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1 ltc3426 3426f 1.2mhz step-up dc/dc converter in sot-23 internal 2a mosfet switch 1.2mhz switching frequency integrated soft-start v in range: 1.6v to 4.3v low r ds(on) switch: 100m ? at 5v output delivers 5v at 800ma from a 3.3v input delivers 3.3v at 800ma from a 2.5v input uses small, low profile external components low profile (1mm) sot-23 (thinsot tm ) package white led driver supply local 3.3v or 5v supply battery back-up the ltc 3426 step-up switching regulator generates an output voltage of up to 5.5v from an input voltage as low as 1.6v. ideal for applications where space is limited, it switches at 1.2mhz, allowing the use of tiny, low cost and low profile external components. its internal 2a, 100m ? nmos switch provides high efficiency even at heavy load, while the constant frequency, current mode architecture results in low, predictable output noise that is easy to filter. antiringing circuitry reduces emi concerns by damping the inductor while in discontinuous mode, and internal soft-start eases inrush current worries. internal frequency compensation is designed to accommodate ceramic out- put capacitors, further reducing noise. the device features very low shutdown current of 0.5 a. the ltc3426 is available in the 6-lead sot-23 package. 3.3v to 5v boost converter efficiency sw 2.2 h v in 3.3v v in ltc3426 shdn 22 f 10 f v out 5v 800ma 3426 ta01 v out fb off on gnd features descriptio u applicatio s u typical applicatio u load current (ma) 1 70 efficiency (%) 75 80 85 90 10 100 1000 3426 ta01b 65 60 55 50 95 100 v in = 3.3v v out = 5v , ltc and lt are registered trademarks of linear technology corporation. thinsot is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. protected by u.s. patents, including 6498466, 6611131
2 ltc3426 3426f a u g w a w u w a r b s o lu t exi t i s v in voltage ................................................. 0.3v to 6v sw voltage .................................................. 0.3v to 6v shdn, fb voltage ....................................... 0.3v to 6v v out ........................................................... 0.3v to 6v operating temperature range (note 2) .. 40 c to 85 c storage temperature range ................. 65 c to 125 c lead temperature (soldering, 10 sec)................ 300 c t jmax = 125 c, ja = 165 c/w, jc = 102 c/w (note 1) order part number ltc3426es6 consult ltc marketing for parts specified with wider operating temperature ranges. package/order i for atio uu w parameter conditions min typ max units input voltage range shdn = v in 1.6 4.3 v output voltage adjust range 2.25 5 v feedback voltage 1.173 1.22 1.247 v feedback input current v fb = 1.23v 0.1 a quiescent current (shutdown) v shdn = 0v, not including switch leakage 1 a quiescent current shdn = v in , not switching 600 1000 a switch leakage v sw = 5v 0.2 10 a switch on resistance v out = 3.3v 0.11 ? v out = 5v 0.10 ? current limit 2 2.3 a maximum duty cycle v fb = 1.15v 80 85 % switching frequency 0.85 1.2 1.5 mhz shdn input high 1v shdn input low 0.4 v shdn input current shdn = 5.5v 1 a the denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v in = 1.8v, v out = 3.3v, unless otherwise specified. co verter characteristics u sw 1 gnd 2 fb 3 6 v in 5 v out 4 shdn top view s6 package 6-lead plastic tsot-23 s6 part marking ltajt note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the ltc3426 is guaranteed to meet performance specifications from 0 c to 70 c. specifications over the 40 c to 85 c operating temperature are assured by design, characterization and correlation with statistical process controls. note 3: this ic includes overtemperature protection that is intended to protect the device during momentary overload conditions. junction temperature will exceed 125 c when overtemperature protection is active. continuous operation above the specified maximum operating junction temperature may impair device reliability.
