iru1175 1 rev. 1.7 04/09/03 www.irf.com 7.5a ultra low dropout positive adjustable regulator the iru1175 is a 7.5a regulator with extremely low drop- out voltage using a proprietary bipolar process that achieves comparable equivalent on resistance to that of discrete mosfets. this product is specifically designed to provide well regulated supply for applications requir- ing very low dropout such as 2.8v from 3.3v atx power supplies where the same efficiency as the switcher can be achieved without the cost and complexity associ- ated with switching regulators. one such application is the new graphic chip sets that require 2.7v supply such as the intel i 740 chip set. description 0.5v dropout at 7.5a (equivalent of 67m v ) fast transient response 1% voltage reference initial accuracy built-in thermal shutdown applications features 3.3v to 2.7v intel i 740 chip set typical application package order information figure 1 - typical application of iru1175. data sheet no. pd94131 3.3v iru1175 2.7v c1 100uf c3 100uf 5v c2 10uf r1 100 1% r2 124 1% 1 2 3 4 5 v sense adj v out v ctrl v in t j (c) 5-pin plastic 5-pin plastic to-263 (m) ultra thin-pak tm (p) 0 to 125 iru1175cm iru1175cp
2 rev. 1.7 04/09/03 iru1175 www.irf.com absolute maximum ratings input voltage (v in ) .................................................... 6v control input voltage (v ctrl ) ..................................... 14v power dissipation ..................................................... internally limited storage temperature range ...................................... -65c to 150c operating junction temperature range ..................... 0c to 150c package information 5-pin plastic to-263 (m) 5-pin plastic ultra thin-pak tm (p) electrical specifications unless otherwise specified, these specifications apply over c in =1 m f, c out =10 m f, and t j =0 to 125 8 c. typical values refer to t j =25 8 c. v out =v sense . u ja =35 c/w for 0.5" square pad u ja =35 c/w for 0.5" square pad parameter sym test condition min typ max units reference voltage line regulation load regulation (note 1) dropout voltage (note 2) (v ctrl - v out ) dropout voltage (note 2) (v in - v out ) current limit minimum load current (note 3) thermal regulation ripple rejection v ctrl =2.75, v in =2v, io=10ma, t j =25 8 c, v adj =0v v ctrl =2.7 to 12v, v in =2.05v to 5.5v, io=10ma to 7.5a, v adj =0v v ctrl =2.5v to 7v, v in =1.75v to 5.5v, io=10ma, v adj =0v v ctrl =2.75v, v in =2.1v, io=10ma to 7.5a, v adj =0v v adj =0v for all conditions below: v in =2.05v, io=1.5a v in =2.05v, io=3a v in =2.05v, io=5a v in =2.05v, io=7.5a v adj =0v for all conditions below: v ctrl =2.75v, io=1.5a v ctrl =2.75v, io=3a v ctrl =2.75v, io=3a v ctrl =2.75v, io=7.5a v ctrl =2.75v, v in =2.05v, d vo=100mv, v adj =0v v ctrl =5v, v in =3.3v, v adj =0v 30ms pulse v ctrl =5v, v in =5v, io=3a, v adj =0v, t j =25 8 c, v ripple =1v pp at 120hz 1.225 1.225 7.7 60 1.250 1.250 0.5 2 0.95 1.00 1.05 1.15 0.100 0.200 0.330 0.500 9 5 0.01 70 1.275 1.275 3 6 1.30 0.130 0.260 0.430 0.650 10 0.02 v mv mv v v a ma %/w db v ref v sense adj v out v ctrl v in 1 2 3 4 5 v sense adj v out v ctrl v in 1 2 3 4 5
iru1175 3 rev. 1.7 04/09/03 www.irf.com pin descriptions note 1: low duty cycle pulse testing with kelvin con- nections are required in order to maintain accurate data. note 2: dropout voltage is defined as the minimum dif- ferential between v in and v out required to maintain regu- lation at v out . it is measured when the output voltage drops 1% below its nominal value. note 3: minimum load current is defined as the mini- mum current required at the output in order for the out- put voltage to maintain regulation. typically the resistor dividers are selected such that it automatically main- tains this current. this pin is the positive side of the reference which allows remote load sensing to achieve excellent load regulation. a resistor divider from this pin to the v out pin and ground sets the output voltage. the output of the regulator. a minimum of 10 m f capacitor must be