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? semiconductor components industries, llc, 2002 may, 2002 rev. 5 1 publication order number: cs52581/d cs5258-1 8.0 a ldo 5-pin adjustable linear regulator this new very low dropout regulator is designed to power the next generation of advanced microprocessors. to achieve very low dropout, the internal pass transistor is powered separately from the control circuitry. furthermore, with the control and power inputs tied together, this device can be used in single supply configuration and still offer a better dropout voltage than conventional pnpnpn based ldo regulators. in this mode the dropout is determined by the minimum control voltage. it is supplied in a fiveterminal to220 package, which allows for the implementation of a remotesense pin permitting very accurate regulation of output voltage directly at the load, where it counts, rather than at the regulator. this remote sensing feature virtually eliminates output voltage variations due to load changes and resistive voltage drops. typical load regulation measured at the sense pin is 1.0 mv for an output voltage of 2.5 v with a load step of 10 ma to 8.0 a. the very fast transient loop response easily meets the needs of the latest microprocessors. in addition, a small capacitor on the adjust pin will further improve the transient capabilities. internal protection circuitry provides for abustproofo operation, similar to threeterminal regulators. this circuitry, which includes overcurrent, short circuit, supply sequencing and overtemperature protection, will self protect the regulator under all fault conditions. the cs52581 is ideal for generating a secondary 2.02.5 v low voltage supply on a motherboard where both 5.0 v and 3.3 v are already available. features ? 1.25 v to 5.0 v v out at 8.0 a ? v power dropout < 0.4 v @ 8.0 a ? v control dropout < 1.15 v @ 8.0 a ? 1.5% trimmed reference ? fast transient response ? remote voltage sensing ? thermal shutdown ? current limit ? short circuit protection ? backwards compatible with 3pin regulators marking diagram a = assembly location wl, l = wafer lot yy, y = year ww, w = work week to220 five lead t suffix case 314d tab = v out pin 1. v sense 2. adjust 3. v out 4. v control 5. v power 1 5 cs52581 awlyww 1 device package shipping ordering information cs52581gt5 to220 five lead 50 units/rail http://onsemi.com
cs52581 http://onsemi.com 2 figure 1. application diagram cs52581 10 m f 10 v v control v power v out v sense adjust 100 m f 5.0 v 0.1 m f 5.0 v 5.0 v 3.3 v 124 1.0% 124 1.0% load 2.5 v @ 8.0 a 300 m f 5.0 v maximum ratings* rating value unit v power input voltage 6.0 v v control input voltage 13 v operating junction temperature range, t j 0 to 150 c storage temperature range 65 to +150 c esd damage threshold 2.0 kv lead temperature soldering: wave solder (through hole styles only) note 1 260 peak c 1. 10 second maximum. *the maximum package power dissipation must be observed. electrical characteristics (0 c t a 70 c; 0 c t j 150 c; v sense = v out and v adj = 0 v; unless otherwise specified.) characteristic test conditions min typ max unit cs52581 reference voltage v control = 2.75 v to 12 v, v power = 2.15 v to 5.5 v, 10 ma i out 8.0 a 1.234 (1.5%) 1.253 1.272 (+1.5%) v line regulation v control = 2.5 v to 12 v, v power = 1.75 v to 5.5 v, i out = 10 ma 0.02 0.2 % load regulation (note 2) v control = 2.75 v, v power = 2.15 v, i out = 10 ma to 8.0 a, with remote sense 0.04 0.2 % minimum load current (note 3) v control = 5.0 v, v power = 3.3 v, d v out = +1.0% 5.0 10 ma control pin current (note 4) v control = 2.75 v, v power = 2.15 v, i out = 100 ma v control = 2.75 v, v power = 2.15 v, i out = 4.0 a v control = 2.75 v, v power = 1.75 v, i out = 4.0 a v control = 2.75 v, v power = 2.15 v, i out = 8.0 a 6.0 30 33 80 10 60 70 180 ma ma ma ma adjust pin current v control = 2.75 v, v power = 2.15 v, i out = 10 ma 60 120 m a current limit v control = 2.75 v, v power = 2.15 v, d v out = 1.5% 8.1 10 a short circuit current v control = 2.75 v, v power = 2.15 v, v out = 0 v 6.0 9.0 a 2. this parameter is guaranteed by design and is not 100% production tested. 3. the minimum load current is the minimum current required to maintain regulation. normally the current in the resistor divider used to set the output voltage is selected to meet the minimum load current requirement. 4. the v control pin current is the drive current required for the output transistor. this current will track output current with roughly a 1:1 00 ratio. the minimum value is equal to the quiescent current of the device.
