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pentium is a registered trademark of intel corporation rev. 1.0.2 www.fairchildsemi.com rc1585 5a adjustable/fixed low dropout linear regulator features fast transient response low dropout voltage at up to 5a load regulation: 0.05% typical trimmed current limit on-chip thermal limiting standard to-220 and to-263 packages applications pentium ? pro and pentium ii gtl+ bus supply low voltage logic supply battery-powered circuitry post regulator for switching supply typical applications description the rc1585 and rc1585-1.5 are low dropout three-terminal regulators with 5a output current capability. these devices have been optimized for low voltage applications including v tt bus termination, where transient response and minimum input voltage are critical. the rc1585 is ideal for low voltage microprocessor applications requiring a regulated output from 1.5v to 3.6v with an input supply of 5v or less. the rc1585-1.5 offers fixed 1.5v with 5a current capabilities for gtl+ bus v tt termination. current limit is trimmed to ensure specified output current and controlled short-circuit current. on-chip thermal limiting provides protection against any combination of overload and ambient temperature that would create excessive junction temperatures. the rc1585 series regulators are available in the industry-standard to-220 and to-263 power packages. 1.5v at 5a rc1585 v in v out adj + + + 22 m f v in = 3.3v 10 m f + + + 22 m f v in = 3.3v 10 m f 1.5v at 5a rc1585-1.5 v in v out gnd + + v in = 3.3v 10 m f 22 m f 124 w 24.9 w
rc1585 product specification 2 pin assignments 3-lead plastic to-263 q ja =30 c/w* 3-lead plastic to-220 q ja =50 c/w *with package soldered to 0.5 square inch copper area over backside ground plane or internal power plane. q ja can vary from 20 c/w to > 40 c/w with other mounting techniques. absolute maximum ratings parameter min. max. unit v in 7v operating junction temperature range control section 0 125 c power transistor 0 150 c storage temperature range -65 150 c lead temperature (soldering, 10 sec.) 300 c rc1585t front view adj out in 1 2 3 rc1585t-1.5 front view gnd out in 1 2 3 RC1585M-1.5 front view gnd out in 1 2 3 RC1585M front adj out in 1 2 3
product specification rc1585 3 parameter conditions min. typ. max. units reference voltage 3 1.5v (v in -v out ) 5.75v, 10ma i out 5a 1.225 (-2%) 1.250 1.275 (+2%) v output voltage 4 3v v in 7v 10ma i out 5a 1.47 1.5 1.53 v line regulation 1,2 (v out + 1.5v) v in 7v, i out = 10ma 0.005 0.2 % load regulation 1,2,3 (v in - v out ) = 3v, 10ma i out 5a 0.05 0.5 % dropout voltage d v ref = 1%, i out = 5a 1.150 1.300 v current limit (v in - v out ) = 2v 5.1 5.5 a adjust pin current 3 35 120 m a adjust pin current change 3 1.5v (v in - v out ) 5.75v, 10ma i out 5a 0.2 5 m a minimum load current 1.5v (v in - v out ) 5.75v 10 ma quiescent current v in = 5v 413ma ripple rejection f = 120hz, c out = 22 m f tantalum, (v in - v out ) = 3v, i out = 5a 60 72 db thermal regulation t a = 25 c, 30ms pulse 0.004 0.02 %/w temperature stability 0.5 % long-term stability t a = 125 c, 1000 hrs. 0.03 1.0 % rms output noise (% of v out ) t a = 25 c, 10hz f 10khz 0.003 % thermal resistance, control section 0.7 c/w junction to case power transistor 3.0 c/w thermal shutdown 150 c electrical characteristics preconditioning: 100% thermal limit functional test. t j =25 c unless otherwise specified. the denotes specifications which apply over the specified operating temperature range. notes: 1. see thermal regulation specifications for changes in output voltage due to heating effects. load and line regulation are measu red at a constant junction temperature by low duty cycle pulse testing. 2. line and load regulation are guaranteed up to the maximum power dissipation (18w). power dissipation is determined by input/ou tput differential and the output current. guaranteed maximum output power will not be available over the full input/output voltage range. 3. rc1585 only. 4. rc1585-1.5 only.
