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iru3034 1 rev. 2.1 07/17/02 www.irf.com 8-pin pwm switcher controller ic with current limiting typical application figure 1 - typical application of iru3034. t a ( c) 8-pin plastic soic (s) 0 to 70 iru3034cs description the iru3034 ic provides a low cost switching controller with true short circuit protection all in a compact 8-pin surface mount package, providing a low cost switching solution for dual supply processor applications that re- quire switching regulator for the 3.3v supply such as the applications with agp on-board. typically in these applications, a dual supply regulator converts 5v to 3.3v for i/o supply and a jumper programmable supply of 1.25v to 3.5v for core supply. the ic uses an internal regulator generated from the 12v supply to power the controller as well as the 12v supply to drive the power mosfet, allowing a low cost n-channel mosfet to be used. the ic also includes an error comparator for fast transient response, a precise voltage reference for set- ting the output voltage as well as a direct drive of the mosfet for the minimum part count. package order information data sheet no. pd94148 notes: p55c, pentium ii are trademarks of intel corp. k5 & k6 are trademarks of amd corp. cyrix 6x86l, m1, m2 are trademarks of cyrix corp. power pc is trademark of ibm corp. v out 5v c1 l1 c3 q2 c2 l2 r4 c7 d1 r2 c4 r5 r1 12v r3 c5 c8 iru3034 r8 r6 c6 r7 drv v 12 v fb v hyst gnd cs- cs+ ss features 8-pin soic switching controller with hiccup current limiting reduces diode power dissipation to less than 1% of normal operation soft-start capacitor allows for smooth output voltage ramp up on-board mosfet driver fastest transient response of any controller method. (0 to 100% duty cycle in 100ns) 1% internal voltage reference internal under-voltage lockout protects mosfet during start-up dual supply low voltage processor applications, such as: p55c ? , cyrix m2 ? , power pc ? and amd k6 ? simple 5v to 3.3v switcher for pentium with agp or pentium ii ? applications applications
iru3034 2 rev. 2.1 07/17/02 www.irf.com absolute maximum ratings v 12 supply voltages .................................................. 20v fb pin voltages ......................................................... -0.3v to 5v storage temperature range ....................................... -65 to 150c operating junction temperature ................................. 0 to 150c package information 8-pin plastic soic (s) fb voltage initial accuracy fb voltage total variation fb voltage line regulation fb input bias current minimum on time minimum off time v hyst pin output-hi v hyst pin output-lo supply current maximum duty cycle minimum duty cycle gate drive rise/fall time cl threshold current cs comp common mode soft-start current electrical specifications unless otherwise specified, the following specification applies over v 12 =12v and t a =0 to 70 8 c. low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. u ja =160 8 c/w drv v 12 v fb v hyst gnd cs- cs+ ss 4 3 2 1 5 6 7 8 top view t j =25 8 c v fb =1.25v v fb is sq wave with 300ns on time and 2 m s off time v fb is sq wave with 300ns off time and 2 m s on time i source =500 m a, v fb =1.5v i sink =500 m a, v fb =1v v fb =1v v fb =1v v fb =1.5v load=irl3303 cs+, cs- from 1.3v to 3.7v v cs+ =v cs- v fb i fb i 12(sw) d max d min v gate i cl parameter sym test condition min typ max units 1.237 1.225 -1 11 0 0 1.250 1.250 0.2 800 800 10 70 20 10 1.262 1.275 +1 1 100 4.5 v v % m a ns ns v v ma % % ns m a v m a
