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1 lt1764a series 1764afb 3a, fast transient response, low noise, ldo regulators optimized for fast transient response output current: 3a dropout voltage: 340mv at 3a low noise: 40 v rms (10hz to 100khz) 1ma quiescent current wide input voltage range: 2.7v to 20v no protection diodes needed controlled quiescent current in dropout fixed output voltages: 1.5v, 1.8v, 2.5v, 3.3v adjustable output from 1.21v to 20v <1 a quiescent current in shutdown stable with 10 f output capacitor* stable with ceramic capacitors* reverse battery protection no reverse current thermal limiting the lt 1764a is a low dropout regulator optimized for fast transient response. the device is capable of supplying3a of output current with a dropout voltage of 340mv. operating quiescent current is 1ma, dropping to < 1 a in shutdown. quiescent current is well controlled; it does notrise in dropout as it does with many other regulators. in addition to fast transient response, the lt1764a has very low output voltage noise which makes the device ideal for sensitive rf supply applications. output voltage range is from 1.21v to 20v. the lt1764a regulators are stable with output capacitors as low as 10 f. internal protection circuitry includes reverse battery pro-tection, current limiting, thermal limiting and reverse cur- rent protection. the device is available in fixed output voltages of 1.5v, 1.8v, 2.5v, 3.3v and as an adjustable device with a 1.21v reference voltage. the lt1764a regu- lators are available in 5-lead to-220 and dd packages, and 16-lead fe packages. dropout voltage 3.3v in to 2.5v out regulator 3.3v to 2.5v logic power supply post regulator for switching supplies features descriptio u applicatio s u typical applicatio u in shdn 10 f* *tantalum, ceramic or aluminum electrolytic 1764 ta01 out v in > 3v sense gnd lt1764a-2.5 2.5v3a 10 f* + + load current (a) 0 0.5 dropout voltage (mv) 1.0 2.0 1.5 2.5 3.0 1764 ta02 400350 300 250 200 150 100 50 0 , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. *see applications information section. downloaded from: http:///
2 lt1764a series 1764afb parameter conditions min typ max units minimum input voltage i load = 0.5a 1.7 v (notes 3, 11) i load = 1.5a 1.9 v e grade: i load = 3a 2.3 2.7 v mp grade: i load = 3a 2.3 2.8 v regulated output voltage lt1764a-1.5 v in = 2.21v, i load = 1ma 1.477 1.500 1.523 v (note 4) 2.7v < v in < 20v, 1ma < i load < 3a 1.447 1.500 1.545 v lt1764a-1.8 v in = 2.3v, i load = 1ma 1.773 1.800 1.827 v 2.8v < v in < 20v, 1ma < i load < 3a 1.737 1.800 1.854 v 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 (note 12) ....... 20v sense pin voltage ............................................... 20v adj pin voltage ...................................................... 7v shdn pin voltage ................................................. 20v the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. (note 2) electrical characteristics output short-circuit duration ......................... indefinite operating junction temperature range e grade ............................................. 40 c to 125 c mp grade ......................................... 55 c to 125 c storage temperature range ................. 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c consult ltc marketing for parts specified with wider operating temperature ranges. order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbflead free part marking: http://www.linear.com/leadfree/ lt1764aetlt1764aet-1.5 lt1764aet-1.8 lt1764aet-2.5 lt1764aet-3.3 order part number lt1764aeqlt1764aeq-1.5 lt1764aeq-1.8 lt1764aeq-2.5 lt1764aeq-3.3 lt1764ampq order part number t jmax = 150 c, ja = 30 c/ w *pin 5 = sense for lt1764a-1.5/lt1764a-1.8/ lt1764a-2.5/lt1764a-3.3 = adj for lt1764a *pin 5 = sense for lt1764a-1.5/lt1764a-1.8/ lt1764a-2.5/lt1764a-3.3 = adj for lt1764a t jmax = 150 c, ja = 50 c/ w q package 5-lead plastic dd tab is gnd front view sense/adj*out gnd in shdn 54 3 2 1 t package 5-lead plastic to-220 sense/adj* out gnd in shdn front view tab is gnd 54 3 2 1 lt1764aefelt1764aefe-1.5 lt1764aefe-1.8 lt1764aefe-2.5 lt1764aefe-3.3 order part number fe part marking lt1764aefelt1764aefe-1.5 lt1764aefe-1.8 lt1764aefe-2.5 lt1764aefe-3.3 fe package 16-lead plastic tssop pin 17 is gnd 12 3 4 5 6 7 8 top view 1615 14 13 12 11 10 9 gnd nc outout out sense/adj* gndgnd gndnc in in in nc shdn gnd 17 t jmax = 150 c, ja = 38 c/ w *pin 6 = sense for lt1764a-1.5/ lt1764a-1.8/lt1764a-2.5/lt1764a-3.3 = adj for lt1764a downloaded from: http:///
