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lt1761 series 1 1761sfe typical application description 100ma, low noise, ldo micropower regulators in tsot-23 the lt ? 1761 series are micropower, low noise, low dropout regulators. with an external 0.01f bypass capacitor, output noise drops to 20v rms over a 10hz to 100khz bandwidth. designed for use in battery-powered systems, the low 20a quiescent current makes them an ideal choice. in shutdown, quiescent current drops to less than 0.1a. the devices are capable of operating over an input voltage from 1.8v to 20v, and can supply 100ma of output current with a dropout voltage of 300mv. quiescent current is well controlled, not rising in dropout as it does with many other regulators. the lt1761 regulators are stable with output capacitors as low as 1f. small ceramic capacitors can be used without the series resistance required by other regulators. internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. the device is available in ? xed output voltages of 1.2v, 1.5v, 1.8v, 2v, 2.5v, 2.8v, 3v, 3.3v and 5v, and as an adjustable device with a 1.22v reference voltage. the lt1761 regulators are available in the 5-lead tsot-23 package. 5v low noise regulator features applications n low noise: 20v rms (10hz to 100khz) n low quiescent current: 20a n wide input voltage range: 1.8v to 20v n output current: 100ma n very low shutdown current: <0.1a n low dropout voltage: 300mv at 100ma n fixed output voltages: 1.2v, 1.5v, 1.8v, 2v, 2.5v, 2.8v, 3v, 3.3v, 5v n adjustable output from 1.22v to 20v n stable with 1f output capacitor n stable with aluminum, tantalum or ceramic capacitors n reverse-battery protected n no reverse current n no protection diodes needed n overcurrent and overtemperature protected n available in tiny 5-lead tsot-23 package n cellular phones n pagers n battery-powered systems n frequency synthesizers n wireless modems 10hz to 100khz output noise in shdn 0.01f 10f 1761 ta01 out v in 5.4v to 20v byp gnd lt1761-5 5v at100ma 20v rms noise 1f + v out 100v/div 20v rms 1761 ta01b l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners.
lt1761 series 2 1761sfe in pin voltage .........................................................20v out pin voltage ......................................................20v input to output differential voltage .........................20v adj pin voltage ...................................................... 7v byp pin voltage .....................................................0.6v shdn pin voltage ................................................. 20v (note 1) absolute maximum ratings 5 out 4 adj in 1 gnd 2 top view s5 package 5-lead plastic tsot-23 byp 3 t jmax = 150c, ja = 250c/w see applications information section 5 out 4 adj in 1 gnd 2 top view s5 package 5-lead plastic tsot-23 shdn 3 t jmax = 150c, ja = 250c/w see applications information section 5 out 4 byp in 1 gnd 2 top view s5 package 5-lead plastic tsot-23 shdn 3 t jmax = 150c, ja = 250c/w see applications information section pin configuration output short-circuit duration ........................ inde? nite operating junction temperature range e, i grade (note 2) ............................. C40c to 125c mp grade (note 2) ............................. C55c to 125c storage temperature range ................... C65c to 150c lead temperature (soldering, 10 sec) .................. 300c lt1761-byp lt1761-sd lt1761-x
lt1761 series 3 1761sfe order information lead free finish tape and reel part marking * package description temperature range lt1761es5-byp#pbf lt1761es5-byp#trpbf ltgc 5-lead plastic tsot-23 C40c to 125c lt1761is5-byp#pbf lt1761is5-byp#trpbf ltgc 5-lead plastic tsot-23 C40c to 125c lt1761es5-sd#pbf lt1761es5-sd#trpbf ltgh 5-lead plastic tsot-23 C40c to 125c lt1761is5-sd#pbf lt1761is5-sd#trpbf ltgh 5-lead plastic tsot-23 C40c to 125c lt1761es5-1.2#pbf lt1761es5-1.2#trpbf ltcds 5-lead plastic tsot-23 C40c to 125c lt1761is5-1.2#pbf lt1761is5-1.2#trpbf ltcds 5-lead plastic tsot-23 C40c to 125c lt1761es5-1.5#pbf lt1761es5-1.5#trpbf ltmt 5-lead plastic tsot-23 C40c to 125c lt1761is5-1.5#pbf lt1761is5-1.5#trpbf ltmt 5-lead plastic tsot-23 C40c to 125c lt1761es5-1.8#pbf lt1761es5-1.8#trpbf ltjm 5-lead plastic tsot-23 C40c to 125c lt1761is5-1.8#pbf lt1761is5-1.8#trpbf ltjm 5-lead plastic tsot-23 C40c to 125c lt1761mps5-1.8#pbf lt1761mps5-1.8#trpbf ltdch 5-lead plastic tsot-23 C55c to 125c lt1761es5-2#pbf lt1761es5-2#trpbf ltje 5-lead plastic tsot-23 C40c to 125c lt1761is5-2#pbf lt1761is5-2#trpbf ltje 5-lead plastic tsot-23 C40c to 125c lt1761es5-2.5#pbf lt1761es5-2.5#trpbf ltgd 5-lead plastic tsot-23 C40c to 125c lt1761is5-2.5#pbf lt1761is5-2.5#trpbf ltgd 5-lead plastic tsot-23 C40c to 125c lt1761es5-2.8#pbf lt1761es5-2.8#trpbf ltlb 5-lead plastic tsot-23 C40c to 125c lt1761is5-2.8#pbf lt1761is5-2.8#trpbf ltlb 5-lead plastic tsot-23 C40c to 125c lt1761es5-3#pbf lt1761es5-3#trpbf ltge 5-lead plastic tsot-23 C40c to 125c lt1761is5-3#pbf lt1761is5-3#trpbf ltge 5-lead plastic tsot-23 C40c to 125c lt1761es5-3.3#pbf lt1761es5-3.3#trpbf ltgf 5-lead plastic tsot-23 C40c to 125c lt1761is5-3.3#pbf lt1761is5-3.3#trpbf ltgf 5-lead plastic tsot-23 C40c to 125c lt1761es5-5#pbf lt1761es5-5#trpbf ltgg 5-lead