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lt3483/LT3483A 1 3483fc typical application features applications description inverting micropower dc/dc converters with schottky the lt ? 3483/LT3483A are micropower inverting dc/dc converters with integrated schottky and one resistor feedback. the small package size, high level of integration and use of tiny surface mount components yield a solution size as small as 40mm 2 . the devices feature a quiescent current of only 40a at no load, which further reduces to 0.1a in shutdown. a current limited, fxed off-time control scheme conserves operating current, resulting in high effciency over a broad range of load current. a precisely trimmed 10a feedback current enables one resistor feedback and virtually eliminates feedback load - ing of the output. the 40v switch enables voltage outputs up to C38v to be generated without the use of costly transformers. the lt3483/LT3483As low 300ns off-time permits the use of tiny low profle inductors and capaci - tors to minimize footprint and cost in space-conscious portable applications. 3.6v to C8v dc/dc converter n internal 40v schottky diode n one resistor feedback (other resistor inside) n internal 40v, 200ma/400ma power switch n generates regulated negative outputs to C38v n low quiescent current: 40a in active mode <1a in shutdown mode n low v cesat switch: 200mv at 150ma n wide input range: 2.5v to 16v n uses small surface mount components n output short-circuit protected n available in a 6-lead sot-23 (lt3483 only) and low profle 8-lead dfn (2mm 2mm 0.75mm) packages n lcd bias n handheld computers n battery backup n digital cameras n oled bias effciency and power loss sw 10h d lt3483 fb 4.7f 0.22f v in 10 806k 5pf 2.2f 3483 ta01a v out ?8v 25ma v in 3.6v shdn gnd load current (ma) 0.1 55 efficiency (%) power loss (mw) 60 65 70 75 0.1 1 10 100 v in = 3.6v power loss 1000 1 10 3483 ta01b 100 efficiency l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks and thinsot is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. protected by u.s. patents, including 7710700.
lt3483/LT3483A 2 3483fc absolute maximum ratings v in voltage ............................................................... 16v sw voltage .............................................................. 40v d voltage ............................................................... C40v fb voltage ............................................................... 2.5v shdn voltage .......................................................... 16v (note 1) top view fb gnd gnd sw shdn d nc v in dc package 8-lead (2mm 2mm) plastic dfn 9 4 1 2 3 6 5 7 8 t jmax = 125c, v ja = 88.5c/w exposed pad (pin 9) is gnd sw 1 gnd 2 fb 3 6 v in 5 d 4 shdn top view s6 package 6-lead plastic tsot-23 t jmax = 125c, v ja = 192c/w pin configuration order information lead free finish tape and reel part marking* package description temperature range lt3483edc #pbf lt3483edc #trpbf lcyt 8-lead (2mm 2mm) plastic dfn C40c to 85c lt3483es6#pbf lt3483es6#trpbf ltbkx 6-lead plastic tsot-23 C40c to 85c LT3483Aedc#pbf LT3483Aedc #trpbf lfxd 8-lead (2mm 2mm) plastic dfn C40c to 85c lt3483idc#pbf lt3483idc#trpbf lcyt 8-lead (2mm 2mm) plastic dfn C40c to 125c lt3483is6#pbf lt3483is6#trpbf ltbkx 6-lead plastic tsot-23 C40c to 125c LT3483Aidc#pbf LT3483Aidc#trpbf lfxd 8-lead (2mm 2mm) plastic dfn C40c to 125c lead based finish tape and reel part marking package description temperature range lt3483edc lt3483edc #tr lcyt 8-lead (2mm 2mm) plastic dfn C40c to 85c lt3483es6 lt3483es6#tr ltbkx 6-lead plastic tsot-23 C40c to 85c 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/ operating ambient temperature range (note 2) lt3483e/LT3483Ae .............................. C 40c to 85c lt3483i/LT3483Ai .............................. C 40c to 125c junction temperature ......................................... 125c storage temperature range .................. C65c to 150c lead temperature (soldering, 10 sec) (tsot-23 package only) .................................. 300c
