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1 lt1761 series 100ma, low noise, ldo micropower regulators in sot-23 n tiny 5-lead sot-23 package n low noise: 20 m v rms (10hz to 100khz) n low quiescent current: 20 m a n wide input voltage range: 1.8v to 20v n output current: 100ma n very low shutdown current: < 0.1 m a n low dropout voltage: 300mv at 100ma n fixed output voltages: 1.8v, 2v, 2.5v, 3v, 3.3v, 5v n adjustable output from 1.22v to 20v n stable with 1 m f 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 the lt ? 1761 series are micropower, low noise, low dropout regulators. with an external 0.01 m f bypass capacitor, output noise drops to 20 m v rms over a 10hz to 100khz bandwidth. designed for use in battery-powered systems, the low 20 m a quiescent current makes them an ideal choice. in shutdown, quiescent current drops to less than 0.1 m a. 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. quies- cent 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 1 m f. small ceramic capacitors can be used without the series resistance required by other regulators. internal protection circuitry includes reverse battery pro- tection, current limiting, thermal limiting and reverse current protection. the device is available in fixed output voltages of 1.8v, 2v, 2.5v, 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 sot-23 package. 10hz to 100khz output noise 5v low noise regulator n cellular phones n pagers n battery-powered systems n frequency synthesizers n wireless modems , ltc and lt are registered trademarks of linear technology corporation. in shdn 0.01 f 10 f 1761 ta01 out v in 5.4v to 20v byp gnd lt1761-5 5v at100ma 20 v rms noise 1 f + features descriptio u applicatio s u typical applicatio u v out 100 v/div 20 v rms 1761 g48
2 lt1761 series absolute m axi m u m ratings w ww u package/order i n for m atio n w u u (note 1) 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 lt1761es5-byp order part number consult factory for industrial and military grade parts. t jmax = 150 c, q ja = 250 c/ w see the applications information section. parameter conditions min typ max units minimum input voltage (note 3) i load = 100ma l 1.8 2.3 v regulated output voltage lt1761-1.8 v in = 2.3v, i load = 1ma 1.775 1.8 1.825 v (note 4) 2.8v < v in < 20v, 1ma < i load < 50ma l 1.750 1.8 1.845 v 2.8v < v in < 20v, 1ma < i load < 100ma l 1.725 1.8 1.860 v lt1761-2 v in = 2.5v, i load = 1ma 1.970 2 2.030 v 3v < v in < 20v, 1ma < i load < 50ma l 1.945 2 2.045 v 3v < v in < 20v, 1ma < i load < 100ma l 1.920 2 2.060 v lt1761-2.5 v in = 3v, i load = 1ma 2.465 2.5 2.535 v 3.5v < v in < 20v, 1ma < i load < 50ma l 2.435 2.5 2.565 v 3.5v < v in < 20v, 1ma < i load < 100ma l 2.415 2.5 2.575 v lt1761-2.8 v in = 3.3v, i load = 1ma 2.762 2.8 2.838 v 3.8v < v in < 20v, 1ma < i load < 50ma l 2.732 2.8 2.868 v 3.8v < v in < 20v, 1ma < i load < 100ma l 2.706 2.8 2.884 v lt1761-3 v in = 3.5v, i load = 1ma 2.960 3 3.040 v 4v < v in < 20v, 1ma < i load < 50ma l 2.930 3 3.070 v 4v < v in < 20v, 1ma < i load < 100ma l 2.900 3 3.090 v the l denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. (note 2) electrical characteristics 5 out 4 adj in 1 gnd 2 top view s5 package 5-lead plastic sot-23 shdn 3 5 out 4 adj in 1 gnd 2 top view s5 package 5-lead plastic sot-23 byp 3 5 out 4 byp in 1 gnd 2 top view s5 package 5-lead plastic sot-23 shdn 3 output short-circut duration .......................... indefinite operating junction temperature range (note 2) ............................................ C 40 c to 125 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c s5 part marking 5 out 4 adj in 1 gnd 2 top view s5 package 5-lead plastic sot-23 byp 3 t jmax = 150 c, q ja = 250 c/ w see the applications information section. lt1761es5-sd order part number s5 part marking ltgc ltgh lt1761es5-1.8 lt1761es5-2 lt1761es5-2.5 lt1761es5-2.8 lt1761es5-3 lt1761es5-3.3 lt1761es5-5 order part number s5 part marking ltjm ltje ltgd ltlb ltge ltgf ltgg t jmax = 150 c, q ja = 250 c/ w see the applications information section.