plastic tsot-23 C40c to 125c lt1761is5-5#pbf lt1761is5-5#trpbf ltgg 5-lead plastic tsot-23 C40c to 125c lead based finish tape and reel part marking * package description temperature range lt1761es5-byp lt1761es5-byp#tr ltgc 5-lead plastic tsot-23 C40c to 125c lt1761is5-byp lt1761is5-byp#tr ltgc 5-lead plastic tsot-23 C40c to 125c lt1761es5-sd lt1761es5-sd#tr ltgh 5-lead plastic tsot-23 C40c to 125c lt1761is5-sd lt1761is5-sd#tr ltgh 5-lead plastic tsot-23 C40c to 125c lt1761es5-1.2 lt1761es5-1.2#tr ltcds 5-lead plastic tsot-23 C40c to 125c lt1761is5-1.2 lt1761is5-1.2#tr ltcds 5-lead plastic tsot-23 C40c to 125c lt1761es5-1.5 lt1761es5-1.5#tr ltmt 5-lead plastic tsot-23 C40c to 125c lt1761is5-1.5 lt1761is5-1.5#tr ltmt 5-lead plastic tsot-23 C40c to 125c lt1761es5-1.8 lt1761es5-1.8#tr ltjm 5-lead plastic tsot-23 C40c to 125c lt1761is5-1.8 lt1761is5-1.8#tr ltjm 5-lead plastic tsot-23 C40c to 125c lt1761mps5-1.8 lt1761mps5-1.8#tr ltdch 5-lead plastic tsot-23 C55c to 125c lt1761es5-2 lt1761es5-2#tr ltje 5-lead plastic tsot-23 C40c to 125c lt1761is5-2 lt1761is5-2#tr ltje 5-lead plastic tsot-23 C40c to 125c lt1761es5-2.5 lt1761es5-2.5#tr ltgd 5-lead plastic tsot-23 C40c to 125c lt1761is5-2.5 lt1761is5-2.5#tr ltgd 5-lead plastic tsot-23 C40c to 125c lt1761es5-2.8 lt1761es5-2.8#tr ltlb 5-lead plastic tsot-23 C40c to 125c lt1761is5-2.8 lt1761is5-2.8#tr ltlb 5-lead plastic tsot-23 C40c to 125c lt1761es5-3 lt1761es5-3#tr ltge 5-lead plastic tsot-23 C40c to 125c lt1761is5-3 lt1761is5-3#tr ltge 5-lead plastic tsot-23 C40c to 125c lt1761es5-3.3 lt1761es5-3.3#tr ltgf 5-lead plastic tsot-23 C40c to 125c lt1761is5-3.3 lt1761is5-3.3#tr ltgf 5-lead plastic tsot-23 C40c to 125c lt1761es5-5 lt1761es5-5#tr ltgg 5-lead plastic tsot-23 C40c to 125c lt1761is5-5 lt1761is5-5#tr ltgg 5-lead plastic tsot-23 C40c to 125c 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/
lt1761 series 4 1761sfe electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. (note 2) parameter conditions min typ max units minimum input voltage (notes 3, 11) i load = 100ma l 1.8 2.3 v regulated output voltage (note 4) lt1761-1.2 v in = 2v, i load = 1ma 2.3v < v in < 20v, 1ma < i load < 50ma 2.3v < v in < 20v, 1ma < i load < 100ma l l 1.185 1.170 1.150 1.2 1.2 1.2 1.215 1.230 1.240 v v v lt1761-1.5 v in = 2v, i load = 1ma 2.5v < v in < 20v, 1ma < i load < 50ma 2.5v < v in < 20v, 1ma < i load < 100ma l l 1.478 1.457 1.436 1.5 1.5 1.5 1.522 1.538 1.555 v v v lt1761-1.8 v in = 2.3v, i load = 1ma 2.8v < v in < 20v, 1ma < i load < 50ma 2.8v < v in < 20v, 1ma < i load < 100ma l l 1.775 1.750 1.725 1.8 1.8 1.8 1.825 1.845 1.860 v v v lt1761-2 v in = 2.5v, i load = 1ma 3v < v in < 20v, 1ma < i load < 50ma 3v < v in < 20v, 1ma < i load < 100ma l l 1.970 1.945 1.920 2 2 2 2.030 2.045 2.060 v v v lt1761-2.5 v in = 3v, i load = 1ma 3.5v < v in < 20v, 1ma < i load < 50ma 3.5v < v in < 20v, 1ma < i load < 100ma l l 2.465 2.435 2.415 2.5 2.5 2.5 2.535 2.565 2.575 v v v lt1761-2.8 v in = 3.3v, i load = 1ma 3.8v < v in < 20v, 1ma < i load < 50ma 3.8v < v in < 20v, 1ma < i load < 100ma l l 2.762 2.732 2.706 2.8 2.8 2.8 2.838 2.868 2.884 v v v lt1761-3 v in = 3.5v, i load = 1ma 4v < v in < 20v, 1ma < i load < 50ma 4v < v in < 20v, 1ma < i load < 100ma l l 2.960 2.930 2.900 3 3 3 3.040 3.070 3.090 v v v lt1761-3.3 v in = 3.8v, i load = 1ma 4.3v < v in < 20v, 1ma < i load < 50ma 4.3v < v in < 20v, 1ma < i load < 100ma l l 3.250 3.230 3.190 3.3 3.3 3.3 3.350 3.370 3.400 v v v lt1761-5 v in = 5.5v, i load = 1ma 6v < v in < 20v, 1ma < i load < 50ma 6v < v in < 20v, 1ma < i load < 100ma l l 4.935 4.900 4.850 5 5 5 5.065 5.100 5.120 v v v adj pin voltage (note 3, 4) lt1761 v in = 2v, i load = 1ma 2.3v < v in < 20v, 1ma < i load < 50ma 2.3v < v in < 20v, 1ma < i load < 100ma l l 1.205 1.190 1.170 1.220 1.220 1.220 1.235 1.250 1.260 v v v line regulation lt1761-1.2 lt1761-1.5 lt1761-1.8 lt1761-2 lt1761-2.5 lt1761-2.8 lt1761-3 lt1761-3.3 lt1761-5 lt1761 (note 3) v in = 2v to 20v, i load = 1ma v in = 2v to 20v, i load = 1ma v in = 2.3v to 20v, i load = 1ma v in = 2.5v to 20v, i load = 1ma v in = 3v to 20v, i load = 1ma v in = 3.3v to 20v, i load = 1ma v in = 3.5v to 20v, i load = 1ma v in = 3.8v to 20v, i load = 1ma v in = 5.5v to 20v, i load = 1ma v in = 2v to 20v, i load = 1ma l l l l l l l l l l 1 1 1 1 1 1 1 1 1 1 10 10 10 10 10 10 10 10 10 10 mv mv mv mv mv mv mv mv mv mv
lt1761 series 5 1761sfe electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. (note 2) parameter conditions min typ max units load regulation lt1761-1.2 v in = 2.3v, i load = 1ma to 50ma v in = 2.3v, i load = 1ma to 50ma v in = 2.3v, i load = 1ma to 100ma v in = 2.3v, i load = 1ma to 100ma l l 1 1 6 12 12 50 mv mv mv mv lt1761-1.5 v in = 2.5v, i load = 1ma to 50ma v in = 2.5v, i load = 1ma to 50ma v in = 2.5v, i load = 1ma to 100ma v in = 2.5v, i load = 1ma to 100ma l l 10 14 20 35 30 55 mv mv mv mv lt1761-1.8 v in = 2.8v, i load = 1ma to 50ma v in = 2.8v, i load = 1ma to 50ma v in = 2.8v, i load = 1ma to 100ma v in = 2.8v, i load = 1ma to 100ma l l 10 15 20 35 30 60 mv mv mv mv lt1761-2 v in = 3v, i load = 1ma to 50ma v in = 3v, i load = 1ma to 50ma v in = 3v, i load = 1ma to 100ma v in = 3v, i load = 1ma to 100ma l l 10 15 20 35 35 65 mv mv mv mv lt1761-2.5 