10-bit-Driver-IC-Using-3-bit-DAC-Embedded-Operatio

IEEEJOURNALOFSOLID-STATECIRCUITS,VOL.42,NO.12,DECEMBER2007291310-bitDriverICUsing3-bitDACEmbeddedOperationalAmplifierforSpatialOpticalModulators(SOMs)Jin-SeongKang,StudentMember,IEEE,Jin-HoKim,StudentMember,IEEE,Seon-YungKim,Jun-YongSong,StudentMember,IEEE,Oh-KyongKwon,Member,IEEE,Yuen-JoongLee,Byung-HoonKim,Chan-WooPark,Kyoung-SooKwon,Won-TaeChoi,Sang-KyeongYun,In-JaeYeo,Kyu-BumHan,Taek-SooKim,andSang-IlParkAbstract—A10-bitdriverICforlaserprojectionfullhigh-defi-nitionTV(HDTV)applicationsusingaspatialopticalmodulator(SOM)hasbeendeveloped.Forhigh-speeddatatransferbe-tweenthetimingcontrolleranddriverIC,thedriverICadoptsamini-LVDSinterfacethatoperatesupto400Mbps.Toreducethechiparea,adigital-to-analogconverter(DAC)structureincludinga7-bitresistor-stringDACandaunity-gainbuffer,whichhasa3-bitlinearDAC,isproposed.TheareaoftheproposedDACis40%smallerthanthatofthetypical8-bitresistor-stringDAC.ThedriverIC,whichhas546channels,isfabricatedusinga0.35-mCMOSprocess,anditsareais21700m3000m.Themea-suredINLandDNLoftheoutputvoltagesarelessthan0.13LSB,andthesettlingtimeis1.93swith40pFcapacitiveloads.TheoutputvoltagedeviationofthedriverICisachievedas1.3mVbycompensatingthenonuniformityamongoutputchannels.IndexTerms—Digital-to-analogconverter(DAC),driverIC,high-definitionTV(HDTV),spatialopticalmodulator(SOM),10-bitgrayscale.I.INTRODUCTIONTHEspatialopticalmodulator(SOM)isakindofdiffractivespatiallightmodulator(SLM),likeadigitalmicro-mirrordevice(DMD)[1],agratinglightvalve(GLV)[2],oragratingelectromechanicalsystem(GEMS)[3].Fig.1(a)showstheop-ticalmodulationschemeandFig.1(b)showsthesingle-pixelribbonstructureoftheSOM[4].AsshowninFig.1(a),whenamonochromaticbeamisincidentontheSOM,itisdiffractedintomultiplespatial-harmonicorders.Accordingtothepositionofthetopmirrorwithrespecttothebottomsurface,thedif-fractedenergycanberedistributedbetweenthezerothandfirstdiffractionorders.ThisSOMutilizespiezoelectricactuationofanindividualgratinglightmicro-mirrortocontrolthedisplacementbetweenthetopmicro-mirrorandthebottomsurface.Theactuatorcon-sistsofathinstructuralmaterialsupportingaleadzirconiumtitanatePbZrTiOPZTlayersandwichedbetweenthetopandbottomelectrodes.TheSOMdeviceisexpectedasoneManuscriptreceivedApril8,2007;revisedAugust6,2007.J.-S.Kang,J.-H.Kim,S.-Y.Kim,J.-Y.Song,andO.-K.KwonarewiththeDivisionofElectricalandComputerEngineering,HanyangUniversity,Seoul133-791,Korea(e-mail:[e-mail];[e-mail]).Y.-J.Lee,B.-H.Kim,C.-W.Park,K.-S.Kwon,W.-T.Choi,S.-K.Yun,I.-J.Yeo,K.-B.Han,T.-S.KimandS.-I.ParkarewithSamsungElectro-MechanicsLtd.,Suwon443-473,Korea.DigitalObjectIdentifier10.1109/JSSC.2007.908690Fig.1.SOM.(a)Theopticalmodulationschemeand(b)thesingle-pixelribbonstructure.ofthecandidatesasadisplaydeviceforprojectiondisplaybe-causethediffractedenergycanbecontrolledbyvoltagesacrossthePZTlayer.SomeotheradvantagesofPZTdevices,suchasfastresponse,lowoperatingvoltage,andgoodsignal-to-noiseratio,alsosupporttheusageofPZTasadisplaydevice.ASOM-basedlaserrear-projectiondisplaysystemwithfullhigh-definition(HD)format,60Hzframerate,and8-bitgrayscalewassuccessfullydevelopedanddemonstrated[4].Nowa-days,becausecustomersdemandHDTVdisplaysystemsthatcandisplayimageswithmoreandmorenaturalcolors,adisplaysystemwithgreaterthan8-bitgrayscaleisexpected.Therefore,wedevelopedthe10-bitSOMdriver.TheSOMdriverICneedstosatisfynotonlythesamede-signrequirementsofthegeneraldisplaydriverICslikehighimagequality,lowcost,andlowpowerconsumption,butalsosomespecificdesignrequirementssuchasdrivingabilityinashorttimeandaconstantslewrate,whicharediscussedinde-tailbelowbecauseoftheuniquefeaturesinitsdrivingmethod,0018-9200/$25.00©2007IEEE2914IEEEJOURNALOFSOLID-STATECIRCUITS,VOL.42,NO.12,DECEMBER2007drivingconditions,andthephysicalcharacteristicsoftheSOMdevice.Variousdisplaydrivingmethodshavebeenreported.Acontrastenhancementmethodhasbeenproposedtoachieveahighcontrastratio[5]andacolortemperaturecontrolmethodhasbeenproposedtoachievewidecolorgamut[6].Todisplayanimagewithfineandnaturalcolor,manyflatpaneldisplayswhichadoptan8-bitdatadrivingsystemexpandthecolordepththroughframeratecontrol[7].Theframerate-controlmethod,however,worksattheexpenseofhigherframefrequencyorreductioninthedatacontentsorresolution.Therefore,researchtoachieveadatadrivingsystemwhichprovidestrue10-bitorhigherbitsignalvoltagesorcurrentshasbeendone[8].However,itshouldbenotedthatitistoodifficultforthedatadrivercircuitstohave10-bitorhighergraylevels.InthecaseofaSOM,itsminimumdynamicrangeislessthan2.4V.The10-bitSOMdriverIC,hence,mustcontrolitsoutputvoltageaccuratelywithinintervalsofaround2mValthoughitdoesnotneedagammacorrection.Therefore,weneedtohaveaccuratedigital-to-analogconverters(DACs)andaccu-rateoutputbuffers.Moreover,becauseonedatadriverIChasseveralhundredsofoutputbuffersandeachoutputbufferhasitsownoffsetvoltagewhichcomesfromtheprocessvariationsinarandommanner,itmustbeabletoeffectivelyreducethechannel-to-channeloffsetvariationsaswellastheabsoluteoffsetvoltageofitsown.TheDACshouldbearea-efficientbecausethecostofthedriverICdependso