DDR3_Interface_Review_and_Design_Considerations (1).pdf

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1、DDR3InterfaceReviewandDesignConsiderationsDesignConsiderationsOctober,2007Dr.WilliamWuShen:QimondaNorthAmericaDr.WilliamWuShen:QimondaNorthAmericaContents•DDR3ZQCalibrations•DDR3AC/DCOutputMeasurementLevels•DDR3OutputDriverVoltage/ThermalSensitivities•DDR3InputSignalSet-upandHoldTiming:–Theac/dc

2、de-ratingsarebasedonslewratesand/ornon-lineartransitionsRON/RTTCalibrationsDDR3SDRAMspermitcalibrationoftheRONandRTTvaluesoverPVT(process,voltageandtemperature)variations,viaexternallytriggeredcalibrationcommandsZQCL&ZQCS.ThesecommandsactivateaDRAMinternalZQcalibrationengine,whichusesanexternalr

3、esistorof240+/-1%tolerance(RZQ)asacalibrationreference.RZQ:•TheRZQresistorisconnectedbetweentheSDRAMZQpinandground.•TheRZQresistorcanbeusedwithasingleDRAMperresistororbesharedbetweenapairofDRAMs(e.g.inadualrankDIMM).ZQCalibrationCommands•TheZQCalibrationcommandisusedtocalibrateDRAMRon&ODTvalues

4、overPVT(process,voltageandtemperature)variations.TherearetwoZQcommandtypes:1.ZQCL:Takesalongertimetocalibrate–e.g.atinitialization2.ZQCS:Takesrelativelylesstimetoperform–e.g.periodiccalibrationsCommandTruthTableforZQCalibration:FunctionAbbreviationCKECS#RAS#CAS#WE#BA0-A13-A12-A10-A0-A9,BA3A15BC#

5、APA11PreviousCurrentCycleCycleZQZQCLHHLHHLXXXHXCalibrationLongZQZQCSHHLHHLXXXLXCalibrationShortZQCalibrationDescriptions•ZQCLisusedtoperformtheinitialcalibrationduringapower-upinitializationsequenceorRESETsequencea.Thiscommandmaybeissuedatanytimebythecontrollerdependingonthesystemenvironment.b.Z

6、QCLcommandtriggersthecalibrationengineinsidetheDRAM,andc.Oncecalibrationisachieved,thecalibratedvaluesaretransferredfromthecalibrationenginetoDRAMIOwhichresultsinupdatedRonandODTvalues.•TimingdifferencesbetweenthefirstcalibrationandasubsequentcalibrationafterRESET:a.ThefirstZQCLcommandissuedafte

7、rresetisallowedatimingperiodoftZQinittoperformthefullcalibrationandthetransferofvalues.b.AllotherZQCLcommandsexceptthefirstZQCLcommandissuedafterRESETareallowedatimingperiodoftZQOper.•ZQCSisusedtoperformperiodiccalibrationst