3 ltc3426 3426f typical perfor a ce characteristics uw oscillator frequency vs temperature temperature ( c) ?0 1.0 frequency (mhz) 1.1 1.2 1.3 1.40 ?0 ?0 10 30 3426 g01 50 70 90 v in (v) 1.8 80 efficiency (%) 84 88 92 2.2 2.6 3 3.4 lt1108 ?tpc12 3.8 96 100 82 86 90 94 98 4.2 figure 1 circuit t a = 25 c i load = 150ma v out = 5v c out = 22 f l = 2.2 h v in (v) 1.8 0.3 i out(max) (a) 0.5 0.7 0.9 1.1 1.3 2.2 2.6 3 3.4 3426 g03 3.8 4.2 figure 1 circuit t a = 25 c v out = 5v c out = 22 f l = 2.2 h efficiency vs v in i out(max) vs v in r ds(on) vs temperature temperature ( c) ?0 0.05 r ds(on) ( ? ) 0.07 0.09 0.11 ?5 0 25 50 3426 g04 75 0.13 0.15 0.06 0.08 0.10 0.12 0.14 100 v out = 2.5v v out = 5v v out = 3.3v temperature ( c) ?0 1.19 fb voltage (v) 1.20 1.21 1.22 1.23 1.25 ?5 02550 3426 g05 75 100 1.24 fb pin voltage v out 500mv/div sw 2v/div 100ns/div v in = 1.8v v out = 3.3v c out = 22 f l = 2.5 h 3426 g06 i l 200ma/div switching waveforms sw pin antiringing operation v out transient response sw 1v/div 100ns/div v in = 1.8v v out = 3.3v 3426 g07 i l 50ma/div 40 s/div v in = 1.8v v out = 3.3v c out = 22 f l = 2.5 h 3426 g08 i l 500ma/div i out 200ma/div v out 500mv/div 250ma 500ma
4 ltc3426 3426f uu u pi fu ctio s sw (pin 1): switch pin. connect inductor between sw and v in . a schottky diode is connected between sw and v out . keep these pcb trace lengths as short and wide as possible to reduce emi and voltage overshoot. if the inductor current falls to zero, an internal 100 ? antiringing switch is connected from sw to v in to minimize emi. gnd (pin 2): signal and power ground. provide a short direct pcb path between gnd and the (? side of the output capacitor(s). fb (pin 3): feedback input to the g m error amplifier. connect resistor divider tap to this pin. the output voltage can be adjusted from 2.5v to 5v by: v r r out =+ ? ? ? ? ? ? 122 1 1 2 . shdn (pin 4): logic controlled shutdown input. shdn = high: normal free running operation shdn = low: shutdown, quiescent current < 1 a typically, shdn should be connected to v in through a 1m pull-up resistor. v out (pin 5): output voltage sense input. the nmos switch gate drive is derived from the greater of v out and v in . v in (pin 6): input supply. must be locally bypassed. block diagra w figure 1 4 shutdown and soft-start 1.22v reference ramp generator 1.2mhz oscillator 3426 f01 pwm logic and driver + 3 fb fb v out shdn sw a1 + + a2 r c r2 (external) r1 (external) 0.02 ? c c 1 gnd 2 v in 6 v out comparator 5
5 ltc3426 3426f operatio u the ltc3426 is a monolithic 1.2mhz boost converter housed in a 6-lead sot-23 package. the device features fixed frequency, current mode pwm control for excellent line and load regulation. the low r ds(on) nmos switch enables the device to maintain high efficiency over a wide range of load current. operation of the feedback loop which sets the peak inductor current to keep the output in regulation can be best understood by referring to the block diagram in figure 1. at the start of each clock cycle a latch in the pwm logic is set and the nmos switch is turned on. the sum of a voltage proportional to the switch current and a slope compensating voltage ramp is fed to the positive input to the pwm comparator. when this voltage exceeds either a voltage proportional to the 2a current limit or the pwm control voltage, the latch in the pwm logic is reset and nmos switch is turned off. the pwm control voltage at the output of the error amplifier is the amplified and compensated difference between the feed- back voltage on the fb pin and the internal reference voltage of 1.22v. if the control voltage increases, more current is delivered to the output. when the control voltage exceeds the i limit reference voltage, the peak current is limited to a minimum of 2a. the current limit helps protect the ltc3426 internal switch and external components connected to it. if the control voltage decreases, less current is delivered to the output. during load transients control voltage may decrease to the point where no switching occurs until the feedback voltage drops below the reference. the ltc3426 has an integrated soft-start feature which slowly ramps up the feedback control node from 0v. the soft-start is initiated when shdn is pulled high. applicatio s i for atio wu uu setting the output voltage the output voltage, v out , is set by a resistive divider from v out to ground. the divider tap is tied to the fb pin. v out is set by the formula: v r r out =+ ? ? ? ? ? ? 