3 lt1761 series electrical characteristics parameter conditions min typ max units the l denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. (note 2) regulated output voltage lt1761-3.3 v in = 3.8v, i load = 1ma 3.250 3.3 3.350 v (note 4) 4.3v < v in < 20v, 1ma < i load < 50ma l 3.230 3.3 3.370 v 4.3v < v in < 20v, 1ma < i load < 100ma l 3.190 3.3 3.400 v lt1761-5 v in = 5.5v, i load = 1ma 4.935 5 5.065 v 6v < v in < 20v, 1ma < i load < 50ma l 4.900 5 5.100 v 6v < v in < 20v, 1ma < i load < 100ma l 4.850 5 5.120 v adj pin voltage lt1761 v in = 2v, i load = 1ma 1.205 1.220 1.235 v (note 3, 4) 2v < v in < 20v, 1ma < i load < 50ma l 1.190 1.220 1.250 v 2v < v in < 20v, 1ma < i load < 100ma l 1.170 1.220 1.260 v line regulation lt1761-1.8 d v in = 2.3v to 20v, i load = 1ma l 110 mv lt1761-2 d v in = 2.5v to 20v, i load = 1ma l 110 mv lt1761-2.5 d v in = 3v to 20v, i load = 1ma l 110 mv lt1761-2.8 d v in = 3.3v to 20v, i load = 1ma l 110 mv lt1761-3 d v in = 3.5v to 20v, i load = 1ma l 110 mv lt1761-3.3 d v in = 3.8v to 20v, i load = 1ma l 110 mv lt1761-5 d v in = 5.5v to 20v, i load = 1ma l 110 mv lt1761(note 3) d v in = 2v to 20v, i load = 1ma l 110 mv load regulation lt1761-1.8 v in = 2.8v, d i load = 1ma to 50ma 10 20 mv v in = 2.8v, d i load = 1ma to 50ma l 35 mv v in = 2.8v, d i load = 1ma to 100ma 15 30 mv v in = 2.8v, d i load = 1ma to 100ma l 60 mv lt1761-2 v in = 3v, d i load = 1ma to 50ma 10 20 mv v in = 3v, d i load = 1ma to 50ma l 35 mv v in = 3v, d i load = 1ma to 100ma 15 35 mv v in = 3v, d i load = 1ma to 100ma l 65 mv lt1761-2.5 v in = 3.5v, d i load = 1ma to 50ma 10 20 mv v in = 3.5v, d i load = 1ma to 50ma l 35 mv v in = 3.5v, d i load = 1ma to 100ma 20 40 mv v in = 3.5v, d i load = 1ma to 100ma l 80 mv lt1761-2.8 v in = 3.8v, d i load = 1ma to 50ma 10 20 mv v in = 3.8v, d i load = 1ma to 50ma l 38 mv v in = 3.8v, d i load = 1ma to 100ma 20 40 mv v in = 3.8v, d i load = 1ma to 100ma l 86 mv lt1761-3 v in = 4v, d i load = 1ma to 50ma 10 20 mv v in = 4v, d i load = 1ma to 50ma l 40 mv v in = 4v, d i load = 1ma to 100ma 20 40 mv v in = 4v, d i load = 1ma to 100ma l 90 mv lt1761-3.3 v in = 4.3v, d i load = 1ma to 50ma 10 20 mv v in = 4.3v, d i load = 1ma to 50ma l 40 mv v in = 4.3v, d i load = 1ma to 100ma 20 40 mv v in = 4.3v, d i load = 1ma to 100ma l 100 mv lt1761-5 v in = 6v, d i load = 1ma to 50ma 15 30 mv v in = 6v, d i load = 1ma to 50ma l 60 mv v in = 6v, d i load = 1ma to 100ma 25 65 mv v in = 6v, d i load = 1ma to 100ma l 150 mv lt1761 (note 3) v in = 2v, d i load = 1ma to 50ma 1 6 mv v in = 2v, d i load = 1ma to 50ma l 12 mv v in = 2v, d i load = 1ma to 100ma 1 12 mv v in = 2v, d i load = 1ma to 100ma l 50 mv
4 lt1761 series parameter conditions min typ max units dropout voltage i load = 1ma 0.10 0.15 v v in = v out(nominal) i load = 1ma l 0.19 v (notes 5, 6) i load = 10ma 0.17 0.22 v i load = 10ma l 0.29 v i load = 50ma 0.24 0.28 v i load = 50ma l 0.38 v i load = 100ma 0.30 0.35 v i load = 100ma l 0.45 v gnd pin current i load = 0ma l 20 45 m a v in = v out(nominal) i load = 1ma l 55 100 m a (notes 5, 7) i load = 10ma l 230 400 m a i load = 50ma l 12 ma i load = 100ma l 2.2 4 ma output voltage noise c out = 10 m f, c byp = 0.01 m f, i load = 100ma, bw = 10hz to 100khz 20 m v rms adj pin bias current (notes 3, 8) 30 100 na shutdown threshold v out = off to on l 0.8 2 v v out = on to off l 0.25 0.65 v shdn pin current v shdn = 0v l 0 0.5 m a (note 9) v shdn = 20v l 13 m a quiescent current in shutdown v in = 6v, v shdn = 0v 0.01 0.1 m a ripple rejection v in C v out = 1v (avg), v ripple = 0.5v p-p , f ripple = 120hz, 55 65 db i load = 50ma current limit v in = 7v, v out = 0v 200 ma v in = v out(nominal) + 1v, d v out = C 5% l 110 ma input reverse leakage current v in = C 20v, v out = 0v l 1ma reverse output current lt1761-1.8 v out = 1.8v, v in < 1.8v 10 20 m a (note 10) lt1761-2 v out = 2v, v in < 2v 10 20 m a lt1761-2.5 v out = 2.5v, v in < 2.5v 10 20 m a lt1761-2.8 v out = 2.8v, v in < 2.8v 10 20 m a lt1761-3 v out = 3v, v in < 3v 10 20 m a lt1761-3.3 v out = 3.3v, v in < 3.3v 10 20 m a lt1761-5 v out = 5v, v in < 5v 10 20 m a lt1761 (note 3) v out = 1.22v, v in < 1.22v 5 10 m a the l denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. (note 2) electrical characteristics external resistor divider (two 250k resistors) for an output voltage of 2.44v. the external resistor divider will add a 5 m a dc load on the output. note 6: dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified 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) and a current source load. this means the device is tested while operating in its dropout region. 