rev. 10/23/00 SPX1585 5a low dropout voltage regulator adjustable & fixed output, fast response features applications ? adjustable output down to 1.2v ? powering vga & sound card ? fixed output voltages 1.5v, 2.5v, 3.3v & 5.0v ? power pc ? supplies ? output current of 5a ? smps post-regulator ? low dropout voltage 1.1v typ @ 5a. ? high efficiency ?green? computer systems ? extremely tight load and line regulation ? high efficiency linear power supplies ? current & thermal limiting ? portable instrumentation ? standard 3-terminal low cost to-220 & to-263 ? constant current regulators ? similar to industry standard lt1085/lt1585 ? adjustable power supplies ? battery charger product description the SPX1585 are low power 5a adjustable and fixed voltage regulators that are very easy to use. it requires only 2 external re sistors to set the output voltage for adjustable version. the SPX1585 are designed for low voltage applications that offer lower dropo ut voltage and faster transient response. this device is an excellent choice for use in powering low voltage microprocessor that require a lower dropout, faster transient response to regulate from +2.5v to 3.8v supplies and as a post regulator for switching supplies applications. the SPX1585 features low dropout of a maximum 1.2 volts. the SPX1585 offers full protection against over-current faults, reversed input polarity, reversed load insertion, and positive and negative transient voltage. on-chip trimming adjusts the reference voltage to 1%. the i q of this device flows into the load, which increases efficiency. the SPX1585 are offered in a 3-pin to-220 and to-263 package compatible with other 3 terminal regulators. for a 8a low dropout regulator refer to the SPX1585 data sheet. pin connections top view to-263-3 (t) 1 2 3 adj/gnd v out v in SPX1585 front view to-220-3 (u) SPX1585 1 2 v in v out adj/gnd 3
rev. 10/23/00 SPX1585 absolute maximum ratings lead temp. (soldering, 10 seconds) .............................. 300c input voltage........................................... ............. 10v storage temperature range ............................ -65 to +150c input to output voltage differential .................... 10v operating junction temperature range SPX1585 control section.......................... -45c +125c SPX1585 power transistor.........................-45c +150c electrical characteristics (note 1) at i out = 10ma, t a =25 c, unless otherwise specified. parameter conditions typ SPX1585a SPX1585 units min max min max 1.5v version 1.485 1.515 1.47 1.53 v output voltage (note 2) SPX1585-1.5v, 0 < i out < 5a, 3.3vSPX1585-2.5v, 0 < i out < 5a, 4.0vSPX1585-3.3v, 0 < i out < 5a, 4.8vSPX1585-5.0v, 0 i out 5a, 6.5v v in 12v 4.900 5.100 4.65 5.15 all voltage options reference voltage (vref) 1.250 1.225 1.270 1.225 1.270 v v in 7v, p p max 1.5v (v in -v out ) 5.75v, 10ma i out 5a min. load current (note 3) 1.5v (v in ?v out ) 5.75v 5 10 10 v line regulation ( ? vref(vin)) 2.75v v in 7v, iout=10ma, t j =25oc (note 3) 0.005 0.2 0.2 v in 7v, i out =0ma, t j =25oc (note 2) 0.005 0.2 0.2 % 10ma i out 5a, (v in -v out )=3v, t j =25oc (note 3) 0.05 0.3 0.3 load regulation( ? vref(iout)) 0 i out 5a, v in =7v, t j =25oc (note 2) 0.05 0.3 0.3 % dropout voltage ? v ref =1% i out = 5a (note 3) i out < 5a (note 2) 1.1 1.2 1.2 v in =7v 6 5.2 5.2 a current limit iout(max) 1.4v (v in - v out ) (note3) long term stability t a =125oc, 1000 hrs. 0.3 (note 2) 1 1 % thermal regulation ( ? vout(pwr)) t a =25oc, 20 ms pulse 0.01 0.020 0.020 %/w temperature stability ( ? vout(t)) 0.25 % output noise, rms 10hz to 10khz t a =25oc 0.003 % vo 3.0 3.0 to-220 junction to tab junction to ambient 60 60 3.0 3.0 thermal resistance dd package junction to tab junction to ambient 60 60 oc/w the bold specifications apply to the full operating temperature range. note 1: changes in output voltage due to heating effects are covered under the specification for thermal regulation. note 2: fixed version only note 3: adjustable version only
rev. 10/23/00 SPX1585 application hints the SPX1585 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 22 f aluminum electrolytic capacitor or a 10 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 10 f for an electrolytic aluminum capacitor or 4.7 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 spx 1585 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 = 10v, v out = 5v, i out = 1.5a, t a = 50 c/w, heatsink case = 6 c/w, heatsink case = 0.5 c/w, jc = 3 c/w power dissipation under this condition p d = (v in ? v out ) * i out = 7.5w junction temperature t j = t a + p d * ( case ? hs + hs jc ) for the control section t j = 50 + 7.5*(0.5 + 6=3) = 121.25 c 121.25 c < t j (max) for the control & power sections. in both case reliable operation is insured by adequate junction temperature.
