practical

Abstract—InthispublicationveralNearField

Communication(NFC)badnsordemonstrationsandrelated

ncludebasictemperature

nsorapplicationsandsomemorecomplexscenarioswith

derdevicecanbea

commercialNFCenabledmobilephoneorspeciallydeveloped

ntheexperiencegatheredwithdemonstrations

andprototypes,themainfeaturesofanoptimalNFCcircuitry

forlowcostbatterylessNFCenablednsordevicesarespecified.

IndexTerms—batteryless,NFCpeer-to-peer,SmartNFC

Interface,ultra-lowpower,wirelessnsors.

UCTION

HFRFIDtechnologyimerginginmobilephonesinthe

formofNearFieldCommunication(NFC).This13.56MHz

technologyisheavilybadonearlierRFIDstandards,butit

alsodefinesnewcommunicationmodesforapplicationssuch

r,

breakthroughisfirstexpectedwithapplicationsthatmake

NFCphonesinteroperablewithlegacyinfrastructurefor

contactlessticketingandpaymentapplications.

Apartfromthecurrentlyenvisionedmainstream

applications,

paper,wediscussNFCasanenablerofwirelessnsorswhich

aretypicallyenasntialbuildingblocksofubiquitous

erest

towardsNFCfromthisperspectiveixplainedprimarilyby

thefactthatmobilephonescanbeenastypicalurdevices

inmanyofsuchscenariosandoftencertainlypreferredto

edtoBluetooth–another

short-rangewirelesstechnologyfoundinmobilephones–

NFCenableslowerpowerconsuming,orevencompletely

batterylessimplementations,whichisamajorfeasibilityissue:

otherhand,theveryshortcommunicationdistanceleadstoa

novel“touchbad”uparadigm,makingthettingupof

ManuscriptreceivedOctober17,rkwasdoneduring

SmartTouchITEAproject(ITEANo05024).

HillukkalaMikaiswithVTTTechnicalRearchCentreofFinland,

Kaitovayla1,1100,FI-90571Oulu,Finland.(correspondingauthor,

phone:+358-20-722-2331;fax:+358-20-722-2320;e-mail:

kala@).

HeiskanenMikkoiswithVTTTechnicalRearchCentreofFinland,

Kaitovayla1,1100,FI-90571Oulu,Finland.(e-mail:

nen@).

Ylisaukko-ojaArtoiswithVTTTechnicalRearchCentreofFinland,

Kaitovayla1,1100,FI-90571Oulu,Finland.(e-mail:kko-

oja@).

connectionsmuchsimplerandmoreexplicitthanincaof

longerrangetechnologies,includingUHFRFID:makingtwo

devicesinteractcanbeassimpleasbringingthemnexttoeach

other[1].IntegrationofRFIDreaderelectronicstoan

everydayobject,forexampleintoamobilephone,makes

consumerapplicationswithwirelessnsorsinvolvedfeasible.

ForUHFRFID,suchatrendisnotforeeninthenearfuture.

Ontheotherhand,nsorapplicationsaretakenintoaccount

inUHFbadEPCglobaldefinitions,whichisnotreallythe

cawithNFC.[2].

Moisturensorembeddedintobathroomwallisan

exampleofapotentialnsorapplicationthatcouldbenefit

fromtheuofNFCasacommunicationtechnology:the

inhabitantscouldoccasionallychecktheconditionofthe

moisturebarrierbyplacinganNFCphoneontopofthensor

insidethewall,therebydetectingtheexcessivemoisture

ceNFCmakespassive

implementationpossible,therewouldbenoneedforbatteries

inthensors–aremarkablebenefit,sinceitwouldbe

impossibletoreplaceabatterywithoutbreakingthewall.

AnNFCchipisaversatiledevice,which,intermsof

traditionalRFID,supportsfunctionalitiesofboththereader

andthetag,

isntialinmobilephonesthatsometimesneedtoreadtags,

rast,for

awell-definedandconstanttasksuchasanNFCenabled

temperaturensor,itwouldbeenoughtosimplysupportthe

functionalityofthetagsidewithonlyoneoftheprotocols

uldgreatlysimplify

thensordeviceandpotentiallymakethesolution

approachwasstudiedfor

exampleinIntelliSenprojectwhereanASICwasdeveloped

r,thischiphadsomeadded

complexitybecauinadditionto13.56MHzHFband,italso

supportedtheUHFbandof860-960MHz[3].Asa

commercialexample,theMicronsysTelid211passive13.56

MHztemperaturensorssupportISO14443-B,whichis

r,thensorsare

notmarketedasNFCcompatible,insteadtheyaremeanttobe

operatedwithspecializedreaderwithappropriatefirmware

installed[4].