lt3483/LT3483A 3 3483fc electrical characteristics 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. the l denotes the specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v in = 3.6v, v shdn = 3.6v unless otherwise specifed. parameter conditions min typ max units v in operating range 2.5 16 v v in undervoltage lockout 2 2.4 v fb comparator trip voltage to gnd (v fb ) fb falling 0 5 12 mv fb output current (note 3) fb = v fb C 5mv C10.2 C10 C9.7 a fb comparator hysteresis fb rising 10 mv quiescent current in shutdown v shdn = gnd 1 a quiescent current (not switching) fb = C0.05v 40 50 a i fb line regulation 2.5v v in 16v 0.07 %/v switch off-time 300 ns switch current limit lt3483 LT3483A 170 340 200 400 230 460 ma ma switch v cesat i sw = 150ma to gnd 200 mv switch leakage current sw = 40v 1 a d pin current limit 350 ma rectifer leakage current d = C 40v 4 a rectifer forward drop i d = 150ma to gnd 0.64 v shdn input low voltage 0.4 v shdn input high voltage 1.5 v shdn pin current 6 10 a note 2: the lt3483e/LT3483Ae are guaranteed to meet specifcations from 0c to 85c. specifcations over the C40c to 85c operating temperature range are assured by design, characterization and correlation with statistical process controls. the lt3483i/LT3483Ai are guaranteed to meet specifcations over the C40c to 125c operating temperature range. note 3: current fows out of the pin.
lt3483/LT3483A 4 3483fc typical performance characteristics v fb current v fb voltage switch off time switch current limit (lt3483) quiescent current shdn pin bias current temperature (c) ?50 v fb current (a) 10.0 10.1 75 100 3483 g01 9.9 9.8 ?25 0 25 50 125 10.2 temperature (c) ?50 v fb voltage (mv) 8 12 75 100 3483 g02 4 0 ?25 0 25 50 125 16 temperature (c) ?50 switch off time (ns) 150 200 250 50 125 3483 g03 100 50 0 ?25 0 25 75 100 300 350 400 temperature (c) ?50 170 switch current limit (ma) 180 190 200 210 220 230 ?25 0 25 50 75 100 3483 g04 125 temperature (c) ?50 quiescent current (a) 30 40 50 75 100 3483 g05 20 10 0 ?25 0 25 50 125 shdn pin voltage (v) 0 shdn pin bias current (a) 4 6 16 3483 g06 2 0 4 8 12 10 t a = 25c 8 switch current limit (LT3483A) temperature (c) ?50 current limit (ma) 400 420 75 100 3483 g07 380 360 ?25 0 25 50 125 440
lt3483/LT3483A 5 3483fc pin functions fb (pin 1/pin 3): feedback. place resistor to negative output here. set resistor value r1 = v out /10a. gnd (pins 2, 3/pin 2): ground. for dfn package, tie both pin 2 and pin 3 together to ground. sw (pin 4/pin 1): switch. connect to external inductor l1 and positive terminal of transfer capacitor. v in (pin 5/pin 6): input supply. must be locally bypassed with 1f or greater. nc (pin 6/na): no internal connection. d (pin 7/pin 5) : anode terminal of integrated schottky diode. connect to negative terminal of transfer capaci - tor and external inductor l2 (fyback confguration) or to cathode of external schottky diode (inverting charge pump confguration). shdn (pin 8/pin 4): shutdown. connect to gnd to turn device off. connect to supply to turn device on. exposed pad (pin 9/na): gnd. the exposed pad should be soldered to the pcb ground to achieve the rated thermal performance. (dfn/tsot-23) block diagram ? + ? + 6 3 1 2 5 a3 300ns delay 1.250v reference s q1 20mv (lt3483) sw d l1b l1a c f ly c out v out 0.1 0.1 gnd 3483 bd ? + 25mv d1 q r q a1 a2 125k r1 r2 v out d d2 v in v in fb optional charge pump configuration. l1b replaced with: pin numbers correspond to the 6-pin tsot-23 package v out ? ?
