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lm1117 800ma low-dropout linear regulator general description the lm1117 is a series of low dropout voltage regulators with a dropout of 1.2v at 800ma of load current. it has the same pin-out as national semiconductor's industry standard lm317. the lm1117 is available in an adjustable version, which can set the output voltage from 1.25v to 13.8v with only two ex- ternal resistors. in addition, it is also available in three fixed voltages, 2.85v, 3.3v, and 5v. the lm1117 offers current limiting and thermal shutdown. its circuit includes a zener trimmed bandgap reference to as- sure output voltage accuracy to within 1 % . the lm1117 series is available in sot-223, to-220, and to-252 d-pak packages. a minimum of 10f tantalum ca- pacitor is required at the output to improve the transient re- sponse and stability. features n available in 2.85v, 3.3v, 5v, and adjustable versions n space saving sot-223 package n current limiting and thermal protection n output current 800ma n temperature range 0c to 125c n line regulation 0.2 % (max) n load regulation 0.4 % (max) applications n 2.85v model for scsi-2 active termination n post regulator for switching dc/dc converter n high efficiency linear regulators n battery charger n battery powered instrumentation typical application active terminator for scsi-2 bus fixed output regulator 1 lm1117 800ma low-dropout linear regulator
ordering information package temperature range packing 0c to +125c 3-lead sot-223 lm1117 -adj-223 tape and reel lm1117 -2.85-223 t ape and reel lm1117 -3.3-223 tape and reel lm1117 -5.0-223 tape and reel 3-lead to-220 lm1117 -adj-220 rails 5 lead available lm1117 -2.85-220 rails suffix add 220-5l lm1117 -3.3-220 rails lm1117 -5.0-220 rails 3-lead to-252 lm1117 -adj-252 tape and reel 5 lead available lm1117-2.85-252 tape and reel suffix add 252-5l lm1117-3.3-252 tape and reel lm1117-5.0-252 tape and reel block diagram 2 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
connection diagrams sot-223 ds100919-4 top view to-220 ds100919-2 top view to-252 ds100919-38 top view 3 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
absolute maximum ratings (note 1) if military/aerospace specified devices are required, please contact the national semiconductor sales office/ distributors for availability and specifications. maximum input voltage (v in to gnd) lm1117-adj, lm1117-3.3, lm1117-5.0 20v power dissipation (note 2) internally limited junction temperature (t j ) (note 2) 150c storage temperature range -65c to 150c lead temperature to-220 package 260c, 10 sec sot-223 package 260c, 4 sec esd tolerance (note 3) 2000v operating ratings (note 1) input voltage (v in to gnd) lm1117-adj, lm1117-3.3, lm1117-5.0 15v lm1117-2.85 10v junction temperature range (t j ) (note 2) 0c to 125c electrical characteristics typicals and limits appearing in normal type apply for t j = 25c. limits appearing in boldface type apply over the entire junc- tion temperature range for operation, 0c to 125c. symbol parameter conditions min (note 5) typ (note 4) max (note 5) units v ref reference voltage lm1117-adj i out =10ma, v in -v out =2v, t j =25c 10ma i out 800ma, 1.4v v in -v out 10v 1.238 1.225 1.250 1.250 1.262 1.270 v v v out output voltage lm1117-2.85 i out =10ma, v in =4.85v, t j =25c o i out 800ma, 4.25v v in 10v o i out 500ma, v in =4.10v 2.820 2.790 2.790 2.850 2.850 2.850 2.880 2.910 2.910 v v v lm1117-3.3 i out =10ma, v in =5v t j =25c o i out 800ma, 4.75v v in 10v 3.267 3.235 3.300 3.300 3.333 3.365 v v lm1117-5.0 i out =10ma, v in =7v, t j =25c o i out 800ma, 6.5v v in 12v 4.950 4.900 5.000 5.000 5.050 5.100 v v d v out line regulation (note 6) lm1117-adj i out =10ma, 1.5v v in -v out 13.75v 0.035 0.2 % lm1117-2.85 i out =0ma, 4.25v v in 10v 1 6 mv lm1117-3.3 i out =0ma, 4.75v v in 15v 1 6 mv lm1117-5.0 i out =0ma, 6.5v v in 15v 1 10 mv d v out load regulation (note 6) lm1117-adj v in -v out =3v, 10 i out 800ma 0.2 0.4 % lm1117-2.85 v in =4.25v, 0 i out 800ma 1 10 mv lm1117-3.3 v in =4.75v, 0 i out 800ma 1 10 mv lm1117-5.0 v in =6.5v, 0 i out 800ma 1 15 mv v in -v out dropout voltage (note 7) i out =100ma 1.10 1.20 v i out =500ma 1.15 1.25 v i out =800ma 1.20 1.30 v i limit current limit v in -v out =5v, t j =25c 800 1200 1500 ma minimum load current (note 8) lm1117-adj v in =15v 1.7 5 ma 4 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
