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lt3593 1 3593f typical application features applications description 1mhz white led driver with output disconnect and one pin current programming the lt ? 3593 is a step-up dc/dc converter designed to drive up to ten white leds in series from a li-ion cell. series connection of the leds provides identical led currents and eliminates the need for ballast resistors. the device features a unique high side led current sense that enables the part to function as a one wire current source where the low side of the led string can be returned to ground anywhere. additional features include output disconnect in shutdown, open led protection and 1-pin shutdown/led current control. the ctrl pin is toggled to adjust the led current via an internal counter and a 5-bit dac. the lt3593 switches at 1mhz, allowing the use of tiny external components. constant frequency switching re- sults in low input noise and a small output capacitor. the lt3593 is available in the 6-lead dfn (2mm 2mm) as well as the 6-lead sot-23 packages. li-ion driver for ten white leds n drives up to ten white leds from a 3v supply n one pin shutdown and current programming n leds disconnected in shutdown n 32:1 linear brightness control range n v in range: 2.7v to 5.5v n 5% output current accuracy at full scale n low shutdown current: 3a n 1mhz switching frequency n requires only 1f output capacitor n low pro? le 6-lead dfn (2mm 2mm 0.75mm) and 6-lead sot-23 packages n cell phones n digital cameras n pdas, handheld computers n mp3 players n gps receivers ctrl v in 10 h v in 3v to 5v 3593 ta01a lt3593 shutdown and current control sw cap led gnd 1 f 1 f conversion ef? ciency led current (ma) 0 effi ciency (%) 90 70 50 80 60 40 30 10 3593 ta01b 20 15 5 v in = 3.6v 10 leds l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners.
lt3593 2 3593f absolute maximum ratings input voltage ...............................................................6v ctrl voltage ..............................................................6v sw voltage ...............................................................45v cap voltage ..............................................................45v led voltage ..............................................................45v (note 1) top view sw cap led v in gnd ctrl dc package 6-lead (2mm 2mm) plastic dfn 4 5 7 6 3 2 1 t jmax = 125c,
lt3593 3 3593f 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. electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v in = 3.6v, v ctrl = 3.6v, unless otherwise speci? ed. parameter conditions min typ max units switch leakage current v sw = 30v 1 a led pin voltage drop (v cap C v led )i led = 20ma 250 mv led pin leakage current ctrl = 0, v cap = 35v 1 a ctrl high threshold 1.6 v ctrl low threshold 0.4 v ctrl t pw programming pulse width (note 3) 250 ns ctrl t sd time from ctrl = 0 to shutdown 95 128 200 s ctrl t en time from ctrl = 1 to enable 95 128 200 s full-scale led current v cap = 16v v cap = 16v l 19 18.5 20 20 21 21.5 ma ma led current programming resolution linear increments 625 a led current limit 45 ma ctrl pin bias current v ctrl = 5.5v 1 a overvoltage protection l 36 38 40 v note 2: the ltc3593e is guaranteed to meet performance speci? cations from 0c to 85c operating junction temperature range. speci? cations over the C40c to 85c operating junction temperature range are assured by design, characterization and correlation with statistical process controls. note 3: guaranteed by design.
