exar corporation 48720 kato road, fremont ca, 94538 ? (510) 668-7000 ? fax (510) 668-7017 ? www.exar.com spx2940 1a low dropout voltage regulator november 3, 2007 rev. f description features n guaranted 1.5a peak current n low quiescent current n low dropout voltage of 280mv at 1a n extremely tight load and line regulation n extremely fast transient response n reverse-battery protection n internal thermal protection n internal short circuit current limit n replacement for lm2940, mic2940a, as2940 n standard to-220 and to-263 packages the spx2940 is a 1a, accurate voltage regulators wi th a low drop out voltage of 280mv (typical) at 1a. these regulators are specifically designed for low voltage applications that require a low dropout voltage and a fast transient response. they are fully fault protected against over-current, reverse battery, and positive and negative voltage transients. the spx2940 is offered in 3-pin to-220 & to-263 pac kages. for a 3a version, refer to the spx29300 data sheet. spx2940 v out v in + 6.8 f + 10 f 1 2 3 figure 1. fixed output linear regulator. typical applications circuit applications n powering vga & sound card n lcd monitors n usb power supply n power pc tm supplies n smps post-regulator n pda or notebook computer n high efficiency linear power supplies n portable instrumentation n constant current regulators n cordless telephones n automotive electronics now available in lead free packaging 1 2 3 spx2940 3 pin to-263 gnd v in v out
spx2940 2 1a low dropout voltage regulator rev. f absolute maximum ratings lead temperature (soldering, 5 seconds) ............ ..................... 260 c storage temperature range ......................... ............ -65 c to +150 c operating junction temperature range ............... .... -40 c to +125 c input voltage (note 5) ................................................................... 16v notes: note 1: dropout voltage is defined as the input to output differential when the output voltage drops to 99% of its normal value. note 2: v in =v out (nominal) + 1v. for example, use v in =4.3v for a 3.3v regulator. employ pulse-testing pr ocedures to minimize temperature rise. note 3: ground pin current is the regulator quiesc ent current. the total current drawn from the sourc e is the sum of the load current to the ground curr ent. note 4: thermal regulation is defined as the change in the output voltage at a time t after a change i n power dissipation is applied, excluding load or l ine regulation effects. note 5: maximum positive supply voltage of 20v must be of limited duration (<100ms) and duty cycle (<1 %). the maximum continuous supply voltage is 16v. at v in =v out + 1v and i out = 10 ma, c in = 6.8 f, c out = 10 f; t a = 25 c, unless otherwise specified. the boldface applies over the junction temperature range. adjustable versions are set at 5.0v. parameter conditions typ min max units 1.8v version output voltage i out = 10ma 1.8 1.746 1.854 v 10ma ! i out ! 1a, 6v ! v in ! 16v 1.8 1.710 1.890 2.5v version output voltage i out = 10ma 2.5 2.425 2.575 v 10ma ! i out ! 1a, 6v ! v in ! 16v 2.5 2.375 2.625 3.3v version output voltage i out = 10ma 3.3 3.201 3.399 v 10ma ! i out ! 1a, 6v ! v in ! 16v 3.3 3.135 3.465 5.0v version output voltage i out = 10ma 5.0 4.850 5.150 v 10ma ! i out ! 1a, 6v ! v in ! 16v 5.0 4.750 5.250 all voltage options line regulation i o =10ma, (v out +1v) ! v in ! 16v 0.2 1.0 % load regulation v in =v out +1v, 10ma ! i out ! 1a 0.3 1.5 % " v output voltage 20 100 ppm/ c " t temperature coef. dropout voltage (note 1) i o =100ma 70 200 mv (except 1.8v version) i o =1a 280 550 ground current (note 3) i o =750ma, v in =v out , + 1v 12 25 ma i o =1a 18 i gnddo ground pin v in =0.1v less than specified v out 1.2 ma current at dropout i out = 10ma current limit v out =0v (note 2) 2.2 1.5 a output noise voltage c l = 10 f 400 v rms 10hz to 100khz) i l =100ma c l =33 f 260 thermal resistance to-220 junction to case, at tab 3 to-220 junction to ambient 60 c/w to-263 junction to case, at tab 3 to-263 junction to ambient 60 electrical characteristics