electrical characteristics (continued) typicals and limits appearing in normal type apply for t j = 25c. limits appearing in boldface type apply over the entire junc- tion temperature range for operation, 0c to 125c. symbol parameter conditions min (note 5) typ (note 4) max (note 5) units quiescent current lm1117-2.85 v in 10v 5 10 ma lm1117-3.3 v in 15v 5 10 ma lm1117-5.0 v in 15v 5 10 ma thermal regulation t a =25c, 30ms pulse 0.01 0.1 % /w ripple regulation f ripple =120hz, v in -v out =3v v ripple =1v pp 60 75 db adjust pin current 60 120 a adjust pin current change 10 i out 800ma, 1.4v v in -v out 10v 0.2 5 a temperature stability 0.5 % long term stability t a =125c, 1000hrs 0.3 % rms output noise ( % of v out ), 10hz f 10khz 0.003 % thermal resistance junction-to-case 3-lead sot-223 3 ,5 -lead to-220 3 ,5 -lead to-252 15.0 3.0 10 c/w c/w c/w thermal resistance junction-to-ambient (no heat sink; no air flow) 3-lead sot-223 3 ,5 -lead to-220 3 ,5 -lead to-252(note 9) 136 79 92 c/w c/w c/w note 1: absolute maximum ratings indicate limits beyond which damage to the device may occur. operating ratings indicate conditions for which the device is i n- tended to be functional, but specific performance is not guaranteed. for guaranteed specifications and the test conditions, see the electrical char acteristics. note 2: the maximum power dissipation is a function of t j(max) , q ja , and t a . the maximum allowable power dissipation at any ambient temperature is p d =(t j - (max) t a )/ q ja . all numbers apply for packages soldered directly into a pc board. note 3: for testing purposes, esd was applied using human body model, 1.5k w in series with 100pf. note 4: typical values represent the most likely parametric norm. note 5: all limits are guaranteed by testing or statistical analysis. note 6: load and line regulation are measured at constant junction room temperature. note 7: the dropout voltage is the input/output differential at which the circuit ceases to regulate against further reduction in input voltage. it is measur ed when the output voltage has dropped 100mv from the nominal value obtained at v in =v out +1.5v. note 8: the minimum output current required to maintain regulation. note 9: minimum pad size of 0.038in 2 5 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
typical performance characteristics dropout voltage (v in -v out ) ds100919-22 short-circuit current ds100919-23 load regulation lm1117-adj ripple rejection lm1117-adj ripple rejection vs. current temperature stability 6 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
typical performance characteristics (continued) lm1117-2.85 load transient response lm1117-5.0 load transient response lm1117-2.85 line transient response lm1117-5.0 line transient response 7 adjust pin current l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
application note 1.0 external capacitors/stability 1.1 input bypass capacitor an input capacitor is recommended. a 10f tantalum on the input is a suitable input bypassing for almost all applications. 1.2 adjust terminal bypass capacitor the adjust terminal can be bypassed to ground with a by- pass capacitor (c adj ) to improve ripple rejection. this by- pass capacitor prevents ripple from being amplified as the output voltage is increased. at any ripple frequency, the im- pedance of the c adj should be less than r1 to prevent the ripple from being amplified: (2 p *f ripple *c adj ) < r1 the r1 is the resistor between the output and the adjust pin. its value is normally in the range of 100-200 w . for example, with r1=124 w and f ripple =120hz, the c adj should be > 11f. 1.3 output capacitor the output capacitor is critical in maintaining regulator stabil- ity, and must meet the required conditions for both minimum amount of capacitance and esr (equivalent series resis- tance). the minimum output capacitance required by the lm1117 is 10f, if a tantalum capacitor is used. any increase of the output capacitance will merely improve the loop stabil- ity and transient response. the esr of the output capacitor should be less than 0.5 w . in the case of the adjustable regu- lator, when the c adj is used, a larger output capacitance (22f tantalum) is required. 