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lt3468/lt3468-1/lt3468-2 1 346812f features descriptio u applicatio s u n digital / film camera flash n pda / cell phone flash n emergency strobe n highly integrated ic reduces solution size n uses small transformers: 5.8mm 5.8mm 3mm n fast photoflash charge times: 4.6s for lt3468 (0v to 320v, 100 m f, v in = 3.6v) 5.7s for lt3468-2 (0v to 320v, 100 m f, v in = 3.6v) 5.5s for lt3468-1 (0v to 320v, 50 m f, v in = 3.6v) n controlled input current: 500ma (lt3468) 375ma (lt3468-2) 225ma (lt3468-1) n supports operation from single li-ion cell, or any supply from 2.5v up to 16v n adjustable output voltage n no output voltage divider needed n charges any size photoflash capacitor n low profile (<1mm) sot-23 package photoflash capacitor chargers in thinsot tm the lt ? 3468/lt3468-1/lt3468-2 are highly integrated ics designed to charge photoflash capacitors in digital and film cameras. a patented control technique* allows for the use of extremely small transformers. each device contains an on-chip high voltage npn power switch. output voltage detection* is completely contained within the device, eliminating the need for any discrete zener diodes or resistors. the output voltage can be adjusted by simply changing the turns ratio of the transformer. the lt3468 has a primary current limit of 1.4a, the lt3468-2 has a 1a limit, and the lt3468-1 has a 0.7a limit. these different current limit levels result in well controlled input currents of 500ma for the lt3468, 375ma for the lt3468-2 and 225ma for the lt3468-1. aside from the differing current limit, the three devices are otherwise equivalent. the charge pin gives full control of the part to the user. driving charge low puts the part in shutdown. the done pin indicates when the part has completed charging. the lt3468 series of parts are available in tiny low profile (1mm) sot-23 packages. , ltc and lt are registered trademarks of linear technology corporation. thinsot is a trademark of linear technology corporation. *u.s. patent # 6, 518, 733 danger high voltage C operation by high voltage trained personnel only lt3468 photoflash charger uses high efficiency 4mm tall transformer lt3468 charge gnd v in sw + done done charge 4.7 f 100k 1:10.2 v in 2.5v to 8v 320v 1 2 4 5 346812 ta01 100 f lt3468 charging waveform 3468 g01 1s/div v in = 3.6v c out = 100 m f v out 50v/div average input current 1a/div typical applicatio u
lt3468/lt3468-1/lt3468-2 2 346812f v in voltage .............................................................. 16v sw voltage ................................................ C0.4v to 50v charge voltage ...................................................... 10v done voltage .......................................................... 10v current into done pin .......................................... 1ma maximum junction temperature .......................... 125 c operating temperature range (note 2) ...C40 c to 85 c storage temperature range ..................C65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c order part number s5 part marking t jmax = 125 c q ja = 150 c on board over ground plane q jc = 90 c/w ltaec ltagq ltbch lt3468es5 lt3468es5-1 lt3468es5-2 absolute axi u rati gs w ww u package/order i for atio uu w (note 1) electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v in = 3v, v charge = v in unless otherwise noted. (note 2) specifications are for the lt3468, lt3468-1 and lt3468-2 unless otherwise noted. parameter conditions min typ max units quiescent current not switching 5 8 ma v charge = 0v 0 1 m a input