dc converter v in : 0.9v to 10v, v out(max) = 34v, i q = 3ma, i sd = <1 # a, thinsot tm package lt1615/lt1615-1 300ma/80ma (i sw ), high ef? ciency step-up dc/dc converters v in : 1v to 15v, v out(max) = 34v, i q = 20 # a, i sd = <1 # a, thinsot package lt1618 1.5a (i sw ), 1.25mhz, high ef? ciency step-up dc/dc converter v in : 1.6v to 18v, v out(max) = 35v, i q = 1.8ma, i sd = <1 # a, ms package lt1930/lt1930a 1a (i sw ), 1.2mhz/2.2mhz, high ef? ciency step-up dc/dc converters v in : 2.6v to 16v, v out(max) = 34v, i q = 4.2ma/5.5ma, i sd = <1 # a, thinsot package lt1935 2a (i sw ), 1.2mhz/2.7mhz, high ef? ciency step-up dc/dc converter v in : 2.3v to 16v, v out(max) = 38v, i q = 3ma, i sd = <1 # a, thinsot package lt1946/lt1946a 1.5a (i sw ), 1.2mhz, high ef? ciency step-up dc/dc converters v in : 2.45v to 16v, v out(max) = 34v, i q = 3.2ma, i sd = <1 # a, ms8 package lt1961 1.5a (i sw ), 1.25mhz, high ef? ciency step-up dc/dc converter v in : 3v to 25v, v out(max) = 35v, i q = 0.9ma, i sd = 6 # a, ms8e package lt3436 3a (i sw ), 1mhz, 34v step-up dc/dc converter v in : 3v to 25v, v out(max) = 34v, i q = 0.9ma, i sd = <6 # a, tssop-16e package lt3464 85ma (i sw ), high ef? ciency step-up dc/dc converter with integrated schottky and pnp disconnect v in : 2.3v to 10v, v out(max) = 34v, i q = 25 # a, i sd = <1 # a, thinsot package lt3467/lt3467a 1.1a (i sw ), 1.3mhz/2.7mhz, high ef? ciency step-up dc/dc converters v in : 2.6v to 16v, v out(max) = 40v, i q = 1.2ma, i sd = <1 # a, thinsot package lt3477 3a (i sw ), 3.5mhz, high ef? ciency step-up dc/dc converter with dual rail-to-rail current sense v in : 2.5v to 24v, v out(max) = 40v, i q = 5ma, i sd = <1 # a, qfn, tssop-20e packages lt3479 3a (i sw ), 3.5mhz, high ef? ciency step-up dc/dc converter v in : 2.5v to 24v, v out(max) = 40v, i q = 5ma, i sd = <1 # a, dfn. tssop-16e packages thinsot is a trademark of linear technology corporation. related parts

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