2.0 output voltage the lm1117 adjustable version develops a 1.25v reference voltage, v ref , between the output and the adjust terminal. as shown in figure 1 , this voltage is applied across resistor r1 to generate a constant current i1. the current i adj from the adjust terminal could introduce error to the output. but since it is very small (60a) compared with the i1 and very constant with line and load changes, the error can be ig- nored. the constant current i1 then flows through the output set resistor r2 and sets the output voltage to the desired level. for fixed voltage devices, r1 and r2 are integrated inside the devices. 3.0 load regulation the lm1117 regulates the voltage that appears between its output and ground pins, or between its output and adjust pins. in some cases, line resistances can introduce errors to the voltage across the load. to obtain the best load regula- tion, a few precautions are needed. figure 2 , shows a typical application using a fixed output regulator. the rt1 and rt2 are the line resistances. it is ob- vious that the v load is less than the v out by the sum of the voltage drops along the line resistances. in this case, the load regulation seen at the r load would be degraded from the data sheet specification. to improve this, the load should be tied directly to the output terminal on the positive side and directly tied to the ground terminal on the negative side. when the adjustable regulator is used ( figure 3 ), the best performance is obtained with the positive side of the resistor r1 tied directly to the output terminal of the regulator rather than near the load. this eliminates line drops from appearing effectively in series with the reference and degrading regula- tion. for example, a 5v regulator with 0.05 w resistance be- tween the regulator and load will have a load regulation due to line resistance of 0.05 w xi l . if r1 (=125 w ) is connected near the load, the effective line resistance will be 0.05 w (1+r2/r1) or in this case, it is 4 times worse. in addition, the ground side of the resistor r2 can be returned near the ground of the load to provide remote ground sensing and im- prove load regulation. 4.0 protection diodes under normal operation, the lm1117 regulators do not need any protection diode. with the adjustable device, the internal resistance between the adjust and output terminals limits the current. no diode is needed to divert the current around the regulator even with capacitor on the adjust terminal. the ad- just pin can take a transient signal of ? 25v with respect to the output voltage without damaging the device. when a output capacitor is connected to a regulator and the input is shorted to ground, the output capacitor will discharge figure 1. basic adjustable regulator figure 2. typical application using fixed output regulator figure 3. best load regulation using adjustable output regulator 8 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
application note (continued) into the output of the regulator. the discharge current de- pends on the value of the capacitor, the output voltage of the regulator, and rate of decrease of v in . in the lm1117 regu- lators, the internal diode between the output and input pins can withstand microsecond surge currents of 10a to 20a. with an extremely large output capacitor ( 3 1000 f), and with input instantaneously shorted to ground, the regulator could be damaged. in this case, an external diode is recommended between the output and input pins to protect the regulator, as shown in figure 4 . 5.0 heatsink requirements when an integrated circuit operates with an appreciable cur- rent, its junction temperature is elevated. it is important to quantify its thermal limits in order to achieve acceptable per- formance and reliability. this limit is determined by summing the individual parts consisting of a series of temperature rises from the semiconductor junction to the operating envi- ronment. a one-dimensional steady-state model of conduc- tion heat transfer is demonstrated in figure 5 . the heat gen- erated at the device junction flows through the die to the die attach pad, through the lead frame to the surrounding case material, to the printed circuit board, and eventually to the ambient environment. below is a list of variables that may af- fect the thermal resistance and in turn the need for a heat- sink. r q jc (component vari- ables) r q ca (application vari- ables) leadframe size & material mounting pad