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1 LT1301 n 12v at 120ma from 5v or 3.3v supply n supply voltage as low as 1.8v n better high current efficiency than cmos n up to 89% efficiency n 120 m a quiescent current n shutdown to 10 m a n programmable 5v or 12v output n low v cesat switch: 170mv at 1a typical n i lim pin programs peak switch current n uses inexpensive surface mount inductors n 8-lead dip or soic package n flash memory v pp generator n palmtop computers n portable instruments n bar-code scanners n personal digital assistants n pcmcia cards the LT1301 is a micropower step-up dc/dc converter that utilizes burst mode? operation. the device can deliver 5v or 12v from a two-cell battery input. it features program- mable 5v or 12v output via a logic-controlled input, no- load quiescent current of 120 m a and a shutdown pin which reduces supply current to 10 m a. the on-chip power switch has a low 170mv saturation voltage at a switch current of 1a, a four-fold reduction over prior designs. a 155khz internal oscillator allows the use of extremely small sur- face mount inductors and capacitors. operation is guaran- teed at 1.8v input. this allows more energy to be extracted from the battery, increasing operating life. the i lim pin can be used for soft start or to program peak switch current with a single resistor allowing the use of even smaller inductors in lighter load applications. the LT1301 is available in an 8-lead soic package, minimizing board space requirements. for a selectable 3.3v/5v step-up converter, please see the lt1300. for higher output power, see the lt1302. descriptio n u features typical applicatio n s n u micropower high efficiency 5v/12v step-up dc/dc converter for flash memory applicatio n s u lt1300 f2 figure 1. 3.3v/5v to 12v step-up converter 1ms/div v in = 5v, v out = 12v load = 100 w output voltage 12v v out 2v/div LT1301 tao1 efficiency load current (ma) 10 100 300 LT1301 ta2 1 0 72 74 efficiency (%) 76 78 80 82 90 84 86 88 v in = 5v v in = 3.3v l1 = coilcraft do3316-333 or sumida cd73-330kc d1 = 1n5817 or motorola mbrs130lt3 c1 = avx tpsd476m016r0100 or sanyo os-con 165a47m c2 = avx tpsd336m020r0100 or sanyo os-con 205a33m shutdown 10v/div burst mode is a trademark of linear technology corporation. c2 33? 20v 12v output + l1 33? d1 c1 47? sw i lim pgnd gnd sense LT1301 select LT1301 f1 5v or 3.3v shdn shutdown n/c v in + 0.1?* *required for 5v output
2 LT1301 absolute m axi m u m ratings w ww u package/order i n for m atio n w u u v in voltage .............................................................. 10v sw1 voltage ............................................................ 20v sense voltage .......................................................... 20v shutdown voltage ................................................... 10v select voltage .......................................................... 10v i lim voltage ............................................................ 0.5v maximum power dissipation ............................. 500mw operating temperature range LT1301c ................................................... 0 c to 70 c LT1301i .................................................. 40 c to 85 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c s8 part marking 1301 1301i symbol parameter conditions min typ max units i q quiescent current v shdn = 0.5v, v sel = 5v, v sense = 5.5v l 120 200 m a v shdn = 1.8v l 715 m a v in input voltage range 1.8 v l 2.0 v v out output sense voltage v sel = 5v l 11.52 12.00 12.48 v v sel = 0v l 4.75 5.00 5.25 v output referred v sel = 5v (note 1) l 50 100 mv comparator hysteresis v sel = 0v (note 1) l 22 50 mv oscillator frequency current limit not asserted. 