1 lt1120a 1120afa n 20 m a supply current n 125ma output current n 2.5v reference n reference output sources 4ma and sinks 4ma n open collector comparator sinks 10ma n logic shutdown n 0.2v dropout voltage n thermal limiting n 8-lead so package the lt ? 1120a is a combination micropower positive regulator and free collector comparator on a single mono- lithic chip. with only 20 m a supply current, the lt1120a can supply over 125ma of output current. input voltage range is from 4.5v to 36v and dropout voltage is 0.6v at 125ma. dropout voltage decreases with lower load cur- rents. also included on the chip is a class b output 2.5v reference that can either source or sink current. this allows it to be used as a supply splitter or auxiliary output. a shutdown pin allows logic shutdown of the output. the comparator can be used for system or battery moni- toring. for example, the comparator can be used to warn of low system voltage. frequency compensation of the comparator for amplifier applications can be obtained by adding external output capacitance. micropower regulator with comparator and shutdown dropout voltage and supply current 5v regulator 1120a ta01 v in > 5.2v i q = 20 m a 10 m f 1m shutdown 1 3 54 2 0.001 m f 25 m f 1m 5v lt1120a v out v in gnd fb + + output current (ma) 0.1 0.01 dropout voltage (v) 1.00 1 1000 1120a ta02 10 0.10 100 0.1 supply current (ma) 10 1 n battery systems n battery backup system n portable terminals n portable instruments n memory keep alive features descriptio u applicatio s u typical applicatio u , ltc and lt are registered trademarks of linear technology corporation.
2 lt1120a 1120afa (note 1) input voltage ........................................................... 36v npn collector voltage ............................................. 36v output short-circuit duration .......................... indefinite power dissipation ............................... internally limited operating temperature range lt1120ac ............................................. 0 c to 100 c lt1120ai ......................................... C 40 c to 100 c storage temperature range ................. C 65 c to 150 c absolute m axi m u m ratings w ww u package/order i n for m atio n w u u order part number lt1120acn8 lt1120acs8 lt1120ais8 t j = 25 c t jmax = 110 c, q ja = 130 c/w (n) t jmax = 110 c, q ja = 190 c/w (s) 1 2 3 4 8 7 6 5 top view gnd feedback shutdown v out ?nput comp out ref v in n8 package 8-lead pdip s8 package 8-lead plastic so s8 part marking 1120a 1120ai consult ltc marketing for parts specified with wider operating temperature ranges. parameter conditions min typ max units reference reference voltage 4.5v v in 36v 2.46 2.50 2.54 v line regulation 4.5v v in 36v 0.01 0.015 %/v load regulation C2.0ma i ref 2ma, v in = 12v 0.3 0.6 % output source current v in = 5v 2 4 ma output sink current v in = 5v 2 4 ma temperature stability 1% regulator supply current v in = 6v, i out 100ma 20 25 m a v in = 36v, i out 100ma 30 40 m a v in = 12v, i out = 125ma 11 20 ma output current (v in C v out ) 3 1v, v in 3 6v 125 ma load regulation (v in C v out ) 3 1v, v in 3 6v 0.2 0.5 % line regulation 6v v in 36v 0.01 0.015 %/v dropout voltage i out = 100ma 0.02 0.05 v i out = 125ma 0.40 0.65 v feedback sense voltage v in = 12v 2.44 2.5 2.56 v shutdown pin voltage normal 0.4 v v out 0.5v shutdown 2.2 1.4 v shutdown pin current v in = 1.4v 10 m a feedback bias current 15 40 na minimum load current v in = 36v 1 5 m a short-circuit current v in = 36v 250 400 ma comparator offset voltage v in = 36v 3 7 mv bias current v in = 36v 15 40 na gain d v out = 29v, r l = 20k 2000 10000 v/v power supply rejection 4.5v v s 36v 80 96 db output sink current v in = 4.5v 10 18 ma saturation voltage i out = 1ma 0.4 0.6 v input voltage range 0 v in C 1 v response time 5 m s leakage current v in = 36v, v(pin 7) = 36v 2 m a electrical characteristics