3 lt1764a series 1764afb lt1764a-2.5 v in = 3v, i load = 1ma 2.462 2.500 2.538 v 3.5v < v in < 20v, 1ma < i load < 3a 2.412 2.500 2.575 v lt1764a-3.3 v in = 3.8v, i load = 1ma 3.250 3.300 3.350 v 4.3v < v in < 20v, 1ma < i load < 3a 3.183 3.300 3.400 v adj pin voltage lt1764a v in = 2.21v, i load = 1ma 1.192 1.210 1.228 v (notes 3, 4) e grade: 2.7v < v in < 20v, 1ma < i load < 3a 1.168 1.210 1.246 v mp grade: 2.8v < v in < 20v, 1ma < i load < 3a 1.168 1.210 1.246 v line regulation lt1764a-1.5 ? v in = 2.21v to 20v, i load = 1ma 2.5 10 mv lt1764a-1.8 ? v in = 2.3v to 20v, i load = 1ma 31 0m v lt1764a-2.5 ? v in = 3v to 20v, i load = 1ma 41 0m v lt1764a-3.3 ? v in = 3.8v to 20v, i load = 1ma 4.5 10 mv lt1764a (note 3) ? v in = 2.21v to 20v, i load = 1ma 21 0m v load regulation lt1764a-1.5 v in = 2.7v, ? i load = 1ma to 3a 3 7 mv v in = 2.7v, ? i load = 1ma to 3a 23 mv lt1764a-1.8 v in = 2.8v, ? i load = 1ma to 3a 4 8 mv v in = 2.8v, ? i load = 1ma to 3a 25 mv lt1764a-2.5 v in = 3.5v, ? i load = 1ma to 3a 4 10 mv v in = 3.5v, ? i load = 1ma to 3a 30 mv lt1764a-3.3 v in = 4.3v, ? i load = 1ma to 3a 4 12 mv v in = 4.3v, ? i load = 1ma to 3a 40 mv lt1764a (note 3) v in = 2.7v, ? i load = 1ma to 3a 2 5 mv e grade: v in = 2.7v, ? i load = 1ma to 3a 20 mv mp grade: v in = 2.8v, ? i load = 1ma to 3a 20 mv dropout voltage i load = 1ma 0.02 0.05 v v in = v out(nominal) i load = 1ma 0.10 v (notes 5, 6, 11) i load = 100ma 0.07 0.13 v i load = 100ma 0.18 v i load = 500ma 0.14 0.20 v i load = 500ma 0.27 v i load = 1.5a 0.25 0.33 v i load = 1.5a 0.40 v i load = 3a 0.34 0.45 v i load = 3a 0.66 v gnd pin current i load = 0ma 1 1.5 ma v in = v out(nominal) + 1v i load = 1ma 1.1 1.6 ma (notes 5, 7) i load = 100ma 3.5 5 ma i load = 500ma 11 18 ma i load = 1.5a 40 75 ma i load = 3a 120 200 ma output voltage noise c out = 10 f, i load = 3a, bw = 10hz to 100khz 40 v rms adj pin bias current (notes 3, 8) 31 0 a shutdown threshold v out = off to on 0.9 2 v v out = on to off 0.25 0.75 v shdn pin current v shdn = 0v 0.01 1 a (note 9) v shdn = 20v 73 0 a quiescent current in shutdown v in = 6v, v shdn = 0v 0.01 1 a ripple rejection v in ?v out = 1.5v (avg), v ripple = 0.5v p-p ,5 5 6 3 d b f ripple = 120hz, i load = 1.5a electrical characteristics parameter conditions min typ max units the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. (note 2) downloaded from: http:///
4 lt1764a series 1764afb current limit v in = 7v, v out = 0v 4 a e grade: lt1764a; lt1764a-1.5; 3.1 a v in = 2.7v, ? v out = 0.1v mp grade: lt1764a 3.1 a v in = 2.8v, ? v out = 0.1v input reverse leakage current v in = 20v, v out = 0v 1m a reverse output current (note 10) lt1764a-1.5 v out = 1.5v, v in < 1.5v 600 1200 a lt1764a-1.8 v out = 1.8v, v in < 1.8v 600 1200 a lt1764a-2.5 v out = 2.5v, v in < 2.5v 600 1200 a lt1764a-3.3 v out = 3.3v, v in < 3.3v 600 1200 a lt1764a (note 3) v out = 1.21v, v in < 1.21v 300 600 a note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolutemaximum rating condition for extended periods may affect device reliability and lifetime. note 2: the lt1764a regulators are tested and specified under pulse load conditions such that t j t a . the lt1764a (e grade) is 100% tested at t a = 25 c; performance at 40 c and 125 c is assured by design, characterization and correlation with statistical process controls. thelt1764a (mp grade) is 100% tested and guaranteed over the ?5 c to 125 c temperature range. note 3: the lt1764a (adjustable version) is 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 possiblecombinations of input voltage and output current. when operating at max- imum input voltage, the output current range must be limited. when operat- ing at maximum output current, the input voltage range must be limited. note 5: to satisfy requirements for minimum input voltage, the lt1764a (adjustable version) is tested and specified for these conditions with anexternal resistor divider (two 4.12k resistors) for an output voltage of 2.42v. the external resistor divider will add a 300 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, theoutput voltage will be equal to: v in ?v dropout . note 7: gnd pin current is tested with v in = v out(nominal) + 1v or v in = 2.7v (e grade) or v in = 2.8v (mp grade), whichever is greater, and a current source load. the gnd pin current will decrease 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 outpin and out the gnd pin. note 11. for the lt1764a, lt1764a-1.5 and lt1764a-1.8 dropout voltage will be limited by the minimum input voltage specification under someoutput voltage/load conditions. note 12. all combinations of absolute maximum input voltage and absolute maximum output voltage cannot be achieved. the absolutemaximum differential from input to output is 20v. for example, with v in = 20v, v out cannot be pulled below ground. electrical characteristics parameter conditions min typ max units the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. (note 2) typical perfor a ce characteristics uw typical dropout voltage output current (a) 0 0 dropout voltage (mv) 100 200 300 400 600 0.5 1.0 1.5 2.0 1764 g01 2.5 3.0 500 t j = 125 c t j = 25 c guaranteed dropout voltage output current (a) 0 700600 500 400 300 200 100 0 1.5 2.5 1764 g02 0.5 1.0 2.0 3.0 guaranteed dropout voltage (mv) = test points t j 125 c t j 25 c temperature ( c) ?0 dropout voltage (mv) 400 500 600 25 75 1764 g03 300 200 ?5 0 50 100 125 100 0 i l = 3a i l = 1.5a i l = 0.5a i l = 100ma i l = 1ma dropout voltage downloaded from: http:///