spx2940 3 rev. f 1a low dropout voltage regulator figure 2. line regulation figure 3. load regulation figure 4. ground current vs load current figure 5. ground current vs input voltage reference thermal shutdown in out gnd o.v i limit 28v r1 r2 1.240v + - ibias block diagram 3.320 3.315 3.310 3.305 3.300 3.295 3.290 3.285 3.280 4 6 8 10 12 14 16 v in (v) v out (v) 3.3v device il = 10ma cl = 10 f 3.310 3.305 3.300 3.295 3.290 3.285 3.280 il (a) v out (v) 0.00 0.25 0.50 0.75 1.00 1.25 1.50 3.3v device v in = 4.3v cl = 10 f 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 il (a) ignd (ma) 0.00 0.25 0.50 0.75 1.00 1.25 1.50 3.3v device v in = 4.3v cl = 10 f 300 280 260 240 220 200 180 4 6 8 10 12 14 16 v in (v) ignd (ma) 3.3v device il = 10ma cl = 10 f typical performance characteristics
spx2940 4 1a low dropout voltage regulator rev. f figure 6. ground current vs current in dropout figure 7. dropout voltage vs load current figure 8. ground current vs temperature at figure 9. output voltage vs temperature at i load = 10ma i load =10ma 100 90 80 70 60 50 40 30 20 10 0 il (a) ignd (ma) 0.00 0.25 0.50 0.75 1.00 1.25 1.50 3.3v device v in = 3.2v cl = 10 f 600 500 400 300 200 100 0 il (a) v dropout (mv) 0.00 0.25 0.50 0.75 1.00 1.25 1.50 3.3v device cl = 10 f 280 270 260 250 240 230 220 210 200 190 180 -40 -20 0 20 40 60 80 temperature ( c) ignd ( a) 3.3v device v in = 4.3v il = 10ma cl = 10 f 120 100 3.320 3.310 3.300 3.290 3.280 3.270 3.260 3.250 3.240 3.230 3.220 -40 -20 0 20 40 60 80 temperature ( c) v out (v) 3.3v device v in = 4.3v il = 10ma cl = 10 f 120 100 7.00 6.80 6.60 6.40 6.20 6.00 5.80 5.60 5.40 5.20 5.00 -40 -20 0 20 40 60 80 temperature ( c) ignd (ma) 3.3v device v in = 4.3v il = 500ma cl = 10 f 120 100 figure 10. ground current vs temperature at figure 11. ground current vs temperature in dropout i load =500ma at i load =750ma 30 29 28 27 26 25 24 23 22 21 20 -40 -20 0 20 40 60 80 temperature ( c) ignd (ma) 3.3v device v in = 3.2v il = 750ma cl = 10 f 120 100 typical performance characteristics 4
spx2940 5 rev. f 1a low dropout voltage regulator 52.0 50.0 48.0 46.0 44.0 42.0 40.0 38.0 36.0 -40 -20 0 20 40 60 80 temperature ( c) ignd (ma) 3.3v device v in = 4.3v il = 1.5a cl = 10 f 120 100 figure 12. ground current vs temperature at i load = 1.5a figure 13. ground current vs temperature in dropout at i load =1.5a 100 95 90 85 80 75 70 -40 -20 0 20 40 60 80 temperature ( c) ignd (ma) 3.3v device v in = 3.2v il = 1.5a cl = 10 f 120 100 350 330 310 290 270 250 230 210 190 170 150 -40 -20 0 20 40 60 80 temperature ( c) v dropout (mv) 120 100 3.3v device il = 750ma cl = 10 f figure 14. dropout voltage vs temperature at i load = 750ma 500 480 460 440 420 400 380 360 340 320 -40 -20 0 20 40 60 80 temperature ( c) v dropout (mv) 120 100 3.3v device il = 750a cl = 10 f figure 15. dropout voltage vs temperature at i load = 1.5ma 35 30 25 20 15 10 50 -40 -20 0 20 40 60 80 temperature ( c) i en ( a) 120 100 3.3v device v in = 3.2v il = 750ma cl = 10 f figure 16. enable current vs temperature for v en = 16v 2.00 1.90 1.80 1.70 1.60 1.50 1.40 1.30 1.20 1.10 1.00 -40 -20 0 20 40 60 80 temperature ( c) v th (v) 120 100 3.3v device v in = 3.2v il = 750ma cl = 10 f figure 17. enable threshold vs temperature typical performance characteristics