3 lt1120a 1120afa temperature ( c) ?0 0 short-circuit current (ma) 350 150 1120a g03 300 250 200 150 100 50 110 ?0 30 70 regulator output current (ma) 0.1 0.01 supply current (ma) 0.1 100 1 1000 1120a g02 10 1 100 10 note 1: absolute maximum ratings are those values beyond which the life to the device may be impaired. regulator load regulation supply current regulator short-circuit current output current (ma) 0.1 ?.3 output voltage change (%) 0.3 10 1000 1120a g01 100 1 0.2 0.1 0 ?.1 ?.2 t j = ?5 c t j = 25 c t j = 125 c pre-load = 100 m a parameter conditions min typ max units reference reference voltage 4.5v v in 36v l 2.40 2.50 2.55 v line regulation 4.5v v in 36v l 0.01 0.02 %/v load regulation C2.0ma i ref 2ma, v in = 12v l 0.4 0.8 % output source current v in = 5v l 2ma output sink current v in = 5v l 2ma regulator supply current v in = 6v, i out 100 m a l 30 40 m a v in = 36v, i out 100 m a l 40 50 m a v in = 12v, i out = 125ma l 11 20 ma output current (v in C v out ) 3 1v, v in 3 6v l 125 ma load regulation (v in C v out ) 3 1v, v in 3 6v l 1% line regulation 6v v in 36v l 0.02 %/v dropout voltage i out = 100 m a l 0.06 v i out = 125ma l 0.85 v feedback sense voltage v in = 12v l 2.38 2.5 2.57 v feedback bias current l 50 na minimum load current v in = 36v l 50 m a short-circuit current v in = 36v l 240 400 ma comparator offset voltage v in = 36v l 10 mv bias current v in = 36v l 15 60 na gain d v out = 29v, r l = 20k l 1000 v/v output sink current (note 2) v in = 4.5v l 510 ma leakage current v in = 36v, v(pin 7) = 36v l 8 m a electrical characteristics note 2 : for t a C40 c output sink current drops to 2.5ma. the l denotes the specifications which apply over the full operating temperature range of t j = 25 c. typical perfor a ce characteristics uw
4 lt1120a 1120afa regulator output current (ma) 0.1 0 feedback pin current (na) 40 1 1000 1120a g10 10 20 100 35 30 25 15 10 5 t j = ?5 c t j = 25 c t j = 125 c regulator output current (ma) 0.1 0.01 regulator input-output differential (v) 1 1 1000 1120a g04 10 0.1 100 d v out = 100mv regulator minimum load current regulator ripple rejection supply current at dropout reference regulation temperature ( c) 70 1 minimum load current ( m a) 100 80 150 1120a g05 110 10 130 90 100 120 140 ripple frequency (hz) 10 30 ripple rejection (db) 70 1k 100k 1120a g06 10k 100 65 60 55 50 45 40 35 i out = 100ma i out = 10ma v in = 10vdc, 1v p-p v out = 5v c out = 10 m f i out = 1ma regulator input-output differential (v) 0 0.01 supply current (ma) 0.1 10 0.2 0.6 1120a g08 0.3 1 0.1 0.5 i out = 100ma i out = 10ma i out = 1ma 0.4 reference output current (ma) ?.5 ? reference voltage change (mv) 4 0 1.5 1120a g09 0.5 ?.0 3 2 1 0 ? ? ? ?.5 1.0 dropout voltage supply current regulator input-output differential (v) 1 0.01 supply current (ma) 0.1 10 10 25 1120a g07 15 1 5 20 i out = 100ma i out = 10ma v out = 5v i out = 1ma feedback pin current regulator thermal regulation turn-on characteristic time (ms) 0 output current (ma) 0.1 180 1120a g11 80 0 ?.1 50 0 20 40 60 100 120 140 160 output voltage change (%) v in = 15v v out = 5v input voltage (v) 0 5.5 1120a g12 0 output voltage (v) 5.0 4.5 4.0 3.5 3.0 2.5 2.0 12 345678 v out = 5v no load r l = 500 w r l = 50 w typical perfor a ce characteristics uw
5 lt1120a 1120afa gnd (pin 1): ground feedback (pin 2): this is the feedback point of the regulator. when operating, it is nominally at 2.5v. optimum source resistance is 200k to 500k. the feedback pin should not be driven below ground or more positive than 5v. shutdown (pin 3): a logic 1 shuts off main regulator. caution: noise or leakage into the shutdown pin can affect output voltage. v out (pin 4): main output, requires 10 m f output capaci- tor. can be shorted to v in or ground without damaging device. v in (pin 5): input supply. bypass with 10 m f capacitor. must always be more positive than ground. ref (pin 6): reference. 