v in = 3.5v, i load = 1ma to 50ma v in = 3.5v, i load = 1ma to 50ma v in = 3.5v, i load = 1ma to 100ma v in = 3.5v, i load = 1ma to 100ma l l 10 20 20 35 40 80 mv mv mv mv lt1761-2.8 v in = 3.8v, i load = 1ma to 50ma v in = 3.8v, i load = 1ma to 50ma v in = 3.8v, i load = 1ma to 100ma v in = 3.8v, i load = 1ma to 100ma l l 10 20 20 38 40 86 mv mv mv mv lt1761-3 v in = 4v, i load = 1ma to 50ma v in = 4v, i load = 1ma to 50ma v in = 4v, i load = 1ma to 100ma v in = 4v, i load = 1ma to 100ma l l 10 20 20 40 40 90 mv mv mv mv lt1761-3.3 v in = 4.3v, i load = 1ma to 50ma v in = 4.3v, i load = 1ma to 50ma v in = 4.3v, i load = 1ma to 100ma v in = 4.3v, i load = 1ma to 100ma l l 10 20 20 40 40 100 mv mv mv mv lt1761-5 v in = 6v, i load = 1ma to 50ma v in = 6v, i load = 1ma to 50ma v in = 6v, i load = 1ma to 100ma v in = 6v, i load = 1ma to 100ma l l 15 25 30 60 65 150 mv mv mv mv lt1761 (note 3) v in = 2.3v, i load = 1ma to 50ma v in = 2.3v, i load = 1ma to 50ma v in = 2.3v, i load = 1ma to 100ma v in = 2.3v, i load = 1ma to 100ma l l 1 1 6 12 12 50 mv mv mv mv dropout voltage v in = v out(nominal) (notes 5, 6, 11) i load = 1ma i load = 1ma l 0.10 0.15 0.19 v v i load = 10ma i load = 10ma l 0.17 0.22 0.29 v v i load = 50ma i load = 50ma l 0.24 0.28 0.38 v v i load = 100ma i load = 100ma 0.30 0.35 0.45 v v
lt1761 series 6 1761sfe electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. (note 2) parameter conditions min typ max units gnd pin current v in = v out(nominal) (notes 5, 7) i load = 0ma i load = 1ma i load = 10ma i load = 50ma i load = 100ma l l l l l 20 55 230 1 2.2 45 100 400 2 4 a a a ma ma output voltage noise c out = 10f, c byp = 0.01f, i load = 100ma, bw = 10hz to 100khz 20 v rms adj pin bias current (notes 3, 8) 30 100 na shutdown threshold v out = off to on v out = on to off l l 0.25 0.8 0.65 2v v shdn pin current (note 9) v shdn = 0v v shdn = 20v l l 0 1 0.5 3 a a quiescent current in shutdown v in = 6v, v shdn = 0v 0.01 0.1 a ripple rejection (note 3) v in C v out = 1.5v (avg), v ripple = 0.5v p-p , f ripple = 120hz, i load = 50ma 55 65 db current limit v in = 7v, v out = 0v v in = v out(nominal) + 1v or 2.3v (note 12), v out = C5% l 110 200 ma ma input reverse leakage current v in = C20v, v out = 0v l 1ma reverse output current (note 10) lt1761-1.2 lt1761-1.5 lt1761-1.8 lt1761-2 lt1761-2.5 lt1761-2.8 lt1761-3 lt1761-3.3 lt1761-5 lt1761 (note 3) v out = 1.2v, v in < 1.2v v out = 1.5v, v in < 1.5v v out = 1.8v, v in < 1.8v v out = 2v, v in < 2v v out = 2.5v, v in < 2.5v v out = 2.8v, v in < 2.8v v out = 3v, v in < 3v v out = 3.3v, v in < 3.3v v out = 5v, v in < 5v v out = 1.22v, v in < 1.22v 10 10 10 10 10 10 10 10 10 5 20 20 20 20 20 20 20 20 20 10 a a a a a a a a a a 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: the lt1761 regulators are tested and speci? ed under pulse load conditions such that t j t a . the lt1761e is 100% production tested at t a = 25c. performance at C40c and 125c is assured by design, characterization and correlation with statistical process controls. the lt1761i is guaranteed over the full C40c to 125c operating junction temperature range. the lt1761mp is 100% tested and guaranteed over the C55c to 125c operating junction temperature range. note 3: the lt1761 (adjustable versions) are tested and speci? ed for these conditions with the adj pin connected to the out pin. note 4: operating conditions are limited by maximum junction temperature. the regulated output voltage speci? cation will not apply for all possible combinations of input voltage and output current. when operating at maximum input voltage, the output current range must be limited. when operating at maximum output current, the input voltage range must be limited. note 5: to satisfy requirements for minimum input voltage, the lt1761 (adjustable version) is tested and speci? ed for these conditions with an external resistor divider (two 250k resistors) for an output voltage of 2.44v. the external resistor divider will add a 5a dc load on the output. note 6: dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a speci? ed output current. in dropout, the output voltage will be equal to: v in C v dropout . note 7: gnd pin current is tested with v in = v out(nominal) or v in = 2.3v (whichever is greater) and a current source load. this means the device is tested while operating in its dropout region or at the minimum input voltage speci? cation. this is the worst-case gnd pin current. the gnd pin current will decrease slightly at higher input voltages. note 8: adj pin bias current ? ows into the adj pin. note 9: shdn pin current ? ows into the shdn pin. note 10: reverse output current is tested with the in pin grounded and the out pin forced to the rated output voltage. this current ? ows into the out pin and out the gnd pin. note 11: for the lt1761, lt1761-1.2, lt1761-1.5, lt1761-1.8 and lt1761-2 dropout voltage will be limited by the minimum input voltage speci? cation under some output voltage/load conditions. see the curve of minimum input voltage in the typical performance characteristics. note 12: to satisfy requirements for minimum input voltage, current limit is tested at v in = v out(nominal) + 1v or v in = 2.3v, whichever is greater.