iru3034 3 rev. 2.1 07/17/02 www.irf.com pin descriptions block diagram figure 2 - simplified block diagram of the iru3034. the pwm output of the switching controller. this pin is a totem pole drive that is con- nected to the gate of the power mosfet. a resistor may be placed from this pin to the gate in order to reduce switching noise. this pin supplies the voltage to the pwm drive and hysteresis circuitry and it is connected to the 12v supply. a 1 m f, high frequency capacitor must be connected from this pin to ground to provide the peak current for charging and discharging of the mosfet. a resistor divider from this pin to the output of the switching regulator and ground sets the core supply voltage. a resistor and a 10pf capacitor is connected from this pin to the v fb pin to set the output ripple voltage for the switching regulator. this pin is connected to the ic substrate and must be connected to the lowest potential in the system. this pin is connected to the minus side of the external current sense resistor. an internal current source together with an external resistor in series with this pin programs the current limit threshold voltage. this voltage divided by the external current sense resistor sets the current limit threshold. this pin is connected to the plus side of the external current sense resistor. a resistor in series with this pin and a capacitor connected between this pin and pin 6 provides a high frequency filtering for the noise spikes of turn on and turn off switching. this pin provides the soft-start for the regulator during power up. it also sets a long off time when the converter goes into current limiting, providing low duty cycle for the catch diode allowing it to survive during short circuit. pin # pin symbol pin description 1 2 3 4 5 6 7 8 drv v 12 v fb v hyst gnd cs- cs+ ss v ref uvlo 1.25v pwm control v 12 v hyst cs+ drv gnd v fb cs- 5 1 2 4 3 7 6 ss 8 5v reg s.s. / hiccup control 20ua r 3r
iru3034 4 rev. 2.1 07/17/02 www.irf.com typical application pentium core supply application (iru3034 and iru3033 dual layout) low cost 4-bit vid figure 3 - typical application of iru3034 in a flexible motherboard with the 4-bit vid output voltage selection. this circuit is done using a dual layout with the iru3033 part. the advantage of this circuit is that it uses a single jumper that programs the output voltage in 16 steps with 0.1v steps from 2v to 3.5v, designed for intel p55, p54, amd k5 & k6 as well as cyrix m1 and m2 applications. 0 = jumper block is installed. 1 = jumper block is not installed. note: r9 can be eliminated if dual layout with iru3033 is not desired. jp1 1-2 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 jp1 3-4 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 jp1 5-6 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 jp1 7-8 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 output voltage 3.5 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 5v 12v c3 r3 c5 c8 r9 l1 q2 c1 l2 r4 c7 1 d1 r2 c4 r5a r5b r5c r5d r5e 2 3 4 5 6 7 8 jp1 r1 v out c2 r8 r6 c6 r7 drv v 12 v fb v hyst gnd cs-/ v fb2 cs+/ drv2 ss/ v 12 u1
iru3034 5 rev. 2.1 07/17/02 www.irf.com ref desig description qty part # manuf u1 ldo/switcher ic 1 iru3034cs (8-pin soic) ir q2 mosfet 1 irl3303 (to-220) ir irl3103s (to-263) (note 1) d1 schottky diode 1 mbr1045ct (to-220) mbrb1545ct (to-263) (note1) motorola l2 inductor 1 core: t50-18, l=4 m h micro metal turns: 10t, 18 awg (core) l1 inductor 1 l=2 m h r1 resistor 1 22 v , 5%, smt 1206 size r2 resistor 1 10 v , 5%, smt 1206 size r3 resistor 1 324k v , 1%, smt 0805 size r4a * resistor 1 806 v , 1%, smt 0805 size r4b * resistor 1 90.9k v , 1%, smt 0805 size r5a resistor 1 1.24k v , 1%, smt 0805 size r5b resistor 1 2.49k v , 1%, smt 0805 size r5c resistor 1 4.99k v , 1%, smt 0805 size r5d resistor 1 10k v , 1%, smt 0805 size r5e resistor 1 1.30 v , 1%, smt 0805 size r6 resistor 1 5m v , 5%, 2w r7 resistor 1 4.99k v , 1%, smt 0805 size r8 resistor 1 4.7k v , 5% for iru3034, open for 3033 r9 resistor 1 open for iru3034, 10 v for iru3033 c1 capacitor 1 6mv1500gx, 1500 m f, 6.3v, elect c2 capacitor 1 6mv1500gx, 1500 m f, 6.3v, elect sanyo c3 capacitor 1 1 m f, ceramic, smt 0805 size c4 capacitor 1 470pf, ceramic, smt 0805 size sanyo c5 capacitor 1 10pf, ceramic, smt 0805 size sanyo c7 capacitor 4 6mv1500gx, 1500 m f, 6.3v, elect sanyo c8 capacitor 1 0.047 m f for 3034 , 0.1 m f for iru3033 c6 capacitor 1 4700pf for iru3034, open for iru3033 hs1 heat sink 1 for mosfet, 577002 aavid hs2 heat sink 1 for schottky diode, 577002 aavid *r4 is a parallel combination of r4a and r4b. note: for the applications where it is desirable to eliminate the heat sink, the irl3103s for q2 and mbr1545ct for d2 in to-263 packages with minimum of 1" square copper pad can be used. pentium core suppl y applica tion parts list (iru3034 and iru3033 dual layout) low cost 4-bit vid