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 flows into the adj pin. note 9: shdn pin current flows 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 flows into the out pin and out the gnd pin. note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the lt1761 regulators are tested and specified under pulse load conditions such that t j ? t a . the lt1761 is 100% production tested at t a = 25 c. performance at C 40 c and 125 c is assured by design, characterization and correlation with statistical process controls. note 3: the lt1761 (adjustable versions) are tested and specified 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 specification 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 specified for these conditions with an
5 lt1761 series typical perfor m a n ce characteristics uw 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 125 c t j 25 c = test points temperature ( c) ?0 quiescent current ( a) 100 1761 g03 050 40 35 30 25 20 15 10 5 0 25 25 75 125 v in = 6v r l = (250k for lt1761-byp, -sd) i l = 0 (5 a for lt1761-byp, -sd) v shdn = v in v shdn = 0v temperature ( c) ?0 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 25 25 75 125 i l = 1ma temperature ( c) ?0 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 25 25 75 125 i l = 1ma temperature ( c) ?0 output voltage (v) 100 1761 g08 050 2.54 2.53 2.52 2.51 2.50 1.49 1.48 1.47 1.46 25 25 75 125 i l = 1ma temperature ( c) ?0 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 25 25 75 125 i l = 1ma guaranteed dropout voltage quiescent current lt1761-1.8 output voltage lt1761-2 output voltage lt1761-3 output voltage lt1761-2.5 output voltage dropout voltage lt1761-3.3 output voltage temperature ( c) ?0 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 25 25 75 125 i l = 1ma temperature ( c) ?0 dropout voltage (mv) 0 50 75 1761 g01.1 ?5 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 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 = 125 c t j = 25 c typical dropout voltage
6 lt1761 series typical perfor m a n ce characteristics uw lt1761-3 quiescent current lt1761-3.3 quiescent current lt1761-5 quiescent current 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 = 25 c 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 = 25 c 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 = 25 c 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 = 25 c r l = 250k i l = 5 a v shdn = v in 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 = 25 c 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 = 25 c r l = v shdn = 0v lt1761-byp, lt1761-sd quiescent current lt1761-1.8 quiescent current lt1761-2 quiescent current lt1761-byp, lt1761-sd adj pin voltage temperature ( c) ?0 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 25 25 75 125 i l = 1ma lt1761-2.5 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 = 25 c r l = v shdn = 0v lt1761-5 output voltage temperature ( c) ?0 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 25 25 75 125 i l = 1ma
7 lt1761 series typical perfor m a n ce characteristics uw lt1761-2.5 gnd pin current lt1761-3 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 g20 0123 4 5 67 8910 t j = 25 c *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 g21 0123 4 5 67 8910 t j = 25 c *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 = 25 c *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* lt1761-3.3 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 g23 0123 4 5 67 8910 t j = 25 c *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 = 25 c *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 lt1761-5 gnd pin current lt1761-byp, lt1761-sd gnd pin current gnd pin current vs i load 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 = 25 c *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* 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 = 25 c *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* lt1761-2 gnd pin current temperature ( c) ?0 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 ?5 25 100 125 i l = 1ma shdn pin threshold (on-to-off) lt1761-1.8 gnd pin current
