iru1176 1 rev. 1.5 07/16/02 www.irf.com 7.5a ultra low dropout positive adjustable regulator with shutdown input the iru1176 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. the iru1176 also provides a conve- nient shutdown pin that allows the regulator to be shut- down and reduce the input current consumption. unlike the pnp type regulators this device does not have high quiescent current during the start up mode making it ideal for applications where there is limited current ca- pability such operation from the 5v standby supply of the computer power supply. one application is the new generation of rdram memory that needs to provide 2.5v from 3.3v input and be able to operate from 5vsb as well. description guaranteed <0.65v dropout at 7.5a 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 t j ( c) 7-pin plastic 7-pin plastic to-263 (m) ultra thin-pak tm (p) 0 to 125 iru1176cm IRU1176CP package order information figure 1 - typical application of iru1176. data sheet no. pd94132 3.3v iru1176 2.7v c1 c3 5v c2 r1 r2 sd enable q1 v sense sd adj v out v ctrl v in v in 1 2 3 4 5 6 7
2 rev. 1.5 07/16/02 iru1176 www.irf.com absolute maximum ratings input voltage (v in ) .................................................... 7v 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 7-pin plastic to-263 (m) 7-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 . v sense sd v out v in v in adj v ctrl front view 1 2 3 4 5 6 7 tab is v out v sense sd v out v in v in adj v ctrl front view 1 2 3 4 5 6 7 tab is v out 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 sd threshold voltage sd input current parameter sym test condition min typ max units v ctrl =2.75v, 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=4a 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=4a 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=4a, v adj =0v, t j =25 8 c, v ripple =1v pp at 120hz v ctrl =5v, sd=0v 1.225 1.225 7.7 60 1.250 1.250 0.5 5 0.95 1.00 1.05 1.15 0.075 0.150 0.200 0.375 9 5 0.01 70 v ctrl -1.4 94 1.275 1.275 10 0.02 v ctrl -2.2 130 v mv mv v v a ma %/w db v m a q ja =35 c/w for 0.5" square pad q ja =35 c/w for 0.5" square pad v ref
iru1176 3 rev. 1.5 07/16/02 www.irf.com pin descriptions note 1: low duty cycle pulse testing with kelvin con- nections is 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. when this pin is pulled lower than 1.4v with respect to the v ctrl pin the device is shut- down. to enable the operation leave this pin open. internal to device, there is a pull-up resistor. 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 descriptions 1 2 3 4 5 6, 7 v sense sd adj v out v ctrl v in control pin current adjust pin current parameter sym test condition min typ max units 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=4a v ctrl =2.75v, v in =2.05v, io=7.5a v ctrl =2.75v, v in =2.05v, v adj =0v 50 120 ma m a i adj
4 rev. 1.5 07/16/02 iru1176 www.irf.com application information introduction the iru1176 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 iru1176 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 iru1176 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 iru1176 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 iru1176 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 iru1176 for programming the output voltage. block diagram figure 2 - simplified block diagram of the iru1176. 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 output shutdown current limit 1.25v thermal shutdown sd + + 6,7 5 2 3 1 4 v out r1 r2 v in v ctrl v ref i adj = 50ua iru1176 v sense sd v out v ctrl v in adj open v out = v ref 3 1+ +i adj 3 r2 r2 r1 ( )
iru1176 5 rev. 1.5 07/16/02 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 iru1176 v sense adj v out v ctrl v in the iru1176 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 iru1176 is 10ma, r1 is typically selected to be a 121 v resistor so that it automatically satisfies this condition. notice that since the iadj 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 iru1176 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 iru1176 with remote sensing. figure 4 - schematic showing connection for best load regulation. stability the iru1176 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 iru1176 takes advantage of this phenomena in making the overall regulator loop stable. 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. shutdown operation the iru1176 can be disabled by pulling the sd pin low using an open collector device such as a low cost 2n3904 general purpose transistor as shown in the application circuit. the current sink of the pin is equal to: thermal design the iru1176 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 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 ) m or p 1.4"x1.4" 25 4.4w 3.6w m or p 1.0"x1.0" 30 3.7w 3.0w m or p 0.7"x0.7" 35 3.1w 2.6w m or p pad size 45 2.4w 2.0w note: above table is based on the maximum junction temperature of 135 8 c. as shown in the above table, any of the two packages will do the job. for lower cost applications the ultra thin- pak is recommended. i sink = where: r=50k v typically (v ctrl - 1.4) r 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 ( )
6 rev. 1.5 07/16/02 iru1176 www.irf.com (m) to-263 package 7-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 14.73 1.40 0.00 2.49 0.43 2.29 0 8 2.41 max 10.31 8.53 4.57 0.91 1.40 15.75 1.68 0.25 2.74 0.58 2.79 8 8 2.67 6.50 ref 7.75 ref 1.27 ref note: all measurements are in millimeters. a e m l n u c b k p v s h g d r l c
iru1176 7 rev. 1.5 07/16/02 www.irf.com (p) ultra thin-pak tm 7-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 1.27 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. 1.5 07/16/02 iru1176 www.irf.com 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 7 7 t & r orientation fig a fig b feed direction figure a feed direction figure b 1 1 1 1 1 1 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
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