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lt1083/lt1084/lt1085 1 108345fg typical application description 7.5a, 5a, 3a low dropout positive adjustable regulators the lt ? 1083 series of positive adjustable regulators are designed to provide 7.5a, 5a and 3a with higher ef? ciency than currently available devices. all internal circuitry is designed to operate down to 1v input-to-output differential and the dropout voltage is fully speci? ed as a function of load current. dropout is guaranteed at a maximum of 1.5v at maximum output current, decreasing at lower load cur- rents. on-chip trimming adjusts the reference voltage to 1%. current limit is also trimmed, minimizing the stress on both the regulator and power source circuitry under overload conditions. the lt1083/lt1084/lt1085 devices are pin compatible with older 3-terminal regulators. a 10f output capacitor is required on these new devices. however, this is included in most regulator designs. unlike pnp regulators, where up to 10% of the output cur- rent is wasted as quiescent current, the lt1083 quiescent current ? ows into the load, increasing ef? ciency. features applications n 3-terminal adjustable n output current of 3a, 5a or 7.5a n operates down to 1v dropout n guaranteed dropout voltage at multiple current levels n line regulation: 0.015% n load regulation: 0.1% n 100% thermal limit functional test n fixed versions available n available in 3-lead plastic to-220, to-3p and dd packages n high ef? ciency linear regulators n post regulators for switching supplies n constant current regulators n battery chargers device output current * lt1083 lt1084 lt1085 7.5a 5.0a 3.0a *for a 1.5a low dropout regulator see the lt1086 data sheet. , lt, ltm and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. 121 1% in out adj 365 1% 10f 5v at 7.5a lt1083 v in 6.5v 1083/4/5 adj ta01 + 10f* tantalum + *required for stability 5v, 7.5a regulator output current 0 input/output voltage differential (v) 2 1 0 1083/4/5 adj ta02 i full load dropout voltage vs output current
lt1083/lt1084/lt1085 2 108345fg preconditioning absolute maximum ratings power dissipation ................................internally limited input-to-output voltage differential c-grades ..............................................................30v i-grades ................................................................30v m-grades (obsolete) .........................................35v operating junction temperature range (note 9) c-grades: control section .................. 0c to 125c power transistor ................ 0c to 150c i-grades: control section ..............C 40c to 125c power transistor ............C 40c to 150c m-grades: (obsolete) control section ..............C 55c to 150c power transistor ............ C55c to 200c storage temperature range ...................C 65c to 150c lead temperature (soldering, 10 sec) .................. 300c 100% thermal shutdown functional test. (note 1) t package 3-lead plastic to-220 front view tab is output 3 2 1 v in v out adj ja = 50c/w v in v out adj p package 3-lead plastic to-3p front view tab is output 3 2 1 ja = 35c/w 1 2 v in case is output bottom view adj k package 2-lead to-3 metal can ja = 35c/w obsolete package v in v out adj 3 2 1 m package 3-lead plastic dd front view tab is output 3 2 1 ja = 30c/w* *with package soldered to 0.5in 2 copper area over backside ground plane or internal power plane. ja can vary from 20c/w to >40c/w depending on mounting technique pin configuration
lt1083/lt1084/lt1085 3 108345fg order information lead free finish tape and reel part marking* package description temperature range lt1083cp#pbf lt1083cp#trpbf lt1083cp 3-lead plastic to-3p control: 0c to 125c power: 0c to 150c lt1084cp#pbf lt1084cp#trpbf lt1084cp 3-lead plastic to-3p control: 0c to 125c power: 0c to 150c lt1084ct#pbf lt1084ct#trpbf lt1084ct 3-lead plastic to-220 control: 0c to 125c power: 0c to 150c lt1084it#pbf lt1084it#trpbf lt1084it 3-lead plastic to-220 control: C40c to 125c power: C40c to 150c lt1085ct#pbf lt1085ct#trpbf lt1085ct 3-lead plastic to-220 control: 0c to 125c power: 0c to 150c lt1085it#pbf lt1085it#trpbf lt1085it 3-lead plastic to-220 control: C40c to 125c power: C40c to 150c lt1085cm#pbf lt1085cm#trpbf