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1 TITLE: PCI-SIG ENGINEERING CHANGE NOTICE OCuLink Cable Spec ECN DATE: March, 0 AFFECTED DOCUMENT: OCuLink.0 SPONSOR: Part I:. Summary o the Functional Changes Alex Haser (Molex), Jay Neer (Molex) The IL/ itted IL requirements have been clariied. The language o this portion o the spec has been reworked to eliminate conusion and provide uniormity in the subsections included in the ollowing document.. Beneits as a Result o the Changes The signal integrity requirements necessary or OCuLink compliance have been clariied. The method or calculating itted IL has been simpliied. The equations or limit lines have been redeined to report values as losses (positive values).. Assessment o the Impact This section o the spec has been made easier to ollow and is thereore less likely to misinterpret.. Analysis o the Hardware Implications Connectors and cables must adhere to the ully speciied signal integrity requirements described in the ollowing text.. Analysis o the Sotware Implications None, this change does not aect sotware. Part II: Changes are relected in Sections. through.. (begins on the next page).

2 0. Mated Cable Assembly Electrical Speciications The OCuLink cable assembly contains insulated conductors terminated in a connector at each end or use as a link segment between host boards. This cable assembly is primarily intended as a point-to-point interace between host boards using controlled impedance cables. All mated cable assembly measurements are to be made between TP and TP with CCB test ixtures, which includes a connector mated to either end o the cable assembly. CCB test ixtures are to be removed beore comparing measured perormance against the speciications listed in this section. It is recommended measurements be de-embedded using a TRL calibration (see Section. or more inormation on de-embedding). All requirements are to be met when analyzed in an Ω reerence rame. The mated cable assembly speciications are based upon twin axial cable characteristics. Table - provides a summary o the cable assembly characteristics and reerences addressing each parameter. Limits apply to. GT/s,.0 GT/s, and.0 GT/s data rates and are written in terms o baud requency. Baud requencies are. GHz, GHz, and GHz or the. GT/s,.0 GT/s, and.0 GT/s data rates, respectively. Note that plots show loss (positive values). Table -. Mated Cable Assembly Dierential Characteristics Summary Description Reerence Value Unit Maximum dierential insertion loss.. Equation - db Minimum dierential return loss.. Equation - db Minimum dierential to common-mode return loss.. Equation - db Minimum dierential to common-mode conversion loss minus insertion loss.. Equation - db Minimum common-mode return loss.. Equation - db Minimum MDNEXT loss.. Equation - db Minimum MDFEXT loss.. Equation - db Maximum total cable assembly, Lane-to-Lane skew (Sc).. 0. ns 0... Characteristic Impedance and Reerence Impedance The nominal dierential characteristic impedance o the cable assembly is Ω. The dierential reerence impedance or cable assembly must be Ω.

3 0... Mated Cable Assembly Dierential Insertion Loss The dierential insertion loss o each pair o a mated OCuLink cable assembly, in db, must be less than the maximum limit deined in Equation -, as illustrated in Figure -.. GT/s,.0 GT/s, and.0 GT/s: Equation - ILCable() = or 0.0 GHz b GHz b ILCable() is the maximum mated cable assembly insertion loss, in db Acceptable Region Figure -: Maximum Mated Cable Assembly Insertion Loss This insertion loss limit is intended to accommodate cables up to m long (using awg).

4 0... Mated Cable Assembly Dierential Return Loss The dierential return loss o each pair o the mated OCuLink cable assembly, in db, must be greater than the minimum limit deined in Equation -, as illustrated in Figure -.. GT/s,.0 GT/s, and.0 GT/s: 0 db or 0.0 GHz GHz Equation - RLCable()= { ( ) db or GHz < b GHz b RLCable() is the maximum mated cable assembly return loss, in db Acceptable Region Figure -: Minimum Mated Cable Assembly Return Loss

5 ... Mated Cable Assembly Dierential to Commonmode Return Loss The dierential to common-mode return loss o the mated OCuLink cable assembly, in db, must be greater than the minimum deined in Equation -, which is illustrated in Figure -.. GT/s,.0 GT/s, and.0 GT/s: 0 Equation - DCMCCable() = 0 ( ) or 0.0 GHz b GHz b DCMCRL() is the minimum mated cable assembly dierential to common-mode return loss, in db Acceptable Region Figure -: Minimum Mated Cable Assembly Dierential to Commonmode Return Loss

6 Mated Cable Assembly Dierential to Commonmode Conversion Loss minus Insertion Loss The dierence between the mated OCuLink cable assembly dierential to common-mode conversion loss and the cable assembly insertion loss, in db, must be greater than the minimum limit deined in Equation -.. GT/s,.0 GT/s, and.0 GT/s: Equation - DCMC-ILCable() = 0 db or 0.0 GHz b GHz b DCMC() ILCable() is the mated cable assembly dierential to common-monde insertion loss, in db is the mated cable assembly dierential insertion loss, in db... Mated Cable Assembly Common-mode Return Loss The common-mode return loss o the mated OCuLink cable assembly, in db must be greater than the minimum limit deined in Equation -.. GT/s,.0 GT/s, and.0 GT/s: Equation - CMRLCable() = db or 0.0 GHz b GHz b CMRLCable() is the minimum mated cable assembly common-mode return loss, in db

7 0... Mated Cable Assembly Crosstalk Crosstalk between dierential pairs inluences the data signals and any subsequent loss and jitter budgets. All system board and cable assembly designs must properly account or any crosstalk that may exist among the various pairs o dierential signals. Crosstalk is due to coupling through a channel, either at the near-end (NEXT) or at the ar-end (FEXT). The total contribution rom all aggressors on a particular victim is captured by the multidisturber or powersum crosstalk. The NEXT loss that couples within a channel is rom Lanes that transmit data in the opposite direction as the victim Lane. Thereore, MDNEXT loss on a receive Lane must be summed across contributions rom the our transmit Lanes at the near end o the mated cable assembly, yielding our aggressors total or a our-lane interace. Similarly, the FEXT loss that couples within a channel is rom the Lanes that transmit data in the same direction as the victim Lane. Thereore, MDFEXT loss on a receive Lane must be summed across contributions rom the three remaining receive Lanes at the ar end o the mated cable assembly, yielding three aggressors total or a our-lane interace. Equation - provides the calculation or MDNEXT loss; Equation - provides the calculation or MDFEXT loss. 0 0 Equation - Equation - i= MDNEXT() = 0 log 0 0 NL i()/0 or 0.0 GHz b GHz i=0 b MDNEXT() is the multi-disturber near-end crosstalk loss at requency NLi() is the NEXT loss at requency o victim-aggressor combination i, in db i is the victim-aggressor pair (0 to ) i= MDFEXT() = 0 log 0 0 FL i()/0 or 0.0 GHz b GHz i=0 b MDFEXT() is the multi-disturber ar-end crosstalk loss at requency FLi() is the FEXT loss at requency o victim-aggressor combination i, in db i is the victim-aggressor pair (0 to )

8 The MDNEXT loss and MDFEXT loss summed on each receive Lane o a mated OCuLink cable must be greater than the limits deined in Equations - and - respectively. These limits are illustrated in Figure -.. GT/s,.0 GT/s, and.0 GT/s: