lp3981 micropower, 300ma ultra low-dropout cmos voltage regulator general description the lp3981's performance is optimized for battery powered systems to deliver ultra low noise, extremely low dropout voltage and low quiescent current. regulator ground current increases only slightly in dropout, further prolonging the battery life. power supply rejection is better than 60 db at low frequen- cies. this high power supply rejection is maintained down to lower input voltage levels common to battery operated cir- cuits. the device is ideal for mobile phone and similar battery powered wireless applications. it provides up to 300 ma, from a 2.5v to 6v input, consuming less than 1a in disable mode and has fast turn-on time less than 200s. the lp3981 is available in msop-8 package. for lp3981 in llp-6 package, contact nsc sales offices. performance is specified for ?40c to +125c temperature range. the de- vice available in the following output voltages; 2.5v, 2.7v, 2.8v, 2.83v, 3.03v and 3.3v as standard. other output op- tions can be made available, please contact your local nsc sales office. key specifications n 2.5 to 6.0v input range n 300ma guaranteed output n 60db psrr at 1khz n 1a quiescent current when shut down n fast turn-on time: 120 s (typ.) n 132mv typ dropout with 300ma load n 35vrms output noise over 10hz to 100khz n ?40 to +125c junction temperature range for operation n 2.5v, 2.7v, 2.8v, 2.83v, 3.03v and 3.3v outputs standard features n small, space saving msop-8 n low thermal resistance in llp-6 package gives excellent power capability n logic controlled enable n stable with ceramic and high quality tantalum capacitors n fast turn-on n thermal shutdown and short-circuit current limit applications n cdma cellular handsets n wideband cdma cellular handsets n gsm cellular handsets n portable information appliances n tiny 3.3v 5% to 2.5v, 300ma converter typical application circuit 20020302 note: pin numbers in parenthesis indicate llp-6 package. october 2001 lp3981 micropower, 300ma ultra low-dropout cmos voltage regulator ? 2001 national semiconductor corporation ds200203 www.national.com
block diagram 20020301 pin descriptions name msop-8 llp-6 function v en 7 6 enable input logic, enable high gnd 5 4 common ground v out 1 1 output voltage of the ldo v in 2 2 input voltage of the ldo bypass 6 5 optional bypass capacitor for noise reduction v out-sense 4 3 output. voltage sense pin. should be connected to v out for proper operation. n.c 3, 8 connection diagrams msop-8 package 20020307 top view see ns package number mua008ae llp-6 package 20020370 top view see ns package number ldc06d lp3981 www.national.com 2
ordering information for llp-6 package * output voltage (v) grade lp3981 supplied as 250 units, tape and reel lp3981 supplied as 3000 units, tape and reel package marking 2.5 std lp3981ild-2.5 lp3981ildx-2.5 lo1ub 2.7 std lp3981ild-2.7 lp3981ildx-2.7 lo1vb 2.8 std lp3981ild-2.8 lp3981ildx-2.8 lo1zb 2.83 std lp3981ild-2.83 lp3981ildx-2.85 l01sb 3.03 std lp3981ild-3.03 lp3981ildx-3.03 lo1yb 3.3 std lp3981ild-3.3 lp3981ildx-3.3 lo1xb for msop-8 package output voltage (v) grade lp3981 supplied as 1000 units, tape and reel lp3981 supplied as 3000 units, tape and reel package marking 2.5 * std lp3981imm-2.5 lp3981immx-2.5 lfkb 2.7 * std lp3981imm-2.7 lp3981immx-2.7 lflb 2.8 * std lp3981imm-2.8 lp3981immx-2.8 lftb 2.83 std lp3981imm-2.83 lp3981immx-2.83 ldub 3.03 std lp3981imm-3.03 lp3981immx-3.03 lfpb 3.3 * std lp3981imm-3.3 lp3981immx-3.3 lfnb * please contact factory for availability. lp3981 www.national.com 3
absolute maximum ratings (notes 1, 2) if military/aerospace specified devices are required, please contact the national semiconductor sales office/ distributors for availability and specifications. v in ,v en ?0.3 to 6.5v v out ,v out-sense ?0.3 to v in + 0.3, max 6.5v junction temperature 150c storage temperature ?65c to +150c lead temp. pad temp. power dissipation (note 3) q ja (msop-8) q ja (llp-6) 210c/w 50c/w maximum power dissipation at 25c msop-8 llp-6 595mw 2.5w esd rating(note 4) human body model machine model 2kv 200v operating ratings (notes 1, 2) v in 2.7 to 6v v en 0tov in junction temperature ?40c to +125c maximum power dissipation (note 5) msop-8 llp-6 476mw 2.0w electrical characteristics unless otherwise specified: v en = 1.2v, v in =v out + 0.5v, c in = 2.2 f, c bp = 0.033 f, i out = 1ma, c out = 2.2 f. typi- cal values and imits appearing in standard typeface are for t j = 25c. limits appearing in boldface type apply over the entire junction temperature range for operation, ?40c to +125c. (notes 6, 7) symbol parameter conditions typ limit units min max d v out output voltage tolerance ?2 ?3 2 3 %of v out(nom) line regulation error v in =v out + 0.5v to 6.0v, t a < +85c 0.005 ?0.1 0.1 %/v v in =v out + 0.5v to 6.0v, t j 125c ?0.2 0.2 %/v load regulation error (note 8) i out = 1 ma to 300 ma 0.0003 0.005 %/ma psrr power supply rejection ratio (note 10) v in =v out(nom) + 1v, f = 1 khz, i out =50ma( figure 2 ) 50 db v in =v out(nom) + 1v, f = 10 khz, i out =50ma( figure 2 ) 55 i q quiescent current v en = 1.2v, i out = 1 ma 70 120 a v en = 1.2v, i out = 1to 300 ma 170 220 v en = 0.4v 0.003 1.0 dropout voltage (note 9) i out =1ma 0.5 5 mv i out = 200 ma 88 133 i out = 300 ma 132 200 i sc short circuit current limit output grounded (steady state) 600 ma e n output noise voltage bw = 10 hz to 100 khz, c bp = 0.033f 35 vrms tsd thermal shutdown temperature 160 c thermal shutdown hysteresis 20 c i out(pk) peak output current v out 3 v out (nom) - 5% 455 300 i en maximum input current at v en v en = 0 and v in 0.001 a v il logic low input threshold v in = 2.7 to 6.0v 0.4 v v ih logic high input threshold v in = 2.7 to 6.0v 1.4 v t on turn-on time (note 11) c bypass = 0.033 f 120 s lp3981 www.national.com 4
electrical characteristics (continued) note 1: absolute maximum ratings are limits beyond which damage to the device may occur. operating ratings are conditions under which operation of the device is guaranteed. operating ratings do not imply guaranteed performance limits. for guaranteed performance limits and associated test conditions, se e the electrical characteristics tables. note 2: all voltages are with respect to the potential at the gnd pin. note 3: the figures given for absolute maximum power disipation for the device are calculated using the following equations: where t j(max) is the maximum junction temperature, t a is the ambient temperature, and q ja is the junction-to-ambient thermal resistance. e.g. for the llp package q ja =50c/w, t j(max) =150c and using t a =25c the maximum power dissipation is found to be 2.5w. the derating factor (?1/ q ja )= ?20mw/c, thus below 25c the power dissipation figure can be increased by 20w per degree, and similarity decreased by this factor for temperatures ab ove 25c note 4: the human body model is 100pf discharged through 1.5k w resistor into each pin. the machine model is a 200 pf capacitor discharged directly into each pin. note 5: as for the maximum power dissipation, the maximum power in operation is dependant on the ambient temperature. this can be calculated in teh same way using t j =125c, giving 2w as the maximum power dissipation for the llp package in operation. the same derating factor applies. note 6: all limits are guaranteed. all electrical characteristics having room-temperature limits are tested during production with t j = 25c or correlated using statistical quality control (sqc) methods. all hot and cold limits are guaranteed by correlating the electrical characteristics to process and temp erature variations and applying statistical process control. note 7: the target output voltage, which is labeled v out(nom) , is the desired voltage option. note 8: an increase in the load current results in a slight decrease in the output voltage and vice versa. note 9: dropout voltage is the input-to-output voltage difference at which the output voltage is 100mv below its nominal value. this specification does not a pply for input voltages below 2.5v. note 10: guaranteed by design. note 11: turn-on time is time measured between the enable input just exceeding v ih and the output voltage just reaching 95% of its nominal value. output capacitor, recommended specification symbol parameter conditions typ limit units min max c out output capacitor capacitance 2.2 22 f esr 5 500 m w 20020308 figure 1. line transient response input perturbation 20020309 figure 2. psrr input perturbation lp3981 www.national.com 5
