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features package option cs5253b-1 3a ldo 5-pin adjustable linear regulator with remote sense applications cs5253b-1 description applications diagram 1 5 lead d 2 pak 1 1. v sense 2. adjust 3. v out 4. v control 5. v power tab = v out december, 1999 - rev. 1 v out range is 1.25v to 5v @ 3a v power dropout < 0.40v @ 3a v control dropout < 1.05v @ 3a 1% trimmed reference fast transient response remote voltage sensing thermal shutdown current limit short circuit protection drop-in replacement for ez1582 backwards compatible with 3-pin regulators very low dropout reduces total power consumption this new very low dropout linear regulator reduces total power dissi- pation in the application. to achieve very low dropout, the inter- nal pass transistor is powered sepa- rately 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 pnp-npn based ldo regulators. in this mode the dropout is deter- mined by the minimum control voltage. the cs5253b-1 is offered in a five- terminal d 2 pak package, which allows for the implementation of a remote-sense pin permitting very accurate regulation of output volt- age directly at the load, where it counts, rather than at the regulator. this remote sensing feature virtual- ly eliminates output voltage varia- tions due to load changes and resis- tive voltage drops. typical load regulation measured at the sense pin is less than 1mv for an output voltage of 2.5v with a load step of 10ma to 3a. the cs5253b-1 has a very fast tran- sient loop response which can be adjusted using a small capacitor on the adjust pin. internal protection circuitry pro- vides for ?ust-proof?operation, similar to three-terminal regulators. this circuitry, which includes over- current, short circuit, and over-tem- perature protection will self protect the regulator under all fault condi- tions. the cs5253b-1 is ideal for generat- ing a 2.5v supply to power graph- ics controllers used on vga cards. its remote sense and low value capacitance requirements make this a low cost, high performance solution. the cs5253b-1 is opti- mized from the cs5253-1 to allow a lower value of output capacitor to be used at the expense of a slower transient response. cs5253b-1 v out v sense v control v power adjust 2.5v @3a 33 f 5v 100 f 5v 10 f 10v +3.3v +5v c load gnd gnd r dis r dis (optional) 124 124 on semiconductor 2000 south county trail, east greenwich, ri 02818 tel: (401)885?600 fax: (401)885?786 n. american technical support: 800-282-9855 web site: www.cherry?emi.com
electrical characteristics: 0? t a 70?; 0? t j 150?; v sense = v out and v adj = 0v; unless otherwise specified. parameter test conditions min typ max unit cs5253b-1 2 absolute maximum ratings v power input voltage.................................................................................................................. .....................................................6v v control input voltage.................................................................................................................. ...............................................13v operating junction temperature range ........................................................................................... .....................0? t j 150? storage temperature range...................................................................................................... ...............................?5? to +150? lead temperature soldering reflow (smd styles only) ......................................................................................60 sec. max above 183?, 230? peak esd damage threshold........................................................................................................... .................................................2kv reference voltage v control = 2.75v to 12v, 1.237 1.250 1.263 v v power = 2.05v to 5.5v, i out = 10ma to 3a (?