lt3593 4 3593f typical performance characteristics switch saturation voltage (v cesat ) shutdown current (v ctrl = 0v) led pin voltage drop (v cap C v led ) switching waveform quiescent current (v ctrl = 3.6v) switching current limit vs temperature t a = 25c unless otherwise speci? ed. transient response v in (v) 2 shutdown current (a) 6 4 2 5 3 1 0 5 3 3593 g02 6 4 C50 c 25 c 100 c led current (ma) 0 v cap C v led (mv) 300 200 100 250 150 50 0 15 5 3593 g04 20 10 C50 c 25 c 100 c v in = 3.6v v cap = 16v temperature (c) C50 led pin current limit (ma) 46 44 45 43 42 75 0 C25 25 3593 g05 100 50 v in = 3.6v v cap = 16v led pin current limit i l 200ma/div 200s/div v in = 3.6v front page application circuit 3393 g08 v ctrl 5v/div v cap 10v/div switch current (ma) 0 switch saturation voltage (mv) 600 400 200 500 300 100 0 400 200 3593 g01 600 300 C50c 100 500 100c 25c v in (v) 2 quiescent current (ma) 3.50 3.00 2.50 3.25 2.75 2.25 2.00 5 3 3593 g03 6 4 C50 c 25 c 100 c temperature (c) C50 switch currnet limit (ma) 750 650 700 600 550 25 50 75 C25 3593 g06 100 0 v in = 3.6v v cap 200mv/div ac coupled 1s/div v in = 3.6v front page application circuit 3393 g07 i l 200ma/div v sw 20v/div
lt3593 5 3593f open-circuit output clamp voltage input current in output open circuit open-circuit output clamp voltage vs temperature input current in output open-circuit vs temperatue switching frequency vs temperature full-scale current vs v in full-scale current vs v cap full-scale current vs temperature typical performance characteristics t a = 25c unless otherwise speci? ed. led current vs ctrl strobe pulses temperature (c) C50 open-circuit clamp voltage (v) 40 38 39 37 36 75 0 C25 25 3593 g11 100 50 v in = 3.6v number of ctrl strobes 0 led current (ma) 20 15 10 0 16 824 3593 g14 32 v in = 3.6v 10leds 5 v cap (v) 5 led current (ma) 21.0 20.5 20.0 19.0 25 20 15 10 30 3593 g16 35 19.5 temperature (c) C50 full scale current (ma) 21.0 20.5 20.0 19.0 0 C25 50 75 25 3593 g17 100 v in = 3.6v 10leds 19.5 v in (v) 2 open-circuit clamp voltage (v) 40 38 39 37 36 5 4 3 3593 g09 6 25c 100c C50c v in (v) 2.0 2.5 input current output open-circuit (ma) 10 8 9 4 5 6 7 2 5.0 5.5 3.0 3.5 3593 g10 6.0 4.0 4.5 3 temperature (c) C50 input current output open-circuit (ma) 8 6 7 5 2 75 0 C25 25 3593 g12 100 50 v in = 3.6v 4 3 temperature (c) C50 switching frequency (khz) 1150 1050 1100 1000 850 75 0 C25 25 3593 g13 100 50 v in = 3.6v 950 900 v in (v) 2.5 led current (ma) 21.0 20.5 19.0 5.0 3.5 3.0 4.0 3593 g15 6.0 5.5 4.5 10 leds 20.0 19.5
lt3593 6 3593f pin functions (dfn/tsot) block diagram v in (pin 1/pin 3): input supply pin. must be locally by- passed with a 1f x5r or x7r type ceramic capacitor. gnd (pin 2/pin 2): ground pin. connect directly to local ground plane. sw (pin 6/pin 4): switch pin. connect inductor between this pin and the v in pin. minimize inductance at this pin to minimize emi. cap (pin 5/pin 5): output pin. connect to output capaci- tor. minimize trace between this pin and output capacitor to reduce emi. ctrl (pin 3/pin 1): current control and shutdown pin. this pin is used to program the led output current. this pin is strobed up to 32 times to decrement the internal 5-bit dacs from full-scale to 1lsb. the counter will stop at 1lsb if the strobing continues beyond 32 counts. the pin must be held high after the ? nal desired positive strobe edge. the data is transferred after a 128s (typ) delay. the part can be reprogrammed to a different value after it has been enabled, however the current will change to the new value after 128s. if ctrl is held low for longer than 128s (typ), the part will go into shutdown. led (pin 4/pin 6): led pin. an internal switch connects this pin to cap . the top of the led string is connected to this pin. when the part is in shutdown, the led pin is switched off from cap so no current runs through the leds. the switch is also used to sense the led current when the part is on. exposed pad (pin 7/na): ground. the exposed pad must be soldered to the pcb. 6 1 C + C + r sw v in cap q s driver overvoltage protection ramp generator oscillator v ref 1.24v shdn q1 r C + led 3593 f01 gnd pin numbers refer to dfn package. refer to pin configuration for tsot pin numbers ctrl shdn a1 r c c c a2 a3 shdn m2 m1 pwm comp 5-bit linear dac 5-bit counter + C 2 7 3 4 5 figure 1. block diagram