spx2940 6 1a low dropout voltage regulator rev. f the spx2940 incorporates protection against over-current faults, reversed load insertion, over temperature operation, and positive and nega- tive transient voltage. thermal considerations although the spx2940 offers limiting circuitry for overload conditions, it is still necessary to insure that the maximum junction temperature is not exceeded in the application. heat will flow through the lowest resistance path, the junction-to-case path. in order to insure the best thermal flow of the component, proper mount- ing is required. consult heatsink manufacturer for thermal resistance and design of heatsink. for example, to-220 design: assume that v in = 10v, v out = 5v, i out = 1.5a, t a = 50 c/w, ! ha = 1 c/w, ! ch = 2 c/w, and ! jc = 3 c/w. where ta = ambient temperature ! ha = heatsink to ambient thermal resistance ! ch = case to heatsink thermal resistance ! jc = junction to case thermal resistance the power calculated under these conditions is: p d = (v in - v out ) * i out = 7.5w. and the junction temperature is calculated as t j = t a + p d * ( ! ha + ! ch + ! jc ) or t j = 50 + 7.5 * (1 + 2 + 3) = 95 c reliable operation is insured. capacitor requirements the output capacitor is needed to insure stability and minimize the output noise. the value of the capacitor varies with the load. however, a minimum value of 10 f aluminum capacitor will guarantee stability over all load conditions. a tantalum capa citor is recommended if a faster load transient response is needed. if the power source has a high ac impedance, a 0.1 f ceramic capacitor between input & ground is recommended. minimum load current to ensure a proper behavior of the regulator under light load, a minimum load of 5ma for spx2940 is required. spx2940 v out v in + 6.8 f + 10 f 1 2 3 figure 18. fixed output linear regulator. application information
spx2940 7 rev. f 1a low dropout voltage regulator figure 19. output cap esr vs. iout. figure 20. 5vout psrr. vin=10v, vout=5v, cout=22uf, iout=10ma. s p x 2940 5.0 v out p s r r -20 -10 0 10 20 30 40 50 60 70 80 1 0 10 0 1 000 10 000 1 000 00 10 000 00 1000 000 0 f req u e n cy (h z ) psrr (db) . o u tp u t c a p a c ito r e s r v s o u tp u t c u r r e n t 0.01 0.1 1 10 100 1000 0 200 400 600 800 1000 o utput c ur rent (ma) output capacitor esr (ohms) s table range uns table range uns table range
spx2940 8 1a low dropout voltage regulator rev. f exar corporation
spx2940 9 rev. f 1a low dropout voltage regulator exar corporation
spx2940 10 1a low dropout voltage regulator rev. f part number acc. output voltage package spx2940u-1-8 3% 1.8v 3 lead to-220 spx2940u-2-5 3% 2.5v 3 lead to-220 spx2940u-3-3 3% 3.3v 3 lead to-220 spx2940u-5-0 3% 5.0v 3 lead to-220 spx2940t-1-8 3% 1.8v 3 lead to-263 spx2940t-1-8/tr 3% 1.8v 3 lead to-263 spx2940t-2-5 3% 2.5v 3 lead to-263 spx2940t-2-5/tr 3% 2.5v 3 lead to-263 spx2940t-3-3 3% 3.3v 3 lead to-263 spx2940t-3-3/tr 3% 3.3v 3 lead to-263 spx2940t-5-0 3% 5.0v 3 lead to-263 spx2940t-5-0/tr 3% 5.0v 3 lead to-263 ordering information to-263-3 package (t) v out gnd v in front view tab = gnd 1 2 3 front view tab = gnd to-220-3 package (u) v in v out gnd 3 2 1 package pinouts available in lead free packaging. to order add " -l" suffix to part number. example: spx2940t-3-3/tr = standard; spx2940t-l-3-3 /tr = lead free /tr = tape and reel pack quantity is 500 for to-263. exar corporation reserves the right to make changes to the products contained in this publication in o rder to improve design, performance or reliability. exar c orporation assumes no responsibility for the use of any circuits described herein, conveys no license under any pate nt or other right, and makes no representation that the circuits are free of patent infringement. charts and schedul es contained here in are only for illustration purp oses and may vary depending upon a user?s specific application. while the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. exar corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be exp ected to cause failure of the life support system o r to significantly affect its safety or effectiveness. p roducts are not authorized for use in such applicat ions unless exar corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damag e has been minimized; (b) the user assumes all such risks; (c) potential liability of exar corporation is adequat ely protected under the circumstances. copyright 2007 exar corporation datasheet november 2007.
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