bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com 5.0a low dropout voltage regulator B1585 adjustable & fix output pin connection ordering information devices package temp. B1585t to-220 0 c to 70 c B1585s to-263 0 c to 70 c B1585j lpdd 0 c to 70 c pldd (j) description the bay linear B1585 is monolithic low power 5.0a adjustable and fixed npn voltage regulator that are easy to use with minimum external components. it is suitable for applications requiring a well-regulated positive output voltage with low input-output differential voltage requirements and output voltage 1.5v, 2.5v, 3.0v, 3.3v, or 5v. the B1585 outstanding features include full power usage up to 5.0amp of load current internal current limiting and thermal shutdown. other fixed versions are also available consult with factory. the B1585 is offered in 3-pin to-220, lpdd & to-263 packages compatible with other 3 terminal regulators. for 7a low dropout regulator refer to the b1584 data sheet. features ? adjustable output down to 1.2v ? fixed output voltages 2.5v, 3.0v 3.3v, and 5.0v ? output current of 5.0a ? low dropout voltage 1.1v typ. ? current & thermal limiting ? standard 3-terminal low cost to-220, lpdd, & d 2 packages ? similar to industry standard lt1084/lt1585 applications ? 3.3v to 2.5v for pentium processor ? smps post regulator ? high efficiency ?green? computer systems ? high efficiency linear power supplies ? 5v to 3.xxv fro pentium processor ? battery charger top view to - 263 - 3 (s) 1 bay linear 2 3 top view to - 263 - 1 bay linear 2 3 bay linear bay linear bay linear bay linear inspire the linear power inspire the linear power inspire the linear power inspire the linear power
bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com B1585 absolute maximum rating parameter symbol value unit maximum input voltage v in 7 v power dissipation p o internally limited w thermal resistance junction to case jc 3 thermal resistance junction to ambient ja 50 c/w operating junction temperature range control section power transistor t j 0 to 125 0 to 150 storage temperature range t stg -65 to 150 lead temperature (soldering 10 sec.) t lead 260 c electrical characteristics (v in = 4.75v to 5.25v; i o = 10ma to 5.0amp, unless otherwise specified) parameter symbol conditions min typ max unit 1.485 1.515 0 bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com B1585 application hints the bay linear B1585 incorporates protection against over-current faults, reversed load insertion, over temperature operation, and positive and negative transient voltage. however, the use of an output capacitor is required in order to insure the stability and the performances. stability the output capacitor is part of the regulator?s frequency compensation system. either a 220 f aluminum electrolytic capacitor or a 47 f solid tantalum capacitor between the output terminal and ground guarantees stable operation for all operating conditions. however, in order to minimize overshoot and undershoot, and therefore optimize the design, please refer to the section ?ripple rejection?. ripple rejection ripple rejection can be improved by adding a capacitor between the adj pin and ground. when adj pin bypassing is used, the value of the output capacitor required increases to its maximum (220 f for an aluminum electrolytic capacitor, or 47 f for a solid tantalum capacitor). if the adj pin is not bypass, the value of the output capacitor can be lowered to 100 f for an electrolytic aluminum capacitor or 15 f for a solid tantalum capacitor. however the value of the adj-bypass capacitor should be chosen with respect to the following equation: c = 1 / ( 6.28 * f r * r 1 ) where c = value of the capacitor in farads (select an equal or larger standard value), f r = ripple frequency in hz, r 1 = value of resistor r 1 in ohms. if an adj-bypass capacitor is use, the amplitude of the output ripple will be independent of the output voltage. if an adj-bypass capacitor is not used, the output ripple will be proportional to the ratio of the output voltage to the reference voltage: m = v out / v ref where m = multiplier for the ripple seen when the adj pin is optimally bypassed. v ref = reference voltage reducing parasitic resistance and inductance one solution to minimize parasitic resistance and inductance is to connect in parallel capacitors. this arrangement will improve the transient response of the power supply if your system requires rapidly changing current load condition. thermal consideration although the B1585 offers some limiting circuitry for overload conditions, it is necessary not to exceed the maximum junction temperature, and therefore to be careful about thermal resistance. the heat flow will follow the lowest resistance path, which is the junction-to-case thermal resistance. in order to insure the best thermal flow of the component, a proper mounting is required. note that the case of the device is electrically connected to the output. in case the case has to be electrically isolated, a thermally conductive spacer can be used. however do not forget to consider its contribution to thermal resistance. assuming: v in = 7v, v out = 5v, i out = 5a, t a = 90 c, case = 1 c/w (no external heat sink, no wind) power dissipation under these conditions p d = (v in ? v out ) * i out = 15w junction temperature t j = t a + p d * ( case + jc ) for the control section t j = 90 c + 15w*(1 c/w + 0.6 c/w) = 114 c 114 c < t junction max for the control section. for the power section t j = 90 c + 15w*(1 c/w + 1.6 c/w) = 129 c 129 c < t junction max for the power transistor. in both case reliable operation is insured by adequate junction temperature.
bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com B1585 basic adjustable regulator output voltage output voltage consider figure 2. the resistance r 1 generates a constant current flow, normally the specified load current of 10ma. this current will go through the resistance r 2 to set the overall output voltage. the current i adj is very small and constant. therefore its contribution to the overall output voltage is very small and can generally be ignored load regulation parasitic line resistance can degrade load regulation. in order not to affect the behavior of the regulator, it is best to connect directly the r 1 resistance from the resistor divider to the case, and not to the load. for the same reason, it is best to connect the resistor r 2 to the negative side of the load. bay B1585 fig.2 basic adjustable regulator v ou t v ou t v ref r 1 r 2 v out = v ref * ( 1 + r 2 /r 1 ) + i adj * r 2 i adj 50a bay B1585 fig.3 basic adjustable regulator v out r 2 r 1 connect r 2 to load r l connect r 1 to case of regulator r p parasitic line resistance
bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com B1585 application diagrams in out adj bay B1585 c 1 r 1 r 2 v out fig 5. typical adjustable regulator v in c 2 v out = v ref (1 + r 2 ) + i adj r 2 r 1 load adj bay B1585 fig.4 5a current output regulator v in c 1 r 1 out in bay B1585 fig. 6 improving ripple rejection v in r 1 r 2 150f 10f* 121? 1% 365? 1% + + 10f c1 *c1 improves ripple rejection. x c should be ~ r1 at ripple frequency. 5v adj in out (note a) note a: v in (min) = ( intended v out ) + ( v dropout (max) ) v out bay B1585 fig.7 5v regulator with shutdown v in 100f 121? 1% 365? 1% + + 10f 5v adj in out (note a) note a: v in (min) = ( intended v out ) + ( v dropout (max) ) 1k 1k ttl output 2n3904
bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com B1585 typical characteristics
bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com B1585 0.103 bsc 0.050 (1.270) 0.600 + - 0.025 0.405 0.005 0.055 (1.397) (10.287 0.127) 0.356 0.005 (9.042 0.127) (15.24 0.635) (2.616) 0.032 + - 0.001 (0.813 0.025) + - 0.176 0.005 0.050 0.002 0.015 + - 0.003 0 8 (0.381 0.074) + - 0.100 0.010 (2.540 0.254) (4.470 0.127) (1.270 0.051) 0.408 0.013 (10.36 0.33) 0.110 0.010 (2.794 0.254) 0.250 0.010 (6.350 0.254) 0.151d 0.002 (3.835 d 0.051) 0.180 0.005 (4.572 0.127) 0.050 0.002 (1.270 0.051) 0.340 0.010 (8.636 0.254) 0.150 min (3.81 min) 0.410 (10.41) 0.100 0.010 (2.540 0.254) 0.032 0.005 (0.813 0.127) 0.540 0.015 (13.720 0.381) 0.050 typ (1.27 typ) 0.200 0.010 (5.080 0.254) 0.015 0.010/-0.002 (0.381 0.254/-0.051) 0.015 0.010/-0.015 (2.667 0.254/-0.381) 1.020 0.015 (25.910 0.381) seating plane tapered 1 o 2 sides 7 o typ.
bay linear, inc 2478 armstrong street, livermore, ca 94550 tel: (925) 606-5950, fax: (925) 940- 9556 www.baylinear.com advance information - these data sheets contain descriptions of products that are in development. the specifications are based on the engineering ca lculations, computer simulations and/ or initial prototype evaluation. preliminary information - these data sheets contain minimum and maximum specifications that are based on the initial device characterizations. these lim its are subject to change upon the completion of the full characterization over the specified temperature and supply voltage ranges. the application circuit examples are only to explain the representative applications of the devices and are not intended to gua rantee any circuit design or permit any industrial property right to other rights to execute. bay linear takes no responsibility for any problems related to any industrial property right resulting from the use of the contents shown in the data book. typical parameters can and do vary in different applications. customer?s technical experts must validate all operating parameters including ? typical? for each customer applic ation. life support and nuclear policy bay linear products are not authorized for and should not be used within life support systems which are intended for surgical implants into the body to support or sustain life, in aircraft, space equipment, submarine, or nuclear facility applications wi thout the specific written consent of bay linear president.
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