rt9173/a ds9173/a-06 march 2002 www.richtek-ic.com.tw 1 1.5a/3a bus termination regulator general description the rt9173/a regulator is designed to convert voltage supplies ranging from 1.8v to 6v into a desired output voltage which adjusted by two external resistors, voltage divider. the regulator is capable of sourcing or sinking up to 1.5a/3a of current while regulating an output voltage to within 2% or less. the rt9173/a, used in conjunction with series termination resistors, provides an excellent voltage source for active termination schemes of high speed transmission lines as those seen in high speed memory buses and distributed backplane designs. the voltage output of the regulator can be used as a termination voltage for ddr sdram. current limits in both sourcing and sinking mode, plus on-chip thermal shutdown make the circuit tolerant of the output fault conditions. applications z computers z disk drives z cd-rom z supply splitter z graph card ordering information rt9173/a ? ? ? features z support both ddr 1 (1.25vtt) and ddr 2 (0.9vtt) requirements z power to-263-5 and sop-8 packages z capable of sourcing and sinking current 1.5a/3a z current-limiting protection z thermal protection z integrated power mosfets z generates termination voltages for sstl-2 z high accuracy output voltage at full-load z adjustable vout by external resistors z minimum external components z shutdown for standby or suspend mode operation with high-impedance output pin configurations part number pin configurations RT9173Acm5 (plastic to-263-5) top view 1. vin 2. gnd 3. vcntl (tab) 4. refen 5. vout rt9173cs (plastic sop-8) top view function block diagram operating temperature range c: commercial standard package type m5 : to-263-5 s : sop-8 3a sink & source 1.5a sink & source thermal current limit ing sen sor vout refen gnd cntl vin vcntl 12 3 4 5 vin gnd refen vout 1 2 3 4 8 7 6 5 vcntl vcntl vcntl vcntl
rt9173/a www.richtek-ic.com.tw ds9173/a-06 march 2002 2 pin description pin name pin function vin power input gnd ground vcntl gate drive voltage refen reference voltage input and chip enable vout output voltage absolute maximum ratings z input voltage 7v z power dissipation internally limited z esd rating 2kv z storage temperature range -65 c to 150 c z lead temperature (soldering, 5 sec.) 260 c z package thermal resistance to-263, jc 7.7 c/w to-263, ja 19.4 c/w sop-8, jc 15.7 c/w sop-8, ja note 45 c/w note: ja is measured with the component mounted on an evaluation pc board in free air that the required area of copper is 300mm 2 or larger. electrical characteristics (limits in standard typeface are for t a = 25 c, unless otherwise specified: v in = 2.5v, v cntl = 3.3v, v refen = 1.25v, c out = 10 f (ceramic)) parameter symbol test conditions min typ max units output offset voltage v os fig.1 -20 0 20 mv i l : 0 1.5a, fig.1 -- 0.8 2 load regulation ? v load i l : 0a -1.5a -- 0.8 2 % v in 1.8 2.5 -- input voltage range (ddr 1) v cntl keep v cntl v in on operation power on and power off sequences -- 3.3 6 v current in shutdown mode i shdn v refen < 0.2v, r l = 180 ? , fig.2 -- 50 90 a short circuit protection rt9173 fig.3,4 2.1 -- -- current limit RT9173A i limit fig.3,4 3.0 -- -- a over temperature protection thermal shutdown temperature t sd 3.3v v cntl 5v 125 150 -- c thermal shutdown hysteresis guaranteed by design -- 50 -- c shutdown function output = high, fig.5 0.8 -- -- shutdown threshold trigger output = low, fig.5 -- -- 0.2 v
rt9173/a ds9173/a-06 march 2002 www.richtek-ic.com.tw 3 typical application circuit test circuit fig.1 output voltage tolerance, ? v out fig.2 current in shutdown mode, i shcln r 1 = r 2 = 100k ? , r tt = 50 ? / 33 ? / 25 ? c out , min = 10 f (ceramic) + 1000 f under the worst case testing condition r dummy = 1k ? as for vout discharge when vin is not present but vcntl is present c ss = 1 f, c in = 470 f (low esr), c cntl = 47 f vin vcntl refen vout gnd r tt v cntl = 3.3v v in = 2.5v en r 2 c ss r 1 c in c out c cntl rt9173/a r dummy 2n 7002 vin vcntl refen rt9173/a vout gnd 1. 25v 2. 5v 3. 3v v ou t c out i l v vin vcntl refen rt9173/a vout gnd 1. 25v 2. 5v 3. 3v v ou t c out v r l a 0. 2v 0v 1. 25v r l and c out time delay
rt9173/a www.richtek-ic.com.tw ds9173/a-06 march 2002 4 fig.3 current limit for high side, i clhigh fig.4 current limit for low side, i cllow fig.5 refen pin shutdown threshold, v trigger vin vcntl refen rt91 73/a vout gnd 1. 25v 2. 5v 3. 3v v ou t c out i l v a power supply with current limit vin vcntl refen rt9173/a vout gnd 1. 25v 2. 5v 3. 3v v out c out v a i l vin vcntl refen rt9173/a vout gnd 2. 5v 3. 3v v ou t c out v r l 0. 2v 0v 1. 25 v 1. 25 v v ou t v refen r l and c out time delay v ou t would be low if vrefen < 0.2v v ou t woul d be high if vrefen > 0.8v
rt9173/a ds9173/a-06 march 2002 www.richtek-ic.com.tw 5 typical operating characteristics time (250 s/div) output transient voltage (mv) transient response 100 50 0 -50 output current (a) 2 1 0 -1 -2 v in = 2.5v v cntl = 3.3v v refen = 1.25v swing frequency = 1khz time (5ms/div) 12 10 8 6 output short circuit (a) 4 2 0 -2 -4 v in = 2.5v v cntl = 3.3v v refen = 1.25v force the output shorted to ground sourcing current (peak) vs. temp. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 -40-200 20406080100120 temperature ( c) sourcing current (a) v cntl = 3.3v v in = 2.5v v out = 1.25v sinking current (peak) vs. temp. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 -40 -20 0 20 40 60 80 100 120 temperature ( c) sinking current (a) v cntl = 3.3v v in = 2.5v v out = 1.25v turn-on threshold vs. temp. 400 450 500 550 600 650 700 -40 -20 0 20 40 60 80 100 120 temperature ( c) threshold voltage (mv) v cntl = 3.3v v in = 2.5v turn-on threshold vs. temp. 400 450 500 550 600 650 700 -40 -20 0 20 40 60 80 100 120 temperature ( c) threshold voltage (mv) v cntl = 5.0v v in = 2.5v
