referencedhaole018.com

haole018.com  时间:2021-03-18  阅读:()
DS90LV018Awww.
ti.
comSNLS014D–JUNE1998–REVISEDAPRIL2013DS90LV018A3VLVDSSingleCMOSDifferentialLineReceiverCheckforSamples:DS90LV018A1FEATURESDESCRIPTIONTheDS90LV018AisasingleCMOSdifferentialline2>400Mbps(200MHz)SwitchingRatesreceiverdesignedforapplicationsrequiringultralow50psDifferentialSkew(Typical)powerdissipation,lownoiseandhighdatarates.
The2.
5nsMaximumPropagationDelaydeviceisdesignedtosupportdataratesinexcessof400Mbps(200MHz)utilizingLowVoltageDifferential3.
3VPowerSupplyDesignSignaling(LVDS)technology.
Flow-ThroughPinoutTheDS90LV018Aacceptslowvoltage(350mVPowerDownHighImpedanceonLVDSInputstypical)differentialinputsignalsandtranslatesthemLowPowerDesign(18mW@3.
3VStatic)to3VCMOSoutputlevels.
ThereceiveralsoInteroperablewithExisting5VLVDSNetworkssupportsopen,shortedandterminated(100Ω)inputfail-safe.
ThereceiveroutputwillbeHIGHforallfail-AcceptsSmallSwing(350mVTypical)safeconditions.
TheDS90LV018Ahasaflow-throughDifferentialSignalLevelsdesignforeasyPCBlayout.
SupportsOpen,ShortandTerminatedInputTheDS90LV018AandcompanionLVDSlinedriverFail-SafeprovideanewalternativetohighpowerPECL/ECLConformstoANSI/TIA/EIA-644Standarddevicesforhighspeedpoint-to-pointinterfaceIndustrialTemperatureOperatingRangeapplications.
–(40°Cto+85°C)AvailableinSOICPackageConnectionDiagramFigure1.
SOICSeePackageNumberD(R-PDSO-G8)FunctionalDiagramTruthTableINPUTSOUTPUT[RIN+][RIN]ROUTVID≥0.
1VHVID≤0.
1VLFullFail-safeOPEN/SHORTorTerminatedH1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
2Alltrademarksarethepropertyoftheirrespectiveowners.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright1998–2013,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
DS90LV018ASNLS014D–JUNE1998–REVISEDAPRIL2013www.
ti.
comThesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
AbsoluteMaximumRatings(1)SupplyVoltage(VCC)0.
3Vto+4VInputVoltage(RIN+,RIN)0.
3Vto+3.
9VOutputVoltage(ROUT)0.
3Vto(VCC+0.
3V)MaximumPackagePowerDissipation@+25°CDPackage1025mWDerateDPackage8.
2mW/°Cabove+25°CStorageTemperatureRange65°Cto+150°CLeadTemperatureRangeSoldering(4sec.
)+260°CMaximumJunctionTemperature+150°CESDRating(HBM1.
5kΩ,100pF)≥7kV(EIAJ0Ω,200pF)≥500V(1)"AbsoluteMaximumRatings"arethosevaluesbeyondwhichthesafetyofthedevicecannotbespecified.
Theyarenotmeanttoimplythatthedevicesshouldbeoperatedattheselimits.
ElectricalCharacteristicsspecifiesconditionsofdeviceoperation.
RecommendedOperatingConditionsMinTypMaxUnitsSupplyVoltage(VCC)+3.
0+3.
3+3.
6VReceiverInputVoltageGND3.
0VOperatingFreeAirTemperature(TA)4025+85°C2SubmitDocumentationFeedbackCopyright1998–2013,TexasInstrumentsIncorporatedProductFolderLinks:DS90LV018ADS90LV018Awww.
ti.
comSNLS014D–JUNE1998–REVISEDAPRIL2013ElectricalCharacteristicsOverSupplyVoltageandOperatingTemperatureranges,unlessotherwisespecified.
(1)(2)SymbolParameterConditionsPinMinTypMaxUnitsVTHDifferentialInputHighThresholdVCM=+1.
2V,0V,3V(3)RIN+,+100mVRINVTLDifferentialInputLowThreshold100mVIINInputCurrentVIN=+2.
8VVCC=3.
6Vor0V10±1+10μAVIN=0V10±1+10μAVIN=+3.
6VVCC=0V-20+20μAVOHOutputHighVoltageIOH=0.
4mA,VID=+200mVROUT2.
73.
1VIOH=0.
4mA,Inputsterminated2.
73.
1VIOH=0.
4mA,Inputsshorted2.
73.