iru3034 6 rev. 2.1 07/17/02 www.irf.com figure 4 - the circuit in figure 4 is the application of the iru3034 which is done using a dual layout with iru3033 in a switching mode only. this circuit can be used to generate a low cost 5v to 3.3v for either pentium application with agp socket or in pentium ii applications where it is desirable to generate an accurate on-board 3.3v supply. typical application 5v to 3.3v for pentium application with agp or pentium ii application without atx power supply switching mode operation. (iru3034 and iru3033 dual layout) ref desig description qty part # manuf u1 ldo/switcher ic 1 iru3034cs (8-pin soic) ir q2 mosfet 1 irl3303 (to-220) ir irl3103s (to-263) (note 1) d1 schottky diode 1 mbr1045ct (to-220) mbrb1545ct (to-263) (note1) motorola l2 inductor 1 core: t50-18, l=4 m h micro metal turns: 10t, 18 awg (core) l1 inductor 1 l=2 m h r1 resistor 1 22 v , 5%, smt 1206 size r9 resistor 1 open for iru3034, 10 v for iru3033 r2 resistor 1 10 v , 5%, smt 1206 size r3 resistor 1 249k v , 1%, smt 0805 size r4 resistor 1 1k v , 1%, smt 0805 size r5 resistor 1 576 v , 1%, smt 0805 size r6 resistor 1 5m v , 5%, 2w r7 resistor 1 4.99k v , 1%, smt 0805 size r8 resistor 1 4.7k v , 5% for iru3034, open for iru3033 c1, 2 capacitor 2 6mv1500gx, 1500 m f, 6.3v, elect sanyo c3 capacitor 1 1 m f, ceramic, smt 0805 size c4 capacitor 1 470pf, ceramic, smt 0805 size sanyo c5 capacitor 1 10pf, ceramic, smt 0805 size sanyo c6 capacitor 1 4700pf for iru3034, open for iru3033 c7 capacitor 2 6mv1500gx, 1500 m f, 6.3v, elect sanyo c8 capacitor 1 0.047 m f for iru3034 , 0.1 m f for 3033 hs1 heat sink 1 for mosfet, 577002 aavid hs2 heat sink 1 for schottky diode, 577002 aavid note: for the applications where it is desirable to eliminate the heat sink, the irl3103s for q2 and mbr1545ct for d2 in to-263 packages with minimum of 1" square copper pad can be used. v out 5v c1 l1 c3 q2 c2 l2 r4 c7 d1 r2 c4 r5 r1 r3 c5 r8 r6 c6 r7 12v c8 r9 drv v 12 v fb v hyst gnd cs-/ v fb2 cs+/ drv2 ss/ v 12 u1
iru3034 7 rev. 2.1 07/17/02 www.irf.com figure 5 - the circuit in figure 5 is designed to provide loss-less output short detection by detecting the dc voltage across the inductor and shutting down the mosfet and entering hiccup mode. note that the current limit point is a function of the inductor resistance and in this application with approximately 8m v resistance the peak cl is set at 10a. see application note on how to set the current limiting threshold. typical application 5v to 3.3v with loss-less short circuit protection (output uvlo detection) ref desig description qty part # manuf u1 switcher ic 1 iru3034cs (8-pin soic) ir q2 mosfet 1 irl3303 (to-263) ir d1 schottky diode 1 pbyr735 (axial thru hole pkg) pbyr1035b (smt, t-263 pkg) motorola l2 inductor 1 core: t50-18, l=4 m h micro metal turns: 7t, 18 awg (core) l1 inductor 1 l= m h r1,2 resistor 2 10 v , 5%, smt r3 resistor 1 182k v , 1%, smt r4 resistor 1 1k v , 1%, smt r5 resistor 1 576 v , 1%, smt r7 resistor 1 3.83k v , 1%, smt r6 resistor 1 1k v , 1%, smt c1 capacitor 1 470 m f, elect c2 capacitor 1 6mv1000gx, 1000 m f, 6.3v, elect sanyo c3 capacitor 1 1 m f, ceramic, smt c5 capacitor 1 10pf, ceramic, smt sanyo c6 capacitor 1 0.1 m f c7 capacitor 2 6mv1000gx, 1000 m f, 6.3v, elect sanyo c8 capacitor 1 0.047 m f v out 5v c1 l1 c3 q2 c2 l2 r4 c7 d1 r2 c4 r5 r1 12v r3 c5 c8 u1 r6 c6 r7 drv v 12 v fb v hyst gnd cs- cs+ ss