lt1085cm 3-lead plastic dd control: 0c to 125c power: 0c to 150c lt1085im#pbf lt1085im#trpbf lt1085im 3-lead plastic dd control: C40c to 125c power: C40c to 150c lead based finish tape and reel part marking* package description temperature range lt1083cp lt1083cp#tr lt1083cp 3-lead plastic to-3p control: 0c to 125c power: 0c to 150c lt1084cp lt1084cp#tr lt1084cp 3-lead plastic to-3p control: 0c to 125c power: 0c to 150c lt1084ct lt1084ct#tr lt1084ct 3-lead plastic to-220 control: 0c to 125c power: 0c to 150c lt1084it lt1084it#tr lt1084it 3-lead plastic to-220 control: C40c to 125c power: C40c to 150c lt1085ct lt1085ct#tr lt1085ct 3-lead plastic to-220 control: 0c to 125c power: 0c to 150c lt1085it lt1085it#tr lt1085it 3-lead plastic to-220 control: C40c to 125c power: C40c to 150c lt1085cm lt1085cm#tr lt1085cm 3-lead plastic dd control: 0c to 125c power: 0c to 150c lt1085im lt1085im#tr lt1085im 3-lead plastic dd control: C40c to 125c power: C40c to 150c lt1083ck lt1083ck#tr lt1083ck 2-lead to-3 metal can control: 0c to 125c power: 0c to 150c lt1083mk lt1083mk#tr lt1083mk 2-lead to-3 metal can control: C55c to 150c power: C55c to 200c lt1084ck lt1084ck#tr lt1084ck 2-lead to-3 metal can control: 0c to 125c power: 0c to 150c lt1084mk lt1084mk#tr lt1084mk 2-lead to-3 metal can control: C55c to 150c power: C55c to 200c lt1085ck lt1085ck#tr lt1085ck 2-lead to-3 metal can control: 0c to 125c power: 0c to 150c lt1085mk lt1085mk#tr lt1085mk 2-lead to-3 metal can control: C55c to 150c power: C55c to 200c obsolete package consult ltc marketing for parts speci? ed with wider operating temperature ranges. *the temperature grade is identi? ed 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 speci? cations, go to: http://www.linear.com/tapeandreel/
lt1083/lt1084/lt1085 4 108345fg electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. parameter conditions min typ max units reference voltage i out = 10ma, t j = 25c, (v in C v out ) = 3v 10ma i out i full_load 1.5v (v in C v out ) 25v (notes 4, 6, 7) l 1.238 1.225 1.250 1.250 1.262 1.270 v v line regulation i load = 10ma, 1.5v (v in C v out ) 15v, t j = 25c (notes 2, 3) l 0.015 0.035 0.2 0.2 % % m-grade: 15v (v in C v out ) 35v (notes 2, 3) l 0.05 0.5 % c-, i-grades: 15v (v in C v out ) 30v (notes 2, 3) l 0.05 0.5 % load regulation (v in C v out ) = 3v, 10ma i out i full_load , t j = 25c (notes 2, 3, 4, 6) l 0.1 0.2 0.3 0.4 % % dropout voltage v ref = 1%, i out = i full_load (notes 5, 6, 8) l 1.3 1.5 v current limit lt1083 lt1084 lt1085 (v in C v out ) = 5v (v in C v out ) = 25v (v in C v out ) = 5v (v in C v out ) = 25v (v in C v out ) = 5v (v in C v out ) = 25v l l l l l l 8.0 0.4 5.5 0.3 3.2 0.2 9.5 1.0 6.5 0.6 4.0 0.5 a a a a a a minimum load current (v in C v out ) = 25v l 510 ma thermal regulation lt1083 lt1084 lt1085 t a = 25c, 30ms pulse 0.002 0.003 0.004 0.010 0.015 0.020 %/w %/w %/w ripple rejection f = 120hz, c adj = 25f, c out = 25f tantalum i out = i full_load , (v in C v out ) = 3v (notes 6, 7, 8) l 60 75 db adjust pin current t j = 25c l 55 120 a a adjust pin current change 10ma i out i full_load , 1.5v (v in C v out ) 25v (note 6) l 0.2 5 a temperature stability l 0.5 % long-term stability t a = 125c, 1000 hrs 0.3 1 % rms output noise (% of v out )t a = 25c, 10hz = f 10khz 0.003 %
lt1083/lt1084/lt1085 5 108345fg 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. note 2: see thermal regulation speci? cations for changes in output voltage due to heating effects. load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing. note 3: line and load regulation are guaranteed up to the maximum power dissipation (60w for the lt1083, 45w for the lt1084 (k, p), 30w for the lt1084 (t) and 30w for the lt1085). power dissipation is determined by the input/output differential and the output current. guaranteed maximum power dissipation will not be available over the full input/output voltage range. note 4: i full_load is de? ned in the current limit curves. the i full_load curve is de? ned as the minimum value of current limit as a function of input-to-output voltage. note that the 60w power dissipation for the lt1083 (45w for the lt1084 (k, p), 30w for the lt1084 (t), 30w for the lt1085) is only achievable over a limited range of