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1 for more information www.linear.com/lt308 9 typical application features description 800ma single resistor rugged linear regulator with monitors the lt ? 3089 is an 800ma low dropout linear regulator designed ? for rugged industrial applications . key features of the ic are the extended safe operating area (soa), output current monitor, temperature monitor and programmable current limit. the lt3089 can be paralleled for higher output current or heat spreading. the device withstands reverse input and reverse output - to - input voltages without reverse current flow. the lt3089s precision 50a reference current source allows a single resistor to program output voltage to any level between zero and 34.5v. the current reference architecture enables load regulation to be independent of output voltage. the lt3089 is stable with or without input and output capacitors. the output current monitor ( i out /5000) and die junction temperature output (1a / c ) provide system monitor - ing and debug capability. in addition, a single resistor programs current limit. internal protection circuitry includes reverse- battery and reverse- current protection, current limiting and thermal lim- iting. the lt3089 is offered in the 12-lead 4 mm 4mm dfn and 16-lead tssop ( both with exposed pad for improved thermal performance ), and 7-lead dd- pak power package. wide safe operating area supply applications n extended safe operating area n maximum output current: 800ma n stable with or without input/output capacitors n wide input voltage range: 1.2v to 36v n single resistor sets output voltage n output current monitor: i mon = i out /5000 n junction temperature monitor: 1a/c n output adjustable to 0v n 50 a set pin current: 1% initial accuracy n output voltage noise: 27v rms n parallel multiple devices for higher current or heat spreading n programmable current limit n reverse-battery and reverse-current protection n <1 mv load regulation typical independent of v out n <0.001%/ v line regulation typical n available in thermally-enhanced 12-lead 4mm 4mm dfn, 16-lead tssop, and 7-lead dd-pak n all surface mount power supply n rugged industrial power supply n post regulator for switching supplies n low output voltage supply n intrinsic safety applications l, lt , lt c , lt m , linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. set pin current 3089 ta01a in 1k 4.12k 10f* *optional i mon i lim out + ? lt3089 i load /5000 i out 1.5v 0.75a v in 499* 1k 1a/c set 30.1k temp 50a lt3089 3089f 75 100 125 150 175 49.5 49.6 49.7 49.8 49.9 i load = 3ma 50.0 50.1 50.2 50.3 50.4 50.5 set pin current (a) 3089 ta01b temperature (c) ?75 ?50 ?25 0 25 50
2 for more information www.linear.com/lt308 9 absolute maximum ratings in pin to out pin differential voltage ..................... 40 v set pin current ( note 6) ..................................... 25 ma set pin voltage ( relative to out , note 6) .............. 10 v temp pin voltage ( relative to out ) ................. 1 v , C40 v i lim pin voltage ( relative to out ) ......................... 0.2 v i mon pin voltage ( relative to out ) ................... 1 v , C40 v output short - circuit duration .......................... indefinite (note 1) all voltages relative to v out . top view 13 out df package 12-lead (4mm 4mm) plastic dfn 12 11 8 9 10 4 5 3 2 1 in in in in temp i mon out out out out i lim set 6 7 t jmax = 125c, ja = 41c/w, jc = 1.6c/w exposed pad (pin 13) is out, must be soldered to pcb fe package 16-lead plastic tssop 1 2 3 4 5 6 7 8 top view 16 15 14 13 12 11 10 9 out out out out out i lim set out out in in in in temp i mon out 17 out t jmax = 125c, ja = 35c/w, jc = 2.3c/w exposed pad (pin 17) is out, must be soldered to pcb r package 7-lead plastic dd front view tab is out nc in temp out i mon set i lim 7 6 5 4 3 2 1 t jmax = 125c, ja = 34c/w, jc = 3c/w pin configuration order information lead free finish tape and reel part marking* package description temperature range lt3089edf#pbf lt3089edf#trpbf 3089 12-lead (4mm 4mm) plastic dfn C40c to 125c lt3089idf#pbf lt3089idf#trpbf 3089 12-lead (4mm 4mm) plastic dfn C40c to 125c lt3089efe#pbf lt3089efe#trpbf 3089fe 16-lead plastic tssop C40c to 125c lt3089ife#pbf lt3089ife#trpbf 3089fe 16-lead plastic tssop C40c to 125c lt3089er#pbf lt3089er #trpbf lt3089r 7-lead plastic dd-pak C40c to 125c lt3089ir#pbf lt3089ir#trpbf lt3089r 7-lead plastic dd-pak C40c to 125c consult lt c marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. some packages are available in 500 unit reels through designated sales channels with #trmpbf suffix. operating junction temperature range ( note 2) e -, i - grades ....................................... C40 c to 125 c storage temperature range .................. C65 c to 150 c lead temperature ( soldering , 10 sec ) fe , r packages only ......................................... 300 c lt3089 3089f
3 for more information www.linear.com/lt308 9 the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t j = 25c. (note 2) electrical characteristics parameter conditions min typ max units set pin current i set v in = 2v, i load = 3ma 2v v in 36v, 3ma i load 800ma l 49.5 48.75 50 50 50.5 51.25 a a offset voltage v os (v out C v set ) v in = 2v, i load = 3ma v in = 2v, i load = 3ma l C1.5 C3.5 0 0 1.5 3.5 mv mv i set load regulation ?i load = 3ma to 800ma C0.1 na v os load regulation ? i load = 3ma to 800ma (note 7) df, fe packages l C0.5 C3 mv r package l C1.5 C4 mv line regulation ? i set ?v os ?v in = 2v to 36v, i load = 3ma ?v in = 2v to 36v, i load = 3ma 1.5 0.001 na/v mv/v minimum load current (note 3) 2v v in 36v l 1.1 3 ma dropout voltage (note 4) i load = 100ma i load = 800ma l 1.21 1.47 1.65 v v internal current limit v in = 5v, v set = 0v, v out = C0.1v l 0.8 1 a i lim programming ratio l 155 175 210 ma/k i lim minimum output current resistance 300 i mon full-scale output current i load = 800ma l 130 160 190 a i mon scale factor 100ma i load 800ma 200 a/a i mon operating range l v out C 40v v out + 0.4v v temp output current (note 9) t j > 5c 1 a/c temp output current absolute error (note 9) 0c 4 for more information www.linear.com/lt308 9 typical performance characteristics offset voltage offset voltage (v out C v set ) offset voltage (v out C v set ) load regulation minimum load current dropout voltage set pin current set pin current t j = 25c unless otherwise specified. offset voltage (v out C v set ) lt3089 3089f 75 ?50 ?25 0 25 50 75 100 125 150 175 100 ?3.0 ?2.5 ?2.0 ?1.5 ?1.0 ?0.5 0 ?150 ?125 ?100 125 ?75 ?50 ?25 0 offset voltage load regulation (mv) set pin current load regulation (na) 3089 g07 v in ? v out = 36v v in ? v out = 2v temperature (c) 150 ?75 ?50 ?25 0 25 50 75 100 125 150 175 175 0 0.25 0.50 0.75 1.00 1.25 1.50 minimum load current (ma) minimum load current 49.5 3089 g08 t j = ?50c t j = 25c t j = 125c load current (a) 0 0.1 0.2 0.3 0.4 49.6 0.5 0.6 0.7 0.8 1.0 1.1 1.2 1.3 1.4 1.5 49.7 1.6 1.7 dropout voltage (v) 3089 g09 n = 1297 set pin current distribution (a) 49 49.5 50 50.5 49.8 51 set pin current 3089 g02 n = 1297 v os distribution (mv) ?2 ?1 0 1 2 49.9 3089 g04 i load = 3ma 50.0 50.1 50.2 50.3 50.4 50.5 set pin current (a) 3089 g01 i load = 3ma temperature (c) temperature (c) ?75 ?50 ?25 0 25 50 75 100 125 150 ?75 175 ?2.0 ?1.5 ?1.0 ?0.5 0 0.5 1.0 1.5 2.0 ?50 offset voltage (mv) out set 3089 g03 i load = 3ma input?to?output differential (v) 0 6 12 18 24 ?25 30 36 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0.0 0.2 0.4 0 0.6 0.8 1.0 offset voltage (mv) out set 3089 g05 t j = 25c t j = 125c load current (a) 0 25 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ?1.6 ?1.2 50 ?0.8 ?0.4 0.0 0.4 offset voltage (mv) out set 3089 g06 ?i load = 3ma to 800ma temperature (c) ?75
