凌力尔特模拟创新杂志 (JULY 2011)

　　PoweroverEthernet,orPoE,isanincreasinglypopularwaytodeliverbothpoweranddataoverexistingEthernetcable,thusfreeingapplicationsfromtheconstraintofAC-powerproximity.AsthenumberPoEsolutionshasgrownsohastheapplications’appetiteforpower.Anewproprietarystandard,LTPoE++™,satisfiesthishungerbyextendingthePoEandPoE+specificationsto90WofPDdeliveredpower.LTPoE++alsodramaticallyreducesengineeringcomplexityinpowersourcingequipment(PSEs)andpowereddevices(PDs)whencomparedtootherpower-expansionsolutions.Plug-and-playsimplicityandsafe,robustpowerdeliveryarehallmarksofLTPoE++.ThecapabilitiesofthisstandardexpandthefieldofEthernet-poweredapplicationsbyseveralordersofmagnitude,enablingentirelynewclassesofPDs,suchaspower-hungrypicocells,basestationsorheatersforpan-tilt-zoomcameras.

　　HISTORYOFPoE

　　PoEisastandardprotocolforsendingDCpowerovercopperEthernetdatawiring.TheIEEEgroupthatadministersthe802.3EthernetdatastandardsaddedPoEcapabilityin2003.TheoriginalPoEspec,knownas802.3af,allowedfor48VDCpoweratupto13W.Althoughtheinitialspecificationwaswidelypopular,the13Wcaplimitedthenumberofpossibleapplica-tions.In2009,theIEEEreleasedanewstandard,knownas802.3atorPoE+,increasingthevoltageandcurrentrequirementstosupply25.5Wofpower.

July2011Volume21Number2INTHISRS485andRS232ISSUELTPoE++ExtendsPoEto90WwithReliableandEasy-to-UseStandardtransceiverscombinedinasingledevice12HeathStewartfast-actingICprotectssensitivecircuitsfromovervoltageandreversePoweroverEthernet,orPoE,isanincreasinglypopularsupplyconnections23waytodeliverbothpoweranddataoverexistingEthernetcable,thusfreeingapplicationsfromtheconst