%) (+1%) line regulation v control = 2.5v to 12v, .02 .20 % v power = 1.75v to 5.5v, i out = 10ma load regulation v control = 2.75v, .04 .30 % v power = 2.05v, i out = 10ma to 3a, with remote sense minimum load current v control = 5v, v power = 3.3v, 5 10 ma (note 1) ? v out = +1% control pin current v control = 2.75v, v power = 2.05v, i out = 100ma 6 10 ma (note 2) v control = 2.75v, v power = 2.05v, i out = 3a 35 120 ma adjust pin current v control = 2.75v, v power = 2.05v, i out = 10ma 60 120 a current limit v control = 2.75v, v power = 2.05v, 3.1 4.0 a ? v out = ?% short circuit current v control = 2.75v, v power = 2.05v, v out = 0v 2.0 3.5 a ripple rejection v control = v power = 3.25v, 60 80 db (note 3) v ripple = 1v p-p @120hz, i out = 3a, c adj = 0.1f thermal regulation 30ms pulse, t a = 25? 0.002 %/w v control dropout voltage v power = 2.05v, i out = 100ma 0.90 1.15 v (minimum v control -v out )v power = 2.05v, i out = 1a 1.00 1.15 v (note 4) v power = 2.05v, i out = 3a 1.05 1.30 v v power dropout voltage v control = 2.75v, i out = 100ma .05 .15 v (minimum v power -v out )v control = 2.75v, i out = 1a .15 .25 v (note 4) v control = 2.75v, i out = 3a .40 .60 v rms output noise freq = 10hz to 10khz, t a = 25? 0.003 %v out temperature stability 0.5 % thermal shutdown (note 5) 150 180 210 ? thermal shutdown hysteresis 25 c v control supply only v control = 13v, v power not connected, 50 ma output current v adjust = v out = v sense = 0v v power supply only v power = 6v, v control not connected, 0.1 1.0 ma output current v adjust = v out = v sense = 0v note 1: the minimum load current is the minimum current required to maintain regulation. normally the current in the resistor di vider used to set the output voltage is selected to meet the minimum load current requirement. note 2: the v control pin current is the drive current required for the output transistor. this current will track output current with roughly a 1:10 0 ratio. the minimum value is equal to the quiescent current of the device. note 3: this parameter is guaranteed by design and is not 100% production tested. note 4: dropout is defined as either the minimum control voltage, (v control) or minimum power voltage (v power ) to output voltage differential required to maintain 1% regulation at a particular load current. note 5: this parameter is guaranteed by design, but not parametrically tested in production. however, a 100% thermal shutdown fu nctional test is performed on each part.
cs5253b-1 package pin description package pin # pin symbol function 3 block diagram ? + + ? v power v control bias and tsd v ref ea ia v out v sense adjust 5lead d 2 pak 1v 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 sensing error amplifier. 2 adjust this pin is connected to the low side of the internally trimmed 1% bandgap reference voltage and carries a bias current of about 50a. a resistor divider from adj to v out and from adj to ground sets the output voltage. also, transient response can be improved by adding a small bypass capacitor from this pin to ground. 3v out this pin is connected to the emitter of the power pass transistor and provides a regulated voltage capable of sourcing 3a of current. 4v control this is the supply voltage for the regulator control circuitry. for the device to regulate, this voltage should be between 0.9v and 1.3v (depending on the output current) greater than the output voltage. the control pin current will be about 1% of the output current. 5v power this is the power input voltage. the pin is physically connected to the collector of the power pass transistor. for the device to regulate, this voltage should be between 0.1v and 0.6v greater than the output voltage, depending on output current. the out- put load current of 3a is supplied through this pin.