8 lt1761 series shdn pin input current adj pin bias current current limit temperature ( c) ?0 shdn pin input current ( a) 0 50 75 1761 g29 ?5 25 100 125 v shdn = 20v 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 temperature ( c) ?0 adj pin bias current (na) 100 90 80 70 60 50 40 30 20 10 0 0 50 75 1761 g30 ?5 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 = 25 c current limit reverse output current reverse output current temperature ( c) ?0 current limit (ma) 0 50 75 1761 g32 ?5 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 = 25 c 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 lt1761-2.5 lt1761-3 temperature ( c) ?0 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 ?5 25 100 125 v in = 0v v out = 1.22v (lt1761-byp, -sd) v out = 1.8v (lt1761-1.8) v out = 2v (lt1761-2) v out = 2.5v (lt1761-2.5) v out = 3v (lt1761-3) v out = 3.3v (lt1761-3.3) v out = 5v (lt1761-5) lt1761-byp,-sd lt1761-1.8,-2, -2.5,-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 = 1 f c out = 10 f lt1761-byp lt1761-5 input ripple rejection 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 shdn pin input current temperature ( c) ?0 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 ?5 25 100 125 i l = 100ma i l = 1ma shdn pin threshold (off-to-on) typical perfor m a n ce characteristics uw
9 lt1761 series 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 = 10 f c byp = 0.01 f c byp = 100pf c byp = 1000pf temperature ( c) ?0 ripple rejection (db) 100 1761 g37 050 80 70 60 50 40 30 20 10 0 25 25 75 125 v in = v out (nominal) + 1v + 0.5v p-p ripple at f = 120hz i l = 50ma lt1761-5 input ripple rejection input ripple rejection typical perfor m a n ce characteristics uw lt1761-byp, lt1761-sd minimum input voltage load regulation d i l = 1ma to 50ma output noise spectral density temperature ( c) ?0 minimum input voltage (v) 2.5 2.0 1.5 1.0 0.5 0 0 50 75 1761 g38 ?5 25 100 125 i l = 100ma i l = 50ma temperature ( c) ?0 load regulation (mv) 100 1761 g39 050 0 ? ?0 ?5 ?0 ?5 ?0 ?5 ?0 25 25 75 125 lt1761-byp, -sd lt1761-1.8 lt1761-2 lt1761-2.5 lt1761-3 lt1761-3.3 lt1761-5 frequency (hz) 10 1k 10k 100k 1761 g41 100 10 1 0.1 0.01 output noise spectral density ( v/ hz) c out = 10 f c byp = 0 i l = 100ma lt1761-byp, -sd lt1761-5 lt1761-3.3 lt1761-3 lt1761-2.5 lt1761-1.8 lt1761-2 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 = 0.01 f c byp = 100pf c out = 10 f 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 = 10 f i l = 100ma f = 10hz to 100khz lt1761-5 lt1761-3.3 lt1761-3 lt1761-2.5 lt1761-1.8, -2 lt1761-byp output noise spectral density rms output noise vs bypass capacitor temperature ( c) ?0 load regulation (mv) 100 1761 g40 050 0 ?0 ?0 ?0 ?0 ?0 ?0 ?0 ?0 ?0 100 25 25 75 125 lt1761-3 lt1761-2 lt1761-2.5 lt1761-5 lt1761-3.3 lt1761-byp, -sd lt1761-1.8 load regulation d i l = 1ma to 100ma
10 lt1761 series typical perfor m a n ce characteristics uw lt1761-5 transient response c byp = 0 lt1761-5 10hz to 100khz output noise c byp = 1000pf v out 100 m v/div lt1761-5 10hz to 100khz output noise c byp = 0.01 m f 1ms/div c out = 10 m f i l = 100ma 1761 g48 v out 100 m v/div 1ms/div c out = 10 m f i l = 100ma 1761 g47 time ( s) 0.2 0.1 0 0.1 0.2 output voltage deviation (v) 100 50 0 load current (ma) 1761 g49 0 400 800 1200 1600 2000 v in = 6v c in = 10 f c out = 10 f time ( s) 0.04 0.02 0 0.02 0.04 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 = 10 f c out = 10 f lt1761-5 transient response c byp = 0.01 m f lt1761-5 10hz to 100khz output noise c byp = 0 v out 100 m v/div lt1761-5 10hz to 100khz output noise c byp = 100pf 1ms/div c out = 10 m f i l = 100ma 1761 g46 v out 100 m v/div 1ms/div c out = 10 m f i l = 100ma 1761 g45 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 = 10 f lt1761-5 lt1761-5 lt1761-byp lt1761-byp c byp = 0 c byp = 0.01 f rms output noise vs load current (10hz to 11khz)
