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应用于12bit50MHz流水线ADC的MDAC的设计.docx

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应用于12bit50MHz流水线ADC的MDAC的设计 Introduction Modernelectronicsystemsrequirehigh-speedandhigh-precisionanalog-to-digitalconverters(ADCs)toconvertanalogsignalsintothedigitalformforprocessing.ThepipelineADCisapopulararchitectureforhigh-speedconversionwithgoodaccuracy.Toachievehighaccuracy,thepipelineADCrequiresahigh-speed,high-linearity,andhigh-resolutionmagnitudedigital-to-analogconverter(MDAC)asoneofitscriticalcomponents.ThispaperpresentsadesignoftheMDACthatcanbeusedina12bit50MHzpipelineADC. MDACDesign TheproposedMDACdesignusesatraditionalop-amp-basedMDACarchitecture.TheMDACconsistsoftwomainstages,amultiplyingdigital-to-analogconverter(MDAC)andanoutputoperationalamplifier(op-amp).TheinputoftheMDACisadigitalcodefromthepipelineADCfront-end,andtheoutputisavoltagethatdrivesthenextstageoftheADC.Toachievehigh-speedsignalprocessing,theMDACneedstohaveafastsettlingtimeandlowdistortion.Thefollowingsectionsdescribethedetaileddesignofthesetwokeycomponents. MultiplyingDAC ThemultiplyingDACisthefirststageoftheMDAC,whichconvertsthedigitalcodetoananalogvoltage.ThemajordesignchallengeofthemultiplyingDACistoachievehighlinearityandlowdistortion.Toovercomethischallenge,theMDACusesaparallel-connectedarrayofswitchedcapacitorstoproduceavoltageproportionaltotheinputdigitalcode.Thesimplevoltagedividermethodisusedtocontrolthechargeinjectionofeachcapacitor,whichleadstoaproportionaloutputvoltage. TheresolutionofthemultiplyingDACisdeterminedbythenumberofcapacitorsinthearray.Inthisdesign,weusea12-bitmultiplyingDACas4096capacitorsinthearray.Eachcapacitorofthearrayisdesignedwithequalvaluestoachievealinearresponse. OutputOperationalAmplifier TheoutputoperationalamplifierisusedtoboostthevoltagefromthemultiplyingDACtotherequiredoutputlevel.Theop-ampplaysacrucialroleintheMDACdesignbyprovidingsufficientgainfortheoverallsystem,reducingnoise,andensuringthattheoutputvoltagesettlesaccuratelyandquicklywithinagivensettlingtime. Theop-ampusedinthisdesignisahigh-gainamplifierwithlowinput-offsetvoltage,lownoise,andh