rc1585 product specification 4 typical performance characteristics temperature ( c) figure 2. load regulation vs. temperature temperature ( c) temperature ( c) figure 3. reference voltage vs. temperature figure 4. output voltage vs. temperature temperature ( c) temperature ( c) figure 5. minimum load current vs. temperature typical performance characteristics (continued) dropout voltage ( v ) output voltage deviation (%) 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 d i=5a -75 C50 C25 0 25 50 75 100 125 150 175 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 reference voltage -75 -50 -25 0 25 50 75 100 125 150 175 output voltage (v) 3.70 3.65 3.60 3.55 3.50 3.45 3.40 3.35 3.30 3.25 3.20 -75 -50 -25 0 25 50 75 100 125 150 175 -75 -50 -25 0 25 50 75 100 125 150 175 -75 -50 -25 0 25 50 75 100 125 150 175 minimum load current ( ma ) 5 4 3 2 1 0 adjust pin current ( m a) 100 90 80 70 60 50 40 30 20 10 0 figure 6. adjust pin current vs. temperature note: 1. rc1585 only note: 1. rc1585 only v out = 3.6v 1 v out = 3.45v 1 v out = 3.38v 1 v out = 3.3v 1 v out set with 1% resistors 8 7 output current (a) figure 1. dropout voltage vs. output current 0 1 2 3 4 5 t=125 c t = 25 c t=0 c 1.250 1.245 1.240 1.235 1.230 1.225 1.220 1.215 1.210 1.205 1.200
product specification rc1585 5 temperature ( c) frequency (hz) figure 7. short-circuit current vs. temperature case temperature figure 9. maximum power dissipation -75 -50 -25 0 25 50 75 100 125 150 175 short-circuit current (a) 50 60 70 80 90 100 110 120 130 140 150 power (w) 20 15 10 5 0 10 100 1k 10k 100k 90 80 70 60 50 40 30 20 10 0 ripple rejections (db) (v in C v out ) 3v 0.5v v ripple 2v i out = 5a figure 8. ripple rejection vs. frequency
rc1585 product specification 6 applications information general the rc1585 and rc1585-1.5 are three-terminal regulators optimized for gtl+ v tt termination and logic applications. these devices are short-circuit protected, safe area protected, and offer thermal shutdown to turn off the regulator when the junction temperature exceeds about 150 c. the rc1585 series provides low dropout voltage and fast transient response. frequency compensation uses capacitors with low esr while still maintaining stability. this is critical in addressing the needs of low voltage high speed microprocessor buses like gtl+. stability the rc1585 series requires an output capacitor as a part of the frequency compensation. it is recommended to use a 22 m f solid tantalum or a 100 m f aluminum electrolytic on the output to ensure stability. the frequency compensation of these devices optimizes the frequency response with low esr capacitors. in general, it is suggested to use capacitors with an esr of < 1 w . it is also recommended to use bypass capacitors such as a 22 m f tantalum or a 100 m f aluminum on the adjust pin of the rc1585 for low ripple and fast transient response. when these bypassing capacitors are not used at the adjust pin, smaller values o f output capacitors provide equally good results. protection diodes in normal operation, the rc1585 series does not require any protection diodes. for the rc1585, internal resistors limit internal current paths on the adjust pin. therefore, even with bypass capacitors on the adjust pin, no protection diode is needed to ensure device safety under short-circuit conditions. a protection diode between the input and output pins is usually not needed. an internal diode between the input and the output pins on the rc1585 series can handle microsecond surge currents of 50a to 100a. even with large value output capacitors it is difficult to obtain those values of surge currents in normal operation. only with large values of output capacitance, such as 1000 m f to 5000 m f, and with the input pin instantaneously shorted to ground can damage occur. a crowbar circuit at the input can generate those levels of current; a diode from output to input is then recommended, as shown in figure 10. usually, normal power supply cycling or system hot plugging and unplugging will not generate current large enough to do any damage. ripple rejection in applications that require improved ripple rejection, a bypass capacitor from the adjust pin of the rc1585 to ground reduces the output ripple by the ratio of v out /1.25v. the impedance of the adjust pin capacitor at the ripple frequency should be less than the value of r1 (typically in the range of 100 w to 120 w ) in the feedback divider network in figure 10. therefore, the value of the required adjust pin capacitor is a function of the input ripple frequency. for example, if r1 equals 100 w and the ripple frequency equals 120hz, the adjust pin capacitor should be 22 m f. at 10khz, only 0.22 m f is needed. v in d1 1n4002 (optional) r2 r1 c1 10 m f c2 22 m f c adj v out rc1585 in out ad j + + + v in c2 22 m f + d1 1n4002 (optional) c1 10 m f v out rc1585-1.5 in out gnd + fi g ure 10. o p tional protection the adjust pin can be driven on a transient basis 7v with respect to the output, without any device degradation. as with any ic regulator, exceeding the maximum input-to-output voltage differential causes the internal transistors to break down and none of the protection circuitry is then functional. output voltage the rc1585 regulator develops a 1.25v reference voltage between the output pin and the adjust pin (see figure 11). placing a resistor r1 between these two terminals causes a constant current to flow through r1 and down through r2 to set the overall output voltage. normally, this current is the specified minimum load current of 10ma.