voltage range l 2.5 16 v switch current limit lt3468 (note 3) 1.1 1.2 1.3 a lt3468-2 0.77 0.87 0.97 a lt3468-1 0.45 0.55 0.65 a switch v cesat lt3468, i sw = 1a 330 430 mv lt3468-2, i sw = 650ma 210 280 mv lt3468-1, i sw = 400ma 150 200 mv v out comparator trip voltage measured as v sw C v in l 31 31.5 32 v v out comparator overdrive 300ns pulse width 200 400 mv dcm comparator trip voltage measured as v sw C v in l 10 36 80 mv charge pin current v charge = 3v 15 40 m a v charge = 0v 0 0.1 m a switch leakage current v in = v sw = 5v, in shutdown l 0.01 1 m a charge input voltage high l 1v charge input voltage low l 0.3 v done output signal high 100k w from v in to done 3 v done output signal low 33 m a into done pin 100 200 mv done leakage current v done = 3v, done npn off 20 100 na consult ltc marketing for parts specified with wider operating temperature ranges. note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the lt3468e/lt3468e-1/lt3468e-2 are guaranteed to meet performance specifications from 0 c to 70 c. specifications over the C40 c to 85 c operating temperature range are assured by design, characterization and correlation with statistical process. note 3: specifications are for static test. current limit in actual application will be slightly higher. 5 vin 4 charge sw 1 top view s5 package 5-lead plastic tsot-23 gnd 2 done 3
lt3468/lt3468-1/lt3468-2 3 346812f lt3468-1 charge time lt3468-1 charging waveform lt3468 input current lt3468-1 input current lt3468 charging waveform lt3468 charge time v in (v) 23456789 charge time (s) 3468 g04 10 9 8 7 6 5 4 3 2 1 0 c out = 50 f c out = 100 f t a = 25 c v in (v) 23456789 charge time (s) 3468 g05 10 9 8 7 6 5 4 3 2 1 0 c out = 20 f c out = 50 f t a = 25 c v out (v) 0 50 100 150 200 250 300 average input current (ma) 3468 g07 800 0 200 400 600 v in = 2.8v v in = 4.2v v in = 3.6v t a = 25 c v out (v) 0 50 100 150 200 250 300 average input current (ma) 3468 g08 400 0 100 200 300 v in = 2.8v v in = 4.2v v in = 3.6v t a = 25 c v in = 3.6v c out = 50 m f 3468 g01 3468 g02 typical perfor a ce characteristics uw 1s/div v in = 3.6v c out = 100 m f v out 50v/div 1s/div average input current 1a/div v out 50v/div average input current 0.5a/div lt3468 curves use the circuit of figure 6, lt3468-1 curves use the circuit of figure 7 and lt3468-2 use the circuit of figure 8 unless otherwise noted. v in = 3.6v c out = 100 f v out 50v/div average input current 0.5a/div 1s/div 3468 g03 v in (v) 2 charge time (s) 10 9 8 7 6 5 4 3 2 1 0 4 6 7 3468 g06 3 5 8 9 c out = 100 f c out = 50 f t a = 25 c v out (v) 0 50 100 150 200 250 300 average input current (ma) 3468 g09 600 0 150 300 450 v in = 2.8v v in = 4.2v v in = 3.6v t a = 25 c lt3468-2 charge time lt3468-2 charging waveform lt3468-2 input current
lt3468/lt3468-1/lt3468-2 4 346812f lt3468-1 switch current limit lt3468-1 output voltage lt3468 output voltage lt3468 switch current limit v in (v) 2345678 v out (v) 3468 g13 324 323 322 318 319 320 321 t a = ?0 c t a = 25 c t a = 85 c v in (v) 2345678 v out (v) 3468 g14 324 323 322 318 319 320 321 t a = ?0 c t a = 25 c t a = 85 c temperature ( c) ?0 ?0 0 20 40 60 100 80 i lim (a) 3468 g16 1.5 1.1 1.2 1.3 1.4 v in = 3v v out = 0v temperature ( c) ?0 ?0 0 20 40 60 100 80 i lim (a) 3468 g17 0.700 0.500 0.540 0.580 0.620 0.660 v in = 3v v out = 0v typical perfor a ce characteristics uw lt3468 curves use the circuit of figure 6, lt3468-1 curves use the circuit of figure 7 and lt3468-2 use the circuit of figure 8 unless otherwise noted. lt3468 efficiency lt3468-1 efficiency v out (v) 50 100 150 200 250 300 efficiency (%) 3468 g10 90 80 40 50 60 70 v in = 2.8v v in = 4.2v t a = 25 c v in = 3.6v v out (v) 50 100 150 200 250 300 efficiency (%) 3468 g11 90 80 40 50 60 70 v in = 2.8v v in = 4.2v v in = 3.6v t a = 25 c temperature ( c) ?0 i lim (a) 1.00 0.96 0.92 0.88 0.84 0.80 0 40 60 34682 g18 ?0 20 80 100 v in = 3v v out = 0v v out (v) 50 efficiency (%) 90 80 70 60 50 40 250 3468 g12 100 150 200 300 t a = 25 c v in = 4.2v v in = 2.8v v in = 3.6v v in (v) v out (v) 319 318 317 316 315 314 313 312 3468 g15 2 3 45678 t a = 25 c t a = 85 c t a = 40 c lt3468-2 switch current limit lt3468-2 output voltage lt3468-2 efficiency
lt3468/lt3468-1/lt3468-2 5 346812f lt3468 switching waveform lt3468/lt3468-1/lt3468-2 switch breakdown voltage lt3468-1 switching waveform v in = 3.6v v out = 100v 3468 g19 1 m s/div v sw 10v/div i pri 1a/div v in = 3.6v v out = 300v 3468 g23 1 m s/div v sw 10v/div i pri 1a/div lt3468 curves use the circuit of figure 6, lt3468-1 curves use the circuit of figure 7 and lt3468-2 use the circuit of figure 8 unless otherwise noted. typical perfor a ce characteristics uw v sw 10v/div i pri 1a/div 1 s/div 3468 g21 v in = 3.6v v out = 100v v sw 10v/div i pri 1a/div 1 s/div 3468 g24 v in = 3.6v v out = 300v switch voltage (v) 0 102030405060708090100 switch current (ma) 3468 g25 10 9 8 7 6 5 4 3 2 1 0 t = ?0 c t = 25 c t = 85 c sw pin is resistive until breakdown voltage due to integrated resistors. this does not increase quiescent current of part v in = v charge = 5v lt3468 switching waveform 3468 g20 1 m s/div v sw 10v/div i pri 1a/div v in = 3.6v v out = 300v lt3468-1 switching waveform v in = 3.6v v out = 100v 3468 g22 1 m s/div v sw 10v/div i pri 1a/div lt3468-2 switching waveform lt3468-2 switching waveform
lt3468/lt3468-1/lt3468-2 6 346812f sw (pin 1): switch pin. this is the collector of the internal npn power switch. minimize the metal trace area con- nected to this pin to minimize emi. tie one side of the primary of the transformer to this pin. the target output voltage is set by the turns ratio of the transformer. choose turns ratio n by the following equation: n v out = + 2 31 5 . where: v out is the desired output voltage. you must tie a schottky diode from gnd to sw, with the anode at gnd for proper operation of the circuit. please refer to the applications section for further information. gnd (pin 2): ground. tie directly to local ground plane. done (pin 3): open npn collector indication pin. when target output voltage is reached, npn turns on. this pin needs a pull-up resistor or current source. charge (pin 4): charge pin. this pin must be brought high (>1v) to enable the part. a low (<0.3v) to high (>1v) transition on this pin puts the part into power delivery mode. once the target output voltage is reached, the part will stop charging the output. toggle this pin to start charging again. ground to shut down . you may bring this pin low during a charge cycle to halt charging at any time. v in (pin 5): input supply pin. must be locally bypassed with a good quality ceramic capacitor. input supply must be 2.5v or higher. uu u pi fu ctio s block diagra w v in sw + done charge c1 t1 r2 60k q1 enable c out photoflash capacitor 36mv 20mv to battery d2 q2 v out d1 lt3468: r sense = 0.015 lt3468-2: r sense = 0.022 lt3468-1: r sense = 0.03 3486 bd 1 gnd 5 3 4 2 + + + + + one- shot one- shot driver primary secondary master latch r sense dcm comparator v out comparator r1 2.5k s rq 1.25v reference q3 q1 qq sr a3 a1 a2 chip enable figure 1
