AC-Coupling Between Differential LVPECL, LVDS, …

1 ApplicationReportSCAA059C March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, ( lvpecl ),low-voltagedifferentialsignals( lvds ),high-speedtransceiverlogic(HSTL),a ndcurrent-modelogic(CML).Fromthesefourdi fferentialsignalinglevels, March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, VVOL= 1 VVOH= Vterm + VVOL= Vterm - VReceiverVIH(MAX)VIH(MIN)VIL(MAX)VIL(MIN )DriverVOH(MAX)VOH(MIN)IOH(MAX)VOL(MAX)V OL(MIN)I/O ParametersVCMAC-CouplingListofTables1 TypicalLVPECL, LVDS, HSTL, , LVDS, CML, (common-modevoltage),whiletheaccomponent (voltageswing) , ,Manchester-codeddata,andANSI fiberchannel8 (PHYs)

2 ThatappearinthetelecomindustryareLVDS,LV PECL,HSTL, , , , LVDS, HSTL,andCMLSCAA059C March2003 50 WVCCVCC83W83W130WZ0= , LVDS, HSTL,andCMLO utputsOUTPUTLVPECLLVDSHSTLCMLVOH(Min) (1) (2)VOL(Max) (1)VDDQ= 10%.(2)VCC= 10% , LVDS, CML,andHSTLI nputLevelsINPUTLVPECLLVDSHSTLCMLVIH(Min) + (Max) (Min)310mV200mV400mV400mVTheonlystandard izedPHYisLVDS(TIA/EIA-644A);therefore, ,Figure26,orSeeFigure28 SeeFigure29 Figure27 The150- resistorisusedtobiastheLVPECL output(atVCC ) ,the150- resistorsareusedtobiastheLVPECL output(atVCC ) March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, ReceiverLVPECL DriverVBB!

3 Z = 50oWZ = VZ0= 50W150W10 resistorisusedtodc-biastheLVPECL output(atVCC ) isusedtoterminatethedifferential100- ,whichiswithinthecommon-modevoltagerange ofanLVDS receiver(seeTIA/EIA-644). resistorinFigure5isnotrequired( ,SN65 LVDT33,SN65 LVDT100,andSN65 LVDT122). ,therearetworesistors,the150 (R-bias) to240 .InthecasewherethedifferentialLVPECL outputislargerthanwhattheCMLreceivercant olerate, , LVDS, HSTL,andCMLSCAA059C March2003 50W50 WVCCO ptionalRa = 25 WOptionalRa = 25WZ0= ,iftheLVPECL outputswingis750mVandtherequiredCMLrecei verinputis400mV, ,whichrequiresRa 23.

4 (optional,butshownforcompleteness) resistorisusedtobiastheLVPECL output(atVCC ) .TheveninresistorsofR1andR2areusedtoterm inatethetraceimpedanceaswellastosettheco mmon-modevoltage(VCM= )fortheHSTL receiver, March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, ,CDC111 CDCVF111 CDCLVP110SN65 LVDS101 HSTLR eceiverLVPECLD riverVCCVCC150W150WZ = 50 OWZ = 50 OWNote:For V= V, use R1 = 220 , R2 = 68 CCWWFor V= V, use R1 = 167 , R2 = 71 For V= V, use R1 = R2 = ,CDCLVD110SN65 LVDS100SN65 LVDS122SN65 LVDS31 lvds DriverLVPECLR eceiverVCCVCC83W130W83W130WZ = 50 OWZ = and130 inFigure9,matchesthe50- transmissionlineimpedanceaswellassetsthe common-modevoltage(VCM=2V) , LVDS, HSTL,andCMLSCAA059C March2003 ,CDCLVD110SN65 LVDS100SN65 LVDS122SN65 LVDS31 lvds DriverLVPECLR eceiverVBBZ = 50 OWZ = 50OW50W50We.

5 G .CDCLVD 110SN 65 lvds 100SN 65 lvds 122SN 65 lvds 104 LVDSD riverLVDSR eceiver100WZ = 50 OWZ = V10 kW10 ( Differential ) March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, ,CDCLVD110SN65 LVDS100SN65 LVDS122SN65 LVDS104 lvds DriverLVDSR eceiverVBBZ = 50 OWZ = ,SN65 LVDS100 CDCLVD110SN65 LVDS104 lvds DriverCMLR eceiverZ = 50 OWZ = 50 OWVCC10 kW10 , resistorsareonlyrequirediftheCMLreceiver isnotself-biasedandmayvaryformonevendort oanother;seethemanufacturer' , pull-upresistorsarerequiredtoterminateth etraceandbiastheSN65 CML100outputstage, , LVDS, HSTL,andCMLSCAA059C March2003 ,CDCLVD110SN65 LVDS100SN65 LVDS104 LVDSD riverHSTL ReceiverR1R2R1R2Z = 50 OWZ = 50 OWVCCVCCNote.