lt1761 series 7 1761sfe typical performance characteristics quiescent current lt1761-1.2 output voltage lt1761-1.5 output voltage lt1761-1.8 output voltage lt1761-2 output voltage lt1761-2.5 output voltage typical dropout voltage guaranteed dropout voltage dropout voltage output current (ma) 500 450 400 350 300 250 200 150 100 50 0 dropout voltage (mv) 1761 g00 0 102030 40 50 60 70 80 90 100 t j = 125c t j = 25c output current (ma) 500 450 400 350 300 250 200 150 100 50 0 dropout voltage (mv) 1761 g01 0 102030 40 50 60 70 80 90 100 t j 125c t j 25c = test points temperature (c) C50 dropout voltage (mv) 0 50 75 1761 g01.1 C25 25 100 125 i l = 100ma i l = 50ma i l = 10ma i l = 1ma 500 450 400 350 300 250 200 150 100 50 0 temperature (c) C50 quiescent current (a) 100 1761 g03 050 40 35 30 25 20 15 10 5 0 C25 25 75 125 v in = 6v r l = (250k for lt1761-byp, -sd) i l = 0 (5a for lt1761-byp, -sd) v shdn = v in v shdn = 0v temperature (c) C50 output voltage (v) 100 1761 g05 050 1.220 1.215 1.210 1.205 1.200 1.195 1.190 1.185 1.180 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g51 050 1.528 1.521 1.514 1.507 1.500 1.493 1.486 1.479 1.472 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g06 050 1.84 1.83 1.82 1.81 1.80 1.79 1.78 1.77 1.76 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g07 050 2.04 2.03 2.02 2.01 2.00 1.99 1.98 1.97 1.96 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g08 050 2.54 2.53 2.52 2.51 2.50 2.49 2.48 2.47 2.46 C25 25 75 125 i l = 1ma
lt1761 series 8 1761sfe typical performance characteristics lt1761-5 output voltage lt1761-byp , lt1761-sd adj pin voltage lt1761-1.2 quiescent current lt1761-1.5 quiescent current lt1761-1.8 quiescent current lt1761-2 quiescent current lt1761-2.8 output voltage lt1761-3 output voltage lt1761-3.3 output voltage temperature (c) C50 output voltage (v) 100 1761 g52 050 2.84 2.83 2.82 2.81 2.80 2.79 2.78 2.77 2.76 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g09 050 3.060 3.045 3.030 3.015 3.000 2.985 2.970 2.955 2.940 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g11 050 3.360 3.345 3.330 3.315 3.300 3.285 3.270 3.255 3.240 C25 25 75 125 i l = 1ma temperature (c) C50 output voltage (v) 100 1761 g12 050 5.08 5.06 5.04 5.02 5.00 4.98 4.96 4.94 4.92 C25 25 75 125 i l = 1ma temperature (c) C50 adj pin voltage (v) 100 1761 g10 050 1.240 1.235 1.230 1.225 1.220 1.215 1.210 1.205 1.200 C25 25 75 125 i l = 1ma input voltage (v) 0 quiescent current (a) 250 225 200 175 150 125 100 75 50 25 0 8 1761 g10b 2 13579 4 6 10 t j = 25c r l = v shdn = 0v v shdn = v in input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g53 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g18 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g19 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v
lt1761 series 9 1761sfe typical performance characteristics lt1761-3.3 quiescent current lt1761-5 quiescent current lt1761-byp , lt1761-sd quiescent current lt1761-1.2 gnd pin current lt1761-1.5 gnd pin current lt1761-1.8 gnd pin current lt1761-2.5 quiescent current lt1761-2.8 quiescent current lt1761-3 quiescent current input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g13 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g54 2 13579 4 6 10 t j = 25c r l = v shdn = 0v v shdn = v in input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g14 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g15 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v input voltage (v) 0 quiescent current (a) 200 175 150 125 100 75 50 25 0 8 1761 g16 2 13579 4 6 10 v shdn = v in t j = 25c r l = v shdn = 0v input voltage (v) 02 6 10 14 18 quiescent current (a) 30 25 20 15 10 5 0 4 8 12 16 1761 g17 20 t j = 25c r l = 250k i l = 5a v shdn = v in v shdn = 0v input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g17b 0123 4 5 67 8910 t j = 25c *for v out = 1.2v r l = 12 i l = 100ma* r l = 24 i l = 50ma* r l = 120 i l = 10ma* r l = 1.2k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g55 0123 4 5 67 8910 t j = 25c *for v out = 1.5v r l = 15 i l = 100ma* r l = 30 i l = 50ma* r l = 150 i l = 10ma* r l = 1.5k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g02 0123 4 5 67 8910 t j = 25c *for v out = 1.8v r l = 18 i l = 100ma* r l = 36 i l = 50ma* r l = 180 i l = 10ma* r l = 1.8k i l = 1ma*