5 for more information www.linear.com/lt308 9 programmable current limit programmable current limit programmable current limit temp pin current i mon pin current dropout voltage internal current limit internal current limit typical performance characteristics t j = 25c unless otherwise specified. i mon pin line regulation lt3089 3089f 50 2 3 4 5 6 0 0.2 0.4 0.6 0.8 75 1.0 1.2 programmed current limit (a) programmable current limit 3089 g14 r ilim 1.50k r ilim 3.01k r set = 20k 100 t j = 25c r ilim 4.53k output current (a) 0 0.25 0.50 0.75 1 0 125 0.2 0.4 0.95 1.00 1.05 output voltage (v) programmable current limit 3089 g15 temperature (c) ?75 150 ?50 ?25 0 25 50 75 100 125 150 175 175 0 20 40 60 80 100 120 140 160 temp pin current (a) 1.0 temp pin current 3089 g16 load current (a) 0 0.1 0.2 0.3 0.4 0.5 0.6 1.1 0.7 0.8 0 20 40 60 80 100 120 140 1.2 160 180 200 i mon pin current (a) mon 3089 g17 i load = 100ma input?to?output differential voltage (v) 0 6 1.3 12 18 24 30 36 0 5 10 15 20 i load = 3ma 1.4 25 i mon pin current (a) i mon pin line regulation 3089 g18 1.5 1.6 1.7 dropout voltage (v) 3089 g10 v in = 7v v out = 0v temperature (c) ?75 i load = 800ma ?50 ?25 0 25 50 75 100 125 150 175 temperature (c) 0 0.25 0.50 0.75 1.00 1.25 1.50 current limit (a) internal current limit 3089 g11 ?75 input?to?output differential (v) 0 6 12 18 24 30 36 0 0.2 ?50 0.4 0.6 0.8 1.0 1.2 current limit (a) internal current limit 3089 g12 r ilim = 4.53k r ilim = 3.01k ?25 r ilim = 1.50k v in = 7v v out = 0v temperature (c) ?75 ?50 ?25 0 25 50 0 75 100 125 150 175 0 0.2 0.4 0.6 0.8 25 1.0 programmed current limit (a) programmable current limit 3089 g13 t j = 25c v in = 7v v out = 0v r ilim (k) 0 1
6 for more information www.linear.com/lt308 9 linear regulator load transient response current source line transient response current source line transient response linear regulator line transient response linear regulator turn -on response linear regulator load transient response linear regulator load transient response linear regulator load transient response typical performance characteristics t j = 25c unless otherwise specified. linear regulator turn -on response lt3089 3089f 40 20 30 40 50 60 70 80 90 100 0 60 0.5 1.0 ?400 ?200 0 200 400 600 load transient response 3089 g22 80 output voltage deviation (mv) load current (ma) r set = 20k r load = 1.25 c out = 2.2f c set = 0.1f time (s) 0 5 10 100 15 20 25 30 35 40 45 50 ?40 ?20 120 0 20 3 4 5 6 input voltage (v) output voltage deviation (mv) line transient response 3089 g23 140 r set = 6.04k r out = 3.01 c out = 0 c set = 30pf 100ma current source configuration time (s) 0 10 20 30 160 40 50 60 70 80 90 100 90 95 100 180 105 3 4 5 6 input voltage (v) output current (ma) line transient response 3089 g24 r set = 6.04k 200 r out = 0.6 c out = 0 c set = 30pf 500ma current source configuration time (s) 0 10 20 30 40 ?100 50 60 70 80 90 100 480 490 500 510 v in = 3v 0 520 3 4 5 6 input voltage (v) output current (ma) 3089 g25 r set = 20k r load = 1.25 100 c out = 2.2f ceramic c set = 0 time (s) 0 5 10 15 20 25 30 ?100 35 40 45 50 ?0.5 0 0.5 1.0 0 1 ?50 2 3 4 input voltage (v) output voltage (v) turn?on response 3089 g26 r set = 20k r load = 1.25 c out = 2.2f ceramic 0 c set = 0.1f time (ms) 0 2 4 6 8 10 12 14 50 16 18 20 ?0.5 0 0.5 1.0 0 1 2 100 3 4 turn?on response 3089 g27 output voltage (v) input voltage (v) load current (ma) load transient response 3089 g19 v out = 1v output voltage deviation (mv) v in = 3v v out = 1v c out = 2.2f c set = 0.1f ?i load = 100ma to 800ma time (s) 0 20 40 c out = 2.2f 60 80 100 120 140 160 180 200 0 0.5 c set = 0.1f 1.0 ?200 ?100 0 100 200 300 load transient response 3089 g20 output voltage deviation (mv) ?i load = 5ma to 100ma load current (ma) v in = 3v v out = 1v c out = 0 c set = 30pf ?i load = 5ma to 100ma t r = t f = 1s time (s) 0 10 time (s) 20 30 40 50 60 70 80 90 100 ?100 0 0 100 ?200 ?100 0 100 200 load transient response 3089 g21 output voltage deviation (mv) 20 load current (ma) v in = 3v v out = 1v c out = 0 c set = 30pf ?i load = 100ma to 800ma t r = t f = 1s time (s) 0 10
7 for more information www.linear.com/lt308 9 ripple rejection ripple rejection output impedance ripple rejection (120hz) residual output voltage with less than minimum load current source turn -on response current source turn -on response typical performance characteristics t j = 25c unless otherwise specified. ripple rejection (10khz) v out set pin = 0v r test v in frequency (hz) 10 1 output impedance () 10 100 1k 10k 100k 1m 10m 100 1k 10k 100k 1m 10m 3089 g33 i source = 10ma i source = 100ma i source = 500ma current source configuration lt3089 3089f 20 100k 1m 10m 0 10 20 30 40 50 60 30 70 80 90 100 ripple rejection (db) 3089 g31 c out = 2.2f ceramic c set = 0.1f i load = 100ma v in = v out + 5v 40 v in = v out + 2v v in = v out + 1.5v frequency (hz) 10 100 1k 10k 100k 1m 10m 50 0 20 40 60 80 100 120 ripple rejection (db) ripple rejection 3089 g32 60 v in = v out(nominal) + 2v ripple = 500mv p?p f = 120hz i load = 100ma c out = 2.2f c set = 0.1f temperature (c) ?75 ?50 ?25 70 0 25 50 75 100 125 150 175 65 70 80 75 80 85 90 95 ripple rejection (db) 3089 g34 v in = v out(nominal) + 2v ripple = 500mv p?p f = 10khz 90 i load = 100ma c out = 2.2f c set = 0.1f temperature (c) ?75 ?50 ?25 0 25 50 100 75 100 125 150 175 50 55 60 65 70 0 ripple rejection (db) 3089 g35 r set = 6.04k 50 100 0 1 2 3 4 turn?on response 3089 g28 output current (ma) r out = 3.01 input voltage (v) r set = 6.04k r out = 0.6 c out = 0 c set = 30pf 500ma current source configuration time (s) 0 10 20 c out = 0 30 40 50 60 70 80 90 100 0 200 c set = 30pf 400 600 0 1 2 3 4 input voltage (v) output current (ma) turn?on response 100ma current source configuration 3089 g29 v in = 5v v in = 36v r test (k) 0 0.5 1 1.5 2 2.5 time (s) 3 3.5 4 4.5 5 0 100 200 300 400 0 500 600 700 800 900 1000 output voltage (mv) less than minimum load 3089 g30 c out = 2.2f ceramic 10 c set = 0.1f v in = v out(nominal) + 2v i load = 100ma i load = 500ma i load = 800ma frequency (hz) 10 100 1k 10k
8 for more information www.linear.com/lt308 9 noise spectral density 10hz to 100khz output voltage noise ripple rejection (1mhz) typical performance characteristics t j = 25c unless otherwise specified. ripple rejection frequency (hz) 10 10 error amplifier noise spectral density (nv/hz) reference current noise spectral density (pa/hz) 100 1000 1 10 100 1k 100 10k 100k 3089 g38 lt3089 3089f ?50 ?25 0 25 50 75 100 125 150 175 v in = v out(nominal) + 2v 35 37 39 41 43 45 ripple rejection (db) ripple rejection (1mhz) 3089 g36 i load = 800ma ripple = 500mv p?p c load = 2.2f 10khz 100khz 1mhz input?to?output differential voltage (v) 1 1.5 2 2.5 3 f = 1mhz 3.5 4 4.5 5 10 20 30 40 50 60 i load = 100ma 70 80 90 ripple rejection (db) 3089 g37 c set = 0.1f c out = 4.7f i load = 800ma noise independent of output voltage c out = 2.2f 1ms/div v out 100v/div 3089 g39 c set = 0.1f temperature (c) ?75
9 for more information www.linear.com/lt308 9 block diagram ? + 50a in i mon temperature dependent current source 1a/c set i lim out 3089 bd programmable current limit current monitor i mon = i load /5000 temp pin functions in: input. this pin supplies power to regulate internal circuitry and supply output load current. for the device to operate properly and regulate, the voltage on this pin must be between the dropout voltage and 36v above the out pin (depending on output load current, see dropout voltage specifications). out : output. this is the power output of the device. the lt3089 requires a 3ma minimum load current for proper output regulation. temp: temperature output. this pin delivers a current proportional to the internal average junction temperature. current output is 1a/c for temperatures above 5c. the temp pin output current typically equals 25a at 25c. the output of the temp pin is valid for voltages from v out + 0.4 v to v out C 40 v. if unused, connect this pin to out. i lim : current limit program. a resistor between this pin and out programs output current limit to a level propor - tional to resistor value. connect this resistor directly to out at the pins of the package. the typical ratio of current limit to resistor value is 175ma/k with a 300? offset. if programmable current limit is not