connected from this pin to ground to insure stability. this pin is the supply pin for the internal control circuitry as well as the base drive for the pass transistor. this pin must always be higher than the v out pin in order for the device to regulate. (see specifications) the input pin of the regulator. typically a large storage capacitor is connected from this pin to ground to insure that the input voltage does not sag below the minimum drop out voltage during the load transient response. this pin must always be higher than v out in order for the device to regulate. (see specifications) pin # pin symbol pin description 1 2 3 4 5 v sense adj v out v ctrl v in parameter sym test condition min typ max units control pin current adjust pin current v adj =0v for all below conditions: v ctrl =2.75v, v in =2.05v, io=1.5a v ctrl =2.75v, v in =2.05v, io=3a v ctrl =2.75v, v in =2.05v, io=5a v ctrl =2.75v, v in =2.05v, io=7.5a v ctrl =2.75v, v in =2.05v, v adj =0v 15 30 50 70 50 120 ma m a i adj
4 rev. 1.7 04/09/03 iru1175 www.irf.com application information introduction the iru1175 adjustable regulator is a five-terminal de- vice designed specifically to provide extremely low drop- out voltages comparable to the pnp type without the disadvantage of the extra power dissipation due to the base current associated with pnp regulators. this is done by bringing out the control pin of the regulator that provides the base current to the power npn and con- necting it to a voltage that is grater than the voltage present at the v in pin. this flexibility makes the iru1175 ideal for applications where dual inputs are available such as a computer mother board with an atx style power sup- ply that provides 5v and 3.3v to the board. one such application is the new graphic chip sets that require any- where from 2.4v to 2.7v supply such as the intel i 740 chip set. the iru1175 can easily be programmed with the addition of two external resistors to any voltages within the range of 1.25 to 5.5v. another major require- ment of these graphic chips is the need to switch the load current from zero to several amps in tens of nano- seconds at the processor pins, which translates to an approximately 300 to 500ns of current step at the regu- lator. in addition, the output voltage tolerances are also extremely tight and they include the transient response as part of the specification. the iru1175 is specifically designed to meet the fast current transient needs as well as providing an accurate initial voltage, reducing the overall system cost with the need for fewer number of output capacitors. another fea- ture of the device is its true remote sensing capability which allows accurate voltage setting at the load rather than at the device. output voltage setting the iru1175 can be programmed to any voltages in the range of 1.25v to 5.5v with the addition of r1 and r2 external resistors according to the following formula: figure 3 - typical application of the iru1175 for programming the output voltage. block diagram figure 2 - simplified block diagram of the iru1175. where: v ref = 1.25v typically i adj = 50 m a typically r 1 & r 2 as shown in figure 3: v ctrl v in v sense adj v out thermal shutdown current limit 1.25v + + 5 4 3 1 2 v out r1 r2 v in v ctrl v ref i adj = 50ua iru1175 v sense adj v out v ctrl v in v out = v ref 3 1+ +i adj 3 r2 r2 r1 ( )
iru1175 5 rev. 1.7 04/09/03 www.irf.com v out = 2.7v v in = 3.3v v ctrl = 5v i out = 2a (dc avg) r1 r2 v in v ctrl r l iru1175 v sense adj v out v ctrl v in for most applications a minimum of 100 m f aluminum electrolytic capacitor such as sanyo, mvgx series, panasonic fa series as well as the nichicon pl series insures both stability and good transient response. thermal design the iru1175 incorporates an internal thermal shutdown that protects the device when the junction temperature exceeds the allowable maximum junction temperature. although this device can operate with junction tempera- tures in the range of 150 8 c, it is recommended that the selected heat sink be