cs52581 http://onsemi.com 3 electrical characteristics (continued) (0 c t a 70 c; 0 c t j 150 c; v sense = v out and v adj = 0 v; unless otherwise specified.) characteristic unit max typ min test conditions cs52581 ripple rejection (note 5) v control = v power = 3.25 v avg v ripple = 1.0 v pp @ 120 hz, i out = 4.0 a, c adj = 0.1 m f 60 80 db thermal regulation 30 ms pulse, t a = 25 c 0.002 %/w v control dropout voltage (minimum v control v out ) (note 6) v power = 2.15 v, i out = 100 ma v power = 2.15 v, i out = 1.0 a v power = 2.15 v, i out = 2.75 a v power = 2.15 v, i out = 4.0 ma v power = 2.15 v, i out = 8.0 a 1.00 1.00 1.00 1.00 1.15 1.15 1.15 1.15 1.15 1.30 v v v v v v power dropout voltage (minimum v power v out ) (note 6) v control = 2.75 v, i out = 100 ma v control = 2.75 v, i out = 1.0 a v control = 2.75 v, i out = 2.75 a v control = 2.75 v, i out = 4.0 ma v control = 2.75 v, i out = 8.0 a 0.10 0.15 0.20 0.26 0.40 0.15 0.20 0.30 0.40 0.70 v v v v v rms output noise freq = 10 hz to 10 khz, t a = 25 c 0.003 %v out temperature stability 0.5 % thermal shutdown (note 7) 150 180 210 c thermal shutdown hysteresis 25 c v control supply only output current v control = 13 v, v power not connected, v adj = v out = v sense = 0 v 50 ma v power supply only output current v power = 6.0 v, v control not connected, v adj = v out = v sense = 0 v 0.1 1.0 ma 5. this parameter is guaranteed by design and is not 100% production tested. 6. dropout is defined as either minimum control voltage (v control ) or minimum power voltage (v power ) to output voltage differential re- quired to maintain 1.5% regulation at a particular load. 7. this parameter is guaranteed by design, but not parametrically tested in production. however, a 100% thermal shutdown functio nal test is performed on each part. package pin description package pin # to220 pin symbol function 1 v sense this kelvin sense pin allows for remote sensing of the output voltage at the load for improved regulation. it is internally connected to the positive input of the voltage sens- ing error amplifier. 2 adjust this pin is connected to the low side of the internally trimmed 1.5% bandgap reference voltage and carries a bias current of about 50 m a. a resistor divider from adjust to v out and from adjust to ground sets the output voltage. also, transient response can be im- proved by adding a small bypass capacitor from this pin to ground. 3 v out this pin is connected to the emitter of the power pass transistor and provides a regulated voltage capable of sourcing 8.0 a of current. 4 v control this is the supply voltage for the regulator control circuitry. for the device to regulate, this voltage should be between 1.0 v and 1.3 v (depending on the output current) greater than the output voltage. the control pin current will be about 1.0% of the power pin output current. 5 v power this is the power input voltage. this pin is physically connected to the collector of the power pass transistor. for the device to regulate, this voltage should be between 0.1 v and 0.7 v greater than the output voltage depending on the output current. the output load current of 8.0 a is supplied through this pin.