typical performance characteristics unless otherwise specified, c in =c out = 2.2 f ceramic, c bp = 0.033 f, v in =v out + 0.2v, t a = 25c, enable pin is tied to v in . ripple rejection ripple rejection 20020371 20020310 load transient response load transient response 20020311 20020312 load transient response load transient response 20020313 20020314 lp3981 www.national.com 6
typical performance characteristics unless otherwise specified, c in =c out = 2.2 f ceramic, c bp = 0.033 f, v in =v out + 0.2v, t a = 25c, enable pin is tied to v in . (continued) enable response 20020315 application hints power dissipation and device operation the permissible power dissipation for any package is a measure of the capability of the device to pass heat from the power source, the junctions of the ic, to the ultimate heat sink, the ambient environment. thus, the power dissipation is dependant on the ambient temperature and the thermal resistance across the various interfaces between the die and ambient air. as stated in notes 3 and 5 in the electrical specifications sections, the allowable power dissipation for the device in a given package can be calculated using the equation: with a q ja = 50c/w, the device in thellp package returns a value of 2.0w with a maximum junction temperature of 125c and an ambient temperature of 25c. the device in a msop package returns a figure of 0.476w, ( q ja = 210c/w). the actual power dissipation across the device can be rep- resented by the following equation: p d =(v in ?v out )xi out this establishes the relationship between the power dissipa- tion allowed due to thermal considerations, the voltage drop across the device, and the continuous current capability of the device. the device can deliver 300ma but care must be taken when choosing the continuous current output for the device under the operating load conditions. external capacitors like any low-dropout regulator, the lp3981 requires external capacitors for regulator stability. the lp3981 is specifically designed for portable applications requiring minimum board space and smallest components. these capacitors must be correctly selected for good performance. input capacitor an input capacitance of ) 2.2f is required between the lp3981 input pin and ground (the amount of the capacitance may be increased without limit). this capacitor must be located a distance of not more than 1cm from the input pin and returned to a clean analog ground. any good quality ceramic, tantalum, or film capacitor may be used at the input. important: tantalum capacitors can suffer catastrophic fail- ures due to surge current when connected to a low-impedance source of power (like a battery or a very large capacitor). if a tantalum capacitor is used at the input, it must be guaranteed by the manufacturer to have a surge current rating sufficient for the application. there are no requirements for the esr on the input capaci- tor, but tolerance and temperature coefficient must be con- sidered when selecting the capacitor to ensure the capaci- tance will be ) 2.2f over the entire operating temperature range. output capacitor the lp3981 is designed specifically to work with very small ceramic output capacitors. a ceramic capacitor (dielectric types z5u, y5v or x7r) in 2.2 to 22 f range with 5m w to 500m w esr range is suitable in the lp3981 application circuit. it may also be possible to use tantalum or film capacitors at the output, but these are not as attractive for reasons of size and cost (see next section capacitor characteristics). the output capacitor must meet the requirement for mini- mum amount of capacitance and also have an esr (equiva- lent series resistance) value which is within a stable range (5 m w to 500 m w ). no-load stability the lp3981 will remain stable and in regulation with no external load. this is specially important in cmos ram keep-alive applications. noise bypass capacitor connecting a 0.033f capacitor between the c bp pin and ground significantly reduces noise on the regulator output. this cap is connected directly to a high impedance node in the bad gap reference circuit. any significant loading on this node will cause a change on the regulated output voltage. for this reason, dc leakage current through this pin must be kept as low as possible for best output voltage accuracy. the types of capacitors best suited for the noise bypass capacitor are ceramic and film. hight-quality ceramic capaci- lp3981 www.national.com 7