used, leave this pin open; the internal current limit of the lt3089 is still active, keeping the device inside safe operating limits. external voltage drops between the current limit resistor and v out will affect the current limit. keep drops below 1mv. i mon : output current monitor. the i mon pin sources a current typically equal to i load /5000 or 200a per amp of output current. terminating this pin with a resistor to gnd produces a voltage proportional to i load . for example, at i load = 800ma, i mon typically sources 160a. with a 1k resistor to gnd, this produces 160mv. the output of the i mon pin is valid for voltages from v out + 0.4v to v out C 40v. if unused, connect this pin to out. set : set. this pin is the error amplifiers noninverting input and also sets the operating bias point of the circuit . a fixed 50a current source flows out of this pin. a single external resistor programs v out . output voltage range is 0v to 34.5v. exposed pad/ tab : output. the exposed pad of the df and fe packages and the tab of the r package are tied internally to out. as such, tie them directly to out (pins 1-4/pins 1-5, 8, 9, 16/ pin 4) at the pcb. the amount of copper area and planes connected to out determine the effective thermal resistance of the packages. nc: no connection. no connect pins have no connection to internal circuitry and may be tied to in, out, gnd or floated. lt3089 3089f
10 for more information www.linear.com/lt308 9 applications information introduction the lt3089 regulator is easy to use and has all the pro- tection features expected in high performance regulators. included are short- circuit protection , reverse- input protec- tion and safe operating area protection, as well as thermal shutdown with hysteresis. safe operating area (soa) for the lt3089 is extended, allowing for use in harsh indus- trial and automotive environments where sudden spikes in input voltage lead to high power dissipation. the lt3089 fits well in applications needing multiple rails. this new architecture adjusts down to zero with a single resistor, handling modern low voltage digital ics as well as allowing easy parallel operation and thermal manage- ment without heat sinks. adjusting to zero output allows shutting off the powered circuitry. a precision 0 tc 50a reference current source connects to the noninverting input of a power operational amplifier. the power operational amplifier provides a low impedance buffered output to the voltage on the noninverting input. a single resistor from the noninverting input to ground sets the output voltage. if this resistor is set to 0, zero output voltage results. therefore, any output voltage can be obtained between zero and the maximum defined by the input power supply is obtainable. the benefit of using a true internal current source as the reference, as opposed to a bootstrapped reference in older regulators, is not so obvious in this architecture . a true reference current source allows the regulator to have gain and frequency response independent of the impedance on the positive input. on older adjustable regulators, such as the lt1086 loop gain changes with output voltage and bandwidth changes if the adjustment pin is bypassed to ground. for the lt3089, the loop gain is unchanged with output voltage changes or bypassing. output regulation is not a fixed percentage of output voltage, but is a fixed fraction of millivolts. use of a true current source allows all of the gain in the buffer amplifier to provide regulation, and none of that gain is needed to amplify up the reference to a higher output voltage. the lt3089 has many additional features that facilitate monitoring and control. current limit is externally pro- grammable via a single resistor between the i lim pin and out. shorting this resistor out disables all output current to the load, only bias currents remain. the i mon pin produces a current output proportional to load current. for every 100ma of load current, the i mon pin sources 20 a of current. this can be sensed using an external resistor to monitor load requirements and detect potential faults . the i mon pin can operate at voltages above out, so it operates even during a short- circuit condition. one additional monitoring function is the temp pin, a cur - rent source that is proportional to average die temperature. for die temperatures above 0c, the temp pin sources a current equal to 1a/c. this pin operates normally during output short- circuit conditions. programming linear regulator output voltage the lt3089 generates a 50a reference current that flows out of the set pin. connecting a resistor from set to ground generates a voltage that becomes the reference point for the error amplifier (see figure 1). the reference voltage equals 50a multiplied by the value of the set pin resistor. any voltage can be generated and there is no minimum output voltage for the regulator. 3089 f01 in set out + ? lt3089 50a r load c set r set c in v out = 50a r set c out figure 1. basic adjustable regulator lt3089 3089f
11 for more information www.linear.com/lt308 9 applications information table 1 lists many common output voltages and the clos- est standard 1% resistor values used to generate that output voltage. regulation of the output voltage requires a minimum load current of 3ma. for true zero voltage output operation, return this 3ma load current to a negative output voltage. table 1. 1% resistors for common output voltages v out (v) r set (k) 1 20 1.2 24.3 1.5 30.1 1.8 35.7 2.5 49.9 3.3 66.5 5 100 with the 50 a current source used to generate the reference voltage, leakage paths to or from the set pin can create errors in the reference and output voltages. high quality insulation should be used (e.g., teflon , kel-f); cleaning of all insulating surfaces to remove fluxes and other residues is required. surface coating may be necessary to provide a moisture barrier in high humidity environments. minimize board leakage by encircling the set pin and circuitry with a guard ring operated at a potential close to itself. tie the guard ring to the out pin. guarding both sides of the circuit board is required . bulk leakage reduction depends on the guard ring width. 50na of leakage into or out of the set pin and its associated circuitry creates a 0.1% reference voltage error. leakages of this magnitude, coupled with other sources of leakage, can cause signifi- cant offset voltage and reference drift, especially over the possible operating temperature range. figure 2 depicts an example guard ring layout. if guard ring techniques are used, this bootstraps any stray capacitance at the set pin. since the set pin is a high impedance node, unwanted signals may couple into the set pin and cause erratic behavior. this will be most noticeable when operating with minimum output capacitors at full load current. the easiest way to remedy this is to bypass the set pin with a small amount of capacitance from set to ground, 10pf to 20pf is sufficient. configuring the lt3089 as a current source setting the lt3089 to operate as a 2-terminal current source is a simple matter . the 50 a reference current from the set pin is used with one resistor to generate a small voltage, usually in the range of 100mv to 1v (200mv is a level that rejects offset voltage, line regulation, and other errors without being excessively large). this voltage is then applied across a second resistor that connect from out to the first resistor. figure 3 shows connections and formulas to calculate a basic current source configuration. 3089 f02 set pin gnd out figure 2. guard ring layout example of df package figure 3. using the lt3089 as a current source i out 3ma v set = 50a ? r set i out = v set r out = 50a ? r set r out in set out + ? lt3089 50a i out v set r set 3089 f03 + ? r out lt3089 3089f