120 155 185 khz oscillator tc 0.2 %/ c dc maximum duty cycle 75 86 95 % t on switch on-time current limit not asserted. 5.6 m s output line regulation 1.8v < v in < 6v l 0.06 0.15 %/v v cesat switch saturation voltage i sw = 700ma l 130 200 mv switch leakage current v sw = 5v, switch off l 0.1 10 m a peak switch current i lim floating (see typical application) 0.75 1.0 1.25 a (internal trip point) i lim grounded 0.4 a v shdnh shutdown pin high l 1.8 v v shdnl shutdown pin low 0.5 v v selh select pin high l 1.5 v v sell select pin low l 0.8 v i shdn shutdown pin bias current v shdn = 5v l 820 m a v shdn = 2v l 3 m a v shdn = 0v l 0.1 1 m a i sel select pin bias current 0v < v sel < 5v l 13 m a electrical characteristics t a = 25 c, v in = 2v unless otherwise noted. the l denotes specifications which apply over the 0 c to 70 c temperature range. order part number note 1: hysteresis specified is dc. output ripple may be higher if output capacitance is insufficient or capacitor esr is excessive. see operation section. LT1301cn8 LT1301cs8 LT1301is8 1 2 3 4 8 7 6 5 top view gnd sel shdn sense pgnd sw v in i lim n8 package 8-lead plastic dip s8 package 8-lead plastic soic t jmax = 100 c, q ja = 150 c/ w
3 LT1301 5ms/div typical perfor m a n ce characteristics u w 5v output efficiency shutdown pin bias current load current (ma) 1 78 efficiency (%) 80 82 84 86 10 100 1000 LT1301 g1 76 74 72 70 88 90 v in = 3.3v v in = 2.5v 200 m s/div i load 120ma 0ma v out 100mv/div ac coupled LT1301 g6 v out 100mv/div ac coupled 120ma 0ma i load LT1301 g7 200 m s/div v out 2v/div 5v v select 10v/div c out = 100 m f, v in = 5v 100 w load LT1301 g8 v select 10v/div 5ms/div LT1301 g9 c out = 100 m f, v in = 3.3v 100 w load saturation voltage vs switch current no-load input current v in = 5v load transient response of figure 1 circuit total quiescent current in shutdown shutdown voltage (v) 0 shutdown current (?) 0 4 6 8 20 12 14 2 4 5 lt1300 g3 2 16 18 10 13 6 7 8 t a = 25? input voltage (v) 0 i shdn + i vin + i sense (?) 40 50 60 8 LT1301 g2 30 20 0 2 4 6 10 80 70 1 3 5 7 t a = 25? switch current (a) 0 0.1 saturation voltage (mv) 150 175 200 225 250 0.8 0.9 LT1301 g4 100 125 50 25 75 0 0.2 0.3 0.4 0.5 0.6 0.7 1 t a = 25? input voltage (v) 2 input current (?) 250 300 350 5 7 LT1301 g5 200 150 100 34 6 400 450 500 v out = 12v v out = 5v load transient response of figure 1 circuit v in = 3.3v 12v 5v 12v select pin transient response select pin transient response v out 2v/div
4 LT1301 pi n fu n ctio n s uuu gnd (pin 1): signal ground. tie to pgnd under the package. sel (pin 2): output select. when tied to v in converter regulates at 12v. when grounded or floating converter regulates at 5v. may be driven under logic control. shdn (pin 3): shutdown. pull high to shut down the LT1301. ground for normal operation. sense (pin 4): output pin. goes to internal resistive divider. if operating at 5v output, a 0.1 m f ceramic capaci- tor is required from sense to ground. i lim (pin 5): float for 1a switch current limit. tie to ground for approximately 400ma. a resistor between i lim and ground sets peak current to some intermediate value . v in (pin 6): supply pin. must be bypassed with a large value electrolytic to ground. keep bypass within 0.2" of the device. sw (pin 7): switch pin. connect inductor and diode here. keep layout short and direct to minimize radio frequency interference. pgnd (pin 8): power ground. tie to signal ground (pin 1) under the package. bypass capacitor from v in should be tied directly to pgnd within 0.2" of the device. figure 2. block diagra m w oscillator 155khz r2 730 w c2 sw r1 3 w q2 1 q1 160 18mv off v in v in i lim pgnd v out enable a1 comparator + + + + 1.25v reference l1 d1 7 2 4 sense a2 current comparator a3 driver bias q3 8.5k 58 shutdown 3 select 2 gnd 69.2k 97.5k 500k c1 1 LT1301 f2