lt3593 7 3593f operation the lt3593 uses a constant frequency, current mode control boost scheme to provide excellent line and load regulation. operation can be best understood by referring to the block diagram in figure 1. output disconnect an internal switch connects between the cap pin and the led pin. the top of the led string is connected to the led pin. the string can be terminated to ground or to v in if a low number of leds are driven. when the part is in shutdown, the switch is off; allowing no current to run through the leds. current programming the led current can be set to 32 different values (625a C 20ma) by strobing the ctrl pin. a 5-bit counter is decremented by 1 on a ctrl pin rising edge, reducing the programmed current by 625a each time. the desired current can be calculated by: i led = 20ma C (n C 1) ? 625a where n is the number of rising edges. when the desired current setting is reached, the ctrl pin must stay high. 128s after the last rising edge on the ctrl pin, the regulator will enable the output and start to regulate the led current to the programmed value. figure 2 shows an example of how the part can be programmed. if a different current is desired, the ctrl pin can be strobed again. the ? rst falling edge will reset the internal register to the 20ma setting. while the new current is being pro- grammed, the device will continue to regulate the previously programmed value until the ctrl pin has remained high for at least 128s, at which time the regulated current will slew to the newly programmed value. figure 3 shows how to program a new led current level. if the ctrl pin is held low for longer than 128s, the part will go into the shutdown mode. figure 2. current programming ctrl 12.5ma 3593 f02 ctrl 15ma ctrl 17.5ma ctrl full current 20ma ctrl led current 128s 20ma 20ma 17.5ma 17.5ma shdn 3593 f03 128s 128s figure 3. current programming and shutdown timing
lt3593 8 3593f applications information inductor selection a 10h inductor is recommended for most lt3593 ap- plications. although small size and high ef? ciency are major concerns, the inductor should have low core losses at 1mhz and low dcr (copper wire resistance). some inductors in this category with small size are listed in table 1. the ef? ciency comparison of different inductors is shown in figure 4. table 1. recommended inductors part l (h) dcr ( ) current rating (ma) vendor lqh43cn100 lqh32cn100 10 10 0.24 0.44 650 450 murata nr3010t100m 10 0.45 500 taiyo yuden vlf4012at-100m vlf3010at-100m 10 10 0.20 0.58 500 490 tdk de2812-1098as-100m db3015c-1068as-100m 10 10 0.29 0.38 580 400 toko capacitor selection the small size of ceramic capacitors makes them ideal for lt3593 applications. use only x5r and x7r types because they retain their capacitance over wider voltage and temperature ranges than other types such as y5v or z5u. a 1f input capacitor and a 1f output capacitor are suf? cient for most applications. table 2 shows a list of several ceramic capacitor manufac- turers. consult the manufacturers for detailed information on their entire selection of ceramic parts. table 2. recommended ceramic capacitor manufacturers taiyo yuden (408) 573-4150 www.t-yuden.com avx (803) 448-9411 www.avxcorp.com murata (714) 852-2001 www.murata.com kemet (408) 986-0424 www.kemet.com diode