1VVOLOutputLowVoltageIOL=2mA,VID=200mV0.
30.
5VIOSOutputShortCircuitCurrentVOUT=0V(4)1550100mAVCLInputClampVoltageICL=18mA1.
50.
8VICCNoLoadSupplyCurrentInputsOpenVCC5.
49mA(1)Currentintodevicepinsisdefinedaspositive.
Currentoutofdevicepinsisdefinedasnegative.
Allvoltagesarereferencedtogroundunlessotherwisespecified(suchasVID).
(2)Alltypicalsaregivenfor:VCC=+3.
3VandTA=+25°C.
(3)VCCisalwayshigherthanRIN+andRINvoltage.
RIN+andRINareallowedtohavevoltagerange0.
05Vto+3.
05V.
VIDisnotallowedtobegreaterthan100mVwhenVCM=0Vor3V.
(4)Outputshortcircuitcurrent(IOS)isspecifiedasmagnitudeonly,minussignindicatesdirectiononly.
Onlyoneoutputshouldbeshortedatatime,donotexceedmaximumjunctiontemperaturespecification.
SwitchingCharacteristicsVCC=+3.
3V±10%,TA=40°Cto+85°C(1)(2)SymbolParameterConditionsMinTypMaxUnitstPHLDDifferentialPropagationDelayHightoLowCL=15pF1.
01.
62.
5nstPLHDDifferentialPropagationDelayLowtoHighVID=200mV1.
01.
72.
5nstSKD1DifferentialPulseSkew|tPHLDtPLHD|(3)(Figure2andFigure3)050400pstSKD3DifferentialParttoPartSkew(4)01.
0nstSKD4DifferentialParttoPartSkew(5)01.
5nstTLHRiseTime325800pstTHLFallTime225800psfMAXMaximumOperatingFrequency(6)200250MHz(1)CLincludesprobeandjigcapacitance.
(2)Generatorwaveformforalltestsunlessotherwisespecified:f=1MHz,ZO=50Ω,trandtf(0%to100%)≤3nsforRIN.
(3)tSKD1isthemagnitudedifferenceindifferentialpropagationdelaytimebetweenthepositive-going-edgeandthenegative-going-edgeofthesamechannel.
(4)tSKD3,parttopartskew,isthedifferentialchannel-to-channelskewofanyeventbetweendevices.
ThisspecificationappliestodevicesatthesameVCCandwithin5°Cofeachotherwithintheoperatingtemperaturerange.
(5)tSKD4,parttopartskew,isthedifferentialchannel-to-channelskewofanyeventbetweendevices.
Thisspecificationappliestodevicesovertherecommendedoperatingtemperatureandvoltageranges,andacrossprocessdistribution.
tSKD4isdefinedas|MaxMin|differentialpropagationdelay.
(6)fMAXgeneratorinputconditions:tr=tf100k),lowcapacitance(<2pF)scopeprobeswithawidebandwidth(1GHz)scope.
Improperprobingwillgivedeceivingresults.
CABLESANDCONNECTORS,GENERALCOMMENTSWhenchoosingcableandconnectorsforLVDSitisimportanttoremember:Usecontrolledimpedancemedia.
Thecablesandconnectorsyouuseshouldhaveamatcheddifferentialimpedanceofabout100.
Theyshouldnotintroducemajorimpedancediscontinuities.
Balancedcables(e.
g.
twistedpair)areusuallybetterthanunbalancedcables(ribboncable,simplecoax)fornoisereductionandsignalquality.
BalancedcablestendtogeneratelessEMIduetofieldcancelingeffectsandalsotendtopickupelectromagneticradiationacommon-mode(notdifferentialmode)noisewhichisrejectedbythereceiver.
Forcabledistances<0.
5M,mostcablescanbemadetoworkeffectively.
Fordistances0.
5M≤d≤10M,CAT3(category3)twistedpaircableworkswell,isreadilyavailableandrelativelyinexpensive.
6SubmitDocumentationFeedbackCopyright1998–2013,TexasInstrumentsIncorporatedProductFolderLinks:DS90LV018ADS90LV018Awww.
ti.
comSNLS014D–JUNE1998–REVISEDAPRIL2013PinDescriptionsPinNo.
NameDescription1RIN-Invertingreceiverinputpin2RIN+Non-invertingreceiverinputpin7ROUTReceiveroutputpin8VCCPowersupplypin,+3.
3V±0.