5 LT1301 test circuit s oscillator test circuit 2v 100 f v in sel sense gnd pgnd shdn sw LT1301 i l 100 w 5v LT1301 tc f out operatio n u operation of the LT1301 is best understood by referring to the block diagram in figure 2. when a1s negative input, related to the sense pin voltage by the appropriate resis- tor-divider ratio is higher that the 1.25v reference voltage, a1s output is low. a2, a3 and the oscillator are turned off, drawing no current. only the reference and a1 consume current, typically 120 m a. when a1s negative input drops below 1.25v, overcoming a1s 6mv hysteresis, a1s out- put goes high enabling the oscillator, current comparator a2, and driver a3. quiescent current increases to 2ma as the device prepares for high current switching. q1 then turns on in controlled saturation for (nominally) 5.3 m s or until comparator a2 trips, whichever comes first. after a fixed off-time of (nominally) 1.2 m s, q1 turns on again. the LT1301s switching causes current to alternately build up in l1 and dump into output capacitor c2 via d1, increasing the output voltage. when the output is high enough to cause a1s output to go to low, switching action ceases. c2 is left to supply current to the load until v out decreases enough to force a1s output high, and the entire cycle repeats. figure 4 details relevant waveforms. a1s cycling causes low-to-mid-frequency ripple voltage on the output. ripple can be reduced by making the output capacitor large. the 33 m f unit specified results in ripple of 100mv to 200mv on the 12v output. a 100 m f capacitor will decrease ripple to 50mv. if operating at 5v ouput a 0.1 m f ceramic capacitor is required at the sense pin in addition to the electrolytic. if switch current reaches 1a, causing a2 to trip, switch on- time is reduced and off-time increases slightly. this allows continuous mode operation during bursts. a2 monitors the voltage across 3 w resistor r1 which is directly related to the switch current. q2s collector current is set by the emitter-area ratio to 0.6% of q1s collector current. when r1s voltage drop exceeds 18mv, corresponding to 1a switch current, a2s output goes high, truncating the on- time portion of the oscillator cycle and increasing off-time to about 2 m s as shown in figure 3, trace a. this pro- grammed peak current can be reduced by tying the i lim pin to ground, causing 15 m a to flow through r2 into q3s collector. q3s current causes a 10.4mv drop in r2 so that only an additional 7.6mv is required across r1 to turn off the switch. this corresponds to a 400ma switch current as shown in figure 3, trace b. the reduced peak switch current reduces i 2 r loses in q1, l1, c1 and d1. efficiency can be increased by doing this provided that the accom- panying reduction in full load current is acceptable. lower peak currents also extend alkaline battery life due to the alkaline cells high internal impedance. figure 3. switch pin current with i lim floating or grounded trace a 500ma/div i lim pin open trace b 500ma/div i lim pin grounded 20 m s/div