12 for more information www.linear.com/lt308 9 applications information again, the lower current levels used in the lt3089 neces- sitate attention to board leakages as error sources (see the programming linear regulator output voltage section). in a current source configuration, programmable cur- rent limit and current monitoring functions are often unused. when not used, tie i mon to out and leave i lim open. the temp pin is still available for use, if unused tie temp to out. selecting r set and r out in current source applications in figure 3, both resistors r set and r out program the value of the output current. the question now arises: the ratio of these resistors is known, but what value should each resistor be? the first resistor to select is r set . the value selected should generate enough voltage to minimize the error caused by the offset between the set and out pins. a reasonable starting level is ~200 mv of voltage across r set ( r set equal to 4.02k). resultant errors due to offset voltage are a few percent . the lower the voltage across r set becomes, the higher the error term due to the offset. from this point, selecting r out is easy, as it is a straight- forward calculation from r set . take note , however , resistor errors must be accounted for as well. while larger voltage drops across r set minimize the error due to offset, they also increase the required operating headroom. obtaining the best temperature coefficient does not require the use of expensive resistors with low ppm temperature coefficients . instead , since the output current of the lt 3089 is determined by the ratio of r set to r out , those resis- tors should have matching temperature characteristics. less expensive resistors made from the same material provide matching temperature coefficients. see resistor manufacturers data sheets for more details. higher output currents necessitate the use of higher watt- age resistors for r out . there may be a difference between the resistors used for r out and r set . a better method to maintain consistency in resistors is to use multiple resis- tors in parallel to create r out , allowing the same wattage and type of resistor as r set . programming current limit externally a resistor placed between i lim and out on the lt3089 externally sets current limit to a level lower than the internal current limit. connect this resistor directly at the out pins for best accuracy. the value of this resistor calculates as: r ilim = i limit /175ma/k + 300 the resistor for a 0.5 a current limit is : r ilim = 0.5 a /175 ma/ k + 300 = 3.16 k. tolerance over temperature is 15%, so current limit is normally set 20% above maximum load current. the 300 offset resistance built in to the pro- grammable current limit allows for lowering the maximum output current to only bias currents ( see curve of minimum load current in typical performance characteristics) us- ing external switches. the lt3089s internal current limit overrides the pro- grammed current limit if the input-to-output voltage dif- ferential in the power transistor is excessive. the internal current limit is 1 a with a foldback characteristic dependent on input-to-output differential voltage, not output voltage per se (see typical performance characteristics). stability and input capacitance the lt3089 does not require an input capacitor to main- tain stability. input capacitors are recommended in linear regulator configurations to provide a low impedance input source to the lt3089. if using an input capacitor, low esr, ceramic input bypass capacitors are acceptable for applications without long input leads. however, applica- tions connecting a power supply to an lt3089 circuit s in and gnd pins with long input wires combined with low esr, ceramic input capacitors are prone to voltage spikes, reliability concerns and application-specific board oscillations. the input wire inductance found in many battery -powered applications, combined with the low esr ceramic input capacitor, forms a high q lc resonant tank circuit . in some instances this resonant frequency beats against the output current dependent ldo bandwidth and interferes with proper operation. simple circuit modifica- tions/solutions are then required. this behavior is not indicative of lt3089 instability, but is a common ceramic input bypass capacitor application issue. lt3089 3089f
13 for more information www.linear.com/lt308 9 applications information the self-inductance, or isolated inductance, of a wire is directly proportional to its length. wire diameter is not a major factor on its self-inductance. for example, the self- inductance of a 2- awg isolated wire (diameter = 0.26") is about half the self-inductance of a 30- awg wire (diameter = 0.01"). one foot of 30- awg wire has about 465nh of self inductance. one of two ways reduces a wires self-inductance. one method divides the current flowing towards the lt3089 between two parallel conductors. in this case, the farther apart the wires are from each other, the more the self- inductance is reduced; up to a 50% reduction when placed a few inches apart. splitting the wires basically connects two equal inductors in parallel, but placing them in close proximity gives the wires mutual inductance adding to the self-inductance. the second and most effective way to reduce overall inductance is to place both forward and return current conductors (the input and gnd wires) in very close proximity. tw o 30- awg wires separated by only 0.02", used as forward and return current conduc- tors, reduce the overall self-inductance to approximately one-fifth that of a single isolated wire. if wiring modifications are not permissible for the applica- tions , including series resistance between the power supply and the input of the lt3089 also stabilizes the application. as little as 0.1 to 0.5, often less, is effective in damp- ing the lc resonance. if the added impedance between the power supply and the input is unacceptable, adding esr to the input capacitor also provides the necessary damping of the lc resonance. however, the required esr is generally higher than the series impedance required. stability and frequency compensation for linear regulator configurations the lt3089 does not require an output capacitor for stability. lt c recommends an output capacitor of 10f with an esr of 0.5 or less to provide good transient performance in linear regulator configurations. larger values of output capacitance decrease peak deviations and provide improved transient response for larger load current changes. bypass capacitors, used to decouple individual components powered by the lt3089, increase the effec- tive output capacitor value. for improvement in transient performance , place a capacitor across the voltage setting resistor. capacitors up to 1f can be used. this bypass capacitor reduces system noise as well, but start-up time is proportional to the time constant of the voltage setting resistor (r set in figure 1) and set pin bypass capacitor. stability and frequency compensation for current source configurations the lt3089 does not require input or output capacitors for stability in many current- source applications. clean, tight pcb layouts provide a low reactance, well controlled operating environment for the lt3089 without requiring capacitors to frequency compensate the circuit . figure 3 highlights the simplicity of using the lt3089 as a current source . some current source applications use a capacitor con- nected in parallel with the set pin resistor to lower the current source s noise. this capacitor also provides a soft-start function for the current source . see quieting the noise section for further details. when operating without output capacitors, the high impedance nature of the set pin as the input of the error amplifier allows signal from the output to couple in, showing as high frequency ring- ing during transients. bypassing the set resistor with a capacitor in the range of 20pf to 30pf dampens the ringing . depending on the pole introduced by a capacitor or other complex impedances presented to the lt3089, external compensation may be required for stability. techniques are discussed to achieve this in the following paragraphs. linear technology strongly recommends testing stability in situ with final components before beginning production . although the lt3089s design strives to be stable without capacitors over a wide variety of operating conditions, it is not possible to test for all possible combinations of input and output impedances that the lt3089 will encounter. these impedances may include resistive, capacitive, and inductive components and may be complex distributed networks. in addition , the current source s value will dif- fer between applications and its connection may be gnd referenced , power supply referenced , or floating in a signal line path. linear technology strongly recommends that stability be tested in situ for any lt3089 application. lt3089 3089f