application hints (continued) tors with either npo or cog dielectric typically have very low leakage. polypropolene and polycarbonate film capaci- tors are available in small surface-mount packages and typically have extremely low leakage current. unlike many other ldo's, addition of a noise reduction capacitor does not effect the transient response of the de- vice. capacitor characteristics the lp3981 is designed to work with ceramic capacitors on the output to take advantage of the benefits they offer: for capacitance values in the range of 1f to 4.7f range, ceramic capacitors are the smallest, least expensive and have the lowest esr values (which makes them best for eliminating high frequency noise). the esr of a typical 1f ceramic capacitor is in the range of 20 m w to 40 m w , which easily meets the esr requirement for stability by the lp3981. the ceramic capacitor's capacitance can vary with tempera- ture. most large value ceramic capacitors ( ) 2.2f) are manufactured with z5u or y5v temperature characteristics, which results in the capacitance dropping by more than 50% as the temperature goes from 25c to 85c. a better choice for temperature coefficient in a ceramic capacitor is x7r, which holds the capacitance within 15%. tantalum capacitors are less desirable than ceramic for use as output capacitors because they are more expensive when comparing equivalent capacitance and voltage ratings in the 1f to 4.7f range. another important consideration is that tantalum capacitors have higher esr values than equivalent size ceramics. this means that while it may be possible to find a tantalum capacitor with an esr value within the stable range, it would have to be larger in capacitance (which means bigger and more costly ) than a ceramic capacitor with the same esr value. it should also be noted that the esr of a typical tantalum will increase about 2:1 as the temperature goes from 25c down to ?40c, so some guard band must be allowed. on/off input operation the lp3981 is turned off by pulling the v en pin low, and turned on by pulling it high. if this feature is not used, the v en pin should be tied to v in to keep the regulator output on at all time. to assure proper operation, the signal source used to drive the v en input must be able to swing above and below the specified turn-on/off voltage thresholds listed in the elec- trical characteristics section under v il and v ih . fast on-time the lp3981 utilizes a speed up circuitry to ramp up the internal v ref voltage to its final value to achieve a fast output turn on time. lp3981 www.national.com 8
physical dimensions inches (millimeters) unless otherwise noted ns package number mua008ae lp3981 www.national.com 9
physical dimensions inches (millimeters) unless otherwise noted (continued) ns package number ldc06d life support policy national's products are not authorized for use as critical components in life support devices or systems without the express written approval of the president and general counsel of national semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. a critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. national semiconductor corporation americas email: support@nsc.com national semiconductor europe fax: +49 (0) 180-530 85 86 email: europe.support@nsc.com deutsch tel: +49 (0) 69 9508 6208 english tel: +44 (0) 870 24 0 2171 fran?ais tel: +33 (0) 1 41 91 8790 national semiconductor asia pacific customer response group tel: 65-2544466 fax: 65-2504466 email: ap.support@nsc.com national semiconductor japan ltd. tel: 81-3-5639-7560 fax: 81-3-5639-7507 www.national.com lp3981 micropower, 300ma ultra low-dropout cmos voltage regulator national does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and national reserves the righ t at any time without notice to change said circuitry and specifications.
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