2.5v can source or sink current. may be shorted to ground or up to 5v. voltages in excess of 5v can damage the device. comp out (pin 7): open collector npn output. may be connected to any voltage from ground to 36v more positive than ground (operates above v in ). short-circuit protected. Cinput (pin 8): inverting comparator input. + 100k 5 7 6 ref 8 ?nput 120k v in comp out 4v out 2 feedback 3 shutdown 1 ground ref 2.5v 1120a bd01 the lt1120a is especially suited for micropower system applications. for example, the comparator section of the lt1120a may be used as a battery checker to provide an indication of low battery. another type of system applica- tion for the lt1120a would be to generate the equivalent of split supplies off of a single power input. the regulator section provides regulated output voltage and the reference, which can both source and sink current is then an artificial system ground providing a split supply for the system. for many applications the comparator can be frequency compensated to operate as an amplifier. compensation values for various gains are given in the data sheet. the comparator gain is purposely low to make it easier to frequency compensate as an amplifier. the npn output is capable of sinking 10ma and can drive loads connected to voltages in excess of the positive power supply. this is useful for driving switches or linear regulators off of a higher input voltage. uu u pi fu ctio s block diagra w applicatio s i for atio wu uu
6 lt1120a 1120afa applicatio n s i n for m atio n wu u u reference internal to the lt1120a is a 2.5v trimmed class b output reference. the reference was designed to be able to source or sink current so it could be used in supply splitting applications as well as a general purpose reference for external circuitry. the design of the reference allows it to source and sink typically 4ma. the available source and sink current decreases as temperature increases. it is sometimes desirable to decrease the ac output imped- ance by placing an output capacitor on pin 6. the reference in the lt1120a becomes unstable with large capacitive loads placed directly on it. when using an output capaci- tor, about 20 w should be used to isolate the capacitor from the reference pin. this 20 w resistor can be placed directly in series with the capacitor or alternatively the reference line can have 20 w placed in series with it and then a capacitor to ground. this is shown in figure 1. other than placing large capacitive loads on the reference, no other precautions are necessary and the reference is stable with nominal stray capacitances. like most other ic regulators, a minimum load is required on the output of the lt1120a to maintain regulation. for most standard regulators this is normally specified at 5ma. of course, for a micropower regulator this would be a tremendously large current. the output current must be large enough to absorb all the leakage current of the pass transistor at the maximum operating temperature. it also affects the transient response; low output currents have long recovery times from load transients. at high operat- ing temperatures the minimum load current increases and having too low of a load current may cause the output to go unregulated. devices are tested for minimum load current at high temperature. the output voltage setting resistors to the feedback terminal can usually be used to provide the minimum load current. frequency compensation the lt1120a is frequency compensated by a dominant pole on the output. an output capacitor of 10 m f is usually large enough to provide good stability. increasing the output capacitor above 10 m f further improves stability . in order to ensure stability, a feedback capacitor is needed between the output pin and the feedback pin. this is because stray capacitance can form another pole with the large value of feedback resistors used with the lt1120a. also, a feedback capacitor minimizes noise pickup and improves ripple rejection. with the large dynamic operating range of the output current, 10000:1, frequency response changes widely. low ac impedance capacitors are needed to insure stability. while solid tantalum are best, aluminum electrolytics can be used but larger capacitor values may be needed. figure 1. bypassing reference 1120a ai01 20 w 6 10 m f output ref + 20 w 6 10 m f ref + output or overload protection the main regulator in the lt1120a is current limited at approximately 250ma. the current limit is stable with both input voltage and temperature.