selection schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for lt3593 ap- plications. the forward voltage drop of a schottky diode represents the conduction losses in the diode, while the diode capacitance (c t or c d ) represents the switching losses. for diode selection, both forward voltage drop and diode capacitance need to be considered. schottky diodes with higher current ratings usually have lower forward voltage drop and larger diode capacitance, which can cause signi? cant switching losses at the 1.0mhz switching frequency of the lt3593. a schottky diode rated at 400ma to 500ma is suf? cient for most lt3593 applications. some recommended schottky diodes are listed in table 3. table 3. recommended schottky diodes part number forward current (ma) voltage drop (v) diode capacitance (pf) manufacturer cmdsh05-4 500 0.47 at 500ma 50 at 1v central 631-435-1110 www.centralsemi.com cmmsh1-40 1000 0.55 at 1a 80 at 4v zll5400 520 0.50 at 400ma 15 at 30v zetex 631-543-7100 www.zetex.com pmeg- 4005aea 500 0.47 at 500ma 50 at 1v phillips +3140 27 24825 www.semiconductors. phillips.com figure 4. ef? ciency comparison of different inductors led current (ma) 0.00 effi ciency (%) 90.00 70.00 50.00 80.00 60.00 40.00 30.00 10.00 3593 f04 20.00 15.00 5.00 nr3010t100m vlf4012-at-100mr50 lqh43cn100k03 vlf3010at-100mr49 lqh32cn100k53 db3015c-1068as-100m
lt3593 9 3593f applications information figure 5. output open-circuit waveform figure 6. two aa cells to three white leds overvoltage protection the lt3593 has an internal open-circuit protection circuit. in the case of an output open circuit, when the leds are disconnected from the circuit or the leds fail open, v cap is clamped at 38v. the lt3593 will then switch at a very low frequency to minimize input current. v cap and input current during output open circuit are shown in the typical performance characteristics. figure 5 shows the transient response when the leds are disconnected. low input voltage applications the lt3593 can be used in low input voltage applications. the input supply voltage to the lt3593 must be 2.7v or higher, but the inductor can be run off a lower battery voltage. this technique allows the leds to be powered off two alkaline cells. most portable devices have a 3.3v logic supply voltage which can be used to power the lt3593. the leds can be driven straight from the battery, resulting in higher ef? ciency. figure 6 shows three leds powered by two aa cells. the battery is connected to the inductors and the chip is powered off a 3.3v logic supply voltage. ctrl c1: taiyo yuden emk107b5105ma c2: murata grm31mr71h105ka88 l1: murata lqh43cn100 d1: central cmdsh05-4 v in l1 10 h 2 aa cells 2v to 3.2v 3.3v 3593 f06 lt3593 shutdown and current control sw cap led gnd c1 1 f c2 1 f c3 1 f d1 v cap 20v/div 400s/div v in = 3.6v front page application circuit 3593 f05 i l 200ma/div v sw 20v/div leds disconnected at this instant
lt3593 10 3593f applications information switching node pin (sw). keep the sense voltage pins (cap and led) away from the switching node. place c2 next to the cap pin. always use a ground plane under the switching regulator to minimize interplane coupling. recommended component placement is shown in figure 7. figure 7. recommended component placement board layout considerations as with all switching regulators, careful attention must be paid to the pcb layout and component placement. to prevent electromagnetic interference (emi) problems, proper layout of high frequency switching paths is essential. minimize the length and area of all traces connected to the 43 52 61 4 5 7 6 3 2 1 c1 c1 v in d1 dfn package tsot-23 package d1 l1 l1 c2 c2 ctrl gnd v in ctrl gnd 3593 f07