product specification rc1585 7 thermal considerations the rc1585 series protect themselves under overload conditions with internal power and thermal limiting circuitry. however, for normal continuous load conditions, do not exceed maximum junction temperature ratings. it is important to consider all sources of thermal resistance from junction-to- ambient. these sources include the junction-to-case resistance, the case-to-heat sink interface resistance, and the heat sink resistance. thermal resistance specifications have been developed to more accurately reflect device temperature and ensure safe operating temperatures. the electrical characteristics section provides a separate thermal resistance and maximum j unction temperature for both the control circuitry and the power transistor. calculate the maximum junction temperature for both sections to ensure that both thermal limits are met. for example, look at using an rc1585t to generate 5a @ 1.5v 2% from a 3.3v source (3.2v to 3.6v). load regulation it is not possible to provide true remote load sensing because the rc1585 series are three-terminal devices. load regulation is limited by the resistance of the wire connecting the regulators to the load. load regulation per the data sheet specification is measured at the bottom of the package. for fixed voltage devices, negative side sensing is a true kelvin connection with the ground pin of the device returned to the negative side of the load. this is illustrated in figure 12. for adjustable voltage devices, negative side sensing is a true kelvin connection with the bottom of the output divider returned to the negative side of the load. the best load regulation is obtained when the top of the resistor divider r1 connects directly to the regulator output and not to the load. figure 13 illustrates this point. if r1 connects to the load, then the effective resistance between the regulator and the load would be: r p (1 + r2/r1), r p = parasitic line resistance figure 13. connection for best load regulation r p parasitic line resistance v in r2* r1* r l rc1585 in out adj *connect r1 to case connect r2 to load v out = v ref (1 + r2/r1) + i adj (r2) v ref i adj 35 m a c2 22 m f r2 r1 c1 10 m f rc1585 in out ad j v out + + v in figure 11. basic regulator circuit r l v in figure 12. connection for best load regulation rc1585 -1.5 in out g nd r p parasitic line resistance the connection shown in figure 13 does not multiply r p by the divider ratio. as an example, r p is about four milliohms per foot with 16-gauge wire. this translates to 4mv per foot at 1a load current. at higher load currents, this drop represents a significant percentage of the overall regulation. it is important to keep the positive lead between the regulator and the load as short as possible and to use large wire or pc board traces. the current out of the adjust pin adds to the current from r1 and is typically 35 m a. its output voltage contribution is small and only needs consideration when a very precise output voltage setting is required.
rc1585 product specification 8 assu m ptions: v in = 3.6v w orst case v out = 1.46v w orst case i out = 5 a c o ntinu o us t a = 60 c q case-to- a m bient = 5 c/w (assu m ing bo th a heatsink and a ther m all y conductive m aterial) t he po w er dissipation in this application is: p d = (v in - v out ) * (i out ) = (3.6 - 1.46) * (5) = 10.7w fro m the specification table, for the po w er section: t j = t a + (p d ) * ( q case-to- a m bient + q jc ) = 60 + (10.7) * (5 + 3) = 14 6 c for the control section: t j = t a + (p d ) * ( q case-to- a m bient + q jc ) = 60 + (10.7) * (5 + 0.7) = 12 1 c in each case, the junction te m perature is belo w the m a x i m u m r a t i n g . table 1. bill of m aterials for application circuit for the rc1585 item quantity m anufacturer part nu m ber description c1 1 xicon l 10v10 10 m f, 1 0 v alu m inum c2, c3 2 xicon l 10v100 100 m f, 1 0 v alu m inum r1 1 g eneric 124 w , 1% r2 1 g eneric 24.9 w , 1% u1 1 fairchild rc1585t 5 a regulator figure 14. application circuit (rc1585) r2 24.9 w r1 124 w c1 10 m f c2 100 m f v o u t 1.5v u1 rc1585 v in v out a d j + + + c3 100 m f v in = 3.3v + + v in = 3.3v + + junction-to-case ther m al resistance is specified fro m the ic j unction to the botto m of the case directl y belo w the die. t his is the lo w est resistance path f or heat f lo w . proper m ounting ensures the best ther m a l flo w fro m this area of the package to the heat sink. use of a ther m all y conductive m aterial at the case-to-heat sink interface is reco m m e nded. use a ther m a ll y conductive spacer if the case of the device m ust be electrically isolated and include its contribution to the total ther m al resistance. t he cases o f the rc1585 series are directl y connected to the output of the device.
