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lt3518 1 3518fd features applications description full-featured led driver with 2.3a switch current the lt ? 3518 is a current mode dc/dc converter with an internal 2.3a, 45v switch specifcally designed to drive leds. the lt3518 operates as a led driver in boost, buck mode and buck-boost mode. it combines a traditional voltage loop and a unique current loop to operate as a constant-current source or constant-voltage source. pro - grammable switching frequency allows optimization of the external components for effciency or component size. the switching frequency of the lt3518 can be synchronized to an external clock signal. the led current is externally programmable with a 100mv sense resistor. the external pwm input provides 3000:1 led dimming. the ctrl pin provides further 10:1 dimming ratio. the lt3518 is available in the tiny footprint 16-lead qfn (4mm 4mm) and the 16-pin tssop package. the lt3518 provides a complete solution for both constant-voltage and constant-current applications. n 3000:1 true color pwm? dimming ratio n 2.3a, 45v internal switch n 100mv high side current sense n open led protection n adjustable frequency: 250khz to 2.5mhz n wide input voltage range: operation from 3v to 30v transient protection to 40v n operates in boost, buck mode and buck-boost mode n gate driver for pmos led disconnect n constant-current and constant-voltage regulation n ctrl pin provides 10:1 analog dimming n low shutdown current: <1a n available in (4mm 4mm) 16-lead qfn and 16-pin tssop packages n display backlighting n automotive and avionic lighting n illumination n scanners 1.5a buck mode led driver effciency l , lt, ltc and ltm are registered trademarks of linear technology corporation. true color pwm is a trademark of linear technology corporation. patent pending. all other trademarks are the property of their respective owners. protected by u.s. patents, including 7199560, 7321203, 7746300. 1.5a 10f 15h 2.2f 0.1f 68m m1 2.2f v ref isp tgen gnd v ref v c 16.9k 1mhz 3518 ta01a 0.1f v in shdn ctrl pwm sync fb ss r t sw pv in 24v v in 3.3v isn lt3518 tg pwm pwm duty cycle (%) 0 40 efficiency (%) 50 60 70 80 90 100 20 40 60 80 3518 ta01b 100 ctrl = v ref typical application
lt3518 2 3518fd absolute maximum ratings v in , shdn , pwm, tgen (note 3) .............................. 40v sw, isp, isn, tg ........................................................ 45v tg pin below isp pin ................................................ 10v fb, sync, ss, ctrl ................................................... 6v v c , r t , v ref ................................................................. 3v operating junction temperature range (notes 2, 4) lt3518e ............................................. C40c to 125c lt3518i .............................................. C40c to 125c lt3518h ............................................ C40c to 150c (note 1) 16 15 14 13 5 6 7 8 top view 17 uf package 16-lead (4mm 4mm) plastic qfn 9 10 11 12 4 3 2 1sw sw v in shdn fb v c ctrl pwm tg isp isn tgen v ref r t sync ss t jmax = 125c, v ja = 36c/w exposed pad (pin 17) is gnd, must be soldered to pcb fe package 16-lead plastic tssop 1 2 3 4 5 6 7 8 top view 16 15 14 13 12 11 10 9 v in shdn v ref r t sync ss pwm ctrl sw sw tg isp isn tgen fb v c 17 gnd t jmax = 150c, v ja = 40c/w, v jc(pad) = 10c/w pin configuration order information lead free finish tape and reel part marking * package description temperature range lt3518euf#pbf lt3518euf#trpbf 3518 16-lead (4mm w 4mm) plastic qfn C40c to 125c lt3518iuf#pbf lt3518iuf#trpbf 3518 16-lead (4mm w 4mm) plastic qfn C40c to 125c lt3518efe#pbf lt3518efe#trpbf 3518fe 16-lead plastic tssop C40c to 125c lt3518ife#pbf lt3518ife#trpbf 3518fe 16-lead plastic tssop C40c to 125c lt3518hfe#pbf lt3518hfe#trpbf 3518fe 16-lead plastic tssop C40c to 150c consult ltc marketing for parts specifed with wider operating temperature ranges. *the temperature grade is identifed by a label on the shipping container. consult ltc marketing for information on non-standard lead based fnish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifcations, go to: http://www.linear.com/tapeandreel/ storage temperature range qfn .................................................... C65c to 125c tssop ............................................... C65c to 150c lead temperature (soldering, 10 sec) tssop .............................................................. 300c