lt3593 11 3593f typical applications li-ion driver for one white led li-ion driver for two white led conversion ef? ciency conversion ef? ciency led v in l1 10 h v in 3v to 5v 3593 ta02a lt3593 sw cap ctrl gnd c2 1 f d1 c1 1 f shutdown and current control c1: taiyo yuden emk107bj105ma c2: taiyo yuden gmk316bj105ml l1: murata lqh43cn100 d1: central cmdsh05-4 led v in l1 10 h v in 3v to 5v 3593 ta03a lt3593 sw cap ctrl gnd c2 1 f d1 c1 1 f shutdown and current control c1: taiyo yuden emk107bj105ma c2: taiyo yuden gmk316bj105ml l1: murata lqh43cn100 d1: central cmdsh05-4 led current (ma) 0 efficiency (%) 70 50 30 60 40 20 10 10 3593 ta02b 20 15 5 v in = 3.6v 1 led led current (ma) 0 efficiency (%) 80 60 40 70 50 30 20 10 3593 ta03b 20 15 5 v in = 3.6v 2 leds
lt3593 12 3593f typical applications li-ion driver for three white leds li-ion driver for four white leds ef? ciency ef? ciency ctrl v in l1 10 h v in 3v to 5v 3593 ta04a lt3593 shutdown and current control sw cap led gnd c1 1 f c2 1 f c1: taiyo yuden emk107bj105ma c2: taiyo yuden gmk316bj105ml l1: murata lqh43cn100 d1: central cmdsh05-4 d1 ctrl v in l1 10 h v in 3v to 5v 3593 ta05a lt3593 shutdown and current control sw cap led gnd c1 1 f c2 1 f c1: taiyo yuden emk107bj105ma c2: taiyo yuden gmk316bj105ml l1: murata lqh43cn100 d1: central cmdsh05-4 d1 ctrl v in l1 10 h v in 3v to 5v 3593 ta06a lt3593 shutdown and current control sw cap led gnd c1 1 f c2 1 f c1: taiyo yuden emk107bj105ma c2: taiyo yuden gmk316bj105ml l1: murata lqh43cn100 d1: central cmdsh05-4 d1 li-ion driver for six white leds led current (ma) 0 efficiency (%) 90 70 50 80 60 40 30 10 3593 ta04b 20 15 5 v in = 3.6v 3 leds led current (ma) 0 efficiency (%) 90 70 50 80 60 40 30 10 3593 ta05b 20 15 5 v in = 3.6v 4 leds ef? ciency led current (ma) 0 efficiency (%) 90 70 50 80 60 40 30 10 3593 ta06b 20 15 5 v in = 3.6v 6 leds
lt3593 13 3593f typical applications li-ion driver for ten white leds ef? ciency ctrl v in l1 10 h v in 3v to 5v 3593 ta07a lt3593 shutdown and current control sw cap led gnd c1 1 f c2 1 f c1: taiyo yuden emk107bj105ma c2: murata grm31mr71h105ka88 l1: murata lqh43cn100 d1: central cmdsh05-4 d1 ctrl v in l1 22 h v in 3v to 5v 3593 ta08a lt3593 shutdown and current control sw cap led gnd c1 1 f c2 2.2 f c1: taiyo yuden emk107bj105ma c2: murata grm31cr71h225ka88 l1: murata lqh43cn220 d1: central cmdsh05-4 d1 led current (ma) 0 efficiency (%) 90 70 50 80 60 40 30 10 3593 ta07b 20 15 5 v in = 3.6v 10 leds ef? ciency li-ion driver for ten white leds led current (ma) 0 efficiency (%) 90 70 50 80 60 40 30 10 3593 ta08b 20 15 5 v in = 3.6v 10 leds
lt3593 14 3593f 2.00 0.10 (4 sides) note: 1. drawing to be made a jedec package outline m0-229 variation of (wccd-2) 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 0.38 0.05 bottom viewexposed pad 0.56 0.05 (2 sides) 0.75 0.05 r = 0.115 typ 1.37 0.05 (2 sides) 1 3 6 4 pin 1 bar top mark (see note 6) 0.200 ref 0.00 C 0.05 (dc6) dfn 1103 0.25 0.05 0.50 bsc 0.25 0.05 1.42 0.05 (2 sides) recommended solder pad pitch and dimensions 0.61 0.05 (2 sides) 1.15 0.05 0.675 0.05 2.50 0.05 package outline 0.50 bsc pin 1 chamfer of exposed pad package description dc package 6-lead plastic dfn (2mm 2mm) (reference ltc dwg # 05-08-1703)
lt3593 15 3593f s6 package 6-lead plastic tsot-23 (reference ltc dwg # 05-08-1636) 1.50 C 1.75 (note 4) 2.80 bsc 0.30 C 0.45 6 plcs (note 3) datum a 0.09 C 0.20 (note 3) s6 tsot-23 0302 rev b 2.90 bsc (note 4) 0.95 bsc 1.90 bsc 0.80 C 0.90 1.00 max 0.01 C 0.10 0.20 bsc 0.30 C 0.50 ref pin one id note: 1. dimensions are in millimeters 2. drawing not to scale 3. dimensions are inclusive of plating 4. dimensions are exclusive of mold flash and metal burr 5. mold flash shall not exceed 0.254mm 6. jedec package reference is mo-193 3.85 max 0.62 max 0.95 ref recommended solder pad layout per ipc calculator 1.4 min 2.62 ref 1.22 ref package description 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.