iru3034 8 rev. 2.1 07/17/02 www.irf.com application information introduction the iru3034 device is an application specific product designed to provide an on-board switching supply for the new generation of microprocessors requiring separate core and i/o supplies where the load current demand from the i/o supply requires this regulator to also be a switching regulator such as the motherboard applica- tions with agp slot or the pentium ii with on-board 5v to 3.3v converter. the iru3034 provides an easy and low cost switching regulator solution for vcore and 3.3v supplies with true short circuit protection. switching controller operation the operation of the switching controller is as follows: after the power is applied, the output drive pin (drv) goes to 100% duty cycle and the current in the inductor charges the output capacitor causing the output voltage to increase. when output reaches a pre-programmed set point the feedback pin (v fb ) exceeds 1.25v causing the output drive to switch low and the v hyst pin to switch high which jumps the feedback pin higher than 1.25v resulting in a fixed output ripple which is given by the following equation: where: rt = resistor connected from v out to the v fb pin of iru3034. rh = resistor connected from v fb pin to v hyst pin. for example, if rt=1k and rh=422k, then the output ripple is: the advantage of fixed output ripple is that when the output voltage changes from 2v to 3.5v, the ripple volt- age remains the same which is important in meeting the intel maximum tolerance specification. soft-start the soft-start capacitor must be selected such that dur- ing the start-up when the output capacitors are charging up, the peak inductor current does not reach the current limit threshold. a minimum of 0.1 m f capacitor insures this for most applications. during start-up the soft-start capacitor is charged up to approximately 6v keeping the output shutdown before an internal 10 m a current source start discharging the soft-start capacitor which slowly ramps up the inverting input of the pwm com- parator, v fb . this insures the output to ramp up at the same rate as the soft-start cap thereby limiting the input current. for example, with 0.1 m f and the 10 m a internal current source the ramp up rate is: assuming that the output capacitance is 6000 m f, the peak input current will be: the soft start capacitor also provides a delay in the turn on of the output which is given by: where: k = 30ms/ m f for example for css=0.1 m f, switcher current limit protection the iru3034 uses an external current sensing resistor and compares the voltage drop across it to a programmed voltage which is set externally via a resistor (r cl ) placed between the cs- terminal of the ic and v out . once the voltage across the sense resistor exceeds the thresh- old, the soft-start capacitor pulls up to 12v, pulling up the inverting pin of the error comparator higher than non- inverting which causes the external mosfet to shut off. at this point the cs comparator changes its state and pulls the soft-start capacitor to vcc which is 12v and shutting the pwm drive. after the output drive is turned off, an internal 10 m a current source slowly dis- charges the soft-start capacitor to approximately 5.7v, before the output starts to turn back on causing a long delay before the mosfet turns back on. this delay causes the catch diode to cool off between the current limit cycles allowing the converter to survive a short cir- cuit condition. an example is given below as how to select the current limiting components. assuming the desired current limit point is set to be 20a and the cur- rent sense resistor rs=5m v , then the current limit pro- gramming resistor, r cl is calculated as: where: i b = 20 m a is the internal current source of iru3034 i in(pk) = css 3 ( d v/ d t) = 6000 m f 3 (0.1v/ms) = 0.6a d vo = (rt/rh) 3 11 d vo = (1/422) 3 11 = 26mv vcs = i cl 3 rs = 20 3 0.005 = 0.1v r cl = vcs/i b = (0.1v)/(20 m a) = 5k v t d = css 3 k t d = 0.1 3 30 = 3ms ( d v/ d t) = i/css = 10/0.1 = 100v/s or 0.1v/ms