14 for more information www.linear.com/lt308 9 applications information in lt3089 applications with long wires or pcb traces, the inductive reactance may cause instability. in some cases, adding series resistance to the input and output lines (as shown in figure 4) may sufficiently dampen these possible high-q lines and provide stability. the user must evaluate the required resistor values against the design s headroom constraints. in general, operation at low output current levels (<20ma) automatically requires higher values of programming resistors and may provide the necessary damping without additional series impedance. if the line impedances in series with the lt3089 are complex enough such that series damping resistors are not sufficient, a frequency compensation network may be necessary . several options may be considered. figure 5 depicts the simplest frequency compensation networks as a single capacitor across the two terminals of the current source . some applications may use the capacitance to stand off dc voltage but allow the transfer of data down a signal line. for some applications, pure capacitance may be unac- ceptable or present a design constraint . one circuit example typifying this is an intrinsically-safe circuit in which an overload or fault condition potentially allows the capacitors stored energy to create a spark or arc . for ap- plications where a single capacitor is unacceptable, figure 5 alternately shows a series rc network connected across the two terminals of the current source . this network has the added benefit of limiting the discharge current of the capacitor under a fault condition, preventing sparks or arcs . in many instances, a series rc network is the best solution for stabilizing the application circuit . typical resis - tor values will range from 100 to 5k. once again, linear technology strongly recommends testing stability in situ for any lt3089 application across all operating conditions , especially ones that present complex impedance networks at the input and output of the current source. if an application refers the bottom of the lt3089 current source to gnd, it may be necessary to bypass the top of the current source with a capacitor to gnd. in some cases, this capacitor may already exist and no additional capacitance is required. for example, if the lt3089 was used as a variable current source on the output of a power supply, the output bypass capacitance would suffice to provide lt3089 stability. other applications may require the addition of a bypass capacitor. a series rc network may also be used as necessary , and depends on the ap- plication requirements. in set out + ? lt3089 50a r set r out r series r series long line reactance/inductance 3089 f04 long line reactance/inductance figure 4. adding series resistance decouples and dampens long line reactances figure 5. compensation from input to output of current source provides stability 3089 f05 in set out + ? lt3089 50a c comp or r set r out r comp c comp lt3089 3089f
15 for more information www.linear.com/lt308 9 applications information in some extreme cases, capacitors or series rc networks may be required on both the lt3089s input and output to stabilize the circuit . figure 6 depicts a general application using input and output capacitor networks rather than an input-to-output capacitor. as the input of the current source tends to be high impedance, placing a capacitor on the input does not have the same effect as placing a capacitor on the lower impedance output . capacitors in the range of 0.1f to 1f usually provide sufficient bypassing on the input, and the value of input capacitance may be increased without limit. pay careful attention to using low esr input capacitors with long input lines (see the stabil- ity and input capacitance section for more information). using ceramic capacitors give extra consideration to the use of ceramic capacitors. ceramic capacitors are manufactured with a variety of di- electrics, each with different behavior across temperature and applied voltage. the most common dielectrics used are specified with eia temperature characteristic codes of z5u, y5v, x5r and x7r. the z5u and y5v dielectrics are good for providing high capacitances in a small package, but they tend to have strong voltage and temperature coefficients as shown in figures 7 and 8. when used with a 5v regulator, a 16v 10f y5v capacitor can exhibit an effective value as low as 1f to 2f for the dc bias voltage applied and over the operating temperature range . the x 5 r and x7r dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. the x7r type has better stability across temperature, while the x5r is less expensive and is available in higher values. care still must be exercised when using x5r and x7r capacitors. the x5r and x7r codes only specify operating temperature range and maximum capacitance change over temperature. capacitance change due to dc bias with x5r and x7r capacitors is better than y5v and z5u capacitors, but can still be significant enough to drop capacitor values below appropriate levels. capacitor dc bias characteristics tend to improve as component case size increases, but expected capacitance at operating voltage should be verified. figure 8. ceramic capacitor dc bias characteristics figure 7. ceramic capacitor temperature characteristics figure 6. input and/or output capacitors may be used for compensation 3089 f06 in set out + ? lt3089 50a i out r set r out c out or v in c out r out c in r in temperature (c) ?50 40 20 0 ?20 ?40 ?60 ?80 ?100 25 75 3089 f07 ?25 0 50 100 125 y5v change in value (%) x5r both capacitors are 16v, 1210 case size, 10f dc bias voltage (v) change in value (%) 3089 f08 20 0 ?20 ?40 ?60 ?80 ?100 0 4 8 10 2 6 12 14 x5r y5v 16 both capacitors are 16v, 1210 case size, 10f lt3089 3089f
16 for more information www.linear.com/lt308 9 applications information voltage and temperature coefficients are not the only sources of problems. some ceramic capacitors have a piezoelectric response. a piezoelectric device generates voltage across its terminals due to mechanical stress. in a ceramic capacitor, the stress can be induced by vibrations in the system or thermal transients. paralleling devices higher output current is obtained by paralleling multiple lt3089s together. tie the individual set pins together and tie the individual in pins together. connect the outputs in common using small pieces of pc trace as ballast resistors to promote equal current sharing. pc trace resistance in milliohms/inch is shown in table 2. ballasting requires only a tiny area on the pcb. table 2. pc board trace resistance weight (oz) 10mil width 20mil width 1 54.3 27.1 2 27.1 13.6 trace resistance is measured in m/in. the worst-case room temperature offset, only 1.5mv between the set pin and the out pin, allows the use of very small ballast resistors. as shown in figure 9, each lt3089 has a small 20m ballast resistor, which at full output current gives better than 80% equalized sharing of the current. the external resistance of 20m (10m for the two devices in paral- lel) only adds about 16mv of output regulation drop at an output of 1.6a. even with an output voltage as low as 1v, this only adds 1.6% to the regulation . of course , paralleling more than two lt3089s yields even higher