11 lt1761 series applicatio n s i n for m atio n wu u u 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 20 m v rms over a 10hz to 100khz bandwidth with the addition of a 0.01 m f 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 (20 m a) drops to less than 1 m a in shutdown. in addition to the low quiescent current, the lt1761 regulators incorporate sev- pi n fu n ctio n s uuu 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 0.01 m f can be used for reducing output voltage noise to a typical 20 m v 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 amplifier. this pin is internally clamped to 7v. it has a bias current of 30na which flows into the pin (see curve of adj pin bias current vs temperature in the typical performance char- acteristics section). the adj pin voltage is 1.22v refer- enced 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 1 m f is required to prevent oscillations. larger output capacitors will be required for applications with large transient loads to limit peak voltage transients. see the applications information section for more information on output capacitance and reverse output characteristics. 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 filter 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 1 m f to 10 m f is sufficient. 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 flow 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 1 m a. 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 . eral 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 flow. 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.
12 lt1761 series applicatio n s i n for m atio n wu u u 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 current, 30na at 25 c, flows 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 current vs temperature appear in the typical performance characteristics. 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 20 m v rms with the addition of a 0.01 m f bypass capacitor. using a bypass capacitor has the added benefit of improving transient response. with no bypass capacitor and a 10 m f output capacitor, a 10ma to 100ma load step will settle to within 1% of its final value in less than 100 m s. with the addition of a 0.01 m f bypass capacitor, the output will stay within 1% for a 10ma to 100ma load step (see lt1761-5 transient reponse in typical performance characteris- tics section). however, regulator start-up time is inversely proportional to the size of the bypass capacitor, slowing to 15ms with a 0.01 m f bypass capacitor and 10 m f output capacitor. 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 1 m f with an esr of 3 w 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, 2.2 m f of output capaci- tor is recommended. with a 330pf bypass capacitor or larger, a 3.3 m f output capacitor is recommended. the shaded region of figure 2 defines the region over which the lt1761 regulators are stable. the minimum esr needed is defined by the amount of bypass capacitance used, while the maximum esr is 3 w . in 1761 f01 r2 lt1761 out v in v out adj gnd r1 + vv r r ir vv ina out adj adj adj =+ ? ? ? ? + ()() = = 122 1 2 1 2 122 30 . . at 25 c output range = 1.22v to 20v figure 1. adjustable operation the adjustable device is tested and specified with the adj pin tied to the out pin for an output voltage of 1.22v. specifications 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) = C 9.8mv
13 lt1761 series applicatio n s i n for m atio n wu u u 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 z5u, y5v, x5r and x7r. the z5u and y5v dielectrics are good for providing high capacitances in a small package, but exhibit strong voltage and tem- perature coefficients as shown in figures 3 and 4. when used with a 5v regulator, a 10 m f y5v capacitor can exhibit an effective value as low as 1 m f to 2 m f over the operating temperature 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 available in higher values. 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, 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. figure 4. ceramic capacitor temperature characteristics figure 3. ceramic capacitor dc bias characteristics temperature ( c) ?0 40 20 0 ?0 ?0 ?0 ?0 100 25 75 1761 g04 ?5 0 50 100 125 y5v change in value (%) x5r both capacitors are 16v, 1210 case size, 10 f 100ms/div 1761 f05 v out 500 m v/div dc bias voltage (v) change in value (%) 1761 f02 20 0 ?0 ?0 ?0 ?0 100 0 4 8 10 26 12 14 x5r y5v 16 both capacitors are 16v, 1210 case size, 10 f figure 5. noise resulting from tapping on a ceramic capacitor lt1761-5 c out = 10 m f c byp = 0.01 m f i load = 100ma figure 2. stability 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