6 LT1301 applicatio n s i n for m atio n wu u u i in 500ma/div v out 5v/div v shdn 10v/div 200 m s/div v in = 5v, v out = 12v lt1300 f5 v out 100mv/div ac coupled v sw 10v/div i l 500ma/div 20 m s/div v in = 5v, v out = 12v, l = 33 m h c out = 33 m f, i load = 90ma lt1300 f4 figure 4. burst mode operation in action figure 5. start-up response output voltage selection the LT1301 can be selected to 5v or 12v under logic control or fixed at either by tying select to ground or v in respectively. it is permissible to tie select to a voltage higher than v in as long as it does not exceed 10v. efficiency in 5v mode will be slightly less that in 12v mode due to the fact that the diode drop is a greater percentage of 5v than 12v. since the bipolar switch in the LT1301 gets its base drive from v in , no reduction in switch efficiency occurs when in 5v mode. when v in exceeds the pro- grammed output voltage the output will follow the input. this is characteristic of the simple step-up or boost converter topology. a circuit example that provides a regulated output with an input voltage above or below the output (known as a buck-boost or sepic) is shown in the typical applications section. shutdown the converter can be turned off by pulling shdn (pin 3) high. quiescent current drops to 10 m a in this condition. bias current of 8 m a to 10 m a flows into the pin (at 5v input). it is recommended that shdn not be left floating. tie the pin to ground if the feature is not used. shdn can be driven high even if v in is floating. i lim function the LT1301s current limit (i lim ) pin can be used for soft start. upon start-up, the LT1301 will draw maximum current from the supply (about 1a) from the supply to charge the output capacitor. figure 5 shows v out and i in waveforms as the device is turned on. the high current flow can create ir drops along supply and ground lines or cause the input supply to drop out momentarily. by adding r1 and c3 as shown in figure 6, the switch current in the LT1301 is initially limited to 400ma until the 15 m a flowing out of the i lim pin charges up c3. input current is held to under 500ma while the output voltage ramps up to 12v as shown in figure 7. r1 provides a discharge path for the capacitor without appreciably de- creasing peak switch current. when using the i lim pin soft- start mode a minimum load of a few hundred microam- peres is recommended to prevent c3 from discharging, as no current flows out of i lim when the LT1301 is not i in 500ma/div 200 m s/div v out 5vdiv v shdn 10v/div lt1300 f5 v in = 5v, v out = 12v figure 7. startup response soft-start circuitry added figure 6. c2 33? c3 0.1? r1 1m l1 33? d1 1n5817 47? sw i lim pgnd gnd sense LT1301 select LT1301 f6 shdn shutdown 12v v in v in 3.3v or 5v + +
7 LT1301 efficiency (%) component part number vendor l ( m h) dcr ( w )v in (v) i lim pin 30ma 60ma 120ma height (mm) phone number do3316-333 coilcraft 33 0.088 3.3 open 84 84 85 5.5 (708) 639C6400 5 open 89 89 90 do1608-223 coilcraft 22 .31 3.3 open 82 82 3.5 3.3 ground 85 5 10k 86 87 5 ground 88 do1608-103 coilcraft 10 .11 2 open 78 3.5 ctx20-1 coiltronics 20 .175 3.3 open 84 84 4.2 (407) 241-7876 5 open 88 88 89 ga10-332 gowanda 33 .077 3.3 open 86 86 87 through-hole (716) 532-2234 5 open 89 89 90 lqh3g220k04m00 murata-erie 22 0.7 3.3 ground 81 2.0 (404) 436-1300 5 ground 85 cd73-330kc sumida 33 0.131 3.3 open 84 85 86 3.5 (708) 956-0666 5 open 88 88 89 cdrh62-330mc sumida 33 0.48 3.3 open 80 80 81 3.0 ground 85 5 open 84 84 85 ground 83 applicatio n s i n for m atio n wu u u table 1. recommended inductors vendor series type phone# avx tps surface mount (803)448C9411 sanyo os-con through-hole (619) 661C6835 panasonic hfq through-hole (201) 348-5200 table 2. recommended capacitors switching. zero load current causes the LT1301 to switch so