lt3483/LT3483A 6 3483fc operation choosing a regulator topology inverting charge pump the inverting charge pump regulator combines an induc - tor-based step-up with an inverting charge pump. this confguration usually provides the best size, effciency and output ripple and is applicable where the magnitude of v out is greater than v in . negative outputs to C38v can be produced with the lt3483/LT3483A in this confguration. for cases where the magnitude of v out is less than or equal to v in , use a 2-inductor or transformer confguration such as the inverting fyback. in the inverting charge pump confguration, a resistor is added in series with the schottky diode between the negative output and the d pin of the lt3483/LT3483A. the purpose of this resistor is to smooth/reduce the current spike in the fying capacitor when the switch turns on. a 10 resistor works well for a li + to C8v application, and the impact to converter effciency is less than 3%. the resistor values recommended in the applications circuits also limit the switch current during a short-circuit condi - tion at the output. inverting flyback the inverting fyback regulator, shown in the C5v application circuit, uses a coupled inductor and is an excellent choice where the magnitude of the output is less than or equal to the supply voltage. the inverting fyback also performs well in a step-up/invert application, but it occupies more board space compared with the inverting charge pump. also, the maximum |v out | using the fyback is less than can be obtained with the charge pumpit is reduced from 38v by the magnitudes of v in and ringing at the switch node. under a short-circuit condition at the output, a pro - prietary technique limits the switch current and prevents damage to the lt3483/LT3483A even with supply voltage as high as 16v. as an option, a 0.47f capacitor may be added between terminals d and sw of lt3483/LT3483A to suppress ringing at sw. inductor selection several recommended inductors that work well with the lt3483/LT3483A are listed in table 1, although there are many other manufacturers and devices that can be used. consult each manufacturer for more detailed information and for their entire selection of related parts. many differ - ent sizes and shapes are available. for inverting charge pump regulators with input and output voltages below 7v, a 4.7h or 6.8h inductor is usually the best choice. for fyback regulators or for inverting charge pump regulators where the input or output voltage is greater than 7v, a 10h inductor is usually the best choice. a larger value inductor can be used to slightly increase the available output current, but limit it to around twice the the lt3483/LT3483A use a constant off-time control scheme to provide high effciency over a wide range of output currents. operation can be best understood by referring to the block diagram. when the voltage at the fb pin is approximately 0v, comparator a3 disables most of the internal circuitry. output current is then provided by external capacitor c out , which slowly discharges until the voltage at the fb pin goes above the hysteresis point of a3. typical hysteresis at the fb pin is 10mv. a3 then enables the internal circuitry, turns on power switch q1, and the currents in external inductors l1a and l1b be - gin to ramp up. once the switch current reaches 200ma (lt3483) or 400ma (LT3483A), comparator a1 resets the latch, which turns off q1 after about 80ns. inductor current fows through the internal schottky d1 to gnd, charging the fying capacitor. once the 300ns off-time has elapsed, and internal diode current drops below 250ma (as detected by comparator a2), q1 turns on again and ramps up to the switch current limit. this switching action continues until the output capacitor charge is replenished (until the fb pin decreases to 0v), then a3 turns off the internal circuitry and the cycle repeats. the inverting charge pump topology replaces l1b with the series combination d2 and r2. applications information