lt3518 3 3518fd electrical characteristics the l denotes the specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. (note 2) v in = 5v, shdn = 5v, pwm = 5v unless otherwise noted. parameter conditions min typ max units minimum v in operating voltage 3 v maximum v in operating voltage continuous operation (note 3) 30 v current sense voltage (v isp C v isn ) v ctrl = 2v, v isp = 24v, v c = 1v v ctrl = 2v, v isp = 0v, v c = 1v l 96 100 100 103 mv mv 10% scale current sense voltage (v isp C v isn ) v ctrl = 100mv, v isp = 24v, v c = 1v 9 mv current sense voltage line regulation 2v < v isp < 45v 0.03 %/v v in supply current pwm > 1.5v, v c = 0v pwm = 0v shdn = 0v 6 4.5 0.1 10 1 ma ma a switching frequency r t = 16.7k r t = 4.03k r t = 91.5k l 0.85 2.25 220 1.0 2.5 250 1.15 2.7 270 mhz mhz khz r t voltage 1 v soft-start pin current ss = 0.5v, out of pin 6 9 12 a sync pull-down current (into the pin) v sync = 2v 60 a sync input low 0.4 v sync input high 1.5 v maximum duty cycle r t = 91.5k (250khz) sync = 300khz clock signal, r t = 91.5k r t = 16.7k (1mhz) r t = 4.03k (2.5mhz) l 95 94 85 97 96 90 74 % % % % switch current limit 2.3 2.8 3.5 a switch v cesat i sw = 1.5a 400 mv switch leakage current v sw = 45v, pwm = 0v 2 a ctrl input bias current current out of pin, v ctrl = 0.1v 20 100 na error amplifer transconductance 550 s v c output impedance 1000 k v c idle input bias current pwm = 0, v c = 1v C20 0 20 na fb pin input bias current current out of pin, v fb = 0.5v 20 100 na fb pin threshold l 0.98 1.01 1.04 v isp , isn idle input bias current pwm = 0v 300 na isp , isn full-scale input bias current isp tied to isn, v isp = 24v, v ctrl = 2v 20 a shdn voltage high l 1.2 v shdn voltage low C40c t j 125c 125c < t j 150c 0.45 0.40 v v shdn pin bias current 60 100 a pwm input high voltage l 1.2 v pwm input low voltage C40c t j 125c 125c < t j 150c 0.45 0.40 v v pwm pin bias current 60 120 a
lt3518 4 3518fd electrical characteristics the l denotes the specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. (note 2) v in = 5v, shdn = 5v, pwm = 5v unless otherwise noted. 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 lt3518e is guaranteed to meet performance specifcations from 0c to 125c junction temperature. specifcations over the C40c to 125c operating junction temperature range are assured by design, characterization and correlation with statistical process controls. the lt3518i is guaranteed over the full C40c to 125c operating junction temperature range. the lt3518h is guaranteed over the full C40c to 150c operating junction temperature range. operating lifetime is derated at junction temperatures greater than 125c. note 3: absolute maximum voltage at v in , shdn , pwm and tgen pins is 40v for nonrepetitive 1 second transients and 30v for continuous operation. note 4: this ic includes overtemperature protection that is intended to protect the device during momentary overload conditions. junction temperature will exceed the maximum operating junction temperature when overtemperature protection is active. continuous operation above the specifed maximum operating junction temperature may impair device reliability. parameter conditions min typ max units tgen input high voltage 1.5 v tgen input low voltage 0.4 v tgen pin bias current tgen = 5v 100 200 a v ref pin voltage i ref = C100a l 1.96 2 2.04 v v ref pin voltage line regulation 3v < v in < 40v 0.03 %/v gate turn-on delay c load = 1nf between isp and tg 200 ns gate turn-off delay c load = 1nf between isp and tg 200 ns top gate drive v gs (v isp C v tg ) v isp = 24v, tgen = 5v pwm = 0v 7 0 0.3 v v
lt3518 5 3518fd typical performance characteristics v isp C v isn threshold vs v ctrl switch current limit vs duty cycle oscillator frequency vs r t v isp C v isn threshold vs temperature switch current limit vs temperature oscillator frequency vs temperature v ctrl (v) 0 0 v isp ? v isn threshold (mv) 20 40 60 80 0.4 0.8 1.2 1.6 3518 g01 100 120 0.2 0.6 1.0 1.4 v in = 5v v isp = 24v v c = 1v t a = 25c duty cycle (%) 0 0 current limit (a) 0.5 1.0 1.5 2.0 2.5 3.0 20 40 60 80 3518 g02 100 t a = 25c r t (k) 1 100 oscillator frequency (khz) 1000 10000 10 100 3518 g03 t a = 25c temperature (c) ?40 v isp ? v isn threshold (mv) 103 20 3518 g04 100 98 ?20 0 40 97 96 104 102 101 99 60 80 100 120 140 160 v in = 5v v isp = 24v v c = 1v v ctrl = 2v temperature (c) ?40 ?15 2.0 current limit (a) 2.4 3.0 ?10 60 85 3518 g05 2.2 2.8 2.6 35 110 135 160 v in = 5v temperature (c) ?40 ?20 1.5 oscillator frequency (mhz) 1.9 2.5 0 40 60 3518 g06 1.7 2.3 2.1 20 80 160 100 120 140 v in = 5v r t = 6.04k reference voltage vs temperature v isp C v isn threshold vs v isp v isp (v) 0 v isp ? v isn threshold (mv) 101 103 105 40 3518 g07 99 97 100 102 104 98 96 95 10 20 30 50 v ctrl = 2v v in = 5v t a = 25c v c = 1v temperature (c) ?40 1.98 v ref (v) 1.99 2.00 2.01 2.02 ?20 0 20 40 3518 g08 60 80 100 120 140 160 v in = 5v quiescent current vs v in v in (v) 0 v in current (ma) 4 5 6 40 3518 g09 3 2 0 10 20 30 1 8 7 t a = 25c v c = 0v