lt3468/lt3468-1/lt3468-2 7 346812f indicating that the part has finished charging. power delivery can only be restarted by toggling the charge pin. the charge pin gives full control of the part to the user. the charging can be halted at any time by bringing the charge pin low. only when the final output voltage is reached will the done pin go low. figure 2 shows these various modes in action. when charge is first brought high, charging commences. when charge is brought low during charging, the part goes into shutdown and v out no longer rises. when charge is brought high again, charging resumes. when the target v out voltage is reached, the done pin goes low and charging stops. finally the charge pin is brought low again so the part enters shutdown and the done pin goes high. operatio u the lt3468/lt3468-1/lt3468-2 are designed to charge photoflash capacitors quickly and efficiently. the opera- tion of the part can be best understood by referring to figure 1. when the charge pin is first driven high, a one shot sets both sr latches in the correct state. the power npn device, q1, turns on and current begins ramping up in the primary of transformer t1. comparator a1 monitors the switch current and when the peak current reaches 1.4a (lt3468), 1a(lt3468-2) or 0.7a (lt3468-1), q1 is turned off. since t1 is utilized as a flyback transformer, the flyback pulse on the sw pin will cause the output of a3 to be high. the voltage on the sw pin needs to be at least 36mv higher than v in for this to happen. during this phase, current is delivered to the photoflash capacitor via the secondary and diode d1. as the second- ary current decreases to zero, the sw pin voltage will begin to collapse. when the sw pin voltage drops to 36mv above v in or lower, the output of a3 (dcm comparator) will go low. this fires a one shot which turns q1 back on. this cycle will continue to deliver power to the output. output voltage detection is accomplished via r2, r1, q2, and comparator a2 (v out comparator). resistors r1 and r2 are sized so that when the sw voltage is 31.5v above v in , the output of a2 goes high which resets the master latch. this disables q1 and halts power delivery. npn transistor q3 is turned on pulling the done pin low, lt3468-2 v in = 3.6v c out = 50 f v out 100v/div v charge 5v/div v done 5v/div 1s/div 3468 f02 figure 2. halting the charging cycle with the charge pin. applicatio s i for atio wu u u choosing the right device (lt3468/lt3468-1/ lt3468-2) the only difference between the three versions of the lt3468 is the peak current level. for the fastest possible charge time, use the lt3468. the lt3468-1 has the lowest peak current capability, and is designed for applications that need a more limited drain on the batteries. due to the lower peak current, the lt3468-1 can use a physically smaller transformer. the lt3468-2 has a current limit in between that of the lt3468 and the lt3468-1. transformer design the flyback transformer is a key element for any lt3468/ lt3468-1/lt3468-2 design. it must be designed carefully and checked that it does not cause excessive current or voltage on any pin of the part. the main parameters that need to be designed are shown in table 1. the first transformer parameter that needs to be set is the turns ratio n. the lt3468/lt3468-1/lt3468-2 accom- plish output voltage detection by monitoring the flyback waveform on the sw pin. when the sw voltage reaches 31.5v higher than the v in voltage, the part will halt power delivery. thus, the choice of n sets the target output voltage as it changes the amplitude of the reflected voltage from the output to the sw pin. choose n according to the following equation: n v out = + 2 31 5 .