input-to-output voltage. note 5: dropout voltage is speci? ed over the full output current range of the device. test points and limits are shown on the dropout voltage curve. note 6: for lt1083 i full_load is 5a for C 55c t j < C 40c and 7.5a for t j C40c. note 7: 1.7v (v in C v out ) 25v for lt1084 at C 55c t j C 40c. note 8: dropout is 1.7v maximum for lt1084 at C 55c t j C40c. note 9: the lt1083/lt1084/lt1085 regulators are tested and speci? ed under pulse load conditions such that t j ? t a . the c-grade lt1083/ lt1084/lt1085 are 100% tested at 25c.the i-grade lt1084/lt1085 are guaranteed over the full C40c to 125c operating ambient temperature range. electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. parameter conditions min typ max units thermal resistance junction-to-case lt1083 lt1084 lt1085 control circuitry/power transistor k package p package k package p package t package k package m, t package 0.6/1.6 0.5/1.6 0.75/2.3 0.65/2.3 0.65/2.7 0.9/3.0 0.7/3.0 c/w c/w c/w c/w c/w c/w c/w
lt1083/lt1084/lt1085 6 108345fg typical performance characteristics output current (a) 0 minimum input/output differential (v) 1 2 lt1083/4/5 adj g01 0 12345678910 indicates guaranteed test point C40c t j 150c 0c t j 125c t j = 150c t j = 25c t j = C55c input/output differential (v) 0 short-circuit current (a) 8 10 12 15 25 lt1083/4/5 adj g02 6 4 510 20 30 35 2 0 25c 150c i full load guaranteed C55c temperature (c) C50 C0.20 output voltage deviation (%) C0.15 C0.10 C0.05 0 050 100 150 lt1083/4/5 adj g03 0.05 0.10 C25 25 75 125 i = 7.5a output current (a) 0 0 minimun input/output differential (v) 1 1 2 34 lt1083/4/5 adj g04 5 2 6 indicates guaranteed test point C55c t j 150c 0c t j 125c t j = 150c t j = C55c t j = 25c input/output differential (v) 0 0 short-circuit current (a) 1 3 4 5 10 7 10 20 25 lt1083/4/5 adj g05 2 8 9 6 5 15 30 35 25c C55c 150c guaranteed i full load temperature (c) C50 C0.20 C0.15 C0.10 C0.05 0.05 0.10 output voltage deviation (%) 0 050 100 150 lt1083/4/5 adj g06 C25 25 75 125 i = 5a temperature (c) C50 C0.20 C0.15 C0.10 C0.05 0.05 0.10 output voltage deviation (%) 0 050 100 150 lt1083/4/5 adj g09 C25 25 75 125 i = 3a input/output differential (v) 0 short-circuit current (a) 4 5 6 15 25 lt1083/4/5 adj g08 3 2 510 20 30 35 1 0 25c C55c i full load guaranteed 150c output current (a) 0 0 minimum input/output differential (v) 1 2 1 2 lt1083/4/5 adj g07 3 4 indicates guaranteed test point t j = 150c t j = 25c C55c t j 150c t j = C55c 0c t j 125c lt1083 dropout voltage lt1083 short-circut current lt1083 load regulation lt1084 dropout voltage lt1084 short-circut current lt1084 load regulation lt1085 dropout voltage lt1085 short-circuit current lt1085 load regulation
lt1083/lt1084/lt1085 7 108345fg typical performance characteristics input/output differential (v) 0 0 minimum operating current (ma) 1 3 4 5 10 7 10 20 25 lt1083/4/5 adj g10 2 8 9 6 5 15 30 35 t j = C55c t j = 150c t j = 25c temperature (c) C50 1.27 1.26 1.25 1.24 1.23 reference voltage (v) 050 100 150 lt1083/4/5 adj g11 C25 25 75 125 temperature (c) C50 100 90 80 70 60 50 40 30 20 10 0 adjust pin current (a) 050 100 150 lt1083/4/5 adj g12 C25 25 75 125 frequency (hz) ripple rejection (db) 100 90 80 70 60 50 40 30 20 10 0 10 1k 10k 100k 1083/4/5 adj g13 100 v ripple 0.5v p-p v ripple 3v p-p (v in C v out ) 3v (v in C v out ) v dropout c adj = 200f at frequencies < 60hz c adj = 25f at frequencies > 60hz i out = 7a output current (a) 0 ripple rejection (db) 100 90 80 70 60 50 40 30 20 10 0 2 4 5 1083/4/5 adj g14 13 6 7 8 v out = 5v c adj = 25f c out = 25f f r = 120hz v ripple 3v p-p f r = 20khz v ripple 0.5v p-p case temperature (c) 50 power (w) 100 90 80 70 60 50 40 30 20 10 0 lt1083/4/5 adj g15 60 70 80 90 100 110 120 130 140 150 lt1083mk lt1083cp lt1083ck * as limited by maximum junction temperature frequency (hz) ripple rejection (db) 100 90 80 70 60 50 40 30 20 10 0 10 1k 10k 100k 1083/4/5 adj g16 100 v ripple 0.5v p-p v ripple 3v p-p (v in C v out ) 3v (v in C v out ) v dropout c adj = 200f at frequencies < 60hz c adj = 25f at frequencies > 60hz i out = 5a output current (a) 0 ripple rejection (db) 100 90 80 70 60 50 40 30 20 10 0 2 4 5 1083/4/5 adj g17 13 v out = 5v c adj = 25f c out = 25f f r = 120hz v ripple 3v p-p f r = 20khz v ripple 0.5v p-p case temperature (c) 50 power (w) 60 50 40 30 20 10 0 lt1083/4/5 adj g18 60 70 80 90 100 110 120 130 140 150 lt1084mk lt1084ct lt1084cp * as limited by maximum junction temperature lt1084ck minimum operating current temperature stability adjust pin current lt1083 ripple rejection lt1083 ripple rejection vs current lt1083 maximum power dissipation* lt1084 maximum power dissipation* lt1084 ripple rejection vs current lt1084 ripple rejection