lt1761 series 10 1761sfe typical performance characteristics lt1761-3 gnd pin current lt1761-3.3 gnd pin current lt1761-5 gnd pin current lt1761-byp , lt1761-sd gnd pin current gnd pin current vs i load shdn pin threshold (on to off) lt1761-2 gnd pin current lt1761-2.5 gnd pin current lt1761-2.8 gnd pin current input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g04 0123 4 5 67 8910 t j = 25c *for v out = 2v r l = 20 i l = 100ma* r l = 40 i l = 50ma* r l = 200 i l = 10ma* r l = 2k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g20 0123 4 5 67 8910 t j = 25c *for v out = 2.5v r l = 25 i l = 100ma r l = 50 i l = 50ma* r l = 250 i l = 10ma* r l = 2.5k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g56 0123 4 5 67 8910 t j = 25c *for v out = 2.8v r l = 28 i l = 100ma r l = 56 i l = 50ma* r l = 280 i l = 10ma* r l = 2.8k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g21 0123 4 5 67 8910 t j = 25c *for v out = 3v r l = 30 i l = 100ma* r l = 60 i l = 50ma* r l = 300 i l = 10ma* r l = 3k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g22 0123 4 5 67 8910 t j = 25c *for v out = 3.3v r l = 33 i l = 100ma* r l = 66 i l = 50ma* r l = 330 i l = 10ma* r l = 3.3k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g23 0123 4 5 67 8910 t j = 25c *for v out = 5v r l = 50 i l = 100ma r l = 100 i l = 50ma* r l = 500 i l = 10ma* r l = 5k i l = 1ma* input voltage (v) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g24 0123 4 5 67 8910 t j = 25c *for v out = 1.22v r l = 12.2 i l = 100ma* r l = 24.4 i l = 50ma* r l = 122 i l = 10ma* r l = 1.22k i l = 1ma* output current (ma) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 gnd pin current (ma) 1761 g25 0 102030 40 50 60 70 80 90 100 v in = v out(nominal) + 1v temperature (c) C50 shdn pin threshold (v) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 50 75 1761 g26 C25 25 100 125 i l = 1ma
lt1761 series 11 1761sfe typical performance characteristics adj pin bias current current limit current limit reverse output current reverse output current input ripple rejection shdn pin threshold (off to on) shdn pin input current shdn pin input current temperature (c) C50 shdn pin threshold (v) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 50 75 1761 g27 C25 25 100 125 i l = 100ma i l = 1ma shdn pin voltage (v) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 shdn pin input current (a) 1761 g28 0123 4 5 67 8910 temperature (c) C50 shdn pin input current (a) 0 50 75 1761 g29 C25 25 100 125 v shdn = 20v 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 temperature ( o c) C50 adj pin bias current (na) 100 90 80 70 60 50 40 30 20 10 0 0 50 75 1761 g30 C25 25 100 125 input voltage (v) 0 short-circuit current (ma) 2 4 5 1761 g31 1 3 6 7 350 300 250 200 150 100 50 0 v out = 0v t j = 25c temperature (c) C50 current limit (ma) 0 50 75 1761 g32 C25 25 100 125 350 300 250 200 150 100 50 0 v in = 7v v out = 0v output voltage (v) 100 90 80 70 60 50 40 30 20 10 0 reverse output current (a) 1761 g33 0123 4 5 67 8910 t j = 25c v in = 0v current flows into output pin v out = v adj (lt1761-byp, -sd) lt1761-byp lt1761-sd lt1761-2 lt1761-3.3 lt1761-5 lt1761-1.8 lt1761-1.5 lt1761-2.5 lt1761-2.8 lt1761-3 lt1761-1.2 temperature (c) C50 reverse output current (a) 25.0 22.5 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0 0 50 75 1761 g34 C25 25 100 125 v in = 0v v out = 1.22v (lt1761-byp, -sd) v out = 1.2v (lt1761-1.2) v out = 1.5v (lt1761-1.5) v out = 1.8v (lt1761-1.8) v out = 2v (lt1761-2) v out = 2.5v (lt1761-2.5) v out = 2.8v (lt1761-2.8) v out = 3v (lt1761-3) v out = 3.3v (lt1761-3.3) v out = 5v (lt1761-5) lt1761-byp,-sd lt1761-1.2,-1.5,-1.8,-2, -2.5,-2.8,-3,-3.3,-5 frequency (hz) ripple rejection (db) 80 70 60 50 40 30 20 10 0 10 1k 10k 1m 1761 g35 100 100k i l = 100ma v in = v out(nominal) + 1v + 50mv rms ripple c byp = 0 c out = 1f c out = 10f lt1761-byp lt1761-5
lt1761 series 12 1761sfe typical performance characteristics load regulation i l = 1ma to 50ma load regulation i l = 1ma to 100ma output noise spectral density output noise spectral density rms output noise vs bypass capacitor lt1761-5 input ripple rejection input ripple rejection lt1761-byp , lt1761-sd minimum input voltage frequency (hz) ripple rejection (db) 80 70 60 50 40 30 20 10 0 10 1k 10k 1m 1761 g36 100 100k i l = 100ma v in = v out(nominal) + 1v + 50mv rms ripple c out = 10f c byp = 0.01f c byp = 100pf c byp = 1000pf temperature (c) C50 ripple rejection (db) 100 1761 g37 050 80 70 60 50 40 30 20 10 0 C25 25 75 125 v in = v out (nominal) + 1v + 0.5v p-p ripple at f = 120hz i l = 50ma temperature (c) C50 minimum input voltage (v) 2.5 2.0 1.5 1.0 0.5 0 0 50 75 1761 g38 C25 25 100 125 i l = 100ma i l = 50ma temperature (c) C50 load regulation (mv) 100 1761 g39 050 0 C5 C10 C15 C20 C25 C30 C35 C40 C25 25 75 125 lt1761-byp, -sd, -1.2 lt1761-1.8 lt1761-1.5 lt1761-2 lt1761-2.5 lt1761-2.8 lt1761-3 lt1761-3.3 lt1761-5 temperature (c) C50 load regulation (mv) 100 1761 g40 050 0 C10 C20 C30 