7 lt1120a 1120afa 1120a ta04 + c1 r1 at a v = 100, slew rate = +0.05v/ m s 6v/ m s 1m c2 r2 in 6 v ref 7 50 m a a v ? ?0 ?00 r1 33 w 100 w 10k c1 0.1 m f 0.047 m f 0.002 m f c2 0.001 m f r2 1m 100k 10k compensating the comparator as an op amp regulator with output voltage monitor 1120a ta03 + logic 500k 5v logic output 7 ref 6 lt1120a 5 v in output 1 gnd feedback 4 8 2 0.001 m f 98k 2k 100k 10 m f output 5v logic output goes low when v out drops by 100mv + v out pin 7 logic output current limited 1 amp regulator lt1120a 1 gnd 1m 100k 220 m f ? + 0.22 m f v out 270 w 2.2k 5 v in 4 2 fb 0.5 w * v in v out 5v at 1a * sets current limit but increases dropout voltage by 0.5v. must have low esr. several 100 m f capacitors can be paralleled. ? 1120a ta06 mje2955 2n3906* battery backup regulator 1120a ta05 v out fb 4 v out 5v 2 0.001 m f 1m 50k 1m 10 m f lt1120a 1 gnd 5 v in battery input v in fb lt1120a 1 gnd v out 5 main power input + 4 2 v in v out internal parasitic diodes of lt1120a 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. typical applicatio s u
8 lt1120a 1120afa lt/tp 0104 1k rev a ? printed in usa ? linear technology corporation 1994 u package descriptio n8 package 8-lead pdip (narrow .300 inch) (reference ltc dwg # 05-08-1510) s8 package 8-lead plastic small outline (narrow .150 inch) (reference ltc dwg # 05-08-1610) n8 1002 .065 (1.651) typ .045 ?.065 (1.143 ?1.651) .130 .005 (3.302 0.127) .020 (0.508) min .018 .003 (0.457 0.076) .120 (3.048) min .008 ?.015 (0.203 ?0.381) .300 ?.325 (7.620 ?8.255) .325 +.035 ?015 +0.889 0.381 8.255 () 12 3 4 87 6 5 .255 .015* (6.477 0.381) .400* (10.160) max note: 1. dimensions are inches millimeters *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .010 inch (0.254mm) .100 (2.54) bsc .016 ?.050 (0.406 ?1.270) .010 ?.020 (0.254 ?0.508) 45 0 ?8 typ .008 ?.010 (0.203 ?0.254) so8 0303 .053 ?.069 (1.346 ?1.752) .014 ?.019 (0.355 ?0.483) typ .004 ?.010 (0.101 ?0.254) .050 (1.270) bsc 1 2 3 4 .150 ?.157 (3.810 ?3.988) note 3 8 7 6 5 .189 ?.197 (4.801 ?5.004) note 3 .228 ?.244 (5.791 ?6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note: 1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm) linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com related parts part number description comments lt1761/lt1762 100ma/150ma, low noise v in : 1.8v to 20v; v out(min) = 1.22v; dropout voltage = 0.30v; i q = 20 m a; i sd < 1 m a; v out = adj, micropower, ldo 1.5v, 1.8v, 2v, 2.5v, 2.8v, 3v, 3.3v, 5v; thinsot tm /ms8 packages. low noise <20 m v rmsp-p lt1763 500ma, low noise micropower, ldo v in : 1.8v to 20v; v out(min) = 1.22v; dropout voltage = 0.30v; i q = 30 m a; i sd < 1 m a; v out = 1.5v, 1.8v, 2.5v,3v, 3.3v, 5v; so-8 package. low noise <20 m v rmsp-p lt1764/lt1764a 3a, low noise, fast transient v in : 2.7v to 20v; v out(min) = 1.21v; dropout voltage = 0.34v; i q = 1ma; i sd < 1 m a; response, ldo v out = 1.8v, 2.5v, 3.3; dd, to220, packages. low noise <40 m v rmsp-p , a version stable with ceramic capacitors lt1962 300ma, low noise micropower, ldo v in : 1.8v to 20v; v out(min) = 1.22v; dropout voltage = 0.27v; i q = 30 m a; i sd < 1 m a; v out = 1.5v, 1.8v, 2.5v,3v, 3.3v, 5v; ms8 package. low noise <20 m v rmsp-p lt1963/lt1963a 1.5a, low noise, fast transient v in : 2.1v to 20v; v out(min) = 1.21v; dropout voltage = 34v; i q = 1ma; i sd < 1 m a; v out = 1.5v response, ldo 1.8v, 2.5v, 3.3; dd, to220, sot-223, so-8 packages. low noise <40 m v rmsp-p , a version stable with ceramic capacitors lt1964 200ma, low noise micropower v in : C0.9v to C20v; v out(min) = C1.21v; dropout voltage = 0.34v; i q = 30 m a; i sd < 3 m a; negative, ldo v out = adj, C5v; thinsot package. low noise <30 m v rmsp-p , stable with ceramic capacitors lt3010 80v, 50ma, low noise linear v in : 1.5v to 80v; v out(min) = 1.28v; dropout voltage = 0.30v; i q = 30 m a; i sd < 1 m a; regulator v out = adj, C5v; ms8e package. low noise <100 m v rmsp-p , stable with ceramic capacitors thinsot is a trademark of linear technology corporation.
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