lt1083/lt1084/lt1085 8 108345fg typical performance characteristics time (s) 0 output voltage deviation (v) load current (a) 0.3 0.2 0.1 0 C0.1 C0.2 C0.3 3 2 1 0 50 1083/4/5 adj g24 100 c adj = 0 c adj = 1f c in = 1f c out = 10f tantalum v out =10v v in =13v preload=100ma frequency (hz) ripple rejection (db) 100 90 80 70 60 50 40 30 20 10 0 10 1k 10k 100k 1083/4/5 adj g19 100 v ripple 0.5v p-p v ripple 3v p-p (v in C v out ) 3v (v in C v out ) v dropout c adj = 200f at frequencies < 60hz c adj = 25f at frequencies > 60hz i out = 3a output current (a) 0 ripple rejection (db) 100 90 80 70 60 50 40 30 20 10 0 1.0 1.5 2.5 3.0 1083/4/5 adj g20 0.5 2.0 v out = 5v c adj = 25f c out = 25f f r = 120hz v ripple 3v p-p f r = 20khz v ripple 0.5v p-p case temperature (c) 50 power (w) 50 40 30 20 10 0 lt1083/4/5 adj g21 60 70 80 90 100 110 120 130 140 150 lt1085mk lt1085ct lt1085ck * as limited by maximum junction temperature time (s) 0 output voltage deviation (v) load current (a) 0.6 0.4 0.2 0 C0.2 C0.4 8 6 4 2 0 50 1083/4/5 adj g22 100 c adj = 0 c adj = 1f c in = 1f c out = 10f tantalum v out =10v v in =13v preload=100ma time (s) 0 output voltage deviation (v) load current (a) 0.6 0.4 0.2 0 C0.2 C0.4 C0.6 6 4 2 0 50 1083/4/5 adj g23 100 c adj = 0 c adj = 1f c in = 1f c out = 10f tantalum v out =10v v in =13v preload=100ma time (s) 0 output voltage deviation (mv) input deviation (v) 60 40 20 0 C20 C40 C60 14 13 12 100 1083/4/5 adj g26 200 c adj = 0 c adj = 1f v out = 10v i in = 0.2a c in = 1f tantalum c out = 10f tantalum time ( s) 0 output voltage deviation (mv) input deviation (v) 60 40 20 0 C20 C40 C60 14 13 12 100 1083/4/5 adj g27 200 c adj = 0 c adj = 1 f v out = 10v i in = 0.2a c in = 1 f tantalum c out = 10 f tantalum time (s) 0 output voltage deviation (mv) input deviation (v) 150 100 50 0 C50 C100 C150 14 13 12 100 1083/4/5 adj g25 200 c adj = 0 c adj = 1f v out = 10v i in = 0.2a c in = 1f tantalum c out = 10f tantalum lt1085 ripple rejection lt1085 ripple rejection vs current lt1085 maximum power dissipation* lt1083 load transient response lt1084 load transient response lt1085 load transient response lt1083 line transient response lt1084 line transient response lt1085 line transient response
lt1083/lt1084/lt1085 9 108345fg block diagram applications information C + thermal limit v adj v out 1083/4/5 adj bd v in the lt1083 family of 3-terminal adjustable regulators is easy to use and has all the protection features that are expected in high performance voltage regulators. they are short-circuit protected, and have safe area protection as well as thermal shutdown to turn off the regulator should the junction temperature exceed about 165c. these regulators are pin compatible with older 3-terminal adjustable devices, offer lower dropout voltage and more precise reference tolerance. further, the reference stability with temperature is improved over older types of regula- tors. the only circuit difference between using the lt1083 family and older regulators is that this new family requires an output capacitor for stability. stability the circuit design used in the lt1083 family requires the use of an output capacitor as part of the device frequency compensation. for all operating conditions, the addition of a 150f aluminium electrolytic or a 22f solid tantalum on the output will ensure stability. normally, capacitors much smaller than this can be used with the lt1083. many different types of capacitors with widely varying charac- teristics are available. these capacitors differ in capacitor tolerance (sometimes ranging up to 100%), equivalent series resistance, and capacitance temperature coef? cient. the 150f or 22f values given will ensure stability. when the adjustment terminal is bypassed to improve the ripple rejection, the requirement for an output capacitor increases. the value of 22f tantalum or 150f aluminum covers all cases of bypassing the adjustment terminal. without bypassing the adjustment terminal, smaller capacitors can be used with equally good results and the table below shows approximately what size capacitors are needed to ensure stability. recommended capacitor values input output adjustment 10f 10f 10f tantalum, 50f aluminum 22f tantalum, 150f aluminum none 20f