size, material, & location no. of conduction pins placement of mounting pad die size pcb size & material die attach material traces length & width molding compound size and material adjacent heat sources volume of air ambient temperatue shape of mounting pad the lm1117 regulators have internal thermal shutdown to protect the device from over-heating. under all possible op- erating conditions, the junction temperature of the lm1117 must be within the range of 0c to 125c. a heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the application. to deter- mine if a heatsink is needed, the power dissipated by the regulator, p d , must be calculated: i in =i l +i g p d =(v in -v out )i l +v in i g figure 6 shows the voltages and currents which are present in the circuit. figure 4. regulator with protection diode figure 5. cross-sectional view of integrated circuit mounted on a printed circuit board. note that the case temperature is measured at the point where the leads contact with the mounting pad surface figure 6. power dissipation diagram 9 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
application note (continued) the next parameter which must be calculated is the maxi- mum allowable temperature rise, t r (max): t r (max)=t j (max)-t a (max) where t j (max) is the maximum allowable junction tempera- ture (125c), and t a (max) is the maximum ambient tem- perature which will be encountered in the application. using the calculated values for t r (max) and p d , the maxi- mum allowable value for the junction-to-ambient thermal re- sistance ( q ja ) can be calculated: q ja =t r (max)/p d if the maximum allowable value for q ja is found to be 3 136c/w for sot-223 package or 3 79c/w for to-220 package or 3 92c/w for to-252 package, no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. if the calculated value for q ja falls below these limits, a heatsink is required. as a design aid, table 1 shows the value of the q ja of sot- 223 and to-252 for different heatsink area. the copper pat- terns that we used to measure these q ja s are shown at the end of the application notes section. figure 7 and figure 8 reflects the same test results as what are in the table 1 figure 9 and figure 10 shows the maximum allowable power dissipation vs. ambient temperature for the sot-223 and to-252 device. figures figure 11 and figure 12 shows the maximum allowable power dissipation vs. copper area (in 2 ) for the sot-223 and to-252 devices. please see an1028 for power enhancement techniques to be used with sot-223 and to-252 packages. table 1. q ja different heatsink area layout copper area thermal resistance top side (in 2 )* bottom side (in 2 )( q ja ,c/w) sot-223 ( q ja ,c/w) to-252 1 0.0123 0 136 103 2 0.066 0 123 87 3 0.3 0 84 60 4 0.53 0 75 54 5 0.76 0 69 52 61 0 66 47 7 0 0.2 115 84 8 0 0.4 98 70 9 0 0.6 89 63 10 0 0.8 82 57 11 0 1 79 57 12 0.066 0.066 125 89 13 0.175 0.175 93 72 14 0.284 0.284 83 61 15 0.392 0.392 75 55 16 0.5 0.5 70 53 *tab of device attached to topside copper figure 7. q ja vs. 1oz copper area for sot-223 figure 8. q ja vs. 2oz copper area for to-252 10 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
application note (continued) figure 9. maximum allowable power dissipation vs. ambient temperature for sot-223 figure 10. maximum allowable power dissipation vs. ambient temperature for to-252 figure 11. maximum allowable power dissipation vs. 1oz copper area for sot-223 figure 12. maximum allowable power dissipation vs. 2oz copper area for to-252 11 l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
typical application circuits adjusting output of fixed regulators regulator with reference 1.25v to 10v adjustable regulator with improved ripple rejection 5v logic regulator with electronic shutdown* battery backed-up regulated supply 12 low dropout negative supply battery backed-up regulated supply l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
13 physical dimensions inches (millimeters) unless otherwise noted (continued) 3-lead to-220 package physical dimensions inches (millimeters) unless otherwise noted (continued) 3-lead t o-252 package l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or
3-lead sot-223 package 14 physicaldimensions inches(millimeters)unlessotherwisenoted l m 1 1 17 800 m a l o w - dr o p o u t li n e ar r e g u l at or

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