ThepracticalNFCnsorimplementationsprentedinthis

paperarebadoncommercialNFCchipsthatbasicallyare

overkillfortheintendedtaskiftheirversatilefeaturesare

r,itshouldbenotedthatthevolumeof

producedNFCchipsistimatedtoritoverybigquantities,

Practicalimplementationsofpassiveand

mi-passiveNFCenablednsors

HillukkalaMika,HeiskanenMikko,Ylisaukko-ojaArto

2009FirstInternationalWorkshoponNearFieldCommunication

978-0-7695-3577-7/09$25.00©2009IEEE

DOI10.1109/NFC.2009.13

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ore,

wirelessnsorimplementationbadonthechipsmaybe

bothtechnicallyandeconomicallyfeasibleinlowtomedium

uireddevelopmenteffortisalso

muchlowerthanincaofadedicatedASIC,forexample.

Inthefollowing,practicalimplementationexamplesofboth

mi-passiveandpassiveNFCenablednsorsaredescribed,

evaluatingapplicabilityoftwodifferentcommercialNFC

-passiveNFC

nsorsuloadmodulationandnevergenerateacarrierof

ensorsuthesame

methodfordatatransmission,buttheyalsotakeallrequired

energyfromthereader’sRFfieldandthusdonotrequireany

additionalenergysourcesuchasabattery.

FCINTERFACE

SmartNFCInterface(SNI)isaprototypingplatform

developedbyVTTTechnicalRearchCentreofFinland[1],

[5].Thedeviceconsistsoftwoprintedcircuitboardsstacked

oneabovetheother,beingapproximatelythesizeofa

eroneiscalled“basicboard”becauit

containsalltheelementaryhardwareblockssuchasbattery

chargingcircuitry,powersupply,crystaloscillatorand8-bit

emory,realtimeclock(RTC),

temperaturensor,LED,buzzer,rialportdriverand

externalconnectorsarealsoinstalledonthisboardascanbe

erboardiscalled“communication

board”becauitcontainsallwirelesscommunication

modules,suchasIrDA,NFC,andBluetooth.

iagramofSmartNFCInterface

WhenNFCcommunicationisud,theNFCchipPN531

[6],installedonSNIdevice,canactasatargetorasan

modesofNFCitisalsocapableofnding

andreceivingdatawithanotherSNIdeviceoranNFCenabled

Ithedevelopercanmodifydifferent

parametersaffectingNFCorBluetoothradiochannels

whereaswithmobilephonesthepossibilitiesarerestricted,

becauthehardwaremodulesarecontrolledby

manufacturerspecificfirmwarethatoffereitherlimitedorno

configurationoptionsfortheur.

SNIisamultifunctionalprototypethatisdesignedforfast

beenthebasicbuildingblockformanydifferentNFC

demonstrations,suchashomeaccesscontrol,bloodgluco

measurement,mobiletemperaturensoranddatalogging

device.

InhomeaccesscontroldemonstrationtheSNIdevicereads

NFCmessagesfrommobilephonesandcontrolsadoorbell,a

cessrights

ofdifferentphonesaremanagedbySNI.

InbloodglucomeasurementtheSNIdeviceisconnected

toacommerciallyavailablebloodglucometer(One-Touch

Ultra2[7])icpatienttakesbloodsample

likehe/shewoulddowiththenormalglucometerandthen

themeasurementresultisautomaticallytransferredtoSNI

hingwiththeNFCphonetheresultis

transferredtothephoneandthentothebackendsystemtobe

obrvedeitherbythepatientorhis/herpersonaldoctor.

Instructionsforadministeringinsulinarentbacktothe

patientasatextmessage.

IndataloggingdemonstrationtheSNIdevicestaysinlow

kenup

periodicallybyinterruptrequestsfromRTC,andwithevery

wakingtimethetemperatureismeasuredandstoredtothe

uleis

poweredupallthetimeandwhenitdetectsareaderdevice

nearby,itndstheBluetoothaddressoftheSNIdeviceto

thatotherNFCdevice(typicallyamobilephone).Thisdevice

thenconnectstoSNIwithgivenBluetoothaddress,and

previouslystoredmeasurementresultsaretransferredthrough

ngwithNFCisafastwayto

configuretwodevicestouBluetoothconnectionfordata

transmission,andwiththehelpoflargercapacityofthe

Bluetoothchannelitispossibletotransferlargeamountsof

datawhilestillkeepingthetouchinteractionshort.