output current. spreading the devices on the pc board also spreads the heat. series input resistors can further spread the heat if the input-to-output difference is high. if the increase in load regulation from the ballast resis- tors is unacceptable, the i mon output can be used to compensate for these drops (see using i mon cancels ballast resistor drop in the typical applications section). regulator paralleling without the use of ballast resistors is accomplished by comparing the i mon outputs of regula- tors (see load current sharing without ballasting in the typical applications section). quieting the noise the lt3089 offers numerous noise performance advan- tages. every linear regulator has its sources of noise. in general, a linear regulators critical noise source is the reference. in addition, consider the error amplifiers noise contribution along with the resistor dividers noise gain. many traditional low noise regulators bond out the voltage reference to an external pin (usually through a large value resistor) to allow for bypassing and noise reduction. the lt3089 does not use a traditional voltage reference like other linear regulators. instead, it uses a 50a reference current. the 50a current source generates noise current levels of 18pa/hz (5.7na rms over a 10hz to 100khz bandwidth). the equivalent voltage noise equals the rms noise current multiplied by the resistor value. the set pin resistor generates spot noise equal to 4ktr (k = boltzmanns constant , 1.38 ? 10 C23 j/k, and t is abso- lute temperature) which is rms summed with the voltage noise. if the application requires lower noise performance , bypass the voltage setting resistor with a capacitor to gnd . note that this noise - reduction capacitor increases start - up time as a factor of the rc time constant. set + ? lt3089 50a 20m 20m in v in 4.8v to 40v v out 3.3v 1.6a out 10f 1f 33k 3089 f09 set + ? lt3089 50a in out figure 9. parallel devices lt3089 3089f
17 for more information www.linear.com/lt308 9 the lt3089 uses a unity-gain follower from the set pin to the out pin. therefore, multiple possibilities exist (besides a set pin resistor) to set output voltage. for example, using a high accuracy voltage reference from set to gnd removes the errors in output voltage due to reference current tolerance and resistor tolerance. active driving of the set pin is acceptable. the typical noise scenario for a linear regulator is that the output voltage setting resistor divider gains up the reference noise, especially if v out is much greater than v ref . the lt3089s noise advantage is that the unity-gain follower presents no noise gain whatsoever from the set pin to the output. thus, noise figures do not increase accordingly. error amplifier noise is typical 85nv/hz(27v rms over a 10hz to 100khz bandwidth). the error amplifiers noise is rms summed with the other noise terms to give a final noise figure for the regulator. paralleling of regulators adds the benefit that output noise is reduced. for n regulators in parallel, the output noise drops by a factor of n. curves in the typical performance characteristics sec- tion show noise spectral density and peak-to -peak noise characteristics for both the reference current and error amplifier over a 10hz to 100khz bandwidth. load voltage regulation the lt3089 is a floating device. no ground pin exists on the packages. thus, the ic delivers all quiescent current and drive current to the load. therefore, it is not possible to provide true remote load sensing. the connection re- sistance between the regulator and the load determines load regulation performance . the data sheet s load regulation specification is kelvin sensed at the packages pins. negative-side sensing is a true kelvin connection by returning the bottom of the voltage setting resistor to the negative side of the load (see figure 10). connected as shown, system load regulation is the sum of the lt3089s load regulation and the parasitic line resistance multiplied by the output current. to minimize load regulation, keep the positive connection between the regulator and load as short as possible. if possible, use large diameter wire or wide pc board traces. temp pin operation (die temperature monitor) the temp pin of the lt 3089 outputs a current proportional to average die temperature. at 25c, the current from the temp pin is 25a, with a slope of 1a /c. the current out of the temp pin is valid for junction temperatures above 0c (absent initial offset considerations). below 0c, the temp pin will not sink current to indicate die temperature. the temp pin output current is valid for voltages up to 40v below and 0.4v above the out pin allowing operation even during short- circuit conditions. connecting a resistor from temp to ground converts the temp pin current into a voltage to allow for monitoring by an adc. with a 1k resistor, 0mv to 150mv indicates 0c to 150c. it should be noted that the temp pin current represents an average temperature and should not be used to guarantee that maximum junction temperature is not exceeded. instantaneous power along with thermal gradients and time constants may cause portions of the die to exceed maximum ratings and thermal shutdown thresholds. be sure to calculate die temperature rise for steady state (>1?minute) as well as impulse conditions. i mon pin operation (current monitor) the lt3089s i mon pin outputs a current proportional to the load current supplied at a ratio of 1:5000. the i mon pin current is valid for voltages up to 40v below and 0.4v above the out pin, allowing operation even during short- circuit conditions. applications information figure 10. connections for best load regulation in set + ? lt3089 50a 3089 f10 out r set r p parasitic resistance r p r p load lt3089 3089f
18 for more information www.linear.com/lt308 9 connecting a resistor from i mon to ground converts the i mon pin current into a voltage to allow for monitoring by an adc. with a 1k resistor, 0mv to 160mv indicates 0a to 800ma of load current. compensating for cable drops with i mon the i mon pin can compensate for resistive drops in wires or cables between the lt3089 and the load. breaking the set resistor into two pieces adjusts the output voltage as a function of load current. the ratio of the output wire/cable impedance to the bottom resistor should be 1:5000. the sum total of the two set resistor values determines the initial output voltage. figure 11 shows a typical application and formulas for calculating resistor values. pc board, copper traces and planes. surface mount heat sinks, plated through-holes and solder -filled vias can also spread the heat generated by power devices. junction-to-case thermal resistance is specified from the ic junction to the bottom of the case directly, or the bot- tom of the pin most directly in the heat path. this is the lowest thermal resistance path for heat flow. only proper device mounting ensures the best possible thermal flow from this area of the packages to the heat sinking material. note that the exposed pad of the dfn and tssop pack- ages and the tab of the dd-pak package are electrically connected to the output (v out ). tables 3 through 5 list thermal resistance as a function of copper areas on a fixed board size. all measurements were taken in still air on a 4-layer fr-4 board with 1oz solid internal planes and 2oz external trace planes with a total finished board thickness of 1.6mm. table 3. df package, 12-lead dfn copper area board area thermal resistance (junction-to-ambient) topside* backside 2500mm 2 2500mm 2 2500mm 2 21c/w 1000mm 2 2500mm 2 2500mm 2 24c/w 225mm 2 2500mm 2 2500mm 2 30c/w 100mm 2 2500mm 2 2500mm 2 35c/w *device is mounted on topside table 4. fe package, 16-lead tssop copper area board area thermal resistance (junction-to-ambient) topside* backside 2500mm 2 2500mm 2 2500mm 2 18c/w 1000 mm 2 2500mm 2 2500mm 2 22c/w 225mm 2 2500mm 2 2500mm 2 27c/w 100mm 2 2500mm 2 2500mm 2 32c/w *device is mounted on topside table 5. r package, 7-lead dd-pak copper area board area thermal resistance (junction-to-ambient) topside* backside 2500mm 2 2500mm 2 2500mm 2 13c/w 1000mm 2 2500mm 2 2500mm 2 14c/w 225mm 2 2500mm 2 2500mm 2 16c/w *device is mounted on topside applications information figure 11. using i mon to compensate for cable drops thermal considerations the lt3089s internal power and thermal limiting circuitry protects itself under overload conditions. for continuous normal load conditions, do not exceed the 125c (e- and i - grades ) maximum junction temperature . carefully consider all sources of thermal resistance from junction- to-ambient. this includes (but is not limited to) junction- to-case, case-to-heat sink interface , heat sink resistance or circuit board-to-ambient as the application dictates. consider all additional, adjacent heat generating sources in proximity on the pcb. surface mount packages provide the necessary heat sinking by using the heat spreading capabilities of the lt3089 in c in 1f c out 10f 3089 f11 out set r set 29.8k r comp = 5000 r cable(total) v out(load) = 50a (r set + r comp ) r cable2 0.02 r cable 0.02 r comp 200 i mon load lt3089 3089f