cs52581 http://onsemi.com 4 figure 2. block diagram + + bias and tsd v ref ea ia v out v sense adjust v power v control typical performance characteristics figure 3. reference voltage vs temperature t j ( c) 10 30 output voltage deviation (%) 0.150 0.050 0.100 0.100 0 20 40 130 i o = 10 ma v control = 2.75 v v power = 2.15 v 0.050 0 0.075 0.075 0.125 0.025 0.025 50 70 60 80 90 110 100 120 figure 4. reference voltage vs temperature figure 5. adjust pin current vs temperature temperature ( c) 20 adjust pin current ( m a) 83 0 40 60 80 100 81 79 77 75 73 71 65 120 140 160 69 67 figure 6. ripple rejection vs frequency v in v out = 2.0 v i out = 4.0 a v ripple = 1.0 v pp c out = 22 m f c adj = 0.1 m f 10 1 frequency (hz) 10 ripple rejection (db) 20 30 40 50 60 70 80 90 10 2 10 3 10 4 10 5 10 6 0 1.0 3.0 2.0 8.0 output current (a) 4.0 6.0 5.0 7.0 output voltage deviation (%) 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 v power = 2.15 v v control = 2.75 v
cs52581 http://onsemi.com 5 figure 7. v power dropout voltage vs i out figure 8. v control dropout vs i out figure 9. minimum load current vs v control v out v control v out (v) 1.0 3.0 minimum load current ( m a) 800 1000 1050 1200 900 950 1100 1150 5.0 7.0 9.0 2.0 4.0 6.0 8.0 10 11 v power = 3.3 v d v out = +1.0% 850 figure 10. current step transient response figure 11. short circuit current vs v power v out v power v out (v) 0 1.0 output current (a) 0 6.0 8.0 14.0 2.0 4.0 10.0 12.0 2.0 3.0 4.0 5.0 0.5 1.5 2.5 3.5 4.5 5.5 v control = 2.75 v figure 12. adjust pin current vs output current adjust pin current ( m a) 77 76 75 74 73 72 0 1.0 3.0 2.0 8.0 output current (a) 4.0 6.0 5.0 7.0 v power = 2.15 v v control = 2.75 v 0 1.0 3.0 2.0 8.0 output current (a) 4.0 6.0 5.0 7.0 v power dropout voltage (v) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 v control = 2.75 v 0 1.0 3.0 2.0 8. 0 output current (a) 4.0 6.0 5.0 7.0 v control dropout voltage (v) 1.25 1.00 0.75 0.50 0.25 0 v power = 2.15 v time ( m s) output voltage deviation (mv) 100 c out = 330 m f c power = 110 m f c control = 10 m f c adj = 0.1 m f v control = 5.0 v v power = 3.3 v v out = 2.5 v 0123 4 0 5 50 0 50 100 0 8.0 current (a)
cs52581 http://onsemi.com 6 figure 13. adjust pin current vs v control v out v control v out (v) 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 11 adjust pin current ( m a) 70 71 72 73 74 75 v power = 2.15 v il = 10 ma v power v out (v) 0.5 1.5 2.5 3.5 4.5 adjust pin current ( m a) 70 73 74 75 71 72 v control = 2.75 v il = 10 ma figure 14. adjust pin current vs v power v out v power v out (v) 0.5 1.5 2.5 3.5 4.5 minimum load current ( m a) 915.4 916.0 916.1 916.2 916.3 916.4 915.5 915.6 915.7 915.8 915.9 v control = 5.0 v d v out = +1.0% figure 15. minimum load current vs v power v out applications notes theory of operation the cs52581 linear regulator provides adjustable voltages from 1.25 v to 5.0 v at currents up to 8.0 a. the regulator is protected against short circuits, and includes a thermal shutdown circuit with hysteresis. the output, which is current limited, consists of a pnpnpn transistor pair and requires an output capacitor for stability. a detailed procedure for selecting this capacitor is included in the stability considerations section. v power function the cs52581 utilizes a two supply approach to maximize efficiency. the collector of the power device is brought out to the v power pin to minimize internal power dissipation under high current loads. v control provides power for the control circuitry and the drive for the output npn transistor. v control should be at least 1.0 v greater than the output volt age. special care has been taken to ensure that there are no supply sequencing problems. the output voltage will not turn on until both supplies are operating. if the control voltage comes up first, the output current will be typically limited to about 3.0 ma until the power input voltage comes up. if the power input voltage comes up first the output will not turn on at all until the control voltage comes up. the output can never come up unregulated. the cs52581 can also be used as a single supply device with the control and power inputs tied together. in this mode, the dropout will be determined by the minimum control voltage. output voltage sensing the cs52581 five terminal linear regulator includes a dedicated v sense function. this allows for true kelvin sensing of the output voltage. this feature can virtually eliminate errors in the output voltage due to load regulation. regulation will be optimized at the point where the sense pin is tied to the output.