3V5GNDGroundpin3,4,6NCNoconnectionCopyright1998–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback7ProductFolderLinks:DS90LV018ADS90LV018ASNLS014D–JUNE1998–REVISEDAPRIL2013www.
ti.
comTypicalPerformanceCharacteristicsOutputHighVoltagevsOutputLowVoltagevsPowerSupplyVoltagePowerSupplyVoltageOutputShortCircuitCurrentvsDifferentialTransitionVoltagevsPowerSupplyVoltagePowerSupplyVoltagePowerSupplyCurrentPowerSupplyCurrentvsvsFrequencyAmbientTemperature8SubmitDocumentationFeedbackCopyright1998–2013,TexasInstrumentsIncorporatedProductFolderLinks:DS90LV018ADS90LV018Awww.
ti.
comSNLS014D–JUNE1998–REVISEDAPRIL2013TypicalPerformanceCharacteristics(continued)DifferentialPropagationDelayvsDifferentialPropagationDelayvsPowerSupplyVoltageAmbientTemperatureDifferentialSkewvsDifferentialSkewvsPowerSupplyVoltageAmbientTemperatureDifferentialPropagationDelayvsDifferentialPropagationDelayvsDifferentialInputVoltageCommon-ModeVoltageCopyright1998–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback9ProductFolderLinks:DS90LV018ADS90LV018ASNLS014D–JUNE1998–REVISEDAPRIL2013www.
ti.
comTypicalPerformanceCharacteristics(continued)TransitionTimevsTransitionTimevsPowerSupplyVoltageAmbientTemperatureDifferentialPropagationDelayTransitionTimevsLoadvsLoadDifferentialPropagationDelayTransitionTimevsLoadvsLoad10SubmitDocumentationFeedbackCopyright1998–2013,TexasInstrumentsIncorporatedProductFolderLinks:DS90LV018ADS90LV018Awww.
ti.
comSNLS014D–JUNE1998–REVISEDAPRIL2013REVISIONHISTORYChangesfromRevisionC(April2013)toRevisionDPageChangedlayoutofNationalDataSheettoTIformat10Copyright1998–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLinks:DS90LV018APACKAGEOPTIONADDENDUMwww.
ti.
com11-Jan-2021Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Leadfinish/Ballmaterial(6)MSLPeakTemp(3)OpTemp(°C)DeviceMarking(4/5)SamplesDS90LV018ATMNRNDSOICD895Non-RoHS&GreenCallTICallTI-40to8590LV018ATMDS90LV018ATM/NOPBACTIVESOICD895RoHS&GreenSNLevel-1-260C-UNLIM-40to8590LV018ATMDS90LV018ATMX/NOPBACTIVESOICD82500RoHS&GreenSNLevel-1-260C-UNLIM-40to8590LV018ATM(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)RoHS:TIdefines"RoHS"tomeansemiconductorproductsthatarecompliantwiththecurrentEURoHSrequirementsforall10RoHSsubstances,includingtherequirementthatRoHSsubstancedonotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,"RoHS"productsaresuitableforuseinspecifiedlead-freeprocesses.
TImayreferencethesetypesofproductsas"Pb-Free".
RoHSExempt:TIdefines"RoHSExempt"tomeanproductsthatcontainleadbutarecompliantwithEURoHSpursuanttoaspecificEURoHSexemption.
Green:TIdefines"Green"tomeanthecontentofChlorine(Cl)andBromine(Br)basedflameretardantsmeetJS709Blowhalogenrequirementsof<=1000ppmthreshold.
Antimonytrioxidebasedflameretardantsmustalsomeetthe<=1000ppmthresholdrequirement.
(3)MSL,PeakTemp.
-TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)Theremaybeadditionalmarking,whichrelatestothelogo,thelottracecodeinformation,ortheenvironmentalcategoryonthedevice.
(5)MultipleDeviceMarkingswillbeinsideparentheses.
OnlyoneDeviceMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireDeviceMarkingforthatdevice.
(6)Leadfinish/Ballmaterial-OrderableDevicesmayhavemultiplematerialfinishoptions.
Finishoptionsareseparatedbyaverticalruledline.
Leadfinish/Ballmaterialvaluesmaywraptotwolinesifthefinishvalueexceedsthemaximumcolumnwidth.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.
TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
Effortsareunderwaytobetterintegrateinformationfromthirdparties.
TIhastakenandcontinuestotakereasonablestepstoproviderepresentativeandaccurateinformationbutmaynothaveconducteddestructivetestingorchemicalanalysisonincomingmaterialsandchemicals.
TIandTIsuppliersconsidercertaininformationtobeproprietary,andthusCASnumbersandotherlimitedinformationmaynotbeavailableforrelease.