19 for more information www.linear.com/lt308 9 applications information for further information on thermal resistance and using thermal information, refer to jedec standard jesd51, notably jesd51-12. pcb layers, copper weight, board layout and thermal vias affect the resultant thermal resistance. tables 3 through 5 provide thermal resistance numbers for best-case 4-layer boards with 1oz internal and 2oz external copper. modern, multilayer pcbs may not be able to achieve quite the same level performance as found in these tables. demo circuit 2318as board layout using multiple inner v out planes and multiple thermal vias achieves 17c/w performance for the df package. calculating junction temperature example: given an output voltage of 0.9v, an in voltage of 2.5v 5%, output current range from 10ma to 0.8a and a maximum ambient temperature of 50c, what is the maximum junction temperature for the dd-pak on a 2500mm 2 board with topside copper of 1000mm 2 ? the power in the circuit equals: p total = (v in C v out )(i out ) the current delivered to the set pin is negligible and can be ignored. v in(max_continuous) = 2.625v (2.5v + 5%) v out = 0.9v, i out = 0.8a, t a = 50c power dissipation under these conditions equals: p total = (v in C v out )(i out ) p total = (2.625v C 0.9v)(0.8a) = 1.38w junction temperature equals: t j = t a + p total ? ja (using tables) t j = 50c + 1.38w ? 14c/w = 69.3c in this case, the junction temperature is below the maxi- mum rating, ensuring reliable operation. reducing power dissipation in some applications it may be necessary to reduce the power dissipation in the lt3089 package without sacrificing output current capability . tw o techniques are available . the first technique, illustrated in figure 12, employs a resis- tor in series with the regulators input. the voltage drop across r s decreases the lt3089s in-to-out differential voltage and correspondingly decreases the lt 3089 s power dissipation. as an example , assume : v in = 7 v , v out = 3.3 v and i out ( max ) = 0.8a. use the formulas from the calculating junction temperature section previously discussed. without series resistor r s , power dissipation in the lt3089 equals: p total = (7v C 3.3v) ? 0.8a = 2.96w if the voltage differential (v diff ) across the lt3089 is chosen as 1.5v, then r s equals: r s = 7v C 3.3v C 1.5v 0.8a = 2.8 ? power dissipation in the lt3089 now equals: p total = 1.5v ? 0.8a = 1.2w the lt3089 s power dissipation is now only 40% compared to no series resistor. r s dissipates 1.8w of power. choose appropriate wattage resistors or use multiple resistors in parallel to handle and dissipate the power properly. 3089 f12 in v in set out + ? lt3089 50a r set r s v out v in c2 c1 figure 12. reducing power dissipation using a series resistor lt3089 3089f
20 for more information www.linear.com/lt308 9 applications information the second technique for reducing power dissipation, shown in figure 13, uses a resistor in parallel with the lt3089. this resistor provides a parallel path for current flow, reducing the current flowing through the lt3089. this technique works well if input voltage is reasonably constant and output load current changes are small. this technique also increases the maximum available output current at the expense of minimum load requirements. r p dissipates 0.85w of power. as with the first technique, choose appropriate wattage resistors to handle and dis- sipate the power properly. with this configuration, the lt3089 supplies only 0.43a. therefore, load current can increase by 0.37a to a total output current of 1.17a while keeping the lt3089 in its normal operating range. protection features the lt3089 incorporates several protection features ideal for harsh industrial and automotive environments, among other applications. in addition to normal monolithic regula- tor protection features such as current limiting and thermal limiting, the lt3089 protects itself against reverse-input voltages, reverse-output voltages, and large out-to-set pin voltages. current limit protection and thermal overload protection protect the ic against output current overload conditions. for normal operation, do not exceed the rated absolute maximum junction temperature. the thermal shutdown circuit s temperature threshold is typically 165c and incorporates about 5c of hysteresis. the lt3089 s in pin withstands 40v voltages with respect to the out and set pins. reverse current flow, if out is greater than in, is less than 1ma (typically under 100a), protecting the lt3089 and sensitive loads. clamping diodes and 400 limiting resistors protect the lt3089 s set pin relative to the out pin voltage. these protection components typically only carry current under transient overload conditions. these devices are sized to handle 10v differential voltages and 25ma crosspin current flow without concern. relative to these applica- tion concerns, note the following two scenarios. the first scenario employs a noise - reducing set pin bypass capacitor while out is instantaneously shorted to gnd . the second scenario follows improper shutdown techniques in which the set pin is reset to gnd quickly while out is held up by a large output capacitance with light load. 3089 f13 in set out + ? lt3089 50a r set v out v in c2 c1 r p figure 13. reducing power dissipation using a parallel resistor as an example, assume: v in = 5 v, v in(max) = 5.5 v, v out ? =? 3.3 v, v out(min) = 3.2v, i out(max) = 0.8a and i out(min) = 0.4a. also, assuming that r p carries no more than 90% of i out(min) = 360ma. calculating r p yields: r p = 5.5v C 3.2v 0.36a = 6.39 ? (5% standard value = 6.2) the maximum total power dissipation is: (5.5 v C 3.2v) ? 0.8a = 1.84w however, the lt3089 supplies only: 0.8a C 5.5v C 3.2v 6.2 ? = 0.43a therefore, the lt3089s power dissipation is only: p diss = (5.5v C 3.2v) ? 0.43a = 0.99w lt3089 3089f
21 for more information www.linear.com/lt308 9 typical applications paralleling regulators using i mon cancels ballast resistor drop in set r set 30.1k 1k temp i mon i lim 20m out + ? lt3089 i set 50a v out 3v 1.6a v in in set 1k temp i mon i lim 20m out + ? lt3089 i set 50a 3.01k 3089 ta02 1k in set r set 15k 1k temp i mon i lim out + ? lt3089 i set 50a v out 1.5v 1.6a v in in set 1k temp i mon i lim r ballast 20m out + ? lt3089 i set 50a 3089 ta03 r comp 50 r ballast 20m lt3089 3089f
22 for more information www.linear.com/lt308 9 typical applications load sharing without ballast resistors load current sharing without ballasting in 22f 20k out v in 3v to 18v i mon set lt3089 0.1f 22f 1k 5.1k in 20k out i mon set lt3089 100k 0.47f 5.1k 5.1k 0.1f 1k in out i mon set lt3089 ? + 20k v out 1v 2.4a 100k 0.47f 5.1k 0.1f 1k 3089 ta04 ? + 1/2 lt1638 1/2 lt1638 in 4.7f 20k out v in 3v to 36v i mon set i lim lt3089 0.1f 2.2f v out 1v 1.6a 0.1f 3089 ta05 100 1k 1k 20k = 2n3904 out in i mon set i lim lt3089 lt3089 3089f