5 lt1764a series 1764afb typical perfor a ce characteristics uw quiescent current lt1764a-1.8 output voltage temperature ( c) ?0 0.8 1.0 1.4 25 75 1764 g04 0.60.4 ?5 0 50 100 125 0.2 0 1.2 quiescent current (ma) lt1764a-1.5/1.8/2.5/3.3 lt1764a v in = 6v r l = i l = 0 v shdn = v in temperature ( c) ?0 output voltage (v) 25 1756 g05 ?5 0 50 1.841.83 1.82 1.81 1.80 1.79 1.78 1.77 1.76 75 100 125 i l = 1ma lt1764a-3.3 output voltage lt1764a adj pin voltage lt1764a-1.8 quiescent current temperature ( c) ?0 output voltage (v) 25 1756 g07 ?5 0 50 3.383.36 3.34 3.32 3.30 3.28 3.26 3.24 3.22 75 100 125 i l = 1ma temperature ( c) ?0 adj pin voltage (v) 25 1756 g08 ?5 0 50 1.2301.225 1.220 1.215 1.210 1.205 1.200 1.195 1.190 75 100 125 i l = 1ma input voltage (v) 0 quiescent current (ma) 4035 30 25 20 15 10 50 8 1764 g09 246 1 0 7 135 9 t j = 25 c r l = v shdn = v in lt1764a-2.5 quiescent current input voltage (v) 0 quiescent current (ma) 4035 30 25 20 15 10 50 8 1764 g10 246 1 0 7 135 9 t j = 25 c r l = v shdn = v in temperature ( c) ?0 output voltage (v) 1.53 25 1764a g40 1.501.48 ?5 0 50 1.47 1.46 1.54 1.52 1.511.49 75 100 125 i l = 1ma lt1764a-2.5 output voltage temperature ( c) ?0 output voltage (v) 25 1756 g06 ?5 0 50 2.582.56 2.54 2.52 2.50 2.48 2.46 2.44 2.42 75 100 125 i l = 1ma lt1764a-1.5 output voltage lt1764a-1.5 quiescent current input voltage (v) 0 quiescent current (ma) 4035 30 25 20 15 10 50 8 1764 g41 246 1 0 7 135 9 t j = 25 c r l = v shdn = v in downloaded from: http:///
6 lt1764a series 1764afb typical perfor a ce characteristics uw lt1764a-1.8 gnd pin current lt1764a-2.5 gnd pin current lt1764a-3.3 gnd pin current lt1764a gnd pin current lt1764a-1.8 gnd pin current input voltage (v) 1 0 gnd pin current (ma) 20.017.5 15.0 12.5 10.0 7.55.0 2.5 0 9 1764 g13 3578 246 1 0 t j = 25 c v shdn = v in *for v out = 1.8v r l = 3.6 ? i l = 500ma* r l = 18 ? i l = 100ma* r l = 6 ? i l = 300ma* input voltage (v) 1 0 gnd pin current (ma) 4035 30 25 20 15 10 50 9 1764 g14 3578 246 1 0 t j = 25 c v shdn = v in *for v out = 2.5v r l = 5 ? i l = 500ma* r l = 25 ? i l = 100ma* r l = 8.33 ? i l = 300ma* input voltage (v) 1 0 gnd pin current (ma) 8070 60 50 40 30 20 10 0 9 1764 g15 3578 246 1 0 t j = 25 c v shdn = v in *for v out = 3.3v r l = 6.6 ? i l = 500ma* r l = 33 ? i l = 100ma* r l = 11 ? i l = 300ma* input voltage (v) 0 gnd pin current (ma) 9 12 15 8 1764 g16 6 3 0 2 4 6 19 3 5 7 10 r l = 2.42 ? i l = 500ma* r l = 12.1 ? i l = 100ma* r l = 4.33 ? i l = 300ma* t j = 25 c v shdn = v in *for v out = 1.21v input voltage (v) 0 gnd pin current (ma) 90 120 150 8 1764 g17 60 30 0 2 4 6 19 3 5 7 10 r l = 0.6 ? i l = 3a* r l = 2.57 ? i l = 0.7a* r l = 1.2 ? i l = 1.5a* t j = 25 c v shdn = v in *for v out = 1.8v lt1764a-3.3 quiescent current lt1764a quiescent current input voltage (v) 0 quiescent current (ma) 4035 30 25 20 15 10 50 8 1764 g11 246 1 0 7 135 9 t j = 25 c r l = v shdn = v in input voltage (v) 0 quiescent current (ma) 1.61.4 1.2 1.0 0.8 0.6 0.4 0.2 0 16 1764 g12 4 8 12 20 14 2 6 10 18 t j = 25 c r l = 4.3k v shdn = v in lt1764a-1.5 gnd pin current input voltage (v) 0 gnd pin current (ma) 20.017.5 15.0 12.5 10.0 7.55.0 2.5 0 8 1764 g42 246 1 0 7 135 9 t j = 25 c v shdn = v in *for v out = 1.5v r l = 3 ? i l = 500ma* r l = 15 ? i l = 100ma* r l = 5 ? i l = 300ma* lt1764a-1.5 gnd pin current input voltage (v) 0 gnd pin current (ma) 90 120 150 8 1764a g43 60 30 0 123 45 67 9 10 t j = 25 c v shdn = v in *for v out = 1.5v r l = 0.5 ? i l = 3a* r l = 1 ? i l = 1.5a* r l = 2.14 ? i l = 0.7a* downloaded from: http:///
7 lt1764a series 1764afb typical perfor a ce characteristics uw shdn pin threshold(on-to-off) shdn pin input current shdn pin input current adj pin bias current temperature ( c) ?0 0 shdn pin threshold (v) 0.1 0.3 0.4 0.5 1.00.7 0 50 75 1764 g22 0.2 0.8 0.90.6 ?5 25 100 125 i l = 1ma shdn pin threshold(off-to-on) temperature ( c) ?0 0 shdn pin threshold (v) 0.1 0.3 0.4 0.5 1.00.7 0 50 75 1764 g23 0.2 0.8 0.90.6 ?5 25 100 125 i l = 3a i l = 1ma shdn pin voltage (v) 0 shdn pin input current ( a) 6 8 10 16 1764 g24 42 5 7 93 1 0 4 8 12 21 8 6 10 14 20 temperature ( c) ?0 0 shdn pin input current ( a) 1 3 4 5 10 7 0 50 75 1764 g25 2 8 96 ?5 25 100 125 v shdn = 20v temperature ( c) ?0 adj pin bias current ( a) 25 1756 g26 ?5 0 50 4.03.5 3.0 2.5 2.0 1.5 1.0 0.5 0 75 100 125 lt1764a-2.5 gnd pin current lt1764a-3.3 gnd pin current lt1764a gnd pin current gnd pin current vs i load input voltage (v) 0 gnd pin current (ma) 120 160 200 8 1764 g18 80 40 0 2 4 6 19 3 5 7 10 r l = 0.83 ? i l = 3a* r l = 3.57 ? i l = 0.7a* r l = 1.66 ? i l = 1.5a* t j = 25 c v shdn = v in *for v out = 2.5v input voltage (v) 0 gnd pin current (ma) 120 160 200 8 1764 g19 80 40 0 2 4 6 19 3 5 7 10 r l = 1.1 ? i l = 3a* r l = 2.2 ? i l = 1.5a* t j = 25 c v shdn = v in *for v out = 3.3v r l = 4.71 ? i l = 0.7a* input voltage (v) 0 gnd pin current (ma) 90 120 150 8 1764 g20 60 30 0 2 4 6 19 3 5 7 10 r l = 0.4 ? i l = 3a* r l = 0.81 ? i l = 1.5a* t j = 25 c v shdn = v in *for v out = 1.21v r l = 1.73 ? i l = 0.7a* output current (a) 0 gnd pin current (ma) 60 80 100 1.5 2.5 1764 g21 40 20 0 0.5 1.0 2.0 120 140 160 3.0 v in = v out(nom) + 1v downloaded from: http:///