cs5253b-1 4 typical performance characteristics 0 20 40 60 80 100 120 reference voltage (v) junction temperature (c) 1.247 1.248 1.249 1.250 1.251 1.252 1.253 reference voltage vs junction temperature 0.5 1.0 1.5 2.0 2.5 output current (a) t j = 120 c t j = 20 c 0 3.0 0.08 0.10 0.12 0 0.02 0.04 0.06 load regulation (%) t j = 0 c load regulation vs output current 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 01 23456 v power - v out (v) output current (a) measured at ? v out = -1% output current vs v power -v out transient response comparison between cs5253-1 and cs5253b-1 v out cs5253b-1 c out = 33 f 15a/ s 80a/ s i load 10ma to 3a v out cs5253-1 c out = 330 f v control = 5v v power =3.3v v out = 2.5v c control = 10 f c adj = 0.1 f transient response i adj ( a) junction temperature (c) 0 20 40 60 80 100 120 140 60 65 70 75 80 85 adjust pin current vs junction temperature 1.0 3.0 4.0 5.0 6.0 7.0 800 minimum load current ( a) v control -v out (v) 9.0 10.0 11.0 2.0 8.0 850 900 950 1000 1050 1100 1150 1200 v power =3.3v ? v out =+1% minimum load current vs v control -v out
cs5253b-1 5 typical performance characteristics short circuit output current limit (a) 3.3 3.4 3.5 3.6 3.7 3.8 3.9 0 20 40 60 80 100 120 140 junction temperature (c) v power = 3.3v v control = 5v short circuit output current vs junction temperature 10.0 10 1 frequency (hz) ripple rejection (db) 20.0 30.0 40.00 60.0 70.0 80.0 90.0 10 2 10 3 10 4 10 6 10 5 50.0 v in ?v out = 2v i out = 3a v ripple = 1v p-p c out = 22 f c adj = 0.1 f ripple rejection vs frequency 0 2 4 6 8 10 12 0 20 40 60 80 100 120 140 junction temperature (c) iout (ma) v control = 13v, v out = 0v, vpower not connected v control only output current vs junction temperature vcontrol dropout voltage (mv) 0.0 output current (a) 800 900 1000 1100 0.5 1.0 3.0 2.5 2.0 1.5 t j = 120 c t j = 20 c t j = 0 c v power = 2.05v v control dropout voltage vs output current vpower dropout voltage (v) 0 0.0 output current (a) 50 150 200 250 300 350 400 450 500 0.5 1.0 3.0 2.5 2.0 1.5 t j = 120 c t j = 20 c t j = 0 c v power dropout voltage vs output current 0.50 1.50 2.50 915.5 minimum load current ( a) v power -v out (v) 3.50 4.50 915.6 915.7 915.8 915.9 916.0 916.1 916.2 916.4 v control =5v ? v out =+1% 915.4 916.3 minimum load current vs v power -v out
cs5253b-1 6 typical performance characteristics: continued v power only output current vs junction temperature the cs5253b-1 linear regulator provides adjustable volt- ages from 1.25v to 5v at currents up to 3a. the regulator is protected against short circuits, and includes a thermal shutdown circuit with hysteresis. the output, which is cur- rent limited, consists of a pnp-npn transistor pair and requires an output capacitor for stability. a detailed proce- dure for selecting this capacitor is included in the stability considerations section. v power function the cs5253b-1 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 for the con- trol circuitry and the drive for the output npn transistor. v control should be at least 1v greater than the output voltage. 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 limited to about three milliamperes 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 cs5253b-1 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 cs5253b-1 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 regula- tion. regulation will be optimized at the point where the sense pin is tied to the output. theory of operation v control supply current vs junction temperature application notes current limit vs v out stability vs esr i out (ua) 0 5 10 15 20 25 30 0 20 40 60 80 100 120 140 junction temperature (c) v power = 6v v out = 0v v control not connected i control (ma) 40 0 20 40 60 80 100 120 140 junction temperature (c) 35 30 25 20 15 10 5 0 i out = 3a i out = 1a i out = 100ma v power = 2.05v v control = 2.75v 5.0 4.5 4.0 3.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 current limit (a) v out (v) v power = 3.3v v control = 5.0v v out set for 2.5v t a = 25 c 6 5 4 3 2 1 0 0 102030405060708090100 esr (ohms) capacitance ( f) unstable stable region v power = 3.3v v control = 5.0v i load = 0 to 3a v out = 2.5v v out shorted to v sense t j = 0 to 150 c