Asanexampleofapower-awareimplementation,the

temperaturensordemonstrationixaminedinmoredetail

mi-passivensordemonstration

wasdesignedtocommunicateinpeer-to-peertargetmode

(usloadmodulationfordatatransmission),andtoutilizeall

possiblepowersavingmethodsthatthehardwaresupports.

Whenthetemperaturensordeviceisstarted,itinitializesthe

NFCchip,whichthengoesautomaticallyintopowersaving

ehostprocessorisputintopowerdownmodein

itiatordevice(anotherSNI

deviceconfiguredasinitiator,oranNFCenabledphone)is

broughtnearby,theNFCchipwakesupandusaninterrupt

requestline(IRQ)towakeupthehostprocessor.

Thehostprocessorthenpowersupthetemperaturensor,

waitsuntilitisstabilizedandthenutilizesanalogtodigital

converter(ADC)tomeasurethevoltagelevelattemperature

edvoltagelevelisfirstconvertedto

Celsiusdegreeformatandthenintohumanreadableformatas

ringisthentransferredtoinitiator

successfultransactiontheNFCchipandhostprocessorare

againputintopowersavingmode.

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Whenthedeviceisinpowersavingmode,thecurrent

consumptionofthewholedeviceis175µrent

consumptionvaluesforinternalblocksofSNIareprentedin

tableItogetherwithpowerconsumptionvaluescalculated

with3,ersupplyoftheSNI

deviceisquitecomplexbecauitwasdesignedtobevery

plelinear

regulatorwasud,thecurrentconsumptionofthepower

supplycouldbeaslittleas1µingtodatasheet[6]

thecurrentconsumptionofNFCchipinpowersavingmode

shouldbeonly30µA.

ONSUMPTIONOFSNIDEVICE

Current

consumption[µA]

Powerconsumption

[µW]

Powersupply2592.5

Microcontroller622.2

Communicationboard518.5

NFCcircuitry139514.3

Wholesystem175647.5

WhenNFCinitiatorstartstogeneratetheRFfield,ittakes

31.5msuntilNFCchipontargetdevicegeneratesanIRQfor

gthofactive

cycleis103.5msandduringthisactiveperiodthehost

processorconsumes40mWandNFCcircuitry60mWpower.

ItemsthattheNFCphoneisslowingthingsdown,becau

inordertomakeNFCcommunicationwork,therehavetobe

longwaitingtimesonSNIsidebeforemessagescanbentto

phone.

IfitisassumedthattheSNIdevicecanutilize85%ofits

originalbatterycapacity(150mAh)andthatthetemperature

isreadtwotimesperday,thedeviceisabletooperate

approximatelyamonthbeforethebatteryneedstobe

erconsumptionduringpowerdownperiod

dominates:iftemperatureisreadtentimesperday,thebattery

kingthecalculationsthe

lfdischargingofthebatterywasnottakenintoaccount.

SSIVETEMPERATURESENSOR

Fortestswiththefullpassiveoperation,theMicroread[8]

NFCchipfromInsideContactlesswaschonbecauithas

ead,

ingeneral,isanRFsinglesiliconchipthatusNFCfor

lesmobiledevicesto

operatelikeRFreaders,contactlesssmartcards,orRFtags

eadhas

beendesignedmainlyfromhandtpoint-of-viewandit

supportsSingleWireProtocol(SWP)forSubscriberIdentity

Module(SIM)cardapplicationsandUARTforothertypeof

lpassiveapplications,

Microreadsupportsabatteryoffmode,wheretheNFCand

SIMsupplyvoltagesarepoweredbythefieldofthereader

device.

rrentmeasurements

Loadcurrentmeasurementswereudtofindouthow

muchthesupplyline,originallydesignedforaSIMcard,can

supplycurrentduringcommunicationwhenMicroreadis

imum

loadcurrentforSIMsupplylineworkingat1.8Vvoltage

levelwasmeasuredbygraduallyaddingresistiveloadtothe

SIMsupplyline,untilthereadingeventwasnolonger

etests,weudtheMicroreadevaluationkit

thatwassubscribedtoemulateanISO14443A-3cardwitha

staticIDnumber.