8 lt1764a series 1764afb typical perfor a ce characteristics uw ripple rejection ripple rejection lt1764a minimum input voltage load regulation output noise spectral density frequency (hz) 20 ripple rejection (db) 30 50 70 80 10 1k 10k 1m 1764 g31 10 100 100k 6040 0 c out = 100 f tantalum + 10 1 f ceramic c out = 10 f tantalum i l = 1.5a v in = v out(nom) + 1v + 50mv rms ripple temperature ( c) 50 ?5 50 ripple rejection (db) 60 75 0 50 75 1764 g32 55 70 65 25 100 125 i l = 1.5a v in = v out(nom) + 1v + 0.5v p-p ripple at f = 120hz temperature ( c) ?0 minimum input voltage (v) 2.0 2.5 3.0 25 75 1764 g33 1.5 1.0 ?5 0 50 100 125 0.5 0 i l = 3a i l = 1.5a i l = 100ma i l = 500ma temperature ( c) ?0 load regulation (mv) 25 1764 g34 ?5 0 50 10 50 ? ?0 ?5 ?0 ?5 ?0 75 100 125 lt1764a lt1764a-3.3 lt1764a-2.5 lt1764a-1.8 ? i l = 1ma to 3a v in = 2.7v (lt1764a/lt1764a-1.5) v in = v out(nom) + 1v (lt1764a-1.8/-2.5/-3.3) lt1764a-1.5 frequency (hz) 10 0.01 output noise spectral density ( v/ hz) 0.1 1 100 1k 10k 100k 1764 g35 lt1764a-3.3 lt1764a-2.5 lt1764a-1.8 lt1764a-1.5 lt1764a c out = 10 f i load = 3a current limit current limit reverse output current reverse output current input/output differential (v) 0 current limit (a) 2 4 61 3 5 4 8 12 16 1764 g27 20 2 0 6 10 14 18 t j = 50 c t j = 125 c t j = 25 c temperature ( c) ?0 current limit (a) 4 5 6 25 75 1764 g28 3 2 ?5 0 50 100 125 1 0 v in = 7v v out = 0v output voltage (v) 0 reverse output current (ma) 3.0 4.0 5.0 8 1764 g29 2.01.0 2.5 3.5 4.51.5 0.5 0 2 4 6 19 3 5 7 10 t j = 25 c v in = 0v current flows into output pin v out = v adj (lt1764a) v out = v fb (lt1764a-1.5/1.8/-2.5/-3.3) lt1764a lt1764a-1.8 lt1764a-2.5 lt1764a-3.3 lt1764a-1.5 temperature ( c) ?0 0 reverse output current (ma) 0.1 0.3 0.4 0.5 1.00.7 0 50 75 1764 g30 0.2 0.8 0.90.6 ?5 25 100 125 v out = 1.21v (lt1764a) v out = 1.5v (lt1764a-1.5) v out = 1.8v (lt1764a-1.8) v out = 2.5v (lt1764a-2.5) v out = 3.3v (lt1764a-3.3) v in = 0v lt1764a-1.5/1.8/-2.5/-3.3 lt1764a downloaded from: http:///
9 lt1764a series 1764afb rms output noise vs load current(10hz to 100khz) lt1764a-3.3 10hz to 100khzoutput noise lt1764a-3.3 transient response load current (a) 10 output noise ( v rms ) 15 25 35 40 0.0001 0.01 0.1 10 1764 g36 5 0.001 1 3020 0 lt1764a-3.3 lt1764a-2.5 lt1764a-1.8 lt1764a c out = 10 f lt1764a-1.5 v out 100 v/div c out = 10 f 1ms/div 1764a g37 i l = 3a time ( s) 0 output voltage deviation (v) load current (a) 0.1 0.1 0.2 0 0.2 16 1764 g38 1.000.50 0.750.25 0 46 2 8 12 14 18 10 20 v in = 4.3v c in = 3.3 f tantalum c out = 10 f tantalum lt1764a-3.3 transient response time ( s) 0 output voltage deviation (v) load current (a) 0.1 0.1 0.2 0 0.2 16 1764 g39 2 31 0 46 2 8 12 14 18 10 20 v in = 4.3v c in = 33 f c out = 100 f tantalum + 10 1 f ceramic typical perfor a ce characteristics uw downloaded from: http:///
10 lt1764a series 1764afb shdn (pin 1/1/10): shutdown. the shdn pin is used to put the lt1764a regulators into a low power shutdownstate. 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 7 a. if unused, the shdn pin must be connected to v in . the device will be in the low power shutdown state if the shdn pin is notconnected. in (pin 2/pin 2/pins 12, 13, 14): input. power is supplied to the device through the in pin. a bypass capacitor isrequired 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 f to 10 f is sufficient. the lt1764a regulators are designed to withstand reverse voltages on the in pin with respect toground 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. nc (pins 2, 11, 15) tssop only: no connect. gnd (pin 3/pin 3/pins 1, 7, 8, 9, 16, 17): ground. out (pin 4/pin 4/pins 3, 4, 5): output. the output supplies power to the load. a minimum output capacitorof 10 f is required to prevent oscillations. larger output capacitors will be required for applications with largetransient loads to limit peak voltage transients. see the figure 1. kelvin sense connection inshdn 1764 f01 r p out v in sense gnd lt1764a r p 3 5 4 1 2 + + load uu u pi fu ctio s applications information section for more information onoutput capacitance and reverse output characteristics. sense (pin 5/pin 5/pin 6): sense. for fixed voltage versions of the lt1764a (lt1764a-1.5/lt1764a-1.8/lt1764a-2.5/lt1764a-3.3), the sense pin is the input to the error amplifier. optimum regulation will be ob- tained at the point where the sense pin is connected to the out pin of the regulator. in critical applications, small voltage drops are caused by the resistance (r p ) of pc traces between the regulator and the load. these may beeliminated by connecting the sense pin to the output at the load as shown in figure 1 (kelvin sense connection). note that the voltage drop across the external pc traces will add to the dropout voltage of the regulator. the sense pin bias current is 600 a at the nominal rated output voltage. the sense pin can be pulled below ground (as ina dual supply system where the regulator load is returned to a negative supply) and still allow the device to start and operate. adj (pin 5/pin 5/pin 6): adjust. for the adjustable lt1764a, this is the input to the error amplifier. this pin is internallyclamped to 7v. it has a bias current of 3 a which flows into the pin. the adj pin voltage is 1.21v referenced toground and the output voltage range is 1.21v to 20v. dd/to-220/tssop downloaded from: http:///