chosen such that during maxi- mum continuous load operation the junction tempera- ture is kept below this number. the example below shows the steps in selecting the proper surface mount package. assuming, the following conditions: calculate the maximum power dissipation using the fol- lowing equation: using table below select the proper package and the amount of copper board needed. pkg copper q ja ( c/w ) max pd max pd area ( t a =25 c ) ( t a =45 c ) to-263 1.4"x1.4" 25 4.4w 3.6w to-263 1.0"x1.0" 30 3.7w 3.0w to-263 0.7"x0.7" 35 3.1w 2.6w to-263 pad size 45 2.4w 2.0w note: above table is based on the maximum junction temperature of 135 8 c. the iru1175 keeps a constant 1.25v between the v sense pin and the v adj pin. by placing a resistor r1 across these two pins and connecting the v sense and v out pin together, a constant current flows through r1, adding to the i adj current and into the r2 resistor producing a volt- age equal to the (1.25/r1) 3 r2 + i adj 3 r2. this voltage is then added to the 1.25v to set the output voltage. this is summarized in the above equation. since the minimum load current requirement of the iru1175 is 10ma, r1 is typically selected to be a 121 v resistor so that it automatically satisfies this condition. notice that since the i adj is typically in the range of 50 m a it adds a small error to the output voltage and should be consid- ered when very precise output voltage setting is required. load regulation since the iru1175 has separate pins for the output (v out ) and the sense (v sense ), it is ideal for providing true re- mote sensing of the output voltage at the load. this means that the voltage drops due to parasitic resistance such as pcb traces between the regulator and the load are compensated for using remote sensing. figure 4 shows a typical application of the iru1175 with remote sensing. figure 4 - schematic showing connection for best load regulation. stability the iru1175 requires the use of an output capacitor as part of the frequency compensation in order to make the regulator stable. typical designs for the microproces- sor applications use standard electrolytic capacitors with typical esr in the range of 50 to 100m v and an output capacitance of 500 to 1000 m f. fortunately as the ca- pacitance increases, the esr decreases resulting in a fixed rc time constant. the iru1175 takes advantage of this phenomena in making the overall regulator loop stable. p d = 2 3 (3.3 - 2.7)+ 3 (5 - 2.7) = 1.28w p d = i out 3 (v in - v out )+ 3 (v ctrl - v out ) 2 60 ( ) i out 60 ( ) ir world headquarters: 233 kansas st., el segundo, california 90245, usa tel: (310) 252-7105 tac fax: (310) 252-7903 visit us at www.irf.com for sales contact information data and specifications subject to change without notice. 02/01
6 rev. 1.7 04/09/03 iru1175 www.irf.com (m) to-263 package 5-pin symbol a b c d e g h k l m n p r s u v min 10.05 8.28 4.31 0.66 1.14 1.575 14.605 1.143 0.00 2.49 0.33 2.286 0 8 1.143 max 10.668 9.169 4.597 0.91 1.40 1.829 15.875 1.68 0.305 2.74 0.58 2.794 8 8 2.67 6.50 ref 7.75 ref note: all measurements are in millimeters. g d a e m l n u c b k p v r s h c l
iru1175 7 rev. 1.7 04/09/03 www.irf.com (p) ultra thin-pak tm 5-pin note: all measurements are in millimeters. symbol a a1 b c d e g h k l m n p r u v min 9.27 8.89 7.87 1.78 0.63 10.41 0.76 0.03 0.89 0.79 3 8 max 9.52 9.14 8.13 2.03 0.79 10.67 1.27 0.13 1.14 1.04 6 8 0.25 nom 1.72 0.25 5.59 nom 7.49 nom a e m l n u c b k p v h g d r l c a1
8 rev. 1.7 04/09/03 iru1175 www.irf.com ir world headquarters: 233 kansas st., el segundo, california 90245, usa tel: (310) 252-7105 tac fax: (310) 252-7903 visit us at www.irf.com for sales contact information data and specifications subject to change without notice. 02/01 pkg desig m p package description to-263 ultra thin-pak tm parts per tube 50 75 parts per reel 750 2500 package shipment method pin count 5 5 t & r orientation fig a fig b feed direction figure a feed direction figure b 1 1 1 1 1 1
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