C40 C50 C60 C70 C80 C90 C100 C25 25 75 125 lt1761-3 lt1761-2 lt1761-2.5 lt1761-2.8 lt1761-5 lt1761-3.3 lt1761-byp, -sd, -1.2 lt1761-1.8 lt1761-1.5 frequency (hz) 10 1k 10k 100k 1761 g41 100 10 1 0.1 0.01 output noise spectral density (v/ hz ) c out = 10f c byp = 0 i l = 100ma lt1761-byp, -sd, 1.2 lt1761-5 lt1761-3.3 lt1761-2.8,-3 lt1761-2.5 lt1761-1.8 lt1761-2 lt1761-1.5 frequency (hz) 10 1k 10k 100k 1761 g42 100 10 1 0.1 0.01 output noise spectral density (v/ hz ) lt1761-byp lt1761-5 c byp = 1000pf c byp = 0.01f c byp = 100pf c out = 10f i l = 100ma c byp (pf) 10 output noise (v rms ) 140 120 100 80 60 40 20 0 100 1k 10k 1761 g43 c out = 10f i l = 100ma f = 10hz to 100khz lt1761-5 lt1761-3.3 lt1761-3 lt1761-2.8 lt1761-2.5 lt1761-1.5 lt1761-1.8, -2 lt1761-byp, -1.2
lt1761 series 13 1761sfe typical performance characteristics rms output noise vs load current (10hz to 100khz) lt1761-5 10hz to 100khz output noise c byp = 0pf lt1761-5 10hz to 100khz output noise c byp = 100pf load current (ma) 0.01 output noise (v rms ) 160 140 120 100 80 60 40 20 0 0.1 1 1761 g44 10 100 c out = 10f lt1761-5 lt1761-5 lt1761-byp lt1761-byp c byp = 0 c byp = 0.01f v out 100v/div 1ms/div c out = 10f i l = 100ma 1761 g45 v out 100v/div 1ms/div c out = 10f i l = 100ma 1761 g46 lt1761-5 10hz to 100khz output noise c byp = 1000pf lt1761-5 10hz to 100khz output noise c byp = 0.01f v out 100v/div 1ms/div c out = 10f i l = 100ma 1761 g46 v out 100v/div 1ms/div c out = 10f i l = 100ma 1761 g48 lt1761-5 transient response c byp = 0pf lt1761-5 transient response c byp = 0.01f time (s) 0.2 0.1 0 C0.1 C0.2 output voltage deviation (v) 100 50 0 load current (ma) 1761 g49 0 400 800 1200 1600 2000 v in = 6v c in = 10f c out = 10f time (s) 0.04 0.02 0 C0.02 C0.04 output voltage deviation (v) 100 50 0 load current (ma) 1761 g50 0 40 60 100 20 80 120 140 180 160 200 v in = 6v c in = 10f c out = 10f
lt1761 series 14 1761sfe pin functions in (pin 1): input. power is supplied to the device through the in pin. a bypass capacitor is required on this pin if the device is more than six inches away from the main input ? lter capacitor. in general, the output impedance of a battery rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits. a bypass capacitor in the range of 1f to 10f is suf? cient. the lt1761 regulators are designed to withstand reverse voltages on the in pin with respect to ground and the out pin. in the case of a reverse input, which can happen if a battery is plugged in backwards, the device will act as if there is a diode in series with its input. there will be no reverse current ? ow into the regulator and no reverse voltage will appear at the load. the device will protect both itself and the load. gnd (pin 2): ground. shdn (pin 3, fixed/-sd devices): shutdown. the shdn pin is used to put the lt1761 regulators into a low power shutdown state. the output will be off when the shdn pin is pulled low. the shdn pin can be driven either by 5v logic or open-collector logic with a pull-up resistor. the pull-up resistor is required to supply the pull-up current of the open-collector gate, normally several microamperes, and the shdn pin current, typically 1a. if unused, the shdn pin must be connected to v in . the device will not function if the shdn pin is not connected. for the lt1761-byp , the shdn pin is internally connected to v in . byp (pins 3/4, fixed/-byp devices): bypass. the byp pin is used to bypass the reference of the lt1761 regula- tors to achieve low noise performance from the regulator. the byp pin is clamped internally to 0.6v (one v be ) from ground. a small capacitor from the output to this pin will bypass the reference to lower the output voltage noise. a maximum value of 0.01f can be used for reducing output voltage noise to a typical 20v rms over a 10hz to 100khz bandwidth. if not used, this pin must be left unconnected. adj (pin 4, adjustable devices only): adjust pin. for the adjustable lt1761, this is the input to the error ampli? er. this pin is internally clamped to 7v. it has a bias current of 30na which ? ows into the pin (see curve of adj pin bias current vs temperature in the typical performance characteristics section). the adj pin voltage is 1.22v referenced to ground and the output voltage range is 1.22v to 20v. out (pin 5): output. the output supplies power to the load. a minimum output capacitor of 1f is required to prevent oscillations. larger output capacitors will be required for applications with large transient loads to limit peak volt- age transients. see the applications information section for more information on output capacitance and reverse output characteristics.