lt1083/lt1084/lt1085 10 108345fg applications information pin instantaneously shorted to ground, can damage occur. a crowbar circuit at the input of the lt1083 can generate those kinds of currents, and a diode from output to input is then recommended. normal power supply cycling or even plugging and unplugging in the system will not generate current large enough to do any damage. the adjustment pin can be driven on a transient basis 25v, with respect to the output without any device deg- radation. of course, as with any ic regulator, exceeding the maximum input to output voltage differential causes the internal transistors to break down and none of the protection circuitry is functional. normally, capacitor values on the order of 100f are used in the output of many regulators to ensure good transient response with heavy load current changes. output capaci- tance can be increased without limit and larger values of output capacitor further improve stability and transient response of the lt1083 regulators. another possible stability problem that can occur in mono- lithic ic regulators is current limit oscillations. these can occur because, in current limit, the safe area protection exhibits a negative impedance. the safe area protection decreases the current limit as the input-to-output volt- age increases. that is the equivalent of having a negative resistance since increasing voltage causes current to decrease. negative resistance during current limit is not unique to the lt1083 series and has been present on all power ic regulators. the value of the negative resistance is a function of how fast the current limit is folded back as input-to-output voltage increases. this negative resistance can react with capacitors or inductors on the input to cause oscillation during current limiting. depending on the value of series resistance, the overall circuitry may end up un- stable. since this is a system problem, it is not necessarily easy to solve; however, it does not cause any problems with the ic regulator and can usually be ignored. protection diodes in normal operation, the lt1083 family does not need any protection diodes. older adjustable regulators re- quired protection diodes between the adjustment pin and the output and from the output to the input to prevent overstressing the die. the internal current paths on the lt1083 adjustment pin are limited by internal resistors. therefore, even with capacitors on the adjustment pin, no protection diode is needed to ensure device safety under short-circuit conditions. diodes between input and output are usually not needed. the internal diode between the input and the output pins of the lt1083 family can handle microsecond surge cur- rents of 50a to 100a. even with large output capacitances, it is very dif? cult to get those values of surge currents in normal operations. only with a high value of output capacitors, such as 1000f to 5000f and with the input r1 r2 in out adj v out lt1083 d1 1n4002 (optional) v in 1083/4/5 adj f00 c out 150f + c adj 10f + overload recovery like any of the ic power regulators, the lt1083 has safe area protection. the safe area protection decreases the current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage. the lt1083 protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown. when power is ? rst turned on, as the input voltage rises, the output follows the input, allowing the regulator to start up into very heavy loads. during the start-up, as the input voltage is rising, the input-to-output voltage differential remains small, allowing the regulator to supply large output currents. with high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. older regulators, such as the 7800 series, also exhibited this phenomenon, so it is not unique to the lt1083.