11 lt1764a series 1764afb the lt1764a series are 3a low dropout regulators opti-mized for fast transient response. the devices are capable of supplying 3a at a dropout voltage of 340mv. the low operating quiescent current (1ma) drops to less than 1 a in shutdown. in addition to the low quiescent current, thelt1764a regulators incorporate several protection fea- tures 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 lt1764a-x acts like it has a diode in series with its output and prevents reverse current flow. additionally, in dual supply applica- tions 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 lt1764a has an output voltage range of 1.21v to 20v. the output voltage is set by the ratio of two external resistors as shown in figure 2. the device servos the output to maintain the voltage at the adj pin at 1.21v referenced to ground. the current in r1 is then equal to 1.21v/r1 and the current in r2 is the current in r1 plus the adj pin bias current. the adj pin bias current, 3 a at 25 c, flows through r2 into the adj pin. the output voltage can be calculated using the formula infigure 2. the value of r1 should be less than 4.17k 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. the adjustable device is tested and specified with the adj pin tied to the out pin for an output voltage of 1.21v. specifications for output voltages greater than 1.21v will be proportional to the ratio of the desired output voltage to 1.21v: v out /1.21v. for example, load regulation for an output current change of 1ma to 3a is 3mv typical at v out = 1.21v. at v out = 5v, load regulation is: (5v/1.21v)(?mv) = 12.4mv applicatio s i for atio wu uu output capacitors and stabilitythe lt1764a regulator is a feedback circuit. like any feedback circuit, frequency compensation is needed to make it stable. for the lt1764a, the frequency compensa- tion is both internal and external?he output capacitor. the size of the output capacitor, the type of the output capacitor, and the esr of the particular output capacitor all affect the stability. in addition to stability, the output capacitor also affects the high frequency transient response. the regulator loop has a finite band width. for high frequency transient loads, recovery from a transient is a combination of the output capacitor and the bandwidth of the regulator. the lt1764a was designed to be easy to use and accept a wide variety of output capacitors. however, the frequency compensation is affected by the output capacitor and optimum frequency stability may require some esr, espe- cially with ceramic capacitors. for ease of use, low esr polytantalum capacitors (poscap) are a good choice for both the transient response and stability of the regulator. these capacitors have intrinsic esr that improves the stability. ceramic capacitors have extremely low esr, and while they are a good choice in many cases, placing a small series resistance element will sometimes achieve optimum stability and minimize ring- ing. in all cases, a minimum of 10 f is required while the maximum esr allowable is 3 ? . the place where esr is most helpful with ceramics is lowoutput voltage. at low output voltages, below 2.5v, some esr helps the stability when ceramic output capacitors are used. also, some esr allows a smaller capacitor value to be used. when small signal ringing occurs with ceramics due to insufficient esr, adding esr or increas- figure 2. adjustable operation in 1764 f02 r2 out v in v out adj gnd lt1764a r1 + vv r r ir vv ia out adj adj adj =+ ? ? ? ? ? ? + () () = = 121 1 2 1 2 121 3 . . at 25 c output range = 1.21v to 20v downloaded from: http:///
12 lt1764a series 1764afb ing the capacitor value improves the stability and reducesthe ringing. table 1 gives some recommended values of esr to minimize ringing caused by fast, hard current transitions. table 1. capacitor minimum esr v out 10 f2 2 f4 7 f 100 f 1.2v 10m ? 5m ? 3m ? 0m ? 1.5v 7m ? 5m ? 3m ? 0m ? 1.8v 5m ? 5m ? 3m ? 0m ? 2.5v 0m ? 0m ? 0m ? 0m ? 3.3v 0m ? 0m ? 0m ? 0m ? 5v 0m ? 0m ? 0m ? 0m ? figures 3 through 8 show the effect of esr on the transientresponse of the regulator. these scope photos show the transient response for the lt1764a at three different output voltages with various capacitors and various val- ues of esr. the output load conditions are the same for all traces. in all cases there is a dc load of 1a. the load steps up to 2a at the first transition and steps back to 1a at the second transition. at the worst case point of 1.2v out with 10 f c out (figure 3), a minimum amount of esr is required. while5m ? is enough to eliminate most of the ringing, a value closer to 20m ? provides a more optimum response. at 2.5v output with 10 f c out (figure 4) the output rings at the transitions with 0 ? esr but still settles to within 10mv in 20 s after the 1a load step. once again a small value of esr will provide a more optimum response.at 5v out with 10 f c out (figure 5) the response is well damped with 0 ? esr. with a c out of 100 f at 0 ? esr and an output of 1.2v (figure 6), the output rings although the amplitude is only10mv p-p . with c out of 100 f it takes only 5m ? to 20m ? of esr to provide good damping at 1.2v output. perfor-mance at 2.5v and 5v output with 100 f c out shows sim- ilar characteristics to the 10 f case (see figures 7-8). at 2.5v out 5m ? to 20m ? can improve transient response. at 5v out the response is well damped with 0 ? esr. capacitor types with inherently higher esr can be com-bined with 0m ? esr ceramic capacitors to achieve both good high frequency bypassing and fast settling time.figure 9 illustrates the improvement in transient response that can be seen when a parallel combination of ceramic and poscap capacitors are used. the output voltage is at the worst case value of 1.2v. trace a, is with a 10 f ceramic output capacitor and shows significant ringingwith a peak amplitude of 25mv. for trace b, a 22 f/45m ? poscap is added in parallel with the 10 f ceramic. the output is well damped and settles to within 10mv in