iru3034 9 rev. 2.1 07/17/02 www.irf.com r b = rt / x x = [ (vo + ( d vo/2)) / v ref ] - 1 x= [ (3.38+ (0.044/2)) / 1.25 ] - 1 = 1.72 r b = 1000 / 1.72 = 580 v ppk = i cl 2 3 rs = 20 2 3 0.005 = 2w p a vg = 0.5 3 ppk 3 dsc t hcp = 0.1 3 200 = 20ms p avg = 0.5 3 2 3 (0.5/20) = 25mw r h = (11 3 rt) / d vo r h = (11 3 1000) / 0.044 = 250k v the bottom resistor of the divider is then calculated us- ing the following equations: where: r b = bottom resistor of the divider v ref = 1.25v typical select r b = 576 v , 1% frequency calculation the iru3034 frequency of operation is calculated using the following formula: where: vo = output voltage (v) d = duty cycle esr = output capacitor esr (v) l = output inductance ( m h) d vo = output ripple voltage (v) for our example: where: vf = forward voltage drop of the schottky diode. the esr=18m v for 2 of the sanyo 1500 m f, 6mv1500gx caps. if l=3.5 m h then, fs is calculated as follows: the peak power dissipated in the cs resistor is: however, the average power dissipated is much lower than 2w due to the long off time caused by the hiccup circuit of iru3034. the average power is in fact the short circuit period divided by the short circuit period plus the off time or "hiccup" period. for example, if the short circuit lasts for tsc=100 m s before the iru3034 enters hiccup, the average power is calculated as: where: dsc = tsc / t hcp t hcp = css 3 m m = 200ms/ m f css = the soft-start capacitor for example: for css=0.1 m f and tsc=500 m s=0.5ms without "hiccup" technique, the power dissipation of the resistor is 2w. switcher output voltage setting the output voltage can be set using the following equations: assuming, vo=3.38v and the selected output ripple is ? 1.3%(44mv) of the output voltage, a set of equations are derived that selects the resistor divider and the hys- teresis resistor: assuming, rt = 1k v , 1%: where: rt = top resistor of the resistor divider r h = hysteresis resistor connected between pins 3 and 4 of the iru3034 d vo = selected output ripple (typically 1% to 2% of output voltage) assuming, d vo=44mv: select r h = 249k v , 1% fs = = 0.087 fs = 87khz [ (3.38 3 (1-0.78) 3 0.018) ] (3.5 3 0.044) d = (3.38 + 0.5) / 5 = 0.78 d ? (vo + vf) / v in fs = [ (vo 3 (1-d) 3 esr) ] / (l 3d vo) (mhz)
iru3034 10 rev. 2.1 07/17/02 www.irf.com iru3034 output voltage 1.22 1.23 1.24 1.25 1.26 1.27 1.28 -40c -25c 0c +25c +50c +75c +100c +125c +150c volts spec max. spec min. vout 7v vout 12v vout 20v max min iru3034 hysteresis frequency 0 10 20 30 40 50 60 70 80 90 -40c -25c 0c +25c +50c +75c +100c +125c +150c kilo hertz oscillation frequency iru3034 supply current 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 -40c -25c 0c +25c +50c +75c +100c +125c +150c mili amps v12 current iru3034 line regulation 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 -40c -25c 0c +25c +50c +75c +100c +125c +150c % error of nominal vout 7v to 20v line reg figure 6 - output voltage. figure 7 - hysteresis frequency. figure 8 - supply current. figure 9 - line regulation. typical performance characteristics 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
iru3034 11 rev. 2.1 07/17/02 www.irf.com (s) soic package 8-pin surface mount, narrow body symbol a b c d e f g h i j k l t min 4.80 0.36 3.81 1.52 0.10 0.19 5.80 0 8 0.41 1.37 max 4.98 0.46 3.99 1.72 0.25 0.25 6.20 8 8 1.27 1.57 1.27 bsc 0.53 ref 7 8 bsc 8-pin note: all measurements are in millimeters. pin no. 1 i k h detail-a detail-a 0.38 6 0.015 x 45 8 t g f d a b c e l j
iru3034 12 rev. 2.1 07/17/02 www.irf.com pkg desig s package description soic, narrow body parts per tube 95 parts per reel 2500 package shipment method pin count 8 t & r orientation fig a feed direction figure a 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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