lt3468/lt3468-1/lt3468-2 8 346812f where: v out is the desired output voltage. the number 2 in the numerator is used to include the effect of the voltage drop across the output diode(s). thus for a 320v output, n should be 322/31.5 or 10.2. for a 300v output, choose n equal to 302/31.5 or 9.6. the next parameter that needs to be set is the primary inductance, l pri . choose l pri according to the following formula: l v ni pri out pk 3 - 200 10 9 where: v out is the desired output voltage. n is the transformer turns ratio. i pk is 1.4 (lt3468), 0.7 (lt3468-1), and 1.0 (lt3468-2). l pri needs to be equal or larger than this value to ensure that the lt3468/lt3468-1/lt3468-2 has adequate time to respond to the flyback waveform. all other parameters need to meet or exceed the recom- mended limits as shown in table 1. a particularly impor- tant parameter is the leakage inductance, l leak . when the power switch of the lt3468/lt3468-1/lt3468-2 turns off, the leakage inductance on the primary of the trans- former causes a voltage spike to occur on the sw pin. the height of this spike must not exceed 40v , even though the absolute maximum rating of the sw pin is 50v. the 50v absolute maximum rating is a dc blocking voltage speci- fication, which assumes that the current in the power npn is zero. figure 3 shows the sw voltage waveform for the circuit of figure 6(lt3468). note that the absolute maxi- mum rating of the sw pin is not exceeded. make sure to check the sw voltage waveform with v out near the target output voltage, as this is the worst case condition for sw voltage. figure 4 shows the various limits on the sw voltage during switch turn off. it is important not to minimize the leakage inductance to a very low level. although this would result in a very low leakage spike on the sw pin, the parasitic capacitance of the transformer would become large. this will adversely effect the charge time of the photoflash circuit. linear technology has worked with several leading mag- netic component manufacturers to produce pre-designed flyback transformers for use with the lt3468/lt3468-1/ lt3468-2. table 2 shows the details of several of these transformers. applicatio s i for atio wu u u figure 4. new transformer design check (not to scale). figure 3. lt3468 sw voltage waveform v in = 5v v out = 320v 3468 g18 100ns/div v sw 10v/div table 1. recommended transformer parameters typical range typical range typical range parameter name lt3468 lt3468-1 lt3468-2 units l pri primary inductance >5 >10 >7 m h l leak primary leakage inductance 100 to 300 200 to 500 200 to 500 nh n secondary: primary turns ratio 8 to 12 8 to 12 8 to 12 v iso secondary to primary isolation voltage >500 >500 >500 v i sat primary saturation current >1.6 >0.8 >1.0 a r pri primary winding resistance <300 <500 <400 m w r sec secondary winding resistance <40 <80 <60 w v sw 3420 f07 0v ? ? must be less than 40v must be less than 50v
lt3468/lt3468-1/lt3468-2 9 346812f table 2. pre-designed transformers - typical specifications unless otherwise noted. size l pri lpri-leakage r pri r sec for use with transformer name (w l h) mm ( m h) (nh) n (m w )( w ) vendor lt3468/lt3468-2 sbl-5.6-1 5.6 8.5 4.0 10 200 max 10.2 103 26 kijima musen lt3468-1 sbl-5.6s-1 5.6 8.5 3.0 24 400 max 10.2 305 55 hong kong office 852-2489-8266 (ph) kijimahk@netvigator.com (email) lt3468 ldt565630t-001 5.8 5.8 3.0 6 200 max 10.4 100 max 10 max tdk lt3468-1 ldt565630t-002 5.8 5.8 3.0 14.5 500 max 10.2 240 max 16.5 max chicago sales office lt3468-2 ldt565630t-003 5.8 5.8 3.0 10.5 550 max 10.2 210 max 14 max (847) 803-6100 (ph) www.components.tdk.com lt3468/lt3468-1 t-15-089 6.4 7.7 