lt1761 series 15 1761sfe applications information the lt1761 series are 100ma low dropout regulators with micropower quiescent current and shutdown. the devices are capable of supplying 100ma at a dropout voltage of 300mv. output voltage noise can be lowered to 20v rms over a 10hz to 100khz bandwidth with the addition of a 0.01f reference bypass capacitor. additionally, the refer- ence bypass capacitor will improve transient response of the regulator, lowering the settling time for transient load conditions. the low operating quiescent current (20a) drops to less than 1a in shutdown. in addition to the low quiescent current, the lt1761 regulators incorporate several protection features which make them ideal for use in battery-powered systems. the devices are protected against both reverse input and reverse output voltages. in battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the lt1761-x acts like it has a diode in series with its output and prevents reverse current ? ow. additionally, in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 20v and still allow the device to start and operate. adjustable operation the adjustable version of the lt1761 has an output voltage range of 1.22v to 20v. the output voltage is set by the ratio of two external resistors as shown in figure 1. the device servos the output to maintain the adj pin voltage at 1.22v referenced to ground. the current in r1 is then equal to 1.22v/r1 and the current in r2 is the current in r1 plus the adj pin bias current. the adj pin bias cur- rent, 30na at 25c, ? ows through r2 into the adj pin. the output voltage can be calculated using the formula in figure 1. the value of r1 should be no greater than 250k to minimize errors in the output voltage caused by the adj pin bias current. note that in shutdown the output is turned off and the divider current will be zero. curves of adj pin voltage vs temperature and adj pin bias cur- rent vs temperature appear in the typical performance characteristics. the adjustable device is tested and speci? ed with the adj pin tied to the out pin for an output voltage of 1.22v. speci? cations for output voltages greater than 1.22v will be proportional to the ratio of the desired output voltage to 1.22v: v out /1.22v. for example, load regulation for an output current change of 1ma to 100ma is C1mv typical at v out = 1.22v. at v out = 12v, load regulation is: (12v/1.22v)(C1mv) = C9.8mv bypass capacitance and low noise performance the lt1761 regulators may be used with the addition of a bypass capacitor from v out to the byp pin to lower output voltage noise. a good quality low leakage capacitor is recommended. this capacitor will bypass the reference of the regulator, providing a low frequency noise pole. the noise pole provided by this bypass capacitor will lower the output voltage noise to as low as 20v rms with the addition of a 0.01f bypass capacitor. using a bypass capacitor has the added bene? t of improving transient response. with no bypass capacitor and a 10f output capacitor, a 10ma to 100ma load step will settle to within 1% of its ? nal value in less than 100s. with the addition of a 0.01f bypass capacitor, the output will stay within 1% for a 10ma to 100ma load step (see lt1761-5 transient response in typical performance characteristics section). however, regulator start-up time is proportional to the size of the bypass capacitor, slowing to 15ms with a 0.01f bypass capacitor and 10f output capacitor. in 1761 f01 r2 lt1761 out v in v out adj gnd r1 + vv r r ir vv ina out adj adj adj | ? o 122 1 2 1 2 122 30 at 25 c output range = 1.22v to 20v figure 1. adjustable operation
lt1761 series 16 1761sfe applications information output capacitance and transient response the lt1761 regulators are designed to be stable with a wide range of output capacitors. the esr of the output capacitor affects stability, most notably with small capaci- tors. a minimum output capacitor of 1f with an esr of 3 or less is recommended to prevent oscillations. the lt1761-x is a micropower device and output transient response will be a function of output capacitance. larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. bypass capacitors, used to decouple individual components powered by the lt1761-x, will increase the effective output capacitor value. with larger capacitors used to bypass the reference (for low noise operation), larger values of output capacitors are needed. for 100pf of bypass capacitance, 2.2f of output capaci- tor is recommended. with a 330pf bypass capacitor or larger, a 3.3f output capacitor is recommended. the shaded region of figure 2 de? nes the region over which the lt1761 regulators are stable. the minimum esr needed is de? ned by the amount of bypass capacitance used, while the maximum esr is 3. extra consideration must be given to the use of ceramic capacitors. ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. the most common dielectrics used are speci? ed with eia temperature char- acteristic 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 output capacitance (f) 1 esr () 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 310 1761 f02 245 6 78 9 stable region c byp = 330pf c byp = 100pf c byp = 0 c byp > 3300pf figure 2. stability and temperature coef? cients as shown in figures 3 and 4. 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 tempera- ture range. the x5r 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 avail- able 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 signi? cant enough to drop capacitor values below appropriate levels. capaci- tor dc bias characteristics tend to improve as component case size increases, but expected capacitance at operating voltage should be veri? ed. dc bias voltage (v) change in value (%) 1761 f03 20 0 C20 C40 C60 C80 C100 0 4 8 10 26 12 14 x5r y5v 16 both capacitors are 16v, 1210 case size, 10f figure 3. ceramic capacitor dc bias characteristics figure 4. ceramic capacitor temperature characteristics temperature (c) C50 40 20 0 C20 C40 C60 C80 C100 25 75 1761 f04 C25 0 50 100 125 y5v change in value (%) x5r both capacitors are 16v, 1210 case size, 10f
lt1761 series 17 1761sfe applications information voltage and temperature coef? cients 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, similar to the way a piezoelectric accelerometer or micro- phone works. for a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. the resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. a ceramic capacitor produced figure 5s trace in response to light tapping from a pencil. similar vibration induced behavior can masquerade as increased output voltage noise. v out 500v/div lt1761-5 c out = 10f c byp = 0.01f i load = 100ma 100ms/div 1761 f05 figure 5. noise resulting from tapping on a ceramic capacitor thermal considerations the power handling capability of the device will be limited by the maximum rated junction temperature (125c). the power dissipated by the device will be made up of two components: 1. output current multiplied by the input/output voltage differential: (i out )(v in C v out ), and 2. gnd pin current multiplied by the input voltage: (i gnd )(v in ). the ground pin current can be found by examining the gnd pin current curves in the typical performance char- acteristics section. power dissipation will be equal to the sum of the two components listed above. the lt1761 series regulators have internal thermal limiting designed to protect the device during