TheudreaderdevicesinourtestswereInside

Contactless’Picoread[9]evaluationkittogetherwithInside’s

MXStudiosoftware,Nokia’s3220and6131NFCmobile

phones,andVTT’umbercouldbereadand

showntotheurbyusingthePicoreadevaluationkit,butnot

ybeduetotheapplicationsin

thereaderdevicesthatrequirespecialsoftwareorhigherlevel

informationfromthecardbeforeprovidingananswerto

phone’ones,thereadingeventwas

interpretedassuccessfulifthedurationoftheRFfield

lengthenedconsiderably,althoughthephonescouldnotshow

theIDnumberoftheMicroread.

Themaximumloadsandtherelatedmaximumreading

distanceswhiletheidentificationwasstillpossibleare

ral,theamountofenergy

possibletotransfertopassivedevicedependsonveral

factorssuchastransmissionpowerofthereader,antennasize,

impedancematchingoftheantennacircuitandtheproperties

,thevaluescanonly

beconsideredassuggestiveloadspossibletouonSIM

supplylineduringcommunication.

MLOADCURRENTSFORSIMSUPPLYLINE

InordertoavoidexcessivepowerconsumptionoftheNFC

enabledphones,dit

isswitchedonforafewmillicondsacoupleoftimesper

thisshort

durationoftheRFfield,thetargetdevicemustbewokenup

andidentifiedbeforethetagorsmartcardmemorycanberead

successfulidentification,theRF

fieldstaysonuntilthedataixchanged.

TobeabletodeterminethetimelimitstbytheNFC

enabledphones,thedurationoftheRFfieldwasmeasured.

ForNFCphonesavailable,thedurationoftheRFpulwas

approximately8msandcannotbemodifiedbythe

roreadandSNIthedurationof

theRFfieldisadjustableandcanevenbetascontinuous.

TableIIIsummarizesthemeasureddurationsoftheRFfields

withdifferentreaderdevices.

Maximum

load[mA]

Maximum

load[mW]

Readingdistance

[mm]

Nokia32203.56.36.0

Nokia61313.56.37.0

Picoread9.016.211.0

SNI---

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ONOFTHERFFIELDWITHDIFFERENTREADERDEVICES

ypedescription

Fordeterminingthelimitationstbythensorside(the

hostmicrocontrollerandtheNFCfront-end)asimplefull

perature

nsorprototypeisanexampleofafullpassivensorthatis

nsorprototypeconsistsofageneralpurpo16-bitTexas

InstrumentsMSP430F1611[10]microcontrollerwithan

inbuilttemperaturensorandnewerversionoftheInside

Contactless’d

readerdevicewasInsideContactless’Picoreadreaderkit

providingcontinuousRFfield.

ThetypicalimplementationofMicroread’sbatteryless

operationistouaSIMcardconnectedtotheSWPlineand

poweredusingMicroread’rthe

batteryoffmodeprovidesonlySWPcapabilityandcannotbe

udwithcommerciallow-endmicrocontrollersbecauSWP

tion,inthiscathe

SIMsupplylinecouldnotprovideenoughpowertostartthe

microcontrollerthatrequiresconsiderablymorepowerduring

ingtooheavyloadin

theSIMsupplyline,thestart-upoftheMicroreadtobattery

onmodewasnotpossible.

Duetothenontypicalcaimplementation,some

T

connectionbetweentheMicroreadevaluationboardandthe

hostmicrocontrollerwasachievedbyusinganexternalLDO

regulatorsothatMicroreadwasalwaysworkinginabattery

ernalLDOregulator

wasinstalledtotheevaluationboardsothattherectified

voltagewasregulatedandfedtoMicroreadchipandthehost

.2prentstheblockdiagramofthebuilt

nsorprototypeandtheimplementedpowerfeed.

iagramofthebuiltnsorprototype

Astheregulator’sinputvoltage,generatedbythereader’s

RFfield,variesgreatlyamongdifferentreadingdistances,the

MSP430’ssupplyvoltagesupervisor(SVS)wasudto

monitorthesupplyvoltagelevelduringthestart-upand

tandstableoperationvoltageisneededfor

accurateoperationofadigitallycontrolledoscillator(DCO)

ck

frequencyformicrocontrollerwaslectedas7MHztoensure

anaccurateUARTcommunicationandfastcodeexecution.