lt3483/LT3483A 7 3483fc applications information value recommended, as too large of an inductance will increase the output voltage ripple without providing much additional output current. table 1. recommended inductors part l (h) max i dc (ma) dcr ( ) height (mm) manufacturer lqh2mcn4r7m02l lqh2mcn6r8m02l lqh2mcn100m02l 4.7 6.8 10 300 255 225 0.84 1.0 1.2 0.95 murata www.murata.com sdq12 coupled inductor 4.7 10 15 1.45 980 780 0.40 0.72 1.15 1.2 cooper electronics tech www.cooperet.com lpd3015 coupled inductor 4.7 10 860 580 0.52 1.0 1.4 coilcraft www.coilcraft.com capacitor selection the small size and low esr of ceramic capacitors make them ideal for lt3483/LT3483A applications. use of x5r and x7r types is recommended because they retain their capacitance over wider voltage and temperature ranges than other dielectric types. always verify the proper volt - age rating. table 2 shows a list of several ceramic capaci - tor manufacturers. consult the manufacturers for more detailed information on their entire selection of ceramic capacitors. a 4.7f ceramic bypass capacitor on the v in pin is rec - ommended where the distance to the power supply or battery could be more than a couple inches. otherwise, a 1f is adequate. a capacitor in parallel with feedback resistor r1 is recom - mended to reduce the output voltage ripple. use a 5pf capacitor for the inverting charge pump, and a 22pf value for the inverting fyback or other dual inductor confgura - tions. output voltage ripple can be reduced to 20mv in some cases using this capacitor in combination with an appropriately selected output capacitor. the output capacitor is selected based on desired output voltage ripple. for low output voltage ripple in the inverting fyback confguration, use a 4.7f to 10f capacitor. the inverting charge pump utilizes values ranging from 0.22f to 4.7f. the following formula is useful to estimate the output capacitor value needed: c o u t = l ? i s w 2 ? v o u t ? ? v o u t where i sw = 0.25a (lt3483) or i sw = 0.5a (LT3483A) and ? v out = 30mv. the fying capacitor in the inverting charge pump confguration ranges from 0.1f to 0.47f. multiply the value predicted by the above equation for c out by 1/10 to determine the value needed for the fying capacitor. table 2. recommended ceramic capacitor manufacturers manufacturer url avx www.avxcorp.com kemet www.kemet.com murata www.murata.com taiyo yuden www.tyuden.com setting the output voltage the output voltage is programmed using one feedback resistor according to the following formula: r 1= ? v o u t 10 a inrush current when v in is increased from ground to operating voltage, an inrush current will fow through the input inductor and integrated schottky diode to charge the fying capacitor. conditions that increase inrush current include a larger, more abrupt voltage step at v in , a larger fying capacitor, and an inductor with a low saturation current. while the internal diode is designed to handle such events, the inrush current should not be allowed to exceed 1.5a. for circuits that use fying capacitors within the recom - mended range and have input voltages less than 5v, inrush current remains low, posing no hazard to the device. in cases where there are large steps at v in , inrush current should be measured to ensure operation within the limits of the device.
lt3483/LT3483A 8 3483fc suggested layout (dfn) for inverting charge pump applications information board layout considerations as with all switching regulators, careful attention must be given to the pcb board layout and component place - ment. proper layout of the high frequency switching path is essential. the voltage signals of the sw and d pins have sharp rising and falling edges. minimize the length and area of all traces connected to the sw and d pins. in particular, it is desirable to minimize the trace length to and from the fying capacitor, since current in this ca - pacitor switches directions within a cycle. always use a ground plane under the switching regulator to minimize interplane coupling. suggested layout (sot-23) for inverting charge pump 1 2 3 6 5 4 + v in gnd shdn c f ly c out 3483 ai01 r1 l1 c in v out v in gnd shdn a k c out c in c f ly 3483 ai02 l1 r1 v out 9 4 1 2 3 6 5 7 8 typical applications 3.6v to C22v dc/dc converter 3.6v to C22v converter effciency and power loss sw l1 10h d lt3483 fb c1 4.7f c2 0.1f d1 v in r s 30 r1 2.2m c1: taiyo yuden lmk316bj475md c2: taiyo yuden tmk107bj104 (x5r) c3: taiyo yuden tmk316bj105md d1: philips pmeg3002aeb l1: murata lqh2mcn100k02l c3 1f 5pf 3483 ta02a v out ?22v 8ma v in 3.6v shdn gnd load current (ma) 0.1 efficiency (%) power loss (mw) 65 70 efficiency 10 3483 ta02b 60 55 1 75 10 100 power loss 1 0.1 1000