lessthan 5 s. for trace c, a 100 f/35m ? poscap is connected in parallel with the 10 f ceramic capacitor. in this case the peak output deviation is less than 20mv and the outputsettles in about 5 s. for improved transient response the value of the bulk capacitor (tantalum or aluminum electro-lytic) should be greater than twice the value of the ceramic capacitor. tantalum and polytantalum capacitors there is a variety of tantalum capacitor types available, with a wide range of esr specifications. older types have esr specifications in the hundreds of m ? to several ohms. some newer types of polytantalum with multi-electrodes have maximum esr specifications as low as 5m ? . in general the lower the esr specification, the larger the size and the higher the price. polytantalum capacitorshave better surge capability than older types and generally lower esr. some types such as the sanyo tpe and tpb series have esr specifications in the 20m ? to 50m ? range, which provide near optimum transient response.aluminum electrolytic capacitors aluminum electrolytic capacitors can also be used with the lt1764. these capacitors can also be used in conjunction with ceramic capacitors. these tend to be the cheapest and lowest performance type of capacitors. care must be used in selecting these capacitors as some types can have esr which can easily exceed the 3 ? maximum value. applicatio s i for atio wu uu downloaded from: http:///
13 lt1764a series 1764afb v out = 1.2v i out = 1a with 1a pulse c out = 10 f ceramic 05 1020 50 r esr (m ? ) figure 3 1764a f03 20 s/div 50mv/div v out = 5v i out = 1a with 1a pulse c out = 10 f ceramic figure 5 05 1020 r esr (m ? ) 1764a f05 20 s/div 50mv/div v out = 2.5v i load = 1a with 1a pulse c out = 100 f ceramic figure 7 r esr (m ? ) 05 1020 1764a f07 20 s/div 20mv/div v out = 2.5v i out = 1a with 1a pulse c out = 10 f ceramic figure 4 05 1020 50 r esr (m ? ) 1764a f04 20 s/div 50mv/div v out = 1.2v i out = 1a with 1a pulse c out = 100 f ceramic figure 6 r esr (m ? ) 05 1020 1764a f06 20 s/div 20mv/div v out = 5v i load = 1a with 1a pulse c out = 100 f ceramic figure 8 r esr (m ? ) 05 1020 1764a f08 20 s/div 20mv/div v out = 1.2v i out = 1a with 1a pulse c out = a = 10 f ceramic b = 10 f ceramic in parallel with 22 f/ 45m ? poly c = 10 f ceramic in parallel with 100 f/ 35m ? poly figure 9 r esr (m ? ) ab c 1764a f09 20 s/div 20mv/div downloaded from: http:///
14 lt1764a series 1764afb applicatio n s i n for m atio n wu u u ceramic capacitorsextra consideration must be given to the use of ceramic capacitors. ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior over 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 f y5v capacitor can exhibit an effective value as low as 1 f to 2 f over the operating temperature range. the x5r and x7r dielectrics result inmore 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 onlysources 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. ?ree?resistance with pc traces the resistance values shown in table 1 can easily be made using a small section of pc trace in series with the output capacitor. the wide range of noncritical esr makes it easy to use pc trace. the trace width should be sized to handle the rms ripple current associated with the load. the output capacitor only sources or sinks current for a few microseconds during fast output current transitions. there temperature ( c) ?0 4020 0 ?0 ?0 ?0 ?0 100 25 75 1764 f11 ?5 0 50 100 125 y5v change in value (%) x5r both capacitors are 16v,1210 case size, 10 f figure 3. ceramic capacitor dc bias characteristics dc bias voltage (v) change in value (%) 1764 f10 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 4. ceramic capacitor temperature characteristics table 2. pc trace resistors 10m ? 20m ? 30m ? 0.5oz c u width 0.011 " (0.28mm) 0.011 " (0.28mm) 0.011 " (0.28mm) length 0.102 " (2.6mm) 0.204 " (5.2mm) 0.307 " (7.8mm) 1.0oz c u width 0.006 " (0.15mm) 0.006 " (0.15mm) 0.006 " (0.15mm) length 0.110 " (2.8mm) 0.220 " (5.6mm) 0.330 " (8.4mm) 2.0oz c u width 0.006 " (0.15mm) 0.006 " (0.15mm) 0.006 " (0.15mm) length 0.224 " (5.7mm) 0.450 " (11.4mm) 0.670 " (17mm) downloaded from: http:///
15 lt1764a series 1764afb is no dc current in the output capacitor. worst case ripple current will occur if the output load is a high frequency (>100khz) square wave with a high peak value and fast edges (< 1 s). measured rms value for this case is 0.5 times the peak-to-peak current change. slower edges orlower frequency will significantly reduce the rms ripple current in the capacitor. this resistor should be made using one of the inner layers of the pc board which are well defined. the resis- tivity is determined primarily by the sheet resistance of the copper laminate with no additional plating steps. table 2 gives some sizes for 0.75a rms current for various copper thicknesses. more detailed information regarding resistors made from pc traces can be found in application note 69, appendix a. overload recovery like many ic power regulators, the lt1764a-x has safe operating area protection. the safe area protection de- creases the current limit as input-to-output voltage in- creases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage. the protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown. when power is first 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 is small, allowing the regulator to supply large output cur- rents. with a high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. other regulators, such as the lt1085, also exhibit this phenomenon, so it is not unique to the lt1764a series. the problem occurs with a heavy output load when the input voltage is high and the output voltage is low. com- mon situations are immediately after the removal of a short circuit or when the shdn pin is pulled high after the input voltage has already been turned on. the load line for such a load may intersect the output current curve at two points. if this happens, there are two stable output operating points for the regulator. with this double applicatio n s i n for m atio n wu u u intersection, the input power supply may need to becycled down to zero and brought up again to make the output recover. output voltage noise the lt1764a regulators have been designed to provide low output voltage noise over the 10hz to 100khz band- width while operating at full load. output voltage noise is typically 50nv hz over this frequency bandwidth for the lt1764a (adjustable version). for higher output voltages(generated by using a resistor divider), the output voltage noise will be gained up accordingly. this results in rms noise over the 10hz to 100khz bandwidth of 15 v rms for the lt1764a increasing to 37 v rms for the lt1764a-3.3. higher values of output voltage noise may be measuredwhen care is not exercised with regards to circuit layout and testing. crosstalk from nearby traces can induce unwanted noise onto the output of the lt1764a-x. power supply ripple rejection must also be considered; the lt1764a regulators do not have unlimited power supply rejection and will pass a small portion of the input noise through to the output. thermal considerations the power handling capability of the device is limited by the maximum rated junction temperature (125 c). the power dissipated by the device is made up of twocomponents: 1. output current multiplied by the input/output voltage differential: (i out )(v in ?v out ), and 2. gnd pin current multiplied by the input voltage: (i gnd )(v in ). the gnd pin current can be found using the gnd pincurrent curves in the typical performance characteris- tics. power dissipation will be equal to the sum of the two components listed above. the lt1764a series regulators have internal thermal lim- iting designed to protect the device during overload con- ditions. for continuous normal conditions, the maximum junction temperature rating of 125 c must not be exceeded. it is important to give careful consideration to downloaded from: http:///
16 lt1764a series 1764afb 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. surface mount heatsinks 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 dif- ferent board sizes and copper areas. all measurements were taken in still air on 1/16" fr-4 board with one ounce copper. table 3. q package, 5-lead dd copper area thermal resistance topside* backside board area (junction-to-ambient) 2500mm 2 2500mm 2 2500mm 2 23 c/w 1000mm 2 2500mm 2 2500mm 2 25 c/w 125mm 2 2500mm 2 2500mm 2 33 c/w *device is mounted on topside.t package, 5-lead to-220 thermal resistance (junction-to-case) = 2.5 c/w calculating junction temperatureexample: given an output voltage of 3.3v, an input voltage range of 4v to 6v, an output current range of 0ma to 500ma 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) ?v out ) + i gnd (v in(max) ) where, i out(max) = 500ma v in(max) = 6v i gnd at (i out = 500ma, v in = 6v) = 10ma so, p = 500ma(6v ?3.3v) + 10ma(6v) = 1.41w using a dd package, the thermal resistance will be in therange of 23 c/w to 33 c/w depending on the copper area. so the junction temperature rise above ambient willbe approximately equal to: 1.41w(28 c/w) = 39.5 c the maximum junction temperature will then be equal tothe maximum junction temperature rise above ambient plus the maximum ambient temperature or: t jmax = 50 c + 39.5 c = 89.5 c protection featuresthe lt1764a 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 voltagesof 20v. current flow into the device will be limited to less than 1ma 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 lt1764a-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 5k or higher, limiting current flow to typically less than 600 a. for adjustable versions, the output will act like an open circuit; no current will flow outof 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 5k) in series with a diode when pulled above ground. applicatio n s i n for m atio n wu u u downloaded from: http:///
17 lt1764a series 1764afb output voltage (v) 012345678910 reverse output current (ma) 1764 f12 5.04.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 lt1764a-2.5 lt1764a-3.3 lt1764a-1.8 lt1764a t j = 25 c v in = ov current flows into output pin v out = v adj (lt1764a) v out = v fb (lt1764a-1.5 lt1764a-1.8, lt1764a-2.5, lt1764a-3.3) lt1764a-1.5 in situations where the adj pin is connected to a resistordivider 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 1.21v 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 out and adj pins 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 5. when the in pin of the lt1764a-x is forced below the out pin or the out pin is pulled above the in pin, input current figure 5. reverse output current will typically drop to less than 2 a. this can happen if the input of the device is connected to a discharged (lowvoltage) 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 typical applicatio s u + a1 lt1006 + c1b 1/2 lt1018 + c1a 1/2 lt1018 lt10041.2v 1764 ta03 1 f 1n4148 1n4148 10k 10k 750 ? 750 ? 2.4k 22 f 1n4002 to all ? + points 200k 34k* 12.1k* 0.1 f v + v + v + v + 10k v + 0.033 f + 10000 f + 22 f v out 3.3v3a + 1n4002 1n4002 1k 10v acat 115v in 1n4148 l1 500 h 90v ac to 140v ac 10v acat 115v in lt1764a-3.3 gnd inshdn out fb l1: coiltronics ctx500-2-52l2: stancor p-8560 *1% film resistor nte5437 l2 nte5437 ?ync scr preregulator provides efficiency over line variations downloaded from: http:///
18 lt1764a series 1764afb q package 5-lead plastic dd pak (reference ltc dwg # 05-08-1461) q(dd5) 1098 0.028 ?0.038 (0.711 ?0.965) 0.143 +0.012 0.020 () 3.632 +0.305 0.508 0.067 (1.70) bsc 0.013 ?0.023 (0.330 ?0.584) 0.095 ?0.115 (2.413 ?2.921) 0.004 +0.008 0.004 () 0.102 +0.203 0.102 0.050 0.012 (1.270 0.305) 0.059 (1.499) typ 0.045 ?0.055 (1.143 ?1.397) 0.165 ?0.180 (4.191 ?4.572) 0.330 ?0.370 (8.382 ?9.398) 0.060 (1.524) typ 0.390 ?0.415 (9.906 ?10.541) 15 typ 0.300 (7.620) 0.075 (1.905) 0.183 (4.648) 0.060 (1.524) 0.060 (1.524) 0.256 (6.502) bottom view of dd pak hatched area is solder plated copper heat sink typical applicatio s u adjustable current source lt1764a-1.8 gnd inshdn r8100k out fb + r7470 ? 4 8 1764 ta04 c23.3 f c3 1 f r1 1k r32k c110 f v in > 2.7v lt1004-1.2 r5 0.01 ? r2 40.2k r42.2k 23 1 r62.2k + load 1/2 lt1366 adjust r1 for 0a to 3a constant current package descriptio n u downloaded from: http:///
19 lt1764a series 1764afb package descriptio n u 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. t package 5-lead plastic to-220 (standard) (reference ltc dwg # 05-08-1421) t5 (to-220) 0399 0.028 ?0.038 (0.711 ?0.965) 0.067 (1.70) 0.135 ?0.165 (3.429 ?4.191) 0.700 ?0.728 (17.78 ?18.491) 0.045 ?0.055 (1.143 ?1.397) 0.095 ?0.115 (2.413 ?2.921) 0.013 ?0.023 (0.330 ?0.584) 0.620 (15.75) typ 0.155 ?0.195* (3.937 ?4.953) 0.152 ?0.202 (3.861 ?5.131) 0.260 ?0.320 (6.60 ?8.13) 0.165 ?0.180 (4.191 ?4.572) 0.147 ?0.155 (3.734 ?3.937) dia 0.390 ?0.415 (9.906 ?10.541) 0.330 ?0.370 (8.382 ?9.398) 0.460 ?0.500 (11.684 ?12.700) 0.570 ?0.620 (14.478 ?15.748) 0.230 ?0.270 (5.842 ?6.858) bsc seating plane * measured at the seating plane fe package 16-lead plastic tssop (4.4mm) (reference ltc dwg # 05-08-1663) exposed pad variation bb fe16 (bb) tssop 0204 0.09 ?0.20 (.0035 ?.0079) 0 ?8 0.25 ref 0.50 ?0.75 (.020 ?.030) 4.30 ?4.50* (.169 ?.177) 134 5 6 7 8 10 9 4.90 ?5.10* (.193 ?.201) 16 1514 13 12 11 1.10 (.0433) max 0.05 ?0.15 (.002 ?.006) 0.65 (.0256) bsc 2.94 (.116) 0.195 ?0.30 (.0077 ?.0118) typ 2 recommended solder pad layout 0.45 0.05 0.65 bsc 4.50 0.10 6.60 0.10 1.05 0.10 2.94 (.116) 3.58 (.141) 3.58 (.141) millimeters (inches) *dimensions do not include mold flash. mold flash shall not exceed 0.150mm (.006") per side note:1. controlling dimension: millimeters 2. dimensions are in 3. drawing not to scale see note 4 4. recommended minimum pcb metal size for exposed pad attachment 6.40 (.252) bsc downloaded from: http:///
20 lt1764a series 1764afb lt 0706 rev b printed in usa ? linear technology corporation 2002 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com related parts part number description comments lt1120 125ma low dropout regulator with 20 a i q includes 2.5v reference and comparator lt1121 150ma micropower low dropout regulator 30 a i q , sot-223 package lt1129 700ma micropower low dropout regulator 50 a quiescent current lt1175 500ma negative low dropout micropower regulator 45 a i q , 0.26v dropout voltage, sot-223 package lt1374 4.5a, 500khz step-down converter 4.5a, 0.07 ? internal switch, so-8 package lt1521 300ma low dropout micropower regulator with shutdown 15 a i q , reverse battery protection lt1529 3a low dropout regulator with 50 a i q 500mv dropout voltage lt1573 ultrafast tm transient response low dropout regulator drives external pnp lt1575 ultrafast transient response low dropout regulator drives external n-channel mosfet ltc1735 synchronous step-down converter high efficiency, opti-loop compensation lt1761 series 100ma, low noise, low dropout micropower regulators in sot-23 20 a quiescent current, 20 v rms noise, thinsot tm package lt1762 series 150ma, low noise, ldo micropower regulators 25 a quiescent current, 20 v rms noise, msop package lt1763 series 500ma, low noise, ldo micropower regulators 30 a quiescent current, 20 v rms noise, so-8 package lt1962 300ma, low noise, ldo micropower regulator 20 v rms noise, msop package lt1963a 1.5a, low noise, fast transient response ldo 40 v rms noise, sot-223 package lt1964 200ma, low noise, negative ldo micropower regulator 30 v rms noise, thinsot package opti-loop is a registered trademark of linear technology corporation. ultrafast and thinsot are trademarks of linear technology corporation. typical applicatio u paralleling of regulators for higher output current lt1764a-3.3 gnd inshdn out fb lt1764a gnd in r66.65k c222 f 3.3v6a shdn out adj shdn + r74.12k r5 1k c3 0.01 f 3 r4 2.2k r2 0.01 ? r3 2.2k 2 1 8 1764 ta05 4 + c1100 f + 1/2 lt1366 r1 0.01 ? v in > 3.7v downloaded from: http:///

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