WhentheRFfieldofthereaderpowersupthensor

device,theMSP430F1611hostprocessorwakesupandnds

veralcommandstoinitializeMicroreadtocardemulation

mode(ISO14443B-3)first

prototype,weimplementedonlyafewcommandsthatmadeit

possibletomodifytheIDnumbertoreprentthetemperature

data,becauitwaasytoverifybyreadingitusingthe

ualdata

transferbetweenMicroreadandthereader,additional

rthiswasnot

implementedinthisstageofevaluation.

ypemeasurements

Theaveragecurrentconsumptionwasdefinedforthe

microcontroller,NFCfront-end,andforthewholesystem.

ThemicrocontrollerboardincludedanoptionalLEDthat

dingdistance,

whentheIDnumberwasshownbytheMXStudio,was

Vshowsthe

currentconsumptionvalues,powerconsumptionvalues

calculatedwith3.3Vinputvoltage,andthecorresponding

readingdistances.

ONSUMPTIONOFTHEPROTOTYPE

LEDoffLEDon

Microcontroller4.0mA/13.2mW6.6mA/21.8mW

NFCfront-end0.5mA/1.7mW0.5mA/1.7mW

Wholesystem4.5mA/14.9mW7.1mA/23.5mW

Readingdistance18mm15mm

WhenthereaderisbroughtneartothensorandtheRF

fieldpowersthensor,therearecertaindelaysrelatedto

start-upandinitializationroutinesbeforethemainapplication

ca,thedelayswere

measuredstartingattherisingedgeoftherectifiedvoltage

thatwasfedtoregulator’ayforregulator’s

outputvoltagetostabilize,tookapproximate9mswhilethe

heregulator’soutputvoltagehad

reachedthet3.3V,ittookadditional5msforthe

le,the

start-upproceduretookapproximately11msbeforethe

executionofmainapplicationcode,measurementandcard

initialization,couldbestarted.

Sinceallthecapacitorsinthesystemneedtobecharged

duringstart-up,currentconsumptionatthisstageismuch

,ontheotherhand,tendsto

droptheinputvoltageoftheregulatorandthereforelengthens

thestart-uptime.

Thetimefornsortomeasurethetemperatureand

initializeMicroreadtothecardemulationmodewiththe

cution

timefortheapplicationcodeismainlyduetothedelaysin

initializationcommandexchangebetweenMicroreadandthe

hedelaysmeasuredfromtheUARTlines

(baudrate115200),whenonecommandwasntfromthe

RFpul[ms]Pulinterval[ms]

Nokia32208.7150-310

Nokia61318.6225-230

Picoread43and18020

SNI133280-470

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hostmicrocontrollertoMicroread,andMicroreadrepliedfirst

withanacknowledgementmessageandthenwitharespon

addition,thehostmustacknowledgetheMicroread’s

delayforonecommandexchangewasveralmilliconds,

andresultedtensofmillicondsdelaywhenallthenecessary

instructionsforinitializationwerent.

inUARTcommunication

Accordingtothemeasurements,badonoursimplefull

passivensorprototype,therearesomefundamental

limitationsthatmustbesolvedbeforetheNFCphone

n

concerninthiscawasthestart-upandidentificationtimeof

thensordevicethatwillnotfitin8mstimelimittbythe

benotedthatresultsprentedin

thivaluationwereobtainedusingpreliminaryengineering

material,sotimingsandfunctionalitiesmaybeimprovedwith

theactualproducts.

UsingIDnumber,aswasdoneinourca,isnotanoptimal

procedureforexchangingdatabecauwhilechangingID

ttings,Microreadwillnotmanagetheanti-collisionand

WaitTimeExtension(WTX)gthe

staticIDnumberforMicroread,theidentificationwouldbe

executedrightafterMicroreadwakesup,andWTXprovides

delay(withactiveRFfield)forhostmicrocontrollertowake-

upandstartdataexchange.

Start-uptimeofthepowersupplycanbespeededupby

carefulsizingofbypasscapacitorsandimplementingthe

regulationcircuitthatprovidesfastwake-upandvoltage

prototype,thevoltagemonitoring

wasimplementedusingmicrocontroller’sinternalsupply

voltagesupervisor,whichslowsdownthestart-upofthe

microcontroller.