lt3518 6 3518fd typical performance characteristics fb pin threshold vs temperature pmos turn-on pmos turn-off pin functions sw: switch pin. minimize trace at this pin to reduce emi. v in : input supply pin. must be locally bypassed. shdn: shutdown pin. tie to 1.5v or higher to enable device or 0.4v or less to disable device. v ref : reference output pin. this pin can supply up to 100a. r t : switching frequency adjustment pin. set switching frequency using a resistor to gnd (see typical performance characteristics for values). for sync function, choose the resistor to program a frequency 20% slower than the sync pulse frequency. do not leave this pin open. sync: frequency synchronization pin. tie an external clock signal here. r t resistor should be chosen to pro- gram a switching frequency 20% slower than sync pulse frequency. synchronization (power switch turn-on) occurs a fxed delay after the rising edge of sync. tie the sync pin to ground if this feature is not used. ss: soft-start pin. place a soft-start capacitor here. leave the pin open if not in use. pwm: pulse width modulated input pin. signal low turns off channel, disables the main switch and makes the tg pin high. tie the pwm pin to shdn pin if not used. there is an equivalent 50k resistor from pwm pin to ground internally. ctrl: led current adjustment pin. sets voltage across sense resistor between isp and isn. connect directly to v ref for full-scale threshold of 100mv, or use signal values between gnd and 1v to modulate led current. tie the ctrl pin to the v ref pin if not used. v c : g m error amplifer output pin. stabilize the loop with an rc network or compensating c. fb: voltage loop feedback pin. works as overvoltage protection for led drivers. if fb is higher than 1v, the main switch is turned off. tgen: top gate enable input pin. tie to 1.5v or higher to enable the pmos driver function. tie the tgen pin to ground if tg function is not used. there is an equivalent 40k resistor from tgen pin to ground internally. isn: current sense (C) pin. the inverting input to the current sense amplifer. isp: current sense (+) pin. the noninverting input to the current sense amplifer. also serves as positive rail for tg pin driver. tg: top gate driver output. an inverted pwm sig - nal drives series pmos device between v isp and (v isp C 7v). an internal 7v clamp protects the v isp pmos gate. leave tg unconnected if not used. ground: exposed pad. solder paddle directly to ground plane. temperature (c) ?40 0.98 fb pin threshold (v) 1.00 0.99 1.01 1.03 1.02 1.04 ?20 0 20 40 3518 g10 60 80 140 160 100 120 v in = 5v 5v pwm 0v 40v tg 30v 200ns/div v isp = 40v 3518 g11 5v pwm 0v 40v tg 30v 200ns/div v isp = 40v 3518 g12
lt3518 7 3518fd block diagram figure 1. buck mode led driver 1v ctrl 1.01v 1v 1v 10a v in ? + + ? + ? + + + a1 x10 r sense isp isn pv in pwm led array a3 a2 ss ? + ? + a4 ? + ? + a5 ? + a7 2v 3518 f01 a6 s main switch driver error amplifier current sense amplifier pwm comparator r q1 main switch q tg v isp v isp ? 7v mosfet driver tgen c filt sw sw gnd c in shdn fb v c sync ss r t v in freq adjust a8 v ref ramp generator 2.5mhz to 250khz oscillator + 100a v in q2
lt3518 8 3518fd operation the lt3518 is a constant frequency, current mode regula - tor with an internal power switch. operation can be best understood by referring to the block diagram in figure 1. at the start of each oscillator cycle, the sr latch is set, which turns on the q1 power switch. a voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the pwm comparator, a4. when this voltage exceeds the level at the negative input of a4, the sr latch is reset, turning off the power switch. the level at the negative input of a4 is set by the error amplifer a3. a3 has two inputs, one from the voltage feedback loop and the other one from the current loop. whichever feedback input is lower takes precedence, and forces the converter into either constant-current or constant-voltage mode. the lt3518 is designed to transi - tion cleanly between these two modes of operation. the current sense amplifer senses the voltage across r sense and provides a pre-gain to amplifer a1. the output of a1 is simply an amplifed version of the difference between the voltage across r sense and the lower of v ctrl /10 or 100mv. in this manner, the error amplifer sets the correct peak switch current level to regulate the current through r sense . if the error amplifers output