122 1 1 2 . inductor selection the ltc3426 can utilize small surface mount inductors due to its 1.2mhz switching frequency. a 1.5 h or 2.2 h inductor will be the best choice for most ltc3426 appli- cations. larger values of inductance will allow greater output current capability by reducing the inductor ripple current. increasing the inductance above 3.3 h will in- crease component size while providing little improve- ment in output current capability. the inductor current ripple is typically set for 20% to 40% of the maximum inductor current (i p ). high frequency ferrite core inductor materials reduce frequency dependent power losses com- pared to cheaper powdered iron types, improving effi- ciency. the inductor should have low dcr (dc resistance) to reduce the i 2 r power losses, and must be able to handle the peak inductor current without saturating. several inductor manufacturers are listed in table 1. table 1. inductor manufacturers tdk www.tdk.com sumida www.sumida.com murata www.murata.com output and input capacitor selection low esr (equivalent series resistance) capacitors should be used to minimize the output voltage ripple. multilayer ceramic capacitors are an excellent choice as they have extremely low esr and are available in small footprints. a 15 f to 30 f output capacitor is sufficient for most applications. x5r and x7r dielectric materials are pre- ferred for their ability to maintain capacitance over wide voltage and temperature ranges. low esr input capacitors reduce input switching noise and reduce the peak current drawn from the input supply. it follows that ceramic capacitors are also a good choice for input decoupling and should be located as close as
6 ltc3426 3426f possible to the device. a 10 f input capacitor is sufficient for most applications. table 2 shows a list of several ceramic capacitor manufacturers. consult the manufac- turers for detailed information in their entire selection of ceramic parts. table 2. ceramic capacitor manufacturers taiyo yuden www.t-yuden.com murata www.murata.com tdk www.component.tdk.com diode selection a schottky diode is recommended for use with the ltc3426. use of a low forward voltage diode such as the on semiconductor mbra210lt3 is recommended. a schot- tky diode rated at 2a is recommended for use with the ltc3426. applicatio s i for atio wu uu pcb layout guidelines the high speed operation of the ltc3426 demands careful attention to board layout. you will not get advertised performance with careless layout. figure 2 shows the recommended component placement. a large ground pin copper area will help to lower the chip temperature. figure 2. recommended component placement for single layer board sw v in v out 3426 f02 gnd fb v in v out shdn 1 2 3 6 5 4
7 ltc3426 3426f typical applicatio s u efficiency sw v in 1.8v v in ltc3426 shdn v out 2.5v 800ma 3426 ta03a v out fb off on gnd l1 1.5 h d1 c2 22 f c1 10 f r1 64.9k 1% r2 61.9k 1% c1: tdk c1608x5r0j106m c2: taiyo yuden jmk316bj226ml d1: on semiconductor mbrm120lt3 l1: tdk rlf7030t-1r5n6r1 efficiency sw l1 2.2 h d1 v in 3.3v v in ltc3426 shdn c2 22 f c1 10 f v out 5v 800ma r1 95.3k 1% r2 30.9k 1% c1: taiyo yuden x5r jmk212bj475ml c2: taiyo yuden x5r jmk316bj226ml d1: on semiconductor mbra210lt3 l1: coilcraft d03316p-222 3426 ta02a v out fb off on gnd load current (ma) 1 70 efficiency (%) 75 80 85 90 10 100 1000 3426 ta02b 65 60 55 50 95 100 load current (ma) 1 50 efficiency (%) 80 90 100 10 100 1000 3426 ta03b 70 60