lt1083/lt1084/lt1085 11 108345fg applications information the problem occurs with a heavy output load when the input voltage is high and the output voltage is low, such as immediately after removal of a short. the load line for such a load may intersect the output current curve at two points. if this happens, there are two stable output operat- ing points for the regulator. with this double intersection, the power supply may need to be cycled down to zero and brought up again to make the output recover. ripple rejection the typical curves for ripple rejection re? ect values for a bypassed adjustment pin. this curve will be true for all values of output voltage. for proper bypassing and ripple rejection approaching the values shown, the impedance of the adjust pin capacitor at the ripple frequency should be less than the value of r1, (normally 100 to 120). the size of the required adjust pin capacitor is a function of the input ripple frequency. at 120hz the adjust pin capacitor should be 25f if r1 = 100. at 10khz only 0.22f is needed. for circuits without an adjust pin bypass capacitor, the ripple rejection will be a function of output voltage. the output ripple will increase directly as a ratio of the output voltage to the reference voltage (v out /v ref ). for example, with the output voltage equal to 5v and no adjust pin capacitor, the output ripple will be higher by the ratio of 5v/1.25v or four times larger. ripple rejection will be degraded by 12db from the value shown on the typical curve. output voltage the lt1083 develops a 1.25v reference voltage between the output and the adjust terminal (see figure 1). by placing a resistor r1 between these two terminals, a constant current is caused to ? ow through r1 and down through r2 to set the overall output voltage. normally this current is the speci? ed minimum load current of 10ma. because i adj is very small and constant when compared with the current through r1, it represents a small error and can usually be ignored. load regulation because the lt1083 is a 3-terminal device, it is not pos- sible to provide true remote load sensing. load regulation will be limited by the resistance of the wire connecting the regulator to the load. the data sheet speci? cation for load regulation is measured at the bottom of the package. negative side sensing is a true kelvin connection, with the bottom of the output divider returned to the negative side of the load. although it may not be immediately obvious, best load regulation is obtained when the top of the resis- tor divider r1 is connected directly to the case not to the load. this is illustrated in figure 2. if r1 were connected to the load, the effective resistance between the regulator and the load would be: r rr r r parasitic line pp ?, 21 1 + ? ? ? ? ? ? = resistan nce figure 1. basic adjustable regulator r1 r2 in out i adj 50a adj v out lt1083 v in 1083/4/5 adj f01 v ref v out =v ref 1 + + i adj r2 r2 r1 ( ) figure 2. connections for best load regulation lt1083 out in v in adj r p parasitic line resistance r1* *connect r1 to case connect r2 to load 1083/4/5 adj f02 r l r2*
lt1083/lt1084/lt1085 12 108345fg applications information connected as shown, r p is not multiplied by the divider ratio. r p is about 0.004 per foot using 16-gauge wire. this translates to 4mv/ft at 1a load current, so it is im- portant to keep the positive lead between regulator and load as short as possible and use large wire or pc board traces. thermal considerations the lt1083 series of regulators have internal power and thermal limiting circuitry designed to protect the device under overload conditions. for continuous normal load conditions however, maximum junction temperature rat- ings must not be exceeded. it is important to give careful consideration to all sources of thermal resistance from junction to ambient. this includes junction-to-case, case- to-heat sink interface, and heat sink resistance itself. new thermal resistance speci? cations have been developed to more accurately re? ect device temperature and ensure safe operating temperatures. the data section for these new regulators provides a separate thermal resistance and maximum junction temperature for both the control sec- tion and the power transistor . previous regulators, with a single junction-to-case thermal resistance speci? cation, used an average of the two values provided here and there- fore could allow excessive junction temperatures under certain conditions of ambient temperature and heat sink resistance. to avoid this possibility, calculations should be made for both sections to ensure that both thermal limits are met. junction-to-case thermal resistance is speci? ed from the ic junction to the bottom of the case directly below the die. this is the lowest resistance path for heat ? ow. proper mounting is required to ensure the best possible thermal ? ow from this area of the package to the heat sink. thermal compound at the case-to-heat sink interface is strongly recommended. if the case of the device must be electri- cally isolated, a thermally conductive spacer can be used, as long as its added contribution to thermal resistance is considered. note that the case of all devices in this series is electrically connected to the output. for example, using an lt1083ck (to-3, commercial) and assuming: v in (max continuous) = 9v, v out = 5v, i out = 6a, t a = 75c, heat sink = 1c/w, case-to-heat sink = 0.2c/w for k package with thermal compound. power dissipation under these conditions is equal to: p d = (v in C v out )(i out ) = 24w junction temperature will be equal to: t j = t a + p d ( heat sink + case-to-heat sink + jc ) for the control section: t j = 75c + 24w (1c/w + 0.2c/w + 0.6c/w) = 118c 118c < 125c = t jmax (control section commercial range) for the power transistor: t j = 75c + 24w (1c/w + 0.2c/w + 1.6c/w) = 142c 142c < 150c = t jmax (power transistor commercial range) in both cases the junction temperature is below the maxi- mum rating for the respective sections, ensuring reliable operation.