increases, more current is delivered to the output; if it decreases, less current is delivered. the current regulated in r sense can be adjusted by changing the input voltage v ctrl . the current sense amplifer provides rail-to-rail current sense operation. the fb voltage loop is implemented by the amplifer a2. when the voltage loop dominates, the error amplifer and the amplifer a2 regulate the fb pin to 1.01v (constant-voltage mode). dimming of the led array is accomplished by pulsing the led current using the pwm pin. when the pwm pin is low, switching is disabled and the error amplifer is turned off so that it does not drive the v c pin. also, all internal loads on the v c pin are disabled so that the charge state of the v c pin will be saved on the external compensation capacitor. this feature reduces transient recovery time. when the pwm input again transitions high, the demand current for the switch returns to the value just before pwm last transitioned low. to further reduce transient recovery time, an external pmos is used to disconnect the led array current loop when pwm is low, stopping c filt from discharging.
lt3518 9 3518fd dimming control there are two methods to control the current source for dimming using the lt3518. the frst method uses the pwm pin to modulate the current source between zero and full current to achieve a precisely programmed aver - age current. to make this method of current control more accurate, the switch demand current is stored on the v c node during the quiescent phase. this feature minimizes recovery time when the pwm signal goes high. to further improve the recovery time, a disconnect switch is used in the led current path to prevent the output capacitor from discharging in the pwm signal low phase. the minimum pwm on or off time will depend on the choice of operating frequency through r t input pin or sync pin. when us- ing the sync function, the sync and pwm signals must have the aligned rising edges to achieve the optimized high pwm dimming ratio. for best current accuracy, the minimum pwm low or high time should be at least six switching cycles (3s for f sw = 2mhz). maximum pwm period is determined by the system and is unlikely to be longer than 12ms. the maximum pwm dimming ratio (pwm ratio ) can be calculated from the maximum pwm period (t max ) and the minimum pwm pulse width (t min ) as follows: pwm ratio = t max t min (1) example: t max = 9ms, t min = 3s (f sw = 2mhz) pwm ratio = 9ms/3s = 3000:1 the second method of dimming control uses the ctrl pin to linearly adjust the current sense threshold during the pwm high state. when the ctrl pin voltage is less than 1v, the led current is: i led = v ctrl 10 ? r sense (2) figure 2 figure 3 applications information when v ctrl is higher than 1v, the led current is clamped to be: i led = 100mv r sense (3) the led current programming feature possibly increases total dimming range by a factor of ten. 49.9k 3518 f02 45.3k 2v v ref 5k ptc ctrl the ctrl pin should not be left open (tie to v ref if not used). the ctrl pin can also be used in conjunction with a ptc thermistor to provide overtemperature protection for the led load. setting output voltage for a boost application, the output voltage can be set by selecting the values of r1 and r2 (see figure 3) according to the following equation: v out = r1 r2 + 1 ? ? ? ? ? ? ? 1.01v (4) lt3518 fb r1 v out r2 3518 f03
lt3518 10 3518fd applications information figure 4 for a buck or a buck-boost confguration, the output voltage is typically level-shifted to a signal with respect to gnd as illustrated in the figure 4. the output can be expressed as: v out = r1 r2 ? 1.01v + v be(q1) (5) lt3518 fb q1 r1 + ? led array v out r2 3518 f04 r sense inductor selection the inductor used with the lt3518 should have a satura - tion current rating of 2a or greater. for buck mode led drivers, the inductor value should be chosen to give a ripple current ?i of ~30% to 40% of the led current. in the buck mode, the inductor value can be estimated using the formula: l h ( ) = d buck ? t sw (s) ? v in ? v led ( ) ? i d buck = v led v in (6) v led is the voltage across the led string, v in is the input voltage to the converter, and t sw is the switching period. in the boost confguration, the inductor can be estimated using the formula: l h ( ) = d boost ? t sw (s) ? v in ? i d boost = v led ? v in v led (7) table 1 provides some recommended inductor vendors. table 1. inductor manufacturers vendor phone web sumida (408) 321-9660 www.sumida.com toko (408) 432-8281 www.toko.com cooper (561) 998-4100 www.cooperet.com vishay (402) 563-6866 www.vishay.com input capacitor