rev. 10/2/00 pin connections as1580 7a ultra low dropout voltage regulator fast response, adjustable & fixed features applications ? low dropout voltage 540mv at 7a full load current ? 3.3v to 2.8v atx power supplies ? adjustable output down to 1.2v from atx power supply ? 3.3v to 2.9v for portable pentium ? ? ? ? processor ? fixed output voltages of 3.3v, 2.8v & 2.5v ? 5v to 3.5v vre supply ? extremely tight voltage and line regulation ? high efficiency ?green? computer systems ? standard 5-terminal low cost to-220 & to-263 ? replacement to industry standard lt1580 product description the as1580 is a 7a low dropout regulator with extremely low dropout voltage. the adjustable version requires only two external resistors to set the output voltage. the fixed version has a preset output of 3.3v, 2.8v or 2.5v and does not require any exte rnal resistors. the as1580 features a low dropout of 540mv(typ.) and offers fast transient response. this device is suitable for pentium applications requiring 2.8v or 2.5v from 3.3v atx power supplies, where a low current input voltage 1v greater than the output voltage is needed. with an external sense pin the load regulation is less than 1mv. this device is an excellent choice for th e use in powering low voltage microprocessors that require a lower dropout, fast transient response to regulate from 3.3v and 5v supplie s. the as1580 is also an excellent choice as a post regulator for switching supplies applications. the as1580 offers protection against over-current faults, reversed input polarity, over temperature operation and positive and negative transient voltage. the as1580 is offered in a 5 pin to-220 and to-263 compatible with industry standard 5-terminal regulators. for 5a, 3a and 1.5 a ultra low dropout versions refer to as1581, as1582 and as1583 data sheets respectively ordering information to-220 5 pin to-263 5 pin output as1580u as1580t adjustable as1580u-x as1580t-x fixed consult with factory for other fixed output voltages. x= output voltage ( 3.3v, 2.8v, or 2.5v) to-263-5 (t) top view 45 as1580 12 3 1. sense 2. adj or fixed 3. v out 4. v ctrl 5. v in to-220-5 (u) front view 5 4 3 2 1 as1580 1. sense 2. adj or fixed 3. v out 4. v ctrl 5. v in
rev. 10/2/00 as1580 absolute maximum ratings power dissipation.................................................... internally limited input supply voltage ................... .......................................6v lead temp (soldering, 10 seconds)........................................... 300 c v ctrl input voltage ..........................................................13v storage temperature range ...................................... -65oc to +150oc operating junction temperature range as1580 control section................................................0oc to +125oc as1580 power transistor .............................................0oc to +150oc electrical characteristics at v s =14v, ta=25 c, io=10ma, c2=100 f, unless otherwise specified. (note 1) (boldface applies over full temperature range). parameters conditions as1580 min typ max units 2.5v version output voltage v ctrl =6.0v to 12v, v in =3.0v to 5.0v, i o =10ma i o =10ma to 7a 2.450 2.400 2.5 2.5 2.550 2.600 v 2.8v version output voltage v ctrl =6.3v to 12v, v in =3.3v to 5.0v, i o =10ma i o =10ma to 7a 2.744 2.688 2.8 2.8 2.856 2.912 v 3.3v version output voltage v ctrl =6.3v to 12v, v in =3.3v to 5.0v, i o =10ma i o =10ma to 7a 3.234 3.168 3.3 3.3 3.366 3.432 v all voltage options reference voltage (note 3) v ctrl =2.75v, v in =2.00v, i o =10ma v ctrl =2.7v to 12v, v in =2.05v to 5.5v, i o =10ma to 7a 1.2375 1.25 1.375 v line regulation v ctrl =2.5v to 12v, v in =1.75v to 5.5v, i o =10ma v adj =0v 1.0 3.0 mv load regulation (note1) v ctrl =2.75v, v in =2.1v, i o =10ma to 7a,v adj =0v 1.0 5.0 mv dropout voltage minimum v ctrl (note2) (v ctrl ? v out ) v adj =0v v in =2.05v, i o =1a 1.00 1.20 v dropout voltage minimum v in (note2) (v in - v out ) v adj =0v v in =2.75v, i o =7a 0.54 0.62 v current limit v ctrl =2.75v, v in =2.05v,dv o =100mv,v adj =0v 7 8 a minimum load current v ctrl =5v, v in =3.3v,v adj =0v 5 10 ma thermal regulation 30ms pulse 0.002 0.02 %w ripple rejection v ctrl =3.75v v in =3.75v, i o =2.7a,v adj =0v t j =25, v ripple =1vpp at 120hz 60 80 db control pin current v adj =0v v ctrl =2.75v, v in =2.05v, i o =7a 60 130 ma adjustable pin current v ctrl =2.75v, v in =2.05v,v adj =0v i o =10ma 50 120 a to-220-5 junction to case ( jc ) 3 c/w junction to ambient ( ja ) 50 c/w junction to case ( jc ) 3 c/w thermal resistance to-263-5 junction to ambient ( ja ) 60 c/w the bold specifications applying to the over full operating temperature range. note 1: low duty cycle pulse testing with kelvin connections is required to order to maintain accurate data. note 2: dropout voltage is defined as the minimum differential between v in and v out or v ctrl and v out required to maintain regulation at v out 99% nominal v out. note 3: v ref is measured across adjust pin to sense pin.