cs5253b-1 7 application notes: continued remote sense remote sense operation can be easily obtained with the cs5253b-1 but some care must be paid to the layout and positioning of the filter capacitors around the part. the ground side of the input capacitors on the +5v and +3.3v lines and the local v out -to-ground local output capacitor on the ic output must be tied close to the ground connect- ed resistor voltage divider feedback network. the top resis- tor of the divider must be connected directly to the v sense pin of the regulator. this will establish the stability of the part. this capacitor-divider resistor connection may then be connected to ground remotely at the load, giving the ground portion remote sense operation. the v sense line can then be tied remotely at the load con- nection, giving the feedback remote sense operation. the remote sense lines should be kelvin connected so as to eliminate the effect of load current voltage drop. an optional bypass capacitor may be used at the load to reduce the effect of load variations and spikes. figure 2. remote sense adjustable operation this ldo adjustable regulator has an output voltage range of 1.25v to 5v. an external resistor divider sets the output voltage as shown in figure 2. the regulator? voltage sens- ing error amplifier maintains a fixed 1.25v reference between the output pin and the adjust pin. a resistor divider network r 1 and r 2 causes a fixed current to flow to ground. this current creates a voltage across r 2 that adds to the 1.25v across r 1 and sets the overall output voltage. the adjust pin current (typically 50a) also flows through r 2 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 = 1.25v + r 2 i adj the term i adj r 2 represents the error added by the adjust pin current. r 1 is chosen so that the minimum load current is at least 10ma. r 1 and r 2 should be of the same composi- tion for best tracking over temperature. figure 2: typical application schematic. the resistor divider sets v out , with the internal 1.260v reference dropped across r1. while not required, a bypass capacitor connected between the adjust pin and ground will improve transient response and ripple rejection. a 0.1f tantalum capacitor is recom- mended for ?irst cut?design. value and type may be var- ied to optimize performance vs. price. other adjustable operation considerations the cs5253b-1 linear regulator has an absolute maximum specification of 6v for the voltage difference between v power and v out . however, the ic may be used to regu- late voltages in excess of 6v. 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 con- trol 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 pow- er 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 tran- sistor out of dropout. in this manner, any output voltage less than 13v may be regulated, provided the v power to v out differential is less than 6v. in the case where v con- trol and v power are shorted, there is no theoretical limit to the regulated voltage as long as the v power to v out dif- ferential of 6v is not exceeded. there is a possibility of damaging the ic when v power - v out is greater than 6v if a short circuit occurs. short cir- cuit conditions will result in the immediate operation of the pass transistor outside of its safe operating area. over- voltage stresses will then cause destruction of the pass transistor before overcurrent or thermal shutdown circuit- v sense v out v control v power cs5253b-1 r1 adjust r2 5v 3.3v 2.5v @3a r 1 +r 2 r 1 + + + + v control v power v sense v out adjust cs5253b-1 local connections 100 f 10 f 33 f optional +load ?oad r dis r dis +5v +3.3v gnd remote connections 124 124 design guidelines
8 cs5253b-1 application notes: continued ry can become active. additional circuitry may be required to clamp the v power to v out differential to less than 6v if fail safe operation is required. one possible clamp circuit is illustrated in figure 3; however, the design of clamp cir- cuitry 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 3: this circuit is an example of how the cs5253b-1 can be short- circuit-protected when operating with v out > 6v. stability considerations the output compensation capacitor helps determine three main characteristics of a linear regulator: loop stability, start-up delay, and load transient response. different capacitor types vary widely in tolerance, esr (equivalent series resistance), esl (equivalent series inductance), and variation over temperature. tantalum and aluminum elec- trolytic capacitors work best, with electrolytic capacitors being less expensive in general, but varying more in capac- itor value and esr over temperature. the cs5253b-1 requires an output capacitor to guarantee loop stability. the stability vs esr graph in the typical per- formance section shows the minimum esr needed to guar- antee stability, but under ideal conditions. these include: having v out connected to v sense directly at the ic pins; the compensation capacitor located right at the pins with a minimum lead length; the adjust feedback resistor divider ground, (bottom of r2 in figure 2), connected right at the capacitor ground; and with power supply decoupling capacitors located close to the ic pins. the actual perfor- mance will vary greatly with board layout for each