lt1083/lt1084/lt1085 13 108345fg typical application 7.5a variable regulator 15v 15v 15v 110vac t1 triad f-269u C + C + + + C + out in lt1083 out in adj c30b c30b 3 20 20 1 2 l 1mh t2 1n4003 1n4148 1n4003 1n914 c1 50,000f 100f lt1004-1.2 1n4003 1f 0.1f 1f 100pf 560 16k* 16k* lt1004-1.2 11k* 11k* 0v to 35v oa to 7.5a 10k 82k 15k 2 2 2 3 3 3 8 8 C15v C15v C15v 15v 4 4 4 7 7 1 1 200k 750* 2k output adjust 2.7k C15v 1.5k 15k 10k 2n3904 nc 8 6 7 1 lt1011 lt1011 lm301a * 1% film resistor l: dale to-5 type t2: stancor 11z-2003 general purpose regulator with scr preregulator to lower power dissipation. about 1.7v differential is maintained across the lt1083 independent of output voltage and load current lt1083/4/5 adj ta05
lt1083/lt1084/lt1085 14 108345fg typical application lt1083 out in v in adj lt1083 0.015 out 2 feet #18 wire* in adj r1 120 r2 *the #18 wire acts as ballast resistance insuring current sharing between both devices lt1083/4/5 adj ta03 v out = 1.25v 1 + i out = 0a to 15a r2 r1 () paralleling regulators remote sensing r1 121 1% in out adj r2 365 1% 10f v out 5v lt1083 v in 1083/4/5 adj ta04 + c1 25f* 150f + + *c1 improves ripple rejection. x c should be < r1 at ripple frequency improving ripple rejection C + lt1083 out in v in v in return adj r p (max drop 300mv) 121 365 25 10f 5f 100f 1083/4/5 adj ta07 r l v out 5v return 25 2 6 7 1 8 100pf 3 4 + 1k lm301a + +
lt1083/lt1084/lt1085 15 108345fg typical application high ef? ciency regulator with switching preregulator C + v in 28v 28v 470 240 2k 28v 4n28 1n914 1n914 lt1011 10k 10k 10k 1k 1m mr1122 1mh 10,000f v out lt1083 out in adj 1083/4/5 adj ta06 + 1.2v to 15v adjustable regulator 5v regulator with shutdown* in v in out ttl adj 1k 1k 10f 100f v out 5v lt1083 2n3904 1083/4/5 adj ta09 + 121 1% 365 1% *output shuts down to 1.3v + in out adj r2 1k c1* 10f v out ? v in lt1083 1083/4/5 adj ta08 + c2 100f + r1 90.9 *needed if device is far from filter capacitors ? v out = 1.25v 1 + r2 r1 ( )
lt1083/lt1084/lt1085 16 108345fg package description obsolete package .050 (1.270) .143 +.012 C.020 () 3.632 +0.305 C0.508 .100 (2.54) bsc .013 C .023 (0.330 C 0.584) .095 C .115 (2.413 C 2.921) .004 +.008 C.004 () 0.102 +0.203 C0.102 .050 .012 (1.270 0.305) .059 (1.499) .045 C .055 (1.143 C 1.397) .165 C .180 (4.191 C 4.572) .330 C .370 (8.382 C 9.398) .060 (1.524) typ .390 C .415 (9.906 C 10.541) 15 .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 m (dd3) 0204 .420 .350 .565 .090 .070 .100 .420 .276 .325 .205 .080 .565 .090 .070 .100 recommended solder pad layout for thicker solder paste applications recommended solder pad layout note: 1. dimensions in inch/(millimeter) 2. drawing not to scale .320 k2 (to-3) 080 .038 C .043 (0.965 C 1.09) .060 C .135 (1.524 C 3.429) .320 C .350 (8.13 C 8.89) .420 C .480 (10.67 C 12.19) .760 C .775 (19.30 C 19.69) .490 C .510 (12.45 C 12.95) r .167 C .177 (4.24 C 4.49) r .151 C .161 (3.86 C 4.09) dia, 2plcs 1.177 C 1.197 (29.90 C 30.40) .655 C .675 (16.64 C 17.15) .067 C .077 (1.70 C 1.96) .210 C .220 (5.33 C 5.59) .425 C .435 (10.80 C 11.05) k package 2-lead to-3 metal can (reference ltc dwg # 05-08-1310) m package 3-lead plastic dd pak (reference ltc dwg # 05-08-1460)