selection for proper operation, it is necessary to place a bypass capacitor to gnd close to the v in pin of the lt3518. a 1f or greater capacitor with low esr should be used. a ceramic capacitor is usually the best choice. in the buck mode confguration, the capacitor at the input to the power converter has large pulsed currents due to the current returned though the schottky diode when the switch is off. for best reliability, this capacitor should have low esr and esl and have an adequate ripple current rating. the rms input current is: i in(rms) = i led ? (1? d) ? d (8) where d is the switch duty cycle. a 2.2f ceramic type capacitor is usually suffcient. output capacitor selection the selection of output capacitor depends on the load and converter confguration, i.e., step-up or step-down. for led applications, the equivalent resistance of the led is typically low, and the output flter capacitor should be sized to attenuate the current ripple. to achieve the same led ripple current, the required flter capacitor value is larger in the boost and buck-boost mode applications than that in the buck mode applications. for led buck mode applications, a 1f ceramic capacitor is usually suffcient. for the led boost and buck-boost mode applications, a 2.2f ceramic capacitor is usually suffcient. very high performance pwm dimming appli - cations may require a larger capacitor value to support the led voltage during pwm transitions.
lt3518 11 3518fd applications information use only ceramic capacitors with x7r, x5r or better dielec - tric as they are best for temperature and dc bias stability of the capacitor value. all ceramic capacitors exhibit loss of capacitance value with increasing dc voltage bias, so it may be necessary to choose a higher value capacitor to get the required capacitance at the operation voltage. always check that the voltage rating of the capacitor is suffcient. table 2 shows some recommended capacitor vendors. table 2. ceramic capacitor manufacturers vendor phone web taiyo yuden (408) 573-4150 www.t-yuden.com avx (843) 448-9411 www.avxcorp.com murata (770) 436-1300 www.murata.com tdk (847) 803-6100 www.tdk.com loop compensation the lt3518 uses an internal transconductance error amplifer whose v c output compensates the control loop. the external inductor, output capacitor, and the compen - sation resistor and capacitor determine the loop stability. the inductor and output capacitor are chosen based on performance, size and cost. the compensation resistor and capacitor at v c are selected to optimize control loop stability. for typical led applications, a 10nf compensation capacitor at v c is adequate, and a series resistor is not required. a compensation resistor may be used to increase the slew rate on the v c pin to maintain tighter regulation of led current during fast transients on v in or ctrl. diode selection the schottky diode conducts current during the interval when the switch is turned off. select a diode rated for the maximum sw voltage. if using the pwm feature for dimming, it is important to consider diode leakage, which increases with the temperature, from the output during the pwm low interval. therefore, choose the schottky diode with suffciently low leakage current. table 3 has some recommended component vendors. table 3. schottky diodes part number v r (v) i ave (a) on semiconductor mbrs260t3 60 2 diodes inc. dfls140l 40 1 zetex zlls2000ta 40 2.2 international rectifer 10mq060n 60 1.5 board layout the high speed operation of the lt3518 demands careful attention to board layout and component placement. the exposed pad of the package is the only gnd terminal of the ic and is also important for thermal management of the ic. it is crucial to achieve a good electrical and thermal contact between the exposed pad and the ground plane of the board. to reduce electromagnetic interference (emi), it is important to minimize the area of the sw node. use a gnd plane under sw and minimize the length of traces in the high frequency switching path between sw and gnd through the diode and the capacitors. since there is a small dc input bias current to the isn and isp inputs, resistance in series with these inputs should be minimized and matched, otherwise there will be an offset. finally, the bypass capacitor on the v in supply to the lt3518 should be placed as close as possible to the v in terminal of the device. soft-start for many applications, it is necessary to minimize the inrush current at start-up. the built-in soft-start circuit signifcantly reduces the start-up current spike and output voltage overshoot. a typical value for the soft-start capacitor is 0.1f.