PACKAGEOPTIONADDENDUMwww.
ti.
com11-Jan-2021Addendum-Page2InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
TAPEANDREELINFORMATION*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQReelDiameter(mm)ReelWidthW1(mm)A0(mm)B0(mm)K0(mm)P1(mm)W(mm)Pin1QuadrantDS90LV018ATMX/NOPBSOICD82500330.
012.
46.
55.
42.
08.
012.
0Q1PACKAGEMATERIALSINFORMATIONwww.
ti.
com24-Aug-2017PackMaterials-Page1*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQLength(mm)Width(mm)Height(mm)DS90LV018ATMX/NOPBSOICD82500367.
0367.
035.
0PACKAGEMATERIALSINFORMATIONwww.
ti.
com24-Aug-2017PackMaterials-Page2www.
ti.
comPACKAGEOUTLINEC.
228-.
244TYP[5.
80-6.
19].
069MAX[1.
75]6X.
050[1.
27]8X.
012-.
020[0.
31-0.
51]2X.
150[3.
81].
005-.
010TYP[0.
13-0.
25]0-8.
004-.
010[0.
11-0.
25].
010[0.
25].
016-.
050[0.
41-1.
27]4X(0-15)A.
189-.
197[4.
81-5.
00]NOTE3B.
150-.
157[3.
81-3.
98]NOTE44X(0-15)(.
041)[1.
04]SOIC-1.
75mmmaxheightD0008ASMALLOUTLINEINTEGRATEDCIRCUIT4214825/C02/2019NOTES:1.
Lineardimensionsareininches[millimeters].
Dimensionsinparenthesisareforreferenceonly.
Controllingdimensionsareininches.
DimensioningandtolerancingperASMEY14.
5M.
2.
Thisdrawingissubjecttochangewithoutnotice.
3.
Thisdimensiondoesnotincludemoldflash,protrusions,orgateburrs.
Moldflash,protrusions,orgateburrsshallnotexceed.
006[0.
15]perside.
4.
Thisdimensiondoesnotincludeinterleadflash.
5.
ReferenceJEDECregistrationMS-012,variationAA.
18.
010[0.
25]CAB54PIN1IDAREASEATINGPLANE.
004[0.
1]CSEEDETAILADETAILATYPICALSCALE2.
800www.
ti.
comEXAMPLEBOARDLAYOUT.
0028MAX[0.
07]ALLAROUND.
0028MIN[0.
07]ALLAROUND(.
213)[5.
4]6X(.
050)[1.
27]8X(.
061)[1.
55]8X(.
024)[0.
6](R.
002)TYP[0.
05]SOIC-1.
75mmmaxheightD0008ASMALLOUTLINEINTEGRATEDCIRCUIT4214825/C02/2019NOTES:(continued)6.
PublicationIPC-7351mayhavealternatedesigns.
7.
Soldermasktolerancesbetweenandaroundsignalpadscanvarybasedonboardfabricationsite.
METALSOLDERMASKOPENINGNONSOLDERMASKDEFINEDSOLDERMASKDETAILSEXPOSEDMETALOPENINGSOLDERMASKMETALUNDERSOLDERMASKSOLDERMASKDEFINEDEXPOSEDMETALLANDPATTERNEXAMPLEEXPOSEDMETALSHOWNSCALE:8XSYMM1458SEEDETAILSSYMMwww.
ti.
comEXAMPLESTENCILDESIGN8X(.
061)[1.
55]8X(.
024)[0.
6]6X(.
050)[1.
27](.
213)[5.
4](R.
002)TYP[0.
05]SOIC-1.
75mmmaxheightD0008ASMALLOUTLINEINTEGRATEDCIRCUIT4214825/C02/2019NOTES:(continued)8.
Lasercuttingapertureswithtrapezoidalwallsandroundedcornersmayofferbetterpasterelease.
IPC-7525mayhavealternatedesignrecommendations.
9.
Boardassemblysitemayhavedifferentrecommendationsforstencildesign.
SOLDERPASTEEXAMPLEBASEDON.
005INCH[0.
125MM]THICKSTENCILSCALE:8XSYMMSYMM1458IMPORTANTNOTICEANDDISCLAIMERTIPROVIDESTECHNICALANDRELIABILITYDATA(INCLUDINGDATASHEETS),DESIGNRESOURCES(INCLUDINGREFERENCEDESIGNS),APPLICATIONOROTHERDESIGNADVICE,WEBTOOLS,SAFETYINFORMATION,ANDOTHERRESOURCES"ASIS"ANDWITHALLFAULTS,ANDDISCLAIMSALLWARRANTIES,EXPRESSANDIMPLIED,INCLUDINGWITHOUTLIMITATIONANYIMPLIEDWARRANTIESOFMERCHANTABILITY,FITNESSFORAPARTICULARPURPOSEORNON-INFRINGEMENTOFTHIRDPARTYINTELLECTUALPROPERTYRIGHTS.