lt3593 16 3593f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2008 lt 0308 ? printed in usa related parts typical application li-ion driver for six leds ef? ciency part number description comments lt1932 constant current, 1.2mhz, high ef? ciency white led boost regulator up to 8 white leds, v in : 1v to 10v, v out(max) = 34v, i q = 1.2ma, i sd < 1a, thinsot tm package lt1937 constant current, 1.2mhz, high ef? ciency white led boost regulator up to 4 white leds, v in : 2.5v to 10v, v out(max) = 34v, i q = 1.9ma, i sd < 1a, thinsot and sc70 packages lt c ? 3200 low noise, 2mhz regulated charge pump white led driver up to 6 white leds, v in : 2.7v to 4.5v, i q = 8ma, i sd < 1a, ms package ltc3200-5 low noise, 2mhz regulated charge pump white led driver up to 6 white leds, v in : 2.7v to 4.5v, i q = 8ma, i sd < 1a, thinsot package ltc3201 low noise, 1.7mhz regulated charge pump white led driver up to 6 white leds, v in : 2.7v to 4.5v, i q = 6.5ma, i sd < 1a, ms package ltc3202 low noise, 1.5mhz regulated charge pump white led driver up to 8 white leds, v in : 2.7v to 4.5v, i q = 5ma, i sd < 1a, ms package ltc3205 high ef? ciency, multidisplay led controller up to 4 (main), 2 (sub) and rgb, v in : 2.8v to 4.5v, i q = 50a, i sd < 1a, 24-lead qfn package ltc3210 low noise charge pump led controller up to 4 white leds and one high current cam led, v in : 2.9v to 4.5v, i q = 4.5ma, i sd < 6a, ud package lt3465/lt3465a constant current, 1.2mhz/2.7mhz, high ef? ciency white led boost regulator with integrated schottky diode up to 6 white leds, v in : 2.7v to 16v, v out(max) = 34v, i q = 1.9ma, i sd < 1a, thinsot package lt3466/lt3466-1 dual full function, 2mhz diodes white led step-up converter with built-in schottkys up to 20 white leds, v in : 2.7v to 24v, v out(max) = 39v, dfn and tssop-16 packages lt3486 dual 1.3a white led converter with 1000:1 true color pwm dimming drives up to 16 100ma white leds. v in : 2.5v to 24v, v out(max) = 36v, dfn and tssop packages lt3491 white led driver with integrated schottky up to 6 white leds, v in : 2.5v to 12v, i q = 2.6ma, i sd < 10a, sc70 and 2mm 2mm dfn packages lt3591 white led driver with integrated schottky up to 10 white leds, v in : 2.5v to 12v, i q = 4ma, i sd < 11a, 3mm 2mm dfn package thinsot is a trademark of linear technology corporation. ctrl v in l1 10 h v in 3v to 5v 3593 ta06a lt3593 shutdown and current control sw cap led gnd c1 1 f c2 1 f c1: taiyo yuden emk107bj105ma c2: taiyo yuden gmk316bj105ml l1: murata lqh43cn100 d1: central cmdsh05-4 d1 led current (ma) 0 efficiency (%) 90 70 50 80 60 40 30 10 3593 ta06b 20 15 5 v in = 3.6v 6 leds

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