infrequently that c3 can completely discharge reducing subsequent peak switch current to 400ma. if a load is suddenly applied, output voltage will sag until c3 can be recharged and peak switch current returns to 1a. if the full capacity of the LT1301 is not required peak current can be reduced by changing the value of r3 as shown in figure 8. with r3 = 0 switch current is limited to approximately 400ma. smaller, less expensive inductors with lower saturation ratings can then be used. inductor selection for full output power, the inductor should have a satura- tion current rating of 1.25a for worst-case current limit, although it is acceptable to bias an inductor 20% or more into saturation. smaller inductors can be used in conjunc- tion with the i lim pin. efficiency is significantly affected by inductor dcr. for best efficiency limit the dcr to 0.03 w or less. toroidal types are preferred in some cases due to their inherent flux containment and emi/rfi superiority. recommended inductors are listed in table 1. figure 8. peak switch current vs. current limit set resistor current limit set resistor ( w ) 500 switch current (ma) 700 800 1000 1100 100 10k 100k 1m LT1301 f8 300 1k 900 600 400 1.6v v in 5v
8 LT1301 applicatio n s i n for m atio n wu u u capacitor selection low esr capacitors are required for both input and output of the LT1301. esr directly affects ripple voltage and efficiency. for surface mount applications avx tps series tantalum capacitors are recommended. these have been specially designed for smps and have low esr along with high surge current ratings. for through-hole applications sanyo os-con capacitors offer extremely low esr in a small size. again, if peak switch current is reduced using the i lim pin, capacitor requirements can be relaxed and smaller, higher esr units can be used. suggested capaci- tor sources are listed in table 2. diode selection best performance is obtained with a schottky rectifier diode such as the 1n5817. phillips components makes this in surface mount as the prll5817. motorola makes the mbrs130lt3 which is slightly better and also in surface mount. for lower output power a 1n4148 can be used although efficiency will suffer substantially. layout considerations the LT1301 is a high speed, high current device. the input capacitor must be no more than 0.2? from v in (pin 6) and ground. connect the pgnd and gnd (pins 8 and 1) together under the package. place the inductor adjacent to sw (pin 7) and make the switch pin trace as short as possible. this keeps radiated noise to a minimum. typical applicatio n s n u four-cell to 5v converter c3 100? l2 33? 0.1? 5v output 200ma 80 to 83% efficient at i load > 10ma + l1 33? c2 100? 1n5817 c1 100? 4 cells sw nc i lim pgnd gnd sense LT1301 select LT1301 tao3 shdn shutdown v in + + 1n5817 2n4403 5v, 200ma + l1* 10? *sumida cd54-100lc coilcraft do3316-223 100? 100? 470 w 0.1? 2 aa cell sw i lim pgnd gnd sense LT1301 select LT1301 ta4 shdn nc nc shutdown v in + step-up converter with automatic output disconnect
9 LT1301 typical applicatio n s n u lcd contrast supply + 100? 22? 35v contrast v out 4v to ?9v 12ma maximum from 1.8v supply (77% efficient) 20ma maximum from 3v supply (83% efficient) 2.2? sw pwm in 0% to 100% cmos drive 0v to 5v 150k 12k 12k 1 10 8 2 9 3 7 4 i lim pgnd gnd sense LT1301 select lt1300 ta5 1n5819 t1 t1 = dale lpe-5047-ao45 (605) 665-9301 shdn shutdown nc nc v in v in 1.8v to 6v + + 0.1? 1? 10? 7.5k 1% 22pf 3kv 0.068? 120 w 1 w wima mkp20 ztx849 ztx849 1n4148 2n3904 ccfl sw i lim pgnd gnd sense LT1301 select 1n5817 l1 47? v in 2v - 6v t1 = coiltronics ctx110654-1 l1 = coilcraft d03316-473 shdn shutdown v in + + 15 ti 4 97 32 0 - 5v dc in intensity adjust 100? to 2ma bulb current lt1300 ta6 nc low-voltage ccfl power supply