14 lt1761 series thermal considerations the power handling capability of the device will be limited by the maximum rated junction temperature (125 c). 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 limit- ing designed to protect the device during overload condi- tions. for continuous normal conditions, the maximum junction temperature rating of 125 c 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 thermal resistance topside* backside board area (junction-to-ambient) 2500mm 2 2500mm 2 2500mm 2 125 c/w 1000mm 2 2500mm 2 2500mm 2 125 c/w 225mm 2 2500mm 2 2500mm 2 130 c/w 100mm 2 2500mm 2 2500mm 2 135 c/w 50mm 2 2500mm 2 2500mm 2 150 c/w *device is mounted on topside. applicatio n s i n for m atio n wu u u 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 50 c, 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 125 c/w to 150 c/w depending on the copper area. so the junction temperature rise above ambient will be approximately equal to: 0.14w(150 c/w) = 21.2 c the maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: t jmax = 50 c + 21.2 c = 71.2 c protection features the lt1761 regulators incorporate several protection features which make them ideal for use in battery-powered 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 opera- tion, the junction temperature should not exceed 125 c. the input of the device will withstand reverse voltages of 20v. current flow into the device will be limited to less than 1ma (typically less than 100 m a) and no negative voltage
15 lt1761 series information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 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 fixed voltage versions, the output will act like a large resistor, typically 500k w or higher, limiting current flow to typically less than 100 m a. for adjustable versions, the output will act like an open circuit; no current will flow 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 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 voltage 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 flow 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 current will typically drop to less than 2 m a. 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. applicatio n s i n for m atio n wu u u figure 6. reverse output current 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 = 25 c 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 lt1761-2.5 lt1761-3
16 lt1761 series 1761f lt/tp 0899 4k ? printed in usa ? linear technology corporation 1999 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com related parts part number description comments lt1120 125ma low dropout regulator with 20 m a i q includes 2.5v reference and comparator lt1121 150ma micropower low dropout regulator 30 m a i q , sot-223 package lt1129 700ma micropower low dropout regulator 50 m a quiescent current lt1175 500ma negative low dropout micropower regulator 45 m a i q , 0.26v dropout voltage, sot-223 package lt1521 300ma low dropout micropower regulator with shutdown 15 m a i q , reverse battery protection lt1529 3a low dropout regulator with 50 m a i q 500mv dropout voltage lt1611 inverting 1.4mhz switching regulator 5v to C 5v at 150ma, low output noise, sot-23 package lt1613 1.4mhz single-cell micropower dc/dc converter sot-23 package, internally compensated ltc1627 high efficiency synchronous step-down switching regulator burst mode tm operation, monolithic, 100% duty cycle lt1682 doubler charge pump with low noise linear regulator low output noise: 60 m v rms (100khz bw) lt1762 series 150ma, low noise, ldo micropower regulator 25 m a quiescent current, 20 m v rms noise lt1763 series 500ma, low noise, ldo micropower regulator 30 m a quiescent current, 20 m v rms noise burst mode is a trademark of linear technology corporation. package descriptio n u dimensions in inched (millimeters) unless otherwise noted. s5 package 5-lead plastic sot-23 (ltc dwg # 05-08-1633) 0.95 (0.037) ref 1.50 ?1.75 (0.059 ?0.069) 0.35 ?0.55 (0.014 ?0.022) 0.35 ?0.50 (0.014 ?0.020) five places (note 2) s5 sot-23 0599 2.80 ?3.00 (0.110 ?0.118) (note 3) 1.90 (0.074) ref 0.90 ?1.45 (0.035 ?0.057) 0.90 ?1.30 (0.035 ?0.051) 0.00 ?0.15 (0.00 ?0.006) 0.09 ?0.20 (0.004 ?0.008) (note 2) 2.60 ?3.00 (0.102 ?0.118) note: 1. dimensions are in millimeters 2. dimensions are inclusive of plating 3. dimensions are exclusive of mold flash and metal burr 4. mold flash shall not exceed 0.254mm 5. package eiaj reference is sc-74a (eiaj)

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