appli- cation. in particular, the use of the remote sensing feature will require a larger capacitor with less esr. for most applications, a minimum of 33f tantalum or 150f alu- minum electrolytic, with an esr less than 1 ? over temper- ature, is recommended. larger capacitors and lower esr will improve stability. the load transient response, during the time it takes the regulator to respond, is also determined by the output capacitor. for large changes in load current, the esr of the output capacitor causes an immediate drop in output volt- age given by: ? v = ? i esr there is then an additional drop in output voltage given by: ? v = ? i t/c where t is the time for the regulation loop to begin to respond. the very fast transient response time of the cs5253b-1 allows the esr effect to dominate. for micro- processor 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 tran- sient response. 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 cs5253b-1 regulator, the discharge path is through a large junction and protection diodes are not usually needed. if the regulator is used with large val- ues of output capacitance and the input voltage is instanta- neously shorted to ground, damage can occur. in this case, a diode connected as shown in figure 4 is recommended. figure 4: diode protection circuit. a rule of thumb useful in determining if a protection diode is required is to solve for current: i = , 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 typi- c v t v sense v out v control v power cs5253b-1 adjust external supply v control v power v adjust v out v sense external supply
9 cs5253b-1 application notes: continued cal short circuit current value provided in the specifica- tions, serious thought should be given to the use of a pro- tection 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 current at approximately 500ma less than its current limit value. this provides for a current foldback function, which reduces power dissipation 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? and to shut down the regulator output. this circuit- ry has 25? of typical hysteresis, thereby allowing the reg- ulator to recover from a thermal fault automatically. calculating power dissipation and heat sink requirements high power regulators such as the cs5253b-1 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 cs5253b-1, electrical isolation may be required for some applications. also, as with all high power packages, thermal compound in 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 follow- ing four factors: junction temperature, ambient tempera- ture, die power dissipation, and the thermal resistance from the die junction to ambient air. the maximum junc- tion temperature can be determined by: t j(max) = t a(max) + pd (max) r ja the maximum ambient temperature and the power dissi- pation 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: 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 ja . this total thermal resistance is comprised of three compo- nents. these resistive terms are measured from junction to case (r jc ), case to heat sink (r cs ), and heat sink to ambi- ent air (r sa ). the equation is: r ja = r jc + r cs + r sa the value for r jc is 2.5?/watt for the cs5253b-1 in the d 2 pak package. for a high current regulator such as the cs5253b-1 the majority of heat is generated in the power transistor section. the value for r sa depends on the heat sink type, while the r cs depends on factors such as pack- age 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 ja can be calculated and the proper heat sink selected. for further discussion on heat sink selection, see our on application note ?hermal management for linear regulators.
10 ordering information thermal data 5lead d 2 pak r jc typ 2.5 ?/w r ja typ 10-50* ?/w *depending on thermal properties of substrate. r ja = r jc + r ca package specification package dimensions in mm (inches) package thermal data part number description cs5253b-1gdp5 5 lead d 2 pak cs5253b-1gdpr5 5 lead d 2 pak (tape & reel) cs5253b-1 5 lead d 2 pak (dp) 1.70 (.067) ref 0.10 (.004) 0.00 (.000) 10.31 (.406) 10.05 (.396) 0.91 (.036) 0.66 (.026) 1.40 (.055) 1.14 (.045) 4.57 (.180) 4.31 (.170) 1.68 (.066) 1.40 (.055) 2.74(.108) 2.49(.098) .254 (.010) ref 2.79 (.110) 2.29 (.090) 15.75 (.620) 14.73 (.580) 8.53 (.336) 8.28 (.326) on semiconductor and the on logo are trademarks of semiconductor components industries, llc (scillc). on semiconductor reserves the right to make changes without further notice to any products herein. for additional infor- mation and the latest available information, please contact your local on semiconductor representative. ?semiconductor components industries, llc, 2000
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