TheseresourcesareintendedforskilleddevelopersdesigningwithTIproducts.
Youaresolelyresponsiblefor(1)selectingtheappropriateTIproductsforyourapplication,(2)designing,validatingandtestingyourapplication,and(3)ensuringyourapplicationmeetsapplicablestandards,andanyothersafety,security,orotherrequirements.
Theseresourcesaresubjecttochangewithoutnotice.
TIgrantsyoupermissiontousetheseresourcesonlyfordevelopmentofanapplicationthatusestheTIproductsdescribedintheresource.
Otherreproductionanddisplayoftheseresourcesisprohibited.
NolicenseisgrantedtoanyotherTIintellectualpropertyrightortoanythirdpartyintellectualpropertyright.
TIdisclaimsresponsibilityfor,andyouwillfullyindemnifyTIanditsrepresentativesagainst,anyclaims,damages,costs,losses,andliabilitiesarisingoutofyouruseoftheseresources.
TI'sproductsareprovidedsubjecttoTI'sTermsofSale(https:www.
ti.
com/legal/termsofsale.
html)orotherapplicabletermsavailableeitheronti.
comorprovidedinconjunctionwithsuchTIproducts.
TI'sprovisionoftheseresourcesdoesnotexpandorotherwisealterTI'sapplicablewarrantiesorwarrantydisclaimersforTIproducts.
IMPORTANTNOTICEMailingAddress:TexasInstruments,PostOfficeBox655303,Dallas,Texas75265Copyright2021,TexasInstrumentsIncorporated

Sharktech:美国/荷兰独立服务器,10Gbps端口/不限流量/免费DDoS防护60G,319美元/月起

sharktech怎么样?sharktech (鲨鱼机房)是一家成立于 2003 年的知名美国老牌主机商,又称鲨鱼机房或者SK 机房,一直主打高防系列产品,提供独立服务器租用业务和 VPS 主机,自营机房在美国洛杉矶、丹佛、芝加哥和荷兰阿姆斯特丹,所有产品均提供 DDoS 防护。此文只整理他们家10Gbps专用服务器,此外该系列所有服务器都受到高达 60Gbps(可升级到 100Gbps)的保护。...

UCloud:美国云服务器,洛杉矶节点大促,低至7元起/1个月

ucloud美国云服务器怎么样?ucloud是国内知名云计算品牌服务商家,目前推出全球多地机房的海外云服务器。UCloud主打的优势是海外多机房,目前正在进行的2021全球大促活动参与促销的云服务器机房就多达18个。UCloud新一代旗舰产品快杰云服务器已上线洛杉矶节点,覆盖北美和亚太地区,火热促销中, 首月低至7元,轻松体验具备优秀性能与极高性价比的快杰云服务器。点击进入:ucloud美国洛杉矶...

统计一下racknerd正在卖的超便宜VPS,值得推荐的便宜美国VPS

racknerd从成立到现在发展是相当迅速,用最低的价格霸占了大部分低端便宜vps市场,虽然VPS价格便宜,但是VPS的质量和服务一点儿都不拉跨,服务器稳定、性能给力,尤其是售后方面时间短技术解决能力强,估计这也是racknerd这个品牌能如此成功的原因吧! 官方网站:https://www.racknerd.com 多种加密数字货币、信用卡、PayPal、支付宝、银联、webmoney,可...

haole018.com为你推荐
乐划锁屏乐视屏幕手机解锁忘记但是指纹可以解开怎么办?老虎数码我想买个一千左右的数码相机!最好低于一千五!再给我说一下像素是多少?比肩工场比肩成局 什么意思百花百游百花净斑方多少钱一盒336.com求一个游戏的网站 你懂得125xx.com115xx.com是什么意思dadi.tv1223tv影院首页地址是什么?1223tv影院在哪里可以找到?www.toutoulu.comSEO行业外链怎么做?www.toutoulu.comWWW【toutoulu】cOM怎么搜不到了?到哪里能看到toutoulu视频?关键词分析怎么样分析关键词?
我的世界服务器租用 工信部域名备案系统 如何申请免费域名 韩国电信 国外空间 网站实时监控 网站挂马检测工具 河南服务器 圣诞促销 web服务器的架设 me空间社区 泉州电信 免费吧 免费phpmysql空间 万网空间购买 免费asp空间 云服务是什么意思 windowsserver2008 windowsserver2008r2 web是什么意思 更多