overload conditions. for continuous normal conditions, the maximum junction temperature rating of 125c must not be exceeded. it is important to give careful consideration to all sources of thermal resistance from junction to ambient. additional heat sources mounted nearby must also be considered. for surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the pc board and its copper traces. copper board stiffeners and plated through-holes can also be used to spread the heat gener- ated by power devices. the following table lists thermal resistance for several different board sizes and copper areas. all measurements were taken in still air on 3/32" fr-4 board with one ounce copper. table 1. measured thermal resistance copper area board area thermal resistance (junction-to-ambient) topside* backside 2500mm 2 2500mm 2 2500mm 2 125c/w 1000mm 2 2500mm 2 2500mm 2 125c/w 225mm 2 2500mm 2 2500mm 2 130c/w 100mm 2 2500mm 2 2500mm 2 135c/w 50mm 2 2500mm 2 2500mm 2 150c/w *device is mounted on topside. calculating junction temperature example: given an output voltage of 3.3v, an input voltage range of 4v to 6v, an output current range of 0ma to 50ma and a maximum ambient temperature of 50c, what will the maximum junction temperature be? the power dissipated by the device will be equal to: i out(max) (v in(max) C v out ) + i gnd (v in(max) ) where, i out(max) = 50ma v in(max) = 6v i gnd at (i out = 50ma, v in = 6v) = 1ma so, p = 50ma(6v C 3.3v) + 1ma(6v) = 0.14w the thermal resistance will be in the range of 125c/w to 150c/w depending on the copper area. so the junction
lt1761 series 18 1761sfe temperature rise above ambient will be approximately equal to: 0.14w(150c/w) = 21.2c the maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: t jmax = 50c + 21.2c = 71.2c protection features the lt1761 regulators incorporate several protection features which make them ideal for use in battery-pow- ered circuits. in addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting, the devices are protected against reverse input voltages, reverse output voltages and reverse voltages from output to input. current limit protection and thermal overload protection are intended to protect the device against current overload conditions at the output of the device. for normal operation, the junction temperature should not exceed 125c. the input of the device will withstand reverse voltages of 20v. current ? ow into the device will be limited to less than 1ma (typically less than 100a) and no negative voltage will appear at the output. the device will protect both itself and the load. this provides protection against batteries which can be plugged in backward. the output of the lt1761-x can be pulled below ground without damaging the device. if the input is left open circuit or grounded, the output can be pulled below ground by 20v. for ? xed voltage versions, the output will act like a large resistor, typically 500k or higher, limiting current ? ow to typically less than 100a. for adjustable versions, the output will act like an open circuit; no current will ? ow out of the pin. if the input is powered by a voltage source, the output will source the short-circuit current of the device and will protect itself by thermal limiting. in this case, grounding the shdn pin will turn off the device and stop the output from sourcing the short-circuit current. the adj pin of the adjustable device can be pulled above or below ground by as much as 7v without damaging the device. if the input is left open circuit or grounded, the applications information adj pin will act like an open circuit when pulled below ground and like a large resistor (typically 100k) in series with a diode when pulled above ground. in situations where the adj pin is connected to a resistor divider that would pull the adj pin above its 7v clamp volt- age if the output is pulled high, the adj pin input current must be limited to less than 5ma. for example, a resistor divider is used to provide a regulated 1.5v output from the 1.22v reference when the output is forced to 20v. the top resistor of the resistor divider must be chosen to limit the current into the adj pin to less than 5ma when the adj pin is at 7v. the 13v difference between output and adj pin divided by the 5ma maximum current into the adj pin yields a minimum top resistor value of 2.6k. in circuits where a backup battery is required, several different input/output conditions can occur. the output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left open circuit. current ? ow back into the output will follow the curve shown in figure 6. when the in pin of the lt1761-x is forced below the out pin or the out pin is pulled above the in pin, input cur- rent will typically drop to less than 2a. this can happen if the input of the device is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or a second regulator circuit. the state of the shdn pin will have no effect on the reverse output current when the output is pulled above the input. output voltage (v) 100 90 80 70 60 50 40 30 20 10 0 reverse output current (a) 1761 f06 0123 4 5 67 8910 t j = 25c v in = 0v current flows into output pin v out = v adj (lt1761-byp, -sd) lt1761-byp lt1761-sd lt1761-2 lt1761-3.3 lt1761-5 lt1761-1.8 lt1761-1.5 lt1761-2.5 lt1761-2.8 lt1761-3 lt1761-1.2 figure 6. reverse output current
lt1761 series 19 1761sfe 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 s5 package 5-lead plastic tsot-23 (reference ltc dwg # 05-08-1635) 1.50 C 1.75 (note 4) 2.80 bsc 0.30 C 0.45 typ 5 plcs (note 3) datum a 0.09 C 0.20 (note 3) s5 tsot-23 0302 rev b pin one 2.90 bsc (note 4) 0.95 bsc 1.90 bsc 0.80 C 0.90 1.00 max 0.01 C 0.10 0.20 bsc 0.30 C 0.50 ref note: 1. dimensions are in millimeters 2. drawing not to scale 3. dimensions are inclusive of plating 4. dimensions are exclusive of mold flash and metal burr 5. mold flash shall not exceed 0.254mm 6. jedec package reference is mo-193 3.85 max 0.62 max 0.95 ref recommended solder pad layout per ipc calculator 1.4 min 2.62 ref 1.22 ref
lt1761 series 20 1761sfe linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2005 lt 0909 rev e ? printed in usa related parts part number description comments lt1120 125ma low dropout regulator with 20a i q includes 2.5v reference and comparator lt1121 150ma micropower low dropout regulator 30a i q , sot-223 package lt1129 700ma micropower low dropout regulator 50a quiescent current lt1175 500ma negative low dropout micropower regulator 45a i q , 0.26v dropout voltage, sot-223 package lt1521 300ma low dropout micropower regulator with shutdown 15a i q , reverse-battery protection lt1529 3a low dropout regulator with 50a i q 500mv dropout voltage lt1762 series 150ma, low noise, ldo micropower regulator 25a quiescent current, 20v rms noise lt1763 series 500ma, low noise, ldo micropower regulator 30a quiescent current, 20v rms noise ltc1928 doubler charge pump with low noise linear regulator low output noise: 60v rms (100khz bw) lt1962 series 300ma, low noise, ldo micropower regulator 30a quiescent current, 20v rms noise lt1963 1.5a, low noise, fast transient response ldo 40v rms , sot-223 package lt1764 3a, low noise, fast transient response ldo 40v rms , 340mv dropout voltage ltc3404 high ef? ciency synchronous step-down switching regulator burst mode ? operation, monolithic, 100% duty cycle burst mode is a registered trademark of linear technology corporation.

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