4.0 12 400 max 10.2 211 max 27 max tokyo coil engineering lt3468-1 t-15-083 8.0 8.9 2.0 20 500 max 10.2 675 max 35 max japan office 0426-56-6262 (ph) www.tokyo-coil.co.jp capacitor selection for the input bypass capacitor, a high quality x5r or x7r type should be used. make sure the voltage capability of the part is adequate. output diode selection the rectifying diode(s) should be low capacitance type with sufficient reverse voltage and forward current rat- ings. the peak reverse voltage that the diode(s) will see is approximately: vvnv pk r out in - =+ () the peak current of the diode is simply: i n pk sec - = 14 . (lt3468) i n pk sec - = 10 . (lt3468-2) i n pk sec - = 07 . (lt3468-1) for the circuit of figure 6 with v in of 5v, v pk-r is 371v and i pk-sec is 137ma. the gsd2004s dual silicon diode is recommended for most lt3468/lt3468-1/lt3468-2 applications. another option is to use the bav23s dual silicon diodes. toshiba makes a dual diode named 1ss306 which also meets all the requirements. the crf02 is a single diode with an 800v reverse voltage rating which is also suitable. table 3 shows the various diodes and relevant specifications. use the appropriate number of diodes to achieve the necessary reverse breakdown volt- age. sw pin clamp diode selection the diode d2 in figure 6 is needed to clamp the sw node. due to the new control scheme of the lt3468/lt3468-1/ lt3468-2, the sw node may go below ground during a switch cycle. the clamp diode prevents the sw node from table 3. recommended output diodes max reverse voltage max forward continuous current capacitance part (v) (ma) (pf) vendor gsd2004s 2x300 225 5 vishay (dual diode) (402) 563-6866 www.vishay.com bav23s 2x250 225 5 philips semiconductor (dual diode) (800) 234-7381 www.philips.com 1ss306 2x250 100 3 toshiba (dual diode) (949) 455-2000 crf02 1x800 500 not specified www.semicon.toshiba.co.jp applicatio s i for atio wu u u
lt3468/lt3468-1/lt3468-2 10 346812f board layout the high voltage operation of the lt3468/lt3468-1/ lt3468-2 demands careful attention to board layout. you will not get advertised performance with careless layout. figure 5 shows the recommended component placement. keep the area for the high voltage end of the secondary as small as possible. also note the larger than minimum spacing for all high voltage nodes in order to meet break- down voltage requirements for the circuit board. it is imperative to keep the electrical path formed by c1, the primary of t1, and the lt3468/lt3468-1/lt3468-2 as short as possible. if this path is haphazardly made long, it will effectively increase the leakage inductance of t1, which may result in an overvoltage condition on the sw pin. applicatio s i for atio wu u u figure 5. suggested layout: keep electrical path formed by c1, transformer primary and lt3468/lt3468-1/lt3468-2 short. d2 r1 d1 (dual diode) c1 secondary primary c out photoflash capacitor t1 v in charge done + 4 5 3 2 1 3468 f05 table 4. recommended clamp diodes max reverse voltage part (v) vendor zhcs400 40 zetex (631) 360-2222 www.zetex.com b0540w 40 diodes inc. (805) 446-4800 www.diodes.com ma2z720 40 panasonic (408) 487-9510 www.panasonic.co.jp typical applicatio s u going too far below ground. the diode is required for proper operation of the circuit. the recommended diode should be a schottky diode with at least a 500ma peak forward current capability. the diode forward voltage drop should be 600mv or less at 500ma of forward current. reverse voltage rating should be 40v or higher. table 4 shows various recommended clamping diodes. lt3468 charge gnd v in sw + done done charge c1 4.7 f r1 100k t1 1:10.2 v in 2.5v to 8v 320v 