rev. 10/2/00 as1580 block diagram applications notes the as1580 is designed as a high performance and low cost solution for application requiring a lower dropout than traditional npn regulators. the as1580 uses a separate input voltage v ctrl (v ctrl v out + 1.3v) to minimize the dropout voltage. this allows the 2.5v power for the load to come from a 3.3v system supply. as added benefit this will reduce the heat dissipation*, and lower heatsink and cooling fan cost. a typical application would use 5v for vin and 3.3v for v ctrl from a motherboard power supply to provide a nominal 2.5v output. using the sense pin allows to kelvin measure the output, reducing resistive-associated errors. the as1580 can power the 2.5v core voltage for microprocessors such as pentium ? , p55c ? , amd5k86 ? and k6 ? and the ibm powerpc ? 603ev and 604ev processors. *the reduction of heat dissipation is a result of the increase of the regulator efficiency (efficiency = v out / v in ). adjustable regulator design 1.25v reference voltage is being developed between the sense pin and the adj pin of the as1580. adding two external resistors (see fig 1.) will allow setting the output voltage from 1.25v to 6v. r 1 is chosen so that this current is specified minimum load current of 10ma. r 2 is given by the formula: v out = v ref (1+ r 2 /r 1 ) + i adj (r 2 ). the current flowing from the adj pin is typically 50 a. this adj pin contributes to the final vout but is usually neglected. connecting the sense pin to the top of the resistor divider will improve load regulation. lowering noise using the sense pin to kelvin the load will increase accuracy of the output voltage during load regulation. for the fixed voltage devices, adding a capacitor at the gnd pin will improve transient response. this capacitor is chosen in the range of 1 f to 0.1 f and will depend on the amount of output capacitance in the system. pin description 1. sense = allows kelvin sense of v out at the load. (positive side of the reference voltage of the device). 2. adj = negative side of the reference voltage for the device. adding a small bypass capacitor from the adj pin to ground will improve the transient response. 3. v out = power output of the device. 4. v ctrl = supply pin for the control circuitry of the device. the current flow into this pin will be about 1% of the output current. v ctrl must be between 1.0v and 1.3v greater than the output voltage for the device to regulate. 5. v in = output load current is supplied through this pin. v in must be between 0.1v and 0.8v greater than the output voltage for the device to regulate. (4) v ctrl v in (5) s.o.a v out (3) limit sense current limit amplifier thermal overload voltage regulation amplifier v ref sense (1) adj (2)
rev. 10/2/00 as1580 typical application as1580 sense adj v in v ctrl r1 124 c4 2 x 330uf c2 10uf c1 330uf 5v v ctrl 3.3v v in c3 .033uf (1) v ctrl needed when v in < 5v. (2) v out = v ref (1 + r2/ r1) + i adj r2. (3) v ref is measured across adjust to sense. 2.5v v out ? r2 124 ? v out fig. 1 adjustable regulator as1580 sense gnd v in v ctrl c4 2 x 330uf c2 10uf c1 330uf 5v v ctrl 3.3v v i n (1) v ctrl is needed when v in <5v. fig.2 typical fixed regulator 2.5v v out v out
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