6 For V= V, use R1 = 220 , R2 = 68 CCWWFor V= V, use R1 = 167 , R2 = 71 For V= V, use R1 = R2 = , ,thenR1andR2are100 each(50 equivalent) (seethenoteinFigure15)R1andR2shouldbecho sensuchthattheirparallelcombinationmatch esthetransmissionlineandthemid-pointisse ttothecommon-modeoftheHSTL receiver(VCM= ). March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, .g .SN 65 CML 100 CMLD riverLVPECLR eceivere .g .CDCLVP 110 CDCVF 111 CDC 111Z = 50 OWZ = , ,SN65 CML100 VBBR1R1 LVPECLR eceiverCML V50W50WZ = 50 OWZ = 50 OWAC-CouplingThe50- incasetheCMLoutputstagelosses,inaddition tothePCBlosses,aretoohightomeettheminimu mdifferentialinputvoltage(VID) ( ),thatis, , , LVDS, HSTL,andCMLSCAA059C March2003.

7 G .SN 65 CML100 CMLD riverLVDSR eceivere .g .SN 65 lvds 104SN 65 lvds 33 CDCLVD 110Z = 50 OWZ = 50OW50W100W10 V10 , ,SN65 CML100 VBBR1R1 lvds ReceiverCML DriverZ = 50OW50WZ = incasetheCMLoutputstagelosses,inaddition tothePCBlosses,aretoohightomeettheminimu m(voltageinputdifferential(VID) (VBB) ;therefore, pull-upresistors,inFigure20,arerequiredt odc-biastheSN65 CML100andsource-terminatethetransmission line,whileotherCMLdrivershaveintegrated5 0- pull-upresistors,whichdonotrequiretheext ernal50- resistorsareonlyrequirediftheCMLreceiver isnotself-biasedandmayvaryfromonevendort oanother.)

8 Seethemanufacturer' March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, ,SN65 CML100 CML DriverCMLR eceiverZ = 50OW50W10 VZ = V50 WVCC100W10 kWR1R1R2R2 CML DriverHSTL , ,CDCLVP110Z = VVCCVCC50 WNote:For V= V, use R1 = 220 , R2 = 68 CCWWFor V= V, use R1 = 167 , R2 = 71 For V= V, use R1 = R2 = 100 CCCCWWWZ = ,the50- (VCM= ). whentheCMLoutputstageandthePCBlossesaret oohightomeettheminimumvoltageinputdiffer ential(VID) , LVDS, HSTL,andCMLSCAA059C March2003 ,SN65 CML100 CML ,CDCLVP110 HSTL ReceiverCLK0 CLK0Z = VZ = ,CDCLVP110 CDCVF111 CDC111 HSTL DriverLVPECL ReceiverVBBZ = 50OW50WZ = ,thesplit50- resistorsareusedtoterminatethetraceimped anceaswellassetthecommon-modevoltage(VCM =2) (CLK1pair)orLVPECL input(CLK0pair) ;nevertheless, March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL.

9 G .CDCLVD 110SN 65 lvds 100Z = 50OW100W10 VZ = 50OW10 ,CDCLVD110SN65 LVDS100 lvds ReceiverVBBHSTL DriverZ = 50OW50WZ = V50W50W50 WAC-CouplingHSTL signalsareusuallyterminatedto(VTT=Vref= ). , (minimum), (maximum) , ( )andtheCDCLVD110( ) , LVDS, HSTL,andCMLSCAA059C March2003 ,SN65 CML100 CMLR eceiverHSTL Driver100WZ = 50 OWZ = 50OW10 kW10 kWVCCHSTLD riverHSTLR eceiver50 WVBIASZ = 50 OWZ = 50OW50 WAC-CouplingThewidecommon-modeinputsrang e( ) .resistorisnotincludedon-chip, resistorsareonlyrequirediftheCMLreceiver isnotself-biasedandmayvaryformonevendort oanother,seethemanufacturer' ( ).

10 Analternativeis100 acrossthedifferentialpairorasplit50 (VTT=Vref= ). resistorisusedtobiastheLVPECL output( ) TheveninresistorsofR1andR2areusedtotermi natethetraceimpedance(theLVPECL output)andtosetthecommon-modevoltage(VCM = ) March2003 RevisedOctober2007AC-CouplingBetweenDiff erentialLVPECL, LVDS, HSTL, = 50OW150W150 WVCCVCCZ = 50 OWNote:For V= V, use R1 = 220 , R2 = 68 CCWWFor V= V, use R1 = 167 , R2 = 71 For V= V, use R1 = R2 = , (equivalent50 ) ,R1andR2shouldbechosensuchthattheirparal lelcombinationmatchesthetransmissionline andthemidpointissettothecommonmodeoftheH STL receiver(VCM= ).