10 LT1301 typical applicatio n s n u 5v to C 5v converter 0.1? l1 33? 33? 33? 4.99k 1% 4.99k 1% shutdown 4 3 1 2 sw i lim pgnd gnd sense nc nc LT1301 or lt1300 select 1n5817 1n965 1n4148 5v ? out 5v 300ma l1 = coiltronics ctx33-4 shdn v in + + 5v LT1301 ta7
11 LT1301 package descriptio n u dimensions in inches (millimeters) unless otherwise noted. n8 0392 0.009 ?0.015 (0.229 ?0.381) 0.300 ?0.320 (7.620 ?8.128) 0.325 +0.025 0.015 +0.635 0.381 8.255 () 0.045 ?0.015 (1.143 ?0.381) 0.100 ?0.010 (2.540 ?0.254) 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.130 ?0.005 (3.302 ?0.127) 0.020 (0.508) min 0.018 ?0.003 (0.457 ?0.076) 0.125 (3.175) min 12 3 4 87 6 5 0.250 ?0.010 (6.350 ?0.254) 0.400 (10.160) max n8 package 8-lead plastic dip s8 package 8-lead plastic s0ic 1 2 3 4 0.150 ?0. (3.810 ?3. 8 7 6 5 0.189 ?0.197* (4.801 ?5.004) 0.228 ?0.244 (5.791 ?6.197) 0.016 ?0.050 0.406 ?1.270 0.010 ?0.020 (0.254 ?0.508) 45 0 8?typ 0.008 ?0.010 (0.203 ?0.254) so8 0294 0.053 ?0.069 (1.346 ?1.752) 0.014 ?0.019 (0.355 ?0.483) 0.004 ?0.010 (0.101 ?0.254) 0.050 (1.270) bsc *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.006 inch (0.15mm). 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.
12 LT1301 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7487 (408) 432-1900 l fax : (408) 434-0507 l telex : 499-3977 ? linear technology corporation 1994 lt/gp 0394 10k ? printed in usa northeast region linear technology corporation one oxford valley 2300 e. lincoln hwy.,suite 306 langhorne, pa 19047 phone: (215) 757-8578 fax: (215) 757-5631 linear technology corporation 266 lowell st., suite b-8 wilmington, ma 01887 phone: (508) 658-3881 fax: (508) 658-2701 u.s. area sales offices southeast region linear technology corporation 17060 dallas parkway suite 208 dallas, tx 75248 phone: (214) 733-3071 fax: (214) 380-5138 central region linear technology corporation chesapeake square 229 mitchell court, suite a-25 addison, il 60101 phone: (708) 620-6910 fax: (708) 620-6977 southwest region linear technology corporation 22141 ventura blvd. suite 206 woodland hills, ca 91364 phone: (818) 703-0835 fax: (818) 703-0517 northwest region linear technology corporation 782 sycamore dr. milpitas, ca 95035 phone: (408) 428-2050 fax: (408) 432-6331 france linear technology s.a.r.l. immeuble "le quartz" 58 chemin de la justice 92290 chatenay malabry france phone: 33-1-41079555 fax: 33-1-46314613 germany linear techonolgy gmbh untere hauptstr. 9 d-85386 eching germany phone: 49-89-3197410 fax: 49-89-3194821 japan linear technology kk 5f yz bldg. 4-4-12 iidabashi, chiyoda-ku tokyo, 102 japan phone: 81-3-3237-7891 fax: 81-3-3237-8010 taiwan linear technology corporation rm. 801, no. 46, sec. 2 chung shan n. rd. taipei, taiwan, r.o.c. phone: 886-2-521-7575 fax: 886-2-562-2285 united kingdom linear technology (uk) ltd. the coliseum, riverside way camberley, surrey gu15 3yl united kingdom phone: 44-276-677676 fax: 44-276-64851 korea linear technology korea branch namsong building, #505 itaewon-dong 260-199 yongsan-ku, seoul korea phone: 82-2-792-1617 fax: 82-2-792-1619 singapore linear technology pte. ltd. 101 boon keng road #02-15 kallang ind. estates singapore 1233 phone: 65-293-5322 fax: 65-292-0398 world headquarters linear technology corporation 1630 mccarthy blvd. milpitas, ca 95035-7487 phone: (408) 432-1900 fax: (408) 434-0507 08/16/93 international sales offices

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