cs52581 http://onsemi.com 7 design guidelines adjustable operation this ldo adjustable regulator has an output voltage range of 1.25 v to 5.0 v. an external resistor divider sets the output voltage as shown in figure 16. the regulator's voltage sensing error amplifier maintains a fixed 1.253v reference between the output pin and the adjust pin. figure 16. an external resistor divider sets the value of v out . the 1.253 v reference voltage drops across r1. cs52581 v control v power v out v sense adjust r2 r1 a resistor divider network r1 and r2 causes a fixed current to flow to ground. this current creates a voltage across r2 that adds to the 1.253 v across r1 and sets the overall output voltage. the adjust pin current (typically 50 m a) also flows through r2 and adds a small error that should be taken into account if precise adjustment of v out is necessary. the output voltage is set according to the formula: v out 1.253 v r1 r2 r1 r2 i adj the term i adj r2 represents the error added by the adjust pin current. r1 is chosen so that the minimum load current is a least 10 ma. r1 and r2 should be of the same composition for best tracking over temperature. the divider resistors should be located as close to the load as possible. while not required, a bypass capacitor connected between the adjust pin and ground will improve transient response and ripple rejection. a 0.1 m f tantalum capacitor is recommended for afirst cuto design. value and type may be varied to optimize performance vs. price. other adjustable operation considerations the cs52581 linear regulator has an absolute maximum specification of 6.0 v for the voltage dif ference between v in and v out . however, the ic may be used to regulate voltages in excess of 6.0 v. the two main considerations in such a design are the sequencing of power supplies and short circuit capability. power supply sequencing should be such that the v control supply is brought up coincidentally with or before the v power supply. this allows the ic to begin charging the output capacitor as soon as the v power to v out differential is large enough that the pass transistor conducts. as v power increases, the pass transistor will remain in dropout, and current is passed to the load until v out is in regulation. further increase in the supply voltage brings the pass transistor out of dropout. in this manner, any output voltage less than 13 v may be regulated, provided the v power to v out differential is less than 6.0 v. in the case where v control and v power are shorted, there is no theoretical limit to the regulated voltage as long as the v power to v out differential of 6.0 v is not exceeded. there is a possibility of damaging the ic when v power v in is greater than 6.0 v if a short circuit occurs. short circuit conditions will result in the immediate operation of the pass transistor outside of its safe operating area. overvoltage stresses will then cause destruction of the pass transistor before overcurrent or thermal shutdown circuitry can become active. additional circuitry may be required to clamp the v power to v out differential to less than 6.0 v if fail safe operation is required. one possible clamp circuit is illustrated in figure 17; however, the design of clamp circuitry must be done on an application by application basis. care must be taken to ensure the clamp actually protects the design. components used in the clamp design must be able to withstand the short circuit condition indefinitely while protecting the ic. figure 17. example clamp circuitry for v power v out > 6.0 v v control v power v sense v out v adj external supply stability considerations the output compensation capacitor helps determine three main characteristics of a linear regulator: startup delay, load transient response, and loop stability. the capacitor value and type is based on cost, availability, size and temperature constraints. a tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capacitor with almost zero esr can cause instability. the aluminum electrolytic capacitor is the least expensive
cs52581 http://onsemi.com 8 solution. however, when the circuit operates at low temperatures, both the value and esr of the capacitor will vary considerably. the capacitor manufacturer's data sheet provides this information. a 300 m f tantalum capacitor will work for most applications, but with high current regulators such as the cs52581 the transient response and stability improve with higher values of capacitor. the majority of applications for this regulator involve large changes in load current so the output capacitor must supply the instantaneous load current. the esr of the output capacitor causes an immediate drop in output voltage given by: v i esr for microprocessor applications it is customary to use an output capacitor network consisting of several tantalum and ceramic capacitors in parallel. this reduces the overall esr and reduces the instantaneous output voltage drop under transient load conditions. the output capacitor network should be as close to the load as possible for the best results. protection diodes when large external capacitors are used with a linear regulator it is sometimes necessary to add protection diodes. if the input voltage of the regulator gets shorted, the output capacitor will discharge into the output of the regulator. the discharge current depends on the value of the capacitor, the output voltage, and the rate at which v control drops. in the cs52581 regulator, the discharge path is through a large junction and protection diodes are not usually needed. if the regulator is used with large values of output capacitance and the input voltage is instantaneously shorted to ground, damage can occur. in this case, a diode connected as shown in figure 18 is recommended. use of the diode has the added benefit of bleeding v out to ground if v control is shorted. this prevents an unregulated output from causing system damage. figure 18. diode protection against v control short circuit conditions cs5257a1 v control v power v out v sense adjust a rule of thumb useful in determining if a protection diode is required is to solve for current i c v t where: i is the current flow out of the