lt3518 12 3518fd applications information switching frequency there are two methods to set the switching frequency of lt3518. both methods require a resistor connected at r t pin. do not leave the r t pin open. also, do not load this pin with a capacitor. a resistor must always be connected for proper operation. one way to set the frequency is simply connecting an external resistor between the r t pin and gnd. see table 4 below or see the oscillator frequency vs r t graph in the typical performance characteristics for resistor values and corresponding switching frequencies. table 4. switching frequency vs r t switching frequency (khz) r t ( k ) 250 90.9 500 39.2 1000 16.9 1500 9.53 2000 6.04 2500 4.02 the other way is to make the lt3518 synchronize with an external clock via sync pin. for proper operation, a resistor should be connected at the r t pin and be able to generate a switching frequency 20% lower than the external clock when external clock is absent. in general, a lower switching frequency should be used where either very high or very low switching duty cycle operation is required, or high effciency is desired. selection of a higher switching frequency will allow use of smaller value external components and yield a smaller solution size and profle. thermal considerations the lt3518 is rated to a maximum input voltage of 30v for continuous operation, and 40v for nonrepetitive one second transients. careful attention must be paid to the internal power dissipation of the lt3518 at higher input voltages to ensure that the maximum junction temperature is not exceeded. this junction limit is especially important when operating at high ambient temperatures. the exposed pad on the bottom of the package must be soldered to a ground plane. this ground should then be connected to an internal copper ground plane with thermal vias placed directly under the package to spread out the heat dissipated by the lt3518.
lt3518 13 3518fd typical applications buck mode 1.5a led driver 1000:1 pwm dimming at 120hz 500ma, 5v to 12v boost converter with accurate input current limit effciency 1.5a d1 c3 10f l1 15h c2 2.2f c4 0.1f r sense 68m m1 c1 2.2f isp tgen gnd v ref v c r t 16.9k 1mhz 3518 ta02a c5 0.1f c1: kemet c0805c225k4rac c2: murata grm31mr71e225ka93 c3: murata grm32dr71e106ka12b c4, c5: murata grm21br71h104ka01b d1: zetex zlls2000ta l1: toko b992as-150m leds: luxeon k2 (white) m1: zetex zxmp6a13gta v in shdn ctrl pwm sync fb ss r t sw pv in 24v v in 3.3v isn lt3518 tg pwm v ref pwm 5v/div i led 1a/div i l 1a/div 2s/div pv in = 24v f osc = 1mhz i led = 1.5a 3518 ta02b sw v c gnd ss v in ctrl pwm shdn tgen v ref fb v out 12v 500ma v in 5v sync r1 549k c2 10f c3 0.1f c4 10nf shdn r t isn lt3518 tgisp d1 r2 49.9k r t 6.04k 2mhz r3 10k 3518 ta03a c2 2.2f l1 4.3h r sense 50m? c1: kemet c0805c225k4rac c2: kemet c1206c106k4rac c3: murata grm21br71h104ka01b c4: murata gcm033r71a103ka03 d1: zetex zlls2000ta l1: toko b992as-4r3n i load (ma) 0 efficiency (%) 70 80 400 3518 ta03b 60 50 100 200 300 500 90