rev. 10/23/00 SPX1585 basic adjustable regulator 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. output voltage the fixed voltage ldo voltage regulators are simple to use regulators since the v out is preset to the specifications. it is important however, to provide the proper output capacitance for stability and improvement. for most operating conditions a capacitance of 22uf tantalum or 100uf electrolytic will ensure stability and prevent oscillation. SPX1585 fig.2 basic adjustable regulator v ref r 1 r 2 v out = v ref * ( 1 + r 2 /r 1 ) + i adj * r 2 i adj adj v in v out 50ua SPX1585 fig.3 basic adjustable regulator v in r 2 r 1 connect r 2 to load r l connect r 1 to case of regulator r p parasitic line resistance v out adj SPX1585 basic fixed regulator v in v out 5v c1 10uf c2 10uf 3.3v
rev. 10/23/00 SPX1585 typical applications in out adj SPX1585 c 1 r 1 v out fig. 5 typical adjustable regulator v in load adj SPX1585 fig. 4 5a current output regulator v in c 1 out in r 2 c 2 v out = v ref (1 + r 2 ) + i adj r 2 r 1 r 1 note a: v in(min) = (intended v out ) + (v dropout (max) ) SPX1585 fig. 6 improving ripple rejection v in r 1 r 2 150f 10f* 121? 1% 365? 1% + + 10f c 1 *c 1 improves ripple rejection. xc should be ~ r 1 at ripple frequency. 5v adj in out (note a) v out SPX1585 fig.7 5v regulator with shutdown v in 100f 121? 1% 365? 1% + + 10f 5v adj in out (note a) 1k 1k ttl input 2n3904 note a: v in(min) = (intended v out ) + (v dropout (max) )
rev. 10/23/00 SPX1585 typical characteristics
rev. 10/23/00 SPX1585 ordering information ordering no. precision output voltage packages SPX1585u 2% adj 3 lead to-220 SPX1585u-1.5 2% 1.5v 3 lead to-220 SPX1585u-2.5 2% 2.5v 3 lead to-220 SPX1585u-3.3 2% 3.3v 3 lead to-220 SPX1585u-5.0 2% 5.0v 3 lead to-220 SPX1585au 1% adj 3 lead to-220 SPX1585au-1.5 1% 1.5v 3 lead to-220 SPX1585au-2.5 1% 2.5v 3 lead to-220 SPX1585au-3.3 1% 3.3v 3 lead to-220 SPX1585au-5.0 1% 5.0v 3 lead to-220 SPX1585t 2% adj 3 lead to-263 SPX1585t-1.5 2% 1.5v 3 lead to-263 SPX1585t-2.5 2% 2.5v 3 lead to-263 SPX1585t-3.3 2% 3.3v 3 lead to-263 SPX1585t-5.0 2% 5.0v 3 lead to-263 SPX1585at 1% adj 3 lead to-263 SPX1585at-1.5 1% 1.5v 3 lead to-263 SPX1585at-2.5 1% 2.5v 3 lead to-263 SPX1585at-3.3 1% 3.3v 3 lead to-263 SPX1585at-5.0 1% 5.0v 3 lead to-263 signal processing excellence sipex corporation headquarters and main offices: 22 linnell circle billerica, ma 01821 tel: (978) 667-8700 fax: (978) 670-9001 e-mail: sales@sipex.com 233 south hillview drive milpitas, ca 95035 tel: (408) 935-7600 fax: (408) 934-7500 sipex corporation reserves the right to make changes to any products described herein. sipex does not assume any liab ility arising out of the application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others. corporation
rev. 10/23/00
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