load capacitance when v control is shorted, c is the value of load capacitance, v is the output voltage, and t is the time duration required for v control to transition from high to being shorted. if the calculated current is greater than or equal to the typical short circuit current value provided in the specifications, serious thought should be given to the use of a protection diode. current limit the internal current limit circuit limits the output current under excessive load conditions. short circuit protection the device includes short circuit protection circuitry that clamps the output cur rent at approximately two amperes less than its current limit value. this provides for a current foldback function, which reduces power dissipation even further under a direct shorted load. thermal shutdown the thermal shutdown circuitry is guaranteed by design to activate above a die junction temperature of approximately 150 c and to shut down the regulator output. this circuitry has 25 c of typical hysteresis, thereby allowing the regulator to recover from a thermal fault automatically. calculating power dissipation and heat sink requirements high power regulators such as the cs52581 family usually operate at high junction temperatures. therefore, it is important to calculate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is used. since the package tab is connected to v out on the cs52581, electrical isolation may be required for some applications. also, as with all high power packages, thermal compound is necessary to ensure proper heat flow. for added safety, this high current ldo includes an internal thermal shutdown circuit. the thermal characteristics of an ic depend on the following four factors: junction temperature, ambient temperature, die power dissipation, and the thermal resistance from the die junction to ambient air. the maximum junction temperature can be determined by: t j(max) t a(max) pd (max) r ja the maximum ambient temperature and the power dissipation are determined by the design while the maximum junction temperature and the thermal resistance depend on the manufacturer and the package type. the maximum power dissipation for a regulator is:
cs52581 http://onsemi.com 9 pd (max) ( v in(max) v out(min) ) i out(max) v in(max) i in(max) a heat sink effectively increases the surface area of the package to improve the flow of heat away from the ic and into the surrounding air. each material in the heat flow path between the ic and the outside environment has a thermal resistance which is measured in degrees per watt. like series electrical resistances, these thermal resistances are summed to determine the total thermal resistance between the die junction and the surrounding air, r q ja . this total thermal resistance is comprised of three components. these resistive terms are measured from junction to case (r q jc ), case to heat sink r q cs ), and heat sink to ambient air (r q sa ). the equation is: r ja r jc r cs r sa the value for r q jc is 1.4 c watt for the cs52581 in the to220 package. for a high current regulator such as the cs52581 the majority of heat is generated in the power transistor section. the value for r q sa depends on the heat sink type, while the r q cs depends on factors such as package type, heat sink interface (is an insulator and thermal grease used?), and the contact area between the heat sink and the package. once these calculations are complete, the maximum permissible value of r q ja can be calculated and the proper heat sink selected. for further discussion on heat sink selection, see our application note athermal management,o document number and8036/d, available through the literature distribution center or via our website at http://www.onsemi.com.
cs52581 http://onsemi.com 10 package dimensions to220 five lead t suffix case 314d04 issue e q 12345 u k d g a b 5 pl j h l e c m q m 0.356 (0.014) t seating plane t dim min max min max millimeters inches a 0.572 0.613 14.529 15.570 b 0.390 0.415 9.906 10.541 c 0.170 0.180 4.318 4.572 d 0.025 0.038 0.635 0.965 e 0.048 0.055 1.219 1.397 g 0.067 bsc 1.702 bsc h 0.087 0.112 2.210 2.845 j 0.015 0.025 0.381 0.635 k 0.990 1.045 25.146 26.543 l 0.320 0.365 8.128 9.271 q 0.140 0.153 3.556 3.886 u 0.105 0.117 2.667 2.972 notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: inch. 3. dimension d does not include interconnect bar (dambar) protrusion. dimension d including protrusion shall not exceed 10.92 (0.043) maximum. package thermal data parameter to220 five lead unit r q jc typical 1.4 c/w r q ja typical 50 c/w
cs52581 http://onsemi.com 11 notes
cs52581 http://onsemi.com 12 on semiconductor and are registered trademarks of semiconductor components industries, llc (scillc). scillc reserves the right to mak e changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and s pecifically disclaims any and all liability, including without limitation special, consequential or incidental damages. atypicalo parameters which may be provided in scillc data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including atypicalso must be validated for each customer application by customer's technical experts. scillc does not convey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body , or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a sit uation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indem nify and hold scillc and its of ficers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and re asonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized u se, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employ er. publication ordering information japan : on semiconductor, japan customer focus center 4321 nishigotanda, shinagawaku, tokyo, japan 1410031 phone : 81357402700 email : r14525@onsemi.com on semiconductor website : http://onsemi.com for additional information, please contact your local sales representative. cs52581/d literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 3036752175 or 8003443860 toll free usa/canada fax : 3036752176 or 8003443867 toll free usa/canada email : onlit@hibbertco.com n. american technical support : 8002829855 toll free usa/canada

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