lt3483/LT3483A 9 3483fc typical applications 3.6v to C8v dc/dc converter low profle, small footprint switching waveform sw l1 10h d lt3483 fb c1 4.7f c2 0.22f d1 v in 10 r1 806k c1: murata grm219r61a475ke34b c2: taiyo yuden lmk107bj224 c3: murata grm219r61c225ka88b d1: philips pmeg2005eb l1: murata lqh2mcn100k02l 5pf c3 2.2f 3483 ta04a v out ?8v 25ma v in 3.6v shdn gnd 3483 ta04b i sw 100ma/div v out 20mv/div 2s/div package description dc package 8-lead plastic dfn (2mm 2mm) (reference ltc dwg # 05-08-1719 rev a) 2.00 0.10 (4 sides) note: 1. drawing is not a jedec package outline 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 0.40 0.10 bottom view?exposed pad 0.64 0.10 (2 sides) 0.75 0.05 r = 0.115 typ r = 0.05 typ 1.37 0.10 (2 sides) 1 4 8 5 pin 1 bar top mark (see note 6) 0.200 ref 0.00 ? 0.05 (dc8) dfn 0409 reva 0.23 0.05 0.45 bsc pin 1 notch r = 0.20 or 0.25 45 chamfer 0.25 0.05 1.37 0.05 (2 sides) recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 0.64 0.05 (2 sides) 1.15 0.05 0.70 0.05 2.55 0.05 package outline 0.45 bsc
lt3483/LT3483A 10 3483fc package description s6 package 6-lead plastic tsot-23 (reference ltc dwg # 05-08-1636 rev b) 1.50 ? 1.75 (note 4) 2.80 bsc 0.30 ? 0.45 6 plcs (note 3) datum ?a? 0.09 ? 0.20 (note 3) s6 tsot-23 0302 rev b 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 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 p ad la yout per ipc calcula tor 1.4 min 2.62 ref 1.22 ref
lt3483/LT3483A 11 3483fc 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 c 09/10 revised entire data sheet to add ltc3483a 1-12 (revision history begins at rev c)
lt3483/LT3483A 12 3483fc linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com linear technology corporation 2004 lt 0910 rev c ? printed in usa related parts typical application C5v step-up/step-down converter effciency and power loss vs load current part number description comments lt1617/lt1617-1 350ma/100ma (i sw ) high effciency micropower inverting dc/dc converter v in : 1.2v to 15v, v out(max) = C34v, i q = 20a, i sd < 1a thinsot package lt1931/lt1931a 1a (i sw ), 1.2mhz/2.2mhz, high effciency micropower inverting dc/dc converter v in : 2.6v to 16v, v out(max) = C34v, i q = 5.8ma, i sd < 1a thinsot package lt1945 dual output, boost/inverter, 350ma (i sw ), constant off-time, high effciency step-up dc/dc converter v in : 1.2v to 15v, v out(max) = 34v, i q = 40a, i sd < 1a, ms10 package lt3463 dual output, boost/inverter, 250ma (i sw ), constant off-time, high effciency step-up dc/dc converter with integrated schottky diodes v in : 2.3v to 15v, v out(max) = 40v, i q = 40a, i sd < 1a dfn package lt3464 85ma (i sw ), high effciency step-up dc/dc converter with integrated schottky and pnp disconnect v in : 2.3v to 10v, v out(max) = 34v, i q = 25a, i sd < 1a thinsot package lt3472 boost (350ma) and inverting (400ma) dc/dc converter for ccd bias with integrated schottkys v in : 2.3v to 15v, v out(max) = 40v, i q = 2.8ma, i sd < 1a dfn package sw l1a 4.7h l1b 4.7h d LT3483A fb c1 4.7f ? ? v in 511k 22pf c2 10f 3483 ta03a v out ?5v v in 2.5v to 6v shdn gnd c1: taiyo yuden emk316bj475ml c2: taiyo yuden jmk316bj106ml l1a, l1b: coiltronics sdq12-4r7 or coilcraft lpd3015-472 load current (ma) 0.1 40 efficiency (%) power loss (mw) 50 60 70 1 10 100 3483 ta03b 30 20 10 0 120 150 180 210 90 60 30 0 v in = 3.6v switching waveforms 3483 ta03c v sw 10v/div i l1a 0.5a/div i l1b 0.5a/div v out 50mv/div ac-coupled 2s/div

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