product specification rc1585 9 table 2. bill of m aterials for application circuit for the rc1585-1.5 item quantity m anufacturer part nu m ber description c1 1 xicon l 10v10 10 m f, 1 0 v alu m inum c3 1 xicon l 10v100 100 m f, 1 0 v alu m inum u1 1 fairchild rc1585 t - 1.5 5 a regulator u1 v o u t 1.5v r c 1585 - 1.5 v in v o u t g n d + + v in = 3.3v c1 10 m f c3 100 m f figure 15. application circuit (rc1585-1.5)
rc1585 product specification 10 mechanical dimensions 3-lead to-263 package inches millimeters symbol min. max. min. max. a .160 .190 4.06 4.83 b .020 .039 0.51 0.99 b2 .049 .051 1.25 1.30 c2 .045 .055 1.14 1.40 d .340 .380 8.64 9.65 e .380 .405 9.65 10.29 e .100 bsc 2.54 bsc l .575 .625 14.61 10.88 l1 .090 .100 2.29 2.79 l2 - .055 - 1.40 r .017 .019 0.43 0.48 a 0 8 0 8 notes: 1. dimensions are exclusive of mold flash and metal burrs. 2. standoff-height is measured from lead tip with ref. to datum Cb-. 3. foot length is measured with ref. to datum Ca- with lead surface (at inner r). 4. dimension exclusive of dambar protrusion or intrusion. 5. formed leads to be planar with respect to one another at seating place Cc-. e e l2 e-pin d l b b2 @pkg/ @heatsink a -c- c2 l1 r ( 2plcs ) -a- -b-
product specification rc1585 11 mechanical dimensions (continued) 3-lead to-220 package inches millimeters symbol min. max. min. max. a .140 .190 3.56 4.83 b .015 .040 .38 1.02 b1 .045 .070 1.14 1.78 c1 .014 .022 .36 .56 ? p .139 .161 3.53 4.09 d .560 .650 14.22 16.51 e .380 .420 9.65 10.67 e .090 .110 2.29 2.79 e1 .190 .210 4.83 5.33 e3 .045 - 1.14 - f .020 .055 .51 1.40 h1 .230 .270 5.94 6.87 j1 .060 .115 2.04 2.92 l .500 .580 12.70 14.73 l1 .250 bsc 6.35 bsc q 1.00 1.35 2.54 3.43 a 3 7 3 7 notes: 1. dimension c1 apply for lead finish. a f d j1 c1 a (5x) e h1 q e-pin ? p l1 l e3 b1 e e1 b
rc1585 product specification 12 ordering information product number package RC1585M to-263 rc1585t to-220 RC1585M-1.5 to-263 rc1585t-1.5 to-220 life support policy fairchilds products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of fairchild semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. a critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. fairchild semiconductor fairchild semiconductor fairchild semiconductor fairchild semiconductor corporation europe hong kong ltd. japan, ltd. americas fax: +49 (0) 1 80-530 85 86 13 th floor, straight block, tel:81-3-5620-6175 customer response center email: europe.support@nec.com ocean center, 5 canto rd. fax:81-3-5620-6179 tel:1-888-522-5372 deutsch tel: +49 (0) 8 141-35-0 taimshatsui, kowloon english tel: +44 (0) 1 793-85-66-56 hong kong italy tel: +39 (0) 2 57 5631 tel: +852 2737-7200 fax: +852 2314-0061

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