SION

OnpreviouschaptersacoupleofNFCnsorprototypes,

developedbyVTTandbadoncommercialNFCchips,were

nourexperienceaboutimplementingultra-

lowpowerNFCenablednsors,wearespecifyingthemain

characteristicsofanoptimallyoperatingNFCreceiver

ldhaveanRFpartoperatingatpeer-to-peer

targetmodewithverylowpowerconsumption,butstillit

shouldbeabletostartthecommunicationwiththeinitiator

withinafewmillicondsaftertheRFfieldisdetected.

Peer-to-peertargetmodeissimplertoimplementthancard

emulationmode,whichbothareenergyefficientdata

transmissionmodesbecautheydonotneedtogeneratetheir

ownRFfield;insteadtheyuloadmodulationfordata

therhandthecardemulationmodeis

bettersupportedbyNFCphonesthanpeer-to-peermodeatthe

moment,buthopefullythiswillchangeatthenearfuture.

BecautheNFCchiputilizesonlypassivecommunication

mode,itdoesnotneedtheabilitytogenerateitsownRFfield.

Thissimplifiesnotonlytheinternalstructureofthechip,but

alsotheantennaanditstuningcomponentscanbesimpler.

TheNFCchipshouldhaveatleastfewbytesofinternal

memory,sothatitsIDnumberandparametersforNFC

pshouldbe

abletocommunicatewithinitiatorandaskformoretime

beforeinitiatortimesout,evenbeforethehostprocessoris

poweredon.

InthecaoffullypassiveNFCnsor,theoptimalNFC

circuitryshouldalsohaveinternalpowerregulationwitha

stableoutputvoltagethatisindependentofvariableinput

wersupplyshouldbeable

tostartimmediatelyafterRFfieldisdetected,anditshould

consumeaslittlepoweraspossiblesothatthemaximum

portionofenergyisconvertedfromNFCantennatopower

regulator’putvoltageshouldbestableenough

nsorsrequiremorerobustpowersupplythandigitalcircuits

becaufluctuatinginputvoltagemightaffecttheaccuracyof

thensoroutput.

Therecouldalsobeatemperaturensorintegratedinthe

waytheNFCcircuitrycouldbeudasalowcost

NFCreadabletemperaturensor,withoutneedforany

roptioncouldalsobetoembeda

hostprocessorintothechipinordertomakeitpossibletoadd

externalnsors,ortochangetheoperationofthedeviceby

cessorshouldhave

ultra-lowpowerconsumption,faststart-uptimefrompower-

offstate,andhighclockfrequencycombinedwithfast

connectiontotheNFCchipinordertosavepowerandin

ordertoprovideinstantaneousurexperiencewithoutlong

beddedhostprocessoroptionwould

alsomakeitpossibletoaddNFCconnectivitytoexisting

electronicdeviceswithalittleeffortandlowcosts.

SION

UsingNFCasanenablingtechnologyforwirelessnsors

hasintriguingpossibilities,consideringbothacademic

rearchofambientintelligence,aswellassimpleconsumer

applicationsbadonusingamobilephoneasareaderdevice.

Inthispaper,weprentedpracticalimplementationsofboth

passiveandmi-passiveNFCnsorprototypes,badon

ethefactthata

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simplensorwouldnothavetosupportcomplete

functionalityofNFC,theNFCchipsintendedmainlyforthe

handtmarketcanstillprovideaneconomicallyfeasible

basisfornsorapplicationsinlowtomediumvolumes.

Thetwoevaluatedchipshadcertaindrawbacksinthiskind

ofapplications,531thatwasudformi-

passiveimplementations,consumes100µWinpowersave

onsumptionofthepowerdownperiod

dominates,rototype,the

consumptionwavenmuchhigherforacurrentlyunknown

,thebatterylifeoftheud150mAhbattery

developedmi-passivesolutionsareNFCmobilephone

compatible.

TheMicroreadchipudforpassivensorimplementation

wasanengineeringsampleandtherelateddocumentationwas

ceptofapassive,batteryless

temperaturensorwasprovenusingareaderwithcontinuous

carriersignalgeneration,butwewerenotabletomakethe

solutionNFCmobilephonecompatible,becaudelaysin

communicationbetweentheNFCchipandthehostprocessor

preventedthedevicetoreacttotheshortburstsofmobile

phoneNFCfieldquicklyenough.

Finally,featuresforanNFCcompatiblechipoptimidfor

nsorapplicationswerelisted.

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