lt1083/lt1084/lt1085 17 108345fg 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 .170 (4.32) max .325 (8.255) .580 (14.732) .560 (14.224) .170 C .2oo (4.32 C 5.08) mounting hole .115 C .145 (2.92 C 3.68) dia .580 C .6oo (14.73 C 15.24) .830 C .870 (21.08 C 22.10) .780 C .800 (19.81 C 20.32) .620 C .64o (15.75 C 16.26) .215 (5.46) bsc .113 C .123 (2.87 C 3.12) .042 C .052 (1.07 C 1.32) .074 C .084 (1.88 C 2.13) .187 C .207 (4.75 C 5.26) .060 C .080 (1.52 C 2.03) 18 C 22 3 C 7 .087 C .102 (2.21 C 2.59) .020 C .040 (0.51 C 1.02) ejector pin marks .105 C .125 (2.67 C 3.18) dia p3 0801 .098 (2.489) .124 (3.149) .700 (17.780) .275 (6.985) bottom view of to-3p hatched area is solder plated copper heat sink .100 (2.540) bsc .028 C .038 (0.711 C 0.965) t3 (to-220) 0801 .045 C .055 (1.143 C 1.397) .165 C .180 (4.191 C 4.572) .095 C .115 (2.413 C 2.921) .013 C .023 (0.330 C 0.584) .520 C .570 (13.208 C 14.478) .980 C 1.070 (24.892 C 27.178) .218 C .252 (5.537 C 6.401) .050 (1.270) typ .147 C .155 (3.734 C 3.937) dia .390 C .415 (9.906 C 10.541) .330 C .370 (8.382 C 9.398) .460 C .500 (11.684 C 12.700) .570 C .620 (14.478 C 15.748) .230 C .270 (5.842 C 6.858) p package 3-lead plastic to-3p (similar to to-247) (reference ltc dwg # 05-08-1450) t package 3-lead plastic to-220 (reference ltc dwg # 05-08-1420)
lt1083/lt1084/lt1085 18 108345fg linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 1994 lt 0409 rev g ? printed in usa related parts typical applications part number description comments lt1086 1.5a low dropout regulator fixed 2.85v, 3.3v, 3.6v, 5v and 12v output lt1117 800ma low dropout regulator fixed 2.85v, 3.3v, 5v or adjustable output lt1584/lt1585/lt1587 7a/4.6a/3a fast response low dropout regulators for high performance microprocessors lt1580 7a very low dropout linear regulator 0.54v dropout at 7a, fixed 2.5v out and adjustable lt1581 10a very low dropout linear regulator 0.43v dropout at 10a, fixed 2.5v out and adjustable lt1430 high power step-down switching regulator 5v to 3.3v at 10a, >90% ef? ciency lt1575 ultrafast ? transient response ldo controller external mosfet pass element lt1573 ultrafast transient response ldo controller external pnp pass element ultrafast is a trademark of linear technology corporation. automatic light control protected high current lamp driver in v in out adj 10 f 100 f lt1083 1083/4/5 adj ta10 1.2k + out ttl or cmos in adj 15v 12v 5a lt1083 1083/4/5 adj ta11 10k

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