23 for more information www.linear.com/lt308 9 typical applications boosting fixed output regulators reference buffer adding soft-start 8.2* 3.3v out 2.3a *4mv drop ensures lt3089 is off with no load multiple lt3089s can be used in set temp i mon i lim 20m 5v out + ? lt3089 i set 50a 3089 ta06 6.2k 10f lt1963-3.3 47f 20m 1k 1k* 1k lt1019 v out *min load 3ma in set temp i mon i lim out + ? lt3089 i set 50a 3089 ta07 1f output gnd 47f input v in 1k 1k v out 3.3v 0.8a in set temp i mon i lim out + ? lt3089 i set 50a 3089 ta08 0.1f 10f 1n4148 v in 4.8v to 36v 66.5k 10f lt3089 3089f
24 for more information www.linear.com/lt308 9 typical applications using a lower value set resistor using an external reference current 20k in set 1k temp i mon i lim out + ? lt3089 i set 50a 1f 3089 ta10 1k in set out + ? lt3092 10a 1ma v in v out 0v to 20v 20k 215 1f r set 2k v out = 0.2v + 5ma r set in set 1k temp i mon i lim out + ? lt3089 i set 50a 4.7f 3089 ta09 1k 4.02k 40.2 v in 12v v out 0.2v to 10v 4.7f lt3089 3089f
25 for more information www.linear.com/lt308 9 package description please refer to http://www .linear.com/product/lt3089#packaging for the most recent package drawings. 4.00 0.10 (4 sides) note: 1. package outline does not conform to jedec mo-229 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 pin 1 top mark (note 6) 0.40 0.10 1 6 12 7 bottom view?exposed pad 2.65 0.10 0.75 0.05 r = 0.115 typ 0.25 0.05 0.50 bsc 2.50 ref 3.38 0.10 0.200 ref 0.00 ? 0.05 (df12) dfn 1112 rev a recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 0.70 0.05 0.25 0.05 0.50 bsc 3.10 0.05 4.50 0.05 package outline pin 1 notch r = 0.20 typ or 0.35 45 chamfer 2.65 0.05 3.38 0.05 2.50 ref df package 12-lead plastic dfn (4mm 4mm) (reference ltc dwg # 05-08-1733 rev a) lt3089 3089f
26 for more information www.linear.com/lt308 9 package description please refer to http://www .linear.com/product/lt3089#packaging for the most recent package drawings. fe16 (bb) tssop rev k 0913 0.09 ? 0.20 (.0035 ? .0079) 0 ? 8 0.25 ref 0.50 ? 0.75 (.020 ? .030) 4.30 ? 4.50* (.169 ? .177) 1 3 4 5 6 7 8 10 9 4.90 ? 5.10* (.193 ? .201) 16 1514 13 12 11 1.10 (.0433) max 0.05 ? 0.15 (.002 ? .006) 0.65 (.0256) bsc 2.94 (.116) 0.195 ? 0.30 (.0077 ? .0118) typ 2 recommended solder pad layout 0.45 0.05 0.65 bsc 4.50 0.10 6.60 0.10 1.05 0.10 2.94 (.116) 3.05 (.120) 3.58 (.141) 3.58 (.141) 4.70 (.185) millimeters (inches) note: 1. controlling dimension: millimeters 2. dimensions are in 3. drawing not to scale 4. recommended minimum pcb metal size for exposed pad attachment see note 4 note 5 note 5 6.40 (.252) bsc fe package 16-lead plastic tssop (4.4mm) (reference ltc dwg # 05-08-1663 rev k) exposed pad variation bb 5. bottom exposed paddle may have metal protrusion in this area. this region must be free of any exposed traces or vias on pbc layout *dimensions do not include mold flash. mold flash shall not exceed 0.150mm (.006") per side detail a detail a is the part of the lead frame feature for reference only no measurement purpose 0.56 (.022) ref 0.53 (.021) ref detail a lt3089 3089f
27 for more information www.linear.com/lt308 9 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. package description please refer to http://www .linear.com/product/lt3089#packaging for the most recent package drawings. r (dd7) 0212 rev f .026 ? .035 (0.660 ? 0.889) typ .143 +.012 ?.020 ( ) 3.632 +0.305 ?0.508 .050 (1.27) bsc .013 ? .023 (0.330 ? 0.584) .095 ? .115 (2.413 ? 2.921) .004 +.008 ?.004 ( ) 0.102 +0.203 ?0.102 .050 .012 (1.270 0.305) .059 (1.499) typ .045 ? .055 (1.143 ? 1.397) .165 ? .180 (4.191 ? 4.572) .330 ? .370 (8.382 ? 9.398) .060 (1.524) typ .390 ? .415 (9.906 ? 10.541) 15 typ .420 .350 .585 .090 .035 .050 .325 .205 .080 .585 recommended solder pad layout for thicker solder paste applications recommended solder pad layout .090 .035 .050 .420 .276 .320 note: 1. dimensions in inch/(millimeter) 2. drawing not to scale .300 (7.620) .075 (1.905) .183 (4.648) .060 (1.524) .060 (1.524) .256 (6.502) bottom view of dd pak hatched area is solder plated copper heat sink r package 7-lead plastic dd pak (reference ltc dwg # 05-08-1462 rev f) detail a detail a 0 ? 7 typ 0 ? 7 typ lt3089 3089f
28 for more information www.linear.com/lt308 9 ? linear technology corporation 2016 lt 0116 ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/lt308 9 related parts typical application high efficiency adjustable supply part number description comments lt1764/ lt1764a 3a, fast transient response, low noise ldo 340mv dropout voltage, low noise: 40v rms , v in = 2.7v to 20v, to-220, tssop and dd-pak, lt1764a version stable also with ceramic capacitors lt1963/ lt1963a 1.5a low noise, fast transient response ldo 340mv dropout voltage, low noise: 40v rms , v in = 2.5v to 20v, lt1963a version stable with ceramic capacitors, to-220, dd, tssop, sot-223 and so-8 packages lt1965 1.1a, low noise, low dropout linear regulator 290mv dropout voltage, low noise: 40v rms , v in : 1.8v to 20v, v out : 1.2v to 19.5v, stable with ceramic capacitors, to-220, dd-pak, msop and 3mm 3mm dfn packages lt3022 1a, low voltage, vldo linear regulator v in : 0.9v to 10v, dropout voltage: 145mv typical, adjustable output (v ref = v out(min) = 200mv), stable with low esr, ceramic output capacitors, 16-pin dfn (5mm 3 mm) and 16-lead msop packages lt3070/ lt3071 5a, low noise, programmable v out , 85mv dropout linear regulator with digital margining dropout voltage: 85mv, digitally programmable v out : 0.8v to 1.8v, digital output margining: 1%, 3% or 5%, low output noise: 25v rms (10hz to 100khz), parallelable: use tw o for a 10a output, stable with low esr ceramic output capacitors (15f minimum), 28-lead 4 mm 5 mm qfn package. lt3071has analog margining. LT3080/ LT3080-1 1.1a, parallelable, low noise, low dropout linear regulator 300mv dropout voltage (2-supply operation), low noise: 40v rms , v in : 1.2v to 36v , v out : 0v to 35.7v , current- based reference with 1-resistor v out set; directly parallelable ( no op amp required), stable with ceramic capacitors, to-220, dd-pak, sot-223, ms8e and 3mm 3mm dfn-8 packages; LT3080-1 version has integrated internal ballast resistor lt3081 1.5a single resistor rugged linear regulator with monitors extended safe operating area (soa). output current: 1.5a stable with/without input/output capacitors. v in range: 1.2v to 36v. 50a set pin current: tssop-16, to-220, dd-pak, 4mm x 4mm dfn-12 packages. lt3082 200ma, parallelable, single resistor, low dropout linear regulator outputs may be paralleled for higher output, current or heat spreading, wide input voltage range: 1.2v to 40v low value input/output capacitors required: 2.2f, single resistor sets output voltage 8-lead sot-23, 3-lead sot-223 and 8-lead 3mm 3mm dfn packages lt3085 500ma, parallelable, low noise, low dropout linear regulator 275mv dropout voltage (2-supply operation), low noise: 40v rms , v in : 1.2v to 36v , v out : 0v to 35.7v , current- based reference with 1-resistor v out set; directly parallelable (no op amp required), stable with ceramic capacitors, ms8e and 2mm 3mm dfn-6 packages lt3092 200ma 2- terminal programmable current source programmable 2- terminal current source, maximum output current = 200ma, wide input voltage range: 1.2v to 40v, resistor ratio sets output current, initial set pin current accuracy = 1%, current limit and thermal shutdown protection, reverse- voltage protection, reverse-current protection , 8-lead sot-23, 3-lead sot-223 and 8-lead 3mm 3mm dfn packages. lt3083 adjustable 3a single resistor low dropout regulator low noise: 40v rms , 50a set pin current, output adjustable to 0 v , wide input voltage range: 1.2v to 23v (dd-pak and to-220), low dropout operation: 310mv (2 supplies) run/ss 0.47f 47f 1f 1f 1000pf v in 6.3v to 36v 6.8h v in bd lt3680 15k 590k 1k 10k 3089 ta11 2n3904 mtd2955 cmdsh-4e mbra340t3 gnd boost in out i mon i lim 1k 1k v c sw fb 63.4k rt pg sync 15k 6.04k lt3089 500k 22f 6v v out 0v to 25v, 0.8a temp set 0.1f lt3089 3089f

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