1 2 4 5 3468 f06 d2 c out photoflash capacitor c1: 4.7 f, x5r or x7r, 10v t1: kijima musen part# sbl-5.6-1, l pri = 10 h, n = 10.2 d1: vishay gsd2004s dual diode connected in series d2: zetex zhcs400 or equivalent r1: pull up resistor needed if done pin used d1 lt3468-1 charge gnd v in sw + done done charge c1 4.7 f r1 100k t1 1:10.2 c out photoflash capacitor v in 2.5v to 8v d2 320v d1 4 3 5 6 c1: 4.7 f, x5r or x7r, 10v t1: kijima musen part# sbl-5.6s-1, l pri = 24 h, n = 10.2 d1: vishay gsd2004s dual diode connected in series d2: zetex zhcs400 or equivalent r1: pull up resistor needed if done pin used 3468 f07 figure 6. lt3468 photoflash charger uses high efficiency 4mm tall transformer figure 7. lt3468-1 photoflash charger uses high efficiency 3mm tall transformer
lt3468/lt3468-1/lt3468-2 11 346812f s5 package 5-lead plastic tsot-23 (reference ltc dwg # 05-08-1635) u package descriptio 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. typical applicatio s u lt3468-2 charge gnd v in sw + done done charge c1 4.7 f r1 100k t1 1:10.2 c out photoflash capacitor v in 2.5v to 8v d2 320v d1 5 8 4 1 c1: 4.7 f, x5r or x7r, 10v t1: tdk ldt565630t-003 l pri = 10.5 h, n = 10.2 d1: vishay gsd2004s dual diode connected in series d2: zetex zhcs400 or equivalent r1: pull up resistor needed if done pin used 3468 f08 figure 8. lt3468-2 photoflash charger uses high efficiency 3mm tall transformer 1.50 ?1.75 (note 4) 2.80 bsc 0.30 ?0.45 typ 5 plcs (note 3) datum ? 0.09 ?0.20 (note 3) s5 tsot-23 0302 pin one 2.90 bsc (note 4) 0.95 bsc 1.90 bsc 0.80 ?0.90 1.00 max 0.01 ?0.10 0.20 bsc 0.30 ?0.50 ref 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
lt3468/lt3468-1/lt3468-2 12 346812f 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 2004 lt/tp 0304 1k ? printed in usa related parts part number description comments ltc3407 dual 600ma (i out ), 1.5mhz, synchronous step-down dc/dc 96% efficiency, v in : 2.5v to 5.5v, v out(min) : 0.6v, i q : 40 m a, converter i sd : <1 m a, ms10e lt3420/lt3420-1 1.4a/1a, photoflash capacitor chargers with charges 220 m f to 320v in 3.7 seconds from 5v, automatic top-off v in : 2.2v to 16v, i q : 90 m a, i sd : <1 m a, ms10 ltc3425 5a i sw , 8mhz, multi-phase synchronous step-up dc/dc 95% efficiency, v in : 0.5v to 4.5v, v out(min) : 5.25v, i q : 12 m a, converter i sd : <1 m a, qfn-32 ltc3440/ltc3441 600ma/1a (i out ), synchronous buck-boost dc/dc converter 95% efficiency, v in : 2.5v to 5.5v, v out(min) : 2.5v to 5.5v, i q : 25 m a, i sd : <1 m a, ms-10, dfn-12 typical applicatio s u lt3468 photoflash circuit uses tiny 3mm tall transformer lt3468-1 photoflash circuit uses tiny 3mm tall transformer lt3468 charge gnd v in sw + done done charge c1 4.7 f r1 100k t1 1:10.4 c out photoflash capacitor v in 2.5v to 8v d2 320v d1 4 3 1 5, 6 7, 8 4 1 5 2 c1: 4.7 f, x5r or x7r, 10v t1: tdk part# ldt565630t-001, l pri = 6 h, n = 10.4 d1: vishay gsd2004s dual diode connected in series d2: zetex zhcs400 or equivalent r1: pull up resistor needed if done pin used 3468 ta03 lt3468-1 charge gnd v in sw + done done charge c1 4.7 f r1 100k t1 1:10.2 c out photoflash capacitor v in 2.5v to 8v d2 320v d1 4 3 1 5 8 4 1 5 2 c1: 4.7 f, x5r or x7r, 10v t1: tdk part# ldt565630t-002, l pri = 14.5 h, n = 10.2 d1: vishay gsd2004s dual diode connected in series d2: zetex zhcs400 or equivalent r1: pull up resistor needed if done pin used 3468 ta04 charge time charge time v in (v) 23456789 charge time (s) 3468 ta05 10 9 8 7 6 5 4 3 2 1 0 c out = 50 f c out = 100 f v in (v) 23456789 charge time (s) 3468 ta06 10 9 8 7 6 5 4 3 2 1 0 c out = 20 f c out = 50 f

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