all contents are subject to change without prior notice ? seaward electronics inc., 2005. ? www.seawardinc.com ? page 1 description the SE9174 regulator is designed to convert voltage supplies ranging from 1.6v to 6v into a desired output voltage, which is adjusted by two external voltage divider resistors. the regulator is capable of sourcing or sinking up to 2.0a of current while regulating an output voltage to within 2% (ddr 1 or ddr 2) or less. the SE9174, 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 back-plane 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. features ? support both ddr 1 (1.25v tt ) and ddr 2 (0.9v tt ) requirements ? sop-8 packages ? capable of sourcing and sinking current 2.0a ? current-limiting protection ? thermal protection ? current-shoot-through protection ? integrated power mosfets ? generates termination voltages for sstl-2 ? high accuracy output voltage at full-load ? adjustable vout by external resistors ? minimum external components ? shutdown for standby or suspend mode operation with high-impedance output pin configuration application ? ddr memory termination ? active termination buses ? supply splitter block diagram vin vout cntl gnd current limiting sensor thermal vcntl refen pin description pin name pin function v in power input gnd ground v cntl gate drive voltage refen reference voltage input and chip enable v out output voltage
all contents are subject to change without prior notice ? seaward electronics inc., 2005. ? www.seawardinc.com ? page 2 absolute maximum rating (1) parameter symbol value unit input voltage v in 6 v power dissipation p d internally limited -- esd rating -- 3 kv storage temperature range t s -65 to 150 c lead temperature (soldering, 5 sec.) t lead 260 c package thermal resistance jc 15.7 oc/w electrical characteristics v in =2.5v, v cntl =3.3v, v refen =1.25v, c out =10f (ceramic)), t a =25oc, unless otherwise specified parameter symbol test conditions min typ max units output offset voltage (2) v os i out = 0a -20 -5 20 mv i l : 0a 2.0a -- 0.5 2 load regulation (ddr 1/2) | ? v load | i l : 0a -2.0a -- 0.5 2 % v in 1.6 2.5/1.8 -- input voltage range (ddr 1/2) 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 ? -- 1 90 a short circuit protection current limit i limit -- 2.5 -- a quiescent current i q i l =2.0a -- 1.4 3 ma over temperature protection thermal shutdown temperature t case 3.3v v cntl 5 v -- 100 -- thermal shutdown hysterresis guaranteed by design -- 30 -- oc shutdown function output=high 0.8 -- -- shutdown threshold trigger output=low -- -- 0.2 v note 1: exceeding the absolute maximum rating may damage the device. note 2 : v os offset is the voltage measurement defined as v out subtracted from v refen
all contents are subject to change without prior notice ? seaward electronics inc., 2005. ? www.seawardinc.com ? page 3 r0 r1 r2 r3 r4 r5 r6 r7 r8 r9 rn rn1 terminator resi s refen SE9174 SE9174 vout vout bus(0) bus(1) bus(2) bus(3) bus(4) bus(5) bus(6) bus(7) bus(8) bus(9) bus(n+1 ) bus(n) application information internal parasitic diode avoid forward-bias internal parasitic diode, v out to v cntl , and v out to v in , the v out should not be forced same voltage respect to ground on this pin while the v cntl or v in 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 v refen is below 0.2v. in addition to item1, 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. layout consideration the SE9174 regulator is packaged in thermally enhanced 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 v cntl pins of the SE9174. the multiple v cntl 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 via to conduct the heat into the buried or backside of pcb layer. the via should be small enough to retain solder when the board is wave-soldered. thermal consideration SE9174 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 150c must not be exceeded. higher continuous 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 noted that with the v cntl equal to 5v, the point of thermal shutdown will be degraded by approx. 20c compared to the v cntl equipped with 3.3v. it is highly recommended that to use the 3.3v rail acting as the v cntl so as to minimize the thermal concern of the SE9174 in the sop-8 package.
all contents are subject to change without prior notice ? seaward electronics inc., 2005. ? www.seawardinc.com ? page 4 application diagram r 1 = r 2 = 100k ? , r tt = 50 ? /33 ? /25 ? c out, min = 10f(ceramic) + 1000f under the worst case testing condition r dummy = 1k ? as for v out discharge when v in is not present but v cntl is present c ss = 1f, c in = 470f(low esr), c cntl = 47f
all contents are subject to change without prior notice ? seaward electronics inc., 2005. ? www.seawardinc.com ? page 5 outline drawing sop-8 contact information seaward electronics incorporated ? china room 1605, building 1, international pioneering park, #1 shangdi xinxi rd. haidian district, beijing 100085, china tel: 86-10-8289-5700/01/05 fax: 86-10-8289-5706 email: sales@seawardinc.com.cn seaward electronics corporation ? taiwan 2f, #181, sec. 3, min quan east rd. ta i p e i , ta i w a n r . o . c tel: 886-2-2712-0307 fax: 886-2-2712-0191 email: sales@seawardinc.com.tw seaward electronics incorporated ? north america 49 showers dr. j126 mountain view, ca 94040, usa tel: 1-408-821-6600 last updated - 3/21/2005 1 2 3 4 5 6 7 8 h e d a1 a b b1 c mi n max mi n max a 0.0532 0.0688 1.35 1.75 a1 0.0040 0.0098 0.10 0.25 b 0.0130 0.0200 0.33 0.51 b1 c 0.0075 0.0098 0.19 0.25 d 0.1890 0.1968 4.80 5.00 h 0.2284 0.2440 5.80 6.20 e 0.1497 0.1574 3.80 4.00 dimensions 0.050 bsc 1.27 bsc dim n inches mm
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