rt9173/a www.richtek-ic.com.tw ds9173/a-06 march 2002 6 applications information internal parasitic diode avoid forward-bias internal parasitic diode, vout to vcntl, and vout to vin, the vout should not be forced some voltage respect to ground on this pin while the vcntl or vin is disappeared. consideration while designs the resistance of voltage divider make sure the sinking current capability of pull-down nmos if the lower resistance was chosen so that the voltage on refen is below 0.2v. in addition to item 1, the capacitor and voltage divider form the low-pass filter. there are two reasons doing this design; one is for output voltage soft-start while another is for noise immunity. how to reduce power dissipation on notebook pc or the dual channel ddr sdram application? in notebook application, using richtek?s patent ?distributed bus terminator topology? with choosing richtek?s product is encouraged. thermal consideration rt9173/a regulators have internal thermal limiting circuitry designed to protect the device during overload conditions. for continuous normal load conditions however, the maximum junction temperature rating of 125c must not be exceeded. higher continous currents or ambient temperature require additional heatsinking. heat sinking to the ic package must consider the worst case power dissipation which may occur. it should also be note that with the vcntl equal to 5v, the point of thermal shutdown will be degraded by approx. 20c compared to the vcntl equipped with 3.3v. it is highly recommended that to use the 3.3v rail acted as the vcntl so as to minimize the thermal concern of the rt9173cs in the sop-8 package. layout consideration the rt9173cs regulator is packaged in plastic sop- 8 package. this small footprint package is unable to convectively dissipate the heat generated when the regulator is operating at high current levels. in order to control die operating temperatures, the pc board layout should allow for maximum possible copper area at the vcntl pins of the rt9173cs. the multiple vcntl pins on the sop-8 package are internally connected, but lowest thermal resistance will result if these pins are tightly connected on the pc board. this will also aid heat dissipation at high power levels. if the large copper around the ic is unavailable, a buried layer may be used as a heat spreader, use vias to conduct the heat into the buried or backside of pcb layer. the vias should be small enough to retain solder when the board is wave-soldered. (see fig.6 shown on next page). distributed bus terminating topology r0 r2 r3 r4 r5 r6 r7 r8 r9 rn bus(0) bus(1) bus(2) bus(3) bus(4) r1 bus(5) bus(6) bus(7) bus(8) bus(9) bus(n+1) rn 1 bus(n) terminator resistor rt9173 rt9173 vout vout refen
rt9173/a ds9173/a-06 march 2002 www.richtek-ic.com.tw 7 fig. 6 layout consideration to prevent this maximum junction temperature from being exceeded, the appropriate power plane heat sink must be used. higher continuous currents or ambient temperature require additional heatsinking. rt9173cs (sop-8) the pcb heat sink copper area should be solder-painted without masked. this approaches a ?best case? pad heat sink. use vias to conduct the heat into the buried or backside of pcb layer . rt9173cs (sop-8) the pcb heat sink copper area should be solder-painted without masked. this approaches a ?best case? pad heat sink. use vias to conduct the heat into the buried or backside of pcb layer .
rt9173/a www.richtek-ic.com.tw ds9173/a-06 march 2002 8 package information dimensions in millimeters dimensions in inches symbol min max min max d 9.652 10.668 0.380 0.420 b 1.143 1.676 0.045 0.066 e 8.128 9.652 0.320 0.380 a 4.064 4.826 0.160 0.190 c 1.143 1.397 0.045 0.055 u 6.223 ref. 0.245 ref. v 7.620 ref. 0.300 ref. l1 14.605 15.875 0.575 0.625 l2 2.286 2.794 0.090 0.110 b 0.660 0.914 0.026 0.036 b2 0.305 0.584 0.012 0.023 e 1.524 1.829 0.060 0.072 5-lead to-263 plastic surface mount package e mark b l1 d e b l2 c a b2 v u
rt9173/a ds9173/a-06 march 2002 www.richtek-ic.com.tw 9 dimensions in millimeters dimensions in inches symbol min max min max a 4.801 5.004 0.189 0.197 b 3.810 3.988 0.150 0.157 c 1.346 1.753 0.053 0.069 d 0.330 0.508 0.013 0.020 m 0.406 1.270 0.016 0.050 f 1.194 1.346 0.047 0.053 i 0.102 0.254 0.004 0.010 j 5.791 6.198 0.228 0.244 h 0.178 0.254 0.007 0.010 8?lead sop plastic package f a j b d i c m h
rt9173/a www.richtek-ic.com.tw ds9173/a-06 march 2002 10 richtek technology corp. headquarter 6f, no. 35, hsintai road, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5510047 fax: (8863)5537749 richtek technology corp. taipei office (marketing) 8f-1, no. 137, lane 235, paochiao road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)89191466 fax: (8862)89191465 email: marketing@richtek-ic.com.tw
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