8 ltc3426 3426f typical applicatio s u sw v in 2.5v v in ltc3426 shdn v out 3.3v 800ma 3426 ta05a v out fb off on gnd l1 2.5 h d1 c2 22 f c1 10 f r1 75k 1% r2 44.2k 1% c1: tdk c1608x5r0j106 c2: taiyo yuden jmk316bj266 d1: on semiconductor mbrm120lt3 l1: sumida cdrh5d28-2r5 2 efficiency sw v in 3v to 4.2v v in ltc3426 shdn v out 5v 750ma at 3v 3426 ta04a v out fb off on gnd l1 2.2 h d1 c2 22 f c1 10 f r1 95.3k 1% r2 30.9k 1% c1: tdk c1608x5r0j475m c2: taiyo yuden jmk316bj226ml d1: on semiconductor mbr120vlsft1 l1: sumida cdrh4d28-2r2 2 efficiency load current (ma) 1 70 efficiency (%) 75 80 85 90 10 100 1000 3426 ta04b 65 60 55 50 95 100 v in = 4.2v v in = 3v load current (ma) 1 50 efficiency (%) 80 90 100 10 100 1000 3426 ta05b 70 60
9 ltc3426 3426f typical applicatio s u efficiency efficiency sw v in 1.8v v in ltc3426 shdn v out 3.3v 540ma 3426 ta06a v out fb off on gnd l1 1.5 h d1 c2 22 f c1 10 f r1 75k 1% r2 44.2k 1% c1: tdk c1608x5r0j106m c2: taiyo yuden jmk316bj226ml d1: on semiconductor mbrm120lt3 l1: tdk rlf7030t-1r5n6r1 sw v in 1.8v v in ltc3426 shdn v out 5v 400ma 3426 ta07a v out fb off on gnd l1 2.2 h d1 c2 22 f c1 10 f r1 95.3k 1% r2 30.9k 1% c1: tdk c1608x5r0j475m c2: taiyo yuden jmk316bj226ml d1: on semiconductor mbr120vlsft1 l1: sumida cdrh4d28-2r2 2 load current (ma) 1 50 efficiency (%) 80 90 100 10 100 1000 3426 ta06b 70 60 load current (ma) 1 40 efficiency (%) 70 80 90 10 100 1000 3426 ta07b 60 50
10 ltc3426 3426f typical applicatio s u efficiency sw v in 2.5v v in ltc3426 shdn v out 5v 550ma 3426 ta08a v out fb off on gnd l1 2.5 h d1 c2 22 f c1 10 f r1 95.3k 1% r2 30.9k 1% c1: tdk c1608x5r0j106 c2: taiyo yuden jmk316bj266 d1: on semiconductor mbrm120lt3 l1: sumida cdrh5d28-2r5 load current (ma) 1 50 efficiency (%) 80 90 100 10 100 1000 3426 ta08b 70 60
11 ltc3426 3426f u package descriptio s6 package 6-lead plastic tsot-23 (reference ltc dwg # 05-08-1636) 1.50 ?1.75 (note 4) 2.80 bsc 0.30 ?0.45 6 plcs (note 3) datum ? 0.09 ?0.20 (note 3) s6 tsot-23 0302 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 pin one id note: 1. dimensions are in millimeters 2. drawing not to scale 3. dimensions are inclusive of plating 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 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 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 ltc3426 3426f ? linear technology corporation 2004 lt/tp 1104 1k ?printed in the usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com part number description comments lt1613 550ma (i sw ), 1.4mhz, high efficiency step-up 90% efficiency, v in : 0.9v to 10v, v out(max) = 34v, i q = 3ma, dc/dc converter i sd < 1 a, thinsot lt1946/lt1946a 1.5a (i sw ), 1.2mhz/2.7mhz, high efficiency step-up high efficiency, v in : 2.45v to 16v, v out(max) = 34v, i q = 3.2ma, dc/dc converter i sd < 1 a, ms8 ltc3400/ltc3400b 600ma (i sw ), 1.2mhz, synchronous step-up 92% efficiency, v in : 0.5v to 5v, v out(max) = 5v, i q = 19 a/300 a, dc/dc converter i sd < 1 a, thinsot ltc3401/ltc3402 1a/2a (i sw ), 3mhz, synchronous step-up dc/dc 97% efficiency, v in : 0.5v to 5v, v out(max) = 5.5v, i q = 38 a, converter i sd < 1 a, ms10 ltc3421 3a (i sw ), 3mhz, synchronous step-up dc/dc converter 95% efficiency, v in : 0.5v to 4.5v, v out(max) = 5.25v, i q = 12 a, with output disconnect i sd < 1 a, qfn24 ltc3425 5a (i sw ), 8mhz, 4-phase synchronous step-up dc/dc 95% efficiency, v in : 0.5v to 4.5v, v out(max) = 5.25v, i q = 12 a, converter with output disconnect i sd < 1 a, qfn32 ltc3429 600ma (i sw ), 550khz, synchronous step-up 90% efficiency, v in : 0.5v to 4.3v, v out(max) = 5v, i q = 20 a, dc/dc converter with soft-start/output disconnect i sd < 1 a, thinsot ltc3436 3a (i sw ), 1mhz, high efficiency step-up dc/dc converter v in : 3v to 25v, v out(max) = 34v, i q = 0.9ma, i sd < 6 a, tssop16e ltc3459 75ma (i sw ), 10v micropower synchronous boost v in : 1.5v to 5.5v, v out(max) = 10v, i q = 10 a, i sd < 1 a, thinsot converter in thinsot ltc3464 85ma (i sw ), high efficiency step-up dc/dc converter v in : 2.3v to 10v, v out(max) = 34v, i q = 25 a, i sd < 1 a, thinsot with schottky and pnp disconnect related parts

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