lt3518 14 3518fd typical applications 3000:1 pwm dimming at 120hz effciency buck-boost mode led driver d1 l1 4.3h r sense 330m shdn v c gnd r t ss r t 6.04k 2mhz 3518 ta04a c3 0.1f c2 4.7f r1 3.92m r2 124k m1 c5 0.22f c1 2.2f c4 0.1f pwm isp fb isn tg tgen v ref ctrl sync 300ma v in 8v to 16v v in lt3518 sw pwm c1: kemet c0806c225k4rac c2: kemet c1206c475k3rac c3, c4: murata grm21br71h104ka01b c5: murata grm21br71h224ka01b d1: zetex zlls2000ta l1: toko b992as-4r3n leds: luxeon i (white) m1: zetex zxmp6a13gta pwm 5v/div i led 200ma/div i l1 1a/div 500ns/div v in = 10v f osc = 2mhz i led = 300ma 3518 ta04b pwm duty cycle (%) 0 70 80 90 80 3518 ta04c 60 50 20 40 60 100 40 30 20 efficiency (%) v in = 10v ctrl = v ref
lt3518 15 3518fd typical applications 1000:1 pwm dimming at 120hz effciency buck mode 1a led driver with open led protection and sync input 1a led1 led6 d1 c3 10f r1 49.9k r2 2.00k fb r3 5.62k l1 10h fb c2 2.2f c4 0.1f r sense 100m m1 c1 2.2f v ref isp tgen gnd v ref v c r t 16.9k 1mhz 3518 ta05a c5 0.1f v in shdn ctrl pwm sync fb ss r t sw pv in 32v v in 3.3v isn lt3518 tg pwm sync 3.3v, 1.2mhz c1: kemet c0806c225k4rac c2: murata grm31mr71e225ka93 c3: murata grm32dr71e106ka12b c4, c5: murata grm21br71h104ka01b d1: zetex zlls2000ta l1: toko b992as-100m leds: luxeon iii (white) m1: zetex zxmp6a13gta q1: philips pmbt3906 q1 pwm 5v/div i led 1a/div i l1 1a/div 2s/div pv in = 32v f osc = 1.2mhz i led = 1a 3518 ta05b pwm duty cycle (%) 0 40 efficiency (%) 50 60 70 80 90 100 20 40 60 80 3518 ta05c 100 ctrl = v ref
lt3518 16 3518fd typical applications boost 300ma led driver with led open protection 3000:1 pwm dimming at 100hz effciency led1 m1 led2 led8 d1 l1 8.2h r sense 330m r1 1m r2 30.1k shdn v c gnd r t ss r t 16.9k 1mhz 3518 ta06a c3 0.1f c2 6.8f c1 2.2f c4 0.1f pwm isp isn tg fb tgen v ref ctrl sync 300ma v in 8v to 16v v in lt3518 sw pwm c1: kemet c1206c225k2rac c2: tdk c5750x7r1h685m c3, c4: murata grm21br71h104ka01b d1: zetex zlls2000ta l1: toko b992as-8r2n leds: luxeon i (white) m1: zetex zxmp6a13gta pwm 5v/div i led 200ma/div i l1 1a/div 1s/div v in = 12v f osc = 1mhz i led = 300ma 3518 ta06b pwm duty cycle (%) 0 efficiency (%) 60 80 100 80 3518 ta06c 40 50 70 90 30 20 20 40 60 100 v in = 12v ctrl = v ref
lt3518 17 3518fd package description uf package 16-lead plastic qfn (4mm 4mm) (reference ltc dwg # 05-08-1692) 4.00 0.10 (4 sides) note: 1. drawing conforms to jedec package outline mo-220 variation (wggc) 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package pin 1 top mark (note 6) 0.55 0.20 1615 1 2 bottom view?exposed pad 2.15 0.10 (4-sides) 0.75 0.05 r = 0.115 typ 0.30 0.05 0.65 bsc 0.200 ref 0.00 ? 0.05 (uf16) qfn 10-04 recommended solder pad pitch and dimensions 0.72 0.05 0.30 0.05 0.65 bsc 2.15 0.05 (4 sides) 2.90 0.05 4.35 0.05 package outline pin 1 notch r = 0.20 typ or 0.35 45 chamfer
lt3518 18 3518fd package description fe16 (ba) tssop rev h 0910 0.09 ? 0.20 (.0035 ? .0079) 0 ? 8 0.25 ref 0.50 ? 0.75 (.020 ? .030) 4.30 ? 4.50* (.169 ? .177) 1 3 4 5 6 7 8 10 9 4.90 ? 5.10* (.193 ? .201) 16 1514 13 12 11 1.10 (.0433) max 0.05 ? 0.15 (.002 ? .006) 0.65 (.0256) bsc 2.74 (.108) 2.74 (.108) 0.195 ? 0.30 (.0077 ? .0118) typ 2 millimeters (inches) *dimensions do not include mold flash. mold flash shall not exceed 0.150mm (.006") per side note: 1. controlling dimension: millimeters 2. dimensions are in recommended solder pad layout 3. drawing not to scale 0.45 0.05 0.65 bsc 4.50 0.10 6.60 0.10 1.05 0.10 2.74 (.108) 2.74 (.108) see note 4 4. recommended minimum pcb metal size for exposed pad attachment 6.40 (.252) bsc fe package 16-lead plastic tssop (4.4mm) (reference ltc dwg # 05-08-1663 rev h) exposed pad variation ba
lt3518 19 3518fd 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. revision history rev date description page number d 01/11 revised electrical characteristics 3 (revision history begins at rev d)
lt3518 20 3518fd linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax : (408) 434-0507 l www.linear.com linear technology corporation 2007 lt 0111 rev d ? printed in usa typical application 5.5v sepic converter with short-circuit protection effciency sw v c gnd ss ctrl sync shdn tgen v ref fb tg isp isn r t v out 5.5v 500ma v in 3v r1 221k c2 10f c5 10f c3 0.1f c4 10nf shdn pwm lt3518 v in d1 r2 49.9k r t 6.04k 2mhz r3 10k 3518 ta07a c1 2.2f l1 2.4h l2 2.4h r sense 0.15 c1: kemet c0805c225k4rac c2, c5: kemet c1206c106k4rac c3: murata grm21br71h104ka01b c4: murata gcm033r71a103ka03 d1: zetex zlls2000ta l1, l2: toko 962bs-2r4m i load (ma) 0 80 90 100 400 3518 ta07b 70 60 100 200 300 500 50 40 30 efficiency (%) part number description comments lt1618 constant current, 1.4mhz, 1.5a boost converter v in : 5v to 18v, v out(max) = 36v, dimming = analog/pwm, i sd < 1a, msop10 package lt3003 3-channel led ballaster with pwm dimming v in : 3v to 48v, dimming = 3000:1 true color pwm, i sd < 5a, msop10 package lt3474 36v, 1a (i led ), 2mhz, step-down led driver v in : 4v to 36v, v out(max) = 13.5v, dimming = 400:1 true color pwm, i sd < 1a, tssop16e package lt3475 dual 1.5a (i led ), 36v 2mhz step-down led driver v in : 4v to 36v, v out(max) = 13.5v, dimming = 3000:1 true color pwm, i sd < 1a, tssop20e package lt3476 quad output 1.5a, 36v, 2mhz high current led driver with 1,000:1 dimming v in : 2.8v to 16v, v out(max) = 36v, dimming = 1000:1 true color pwm, i sd < 10a, 5mm w 7mm qfn package lt3477 3a, 42v, 3mhz boost, buck-boost, buck led driver v in : 2.5v to 25v, v out(max) = 40v, dimming = analog/pwm, i sd < 1a, qfn, tssop20e packages lt3478/lt3478-1 4.5a, 42v, 2.5mhz high current led driver with 3,000:1 dimming v in : 2.8v to 36v, v out(max) = 42v, dimming = 3000:1 true color pwm, i sd < 3a, tssop16e packages lt3479 3a, full featured dc/dc converter with soft-start and inrush current protection v in : 2.5v to 24v, v out(max) = 40v, i q = 6.5ma, i sd < 1a, dfn and tssop packages lt3486 dual 1.3a, 2mhz high current led driver v in : 2.5v to 24v, v out(max) = 36v, dimming = 1000:1 true color pwm, i sd < 1a, 5mm w 3mm dfn, tssop16e lt3496 triple output led driver v in : 3v to 40v, v out(max) = 45v, dimming = 3000:1 true color pwm, i sd < 10a, 4mm w 5mm qfn package lt3517 full-featured led driver with 1.5a switch current v in : 3v to 40v, v out(max) = 45v, dimming = 5000:1 true color pwm, i sd < 1a, 4mm w 4mm qfn and tssop packages lt3590 48v buck mode 50ma led driver v in : 4.5v to 55v, drives up to 10 leds, 200:1 dimming, i so = 15ma, 2mm w 2mm dfn sc70 lt3595 16 channel buck led driver mode v in : 4.5v to 45v, drives up to 160 leds, 5000:1 dimming, 5mm w 9mm qfn lt c ? 3783 high current led controller v in : 3v to 36v, v out(max) = ext fet, dimming = 3000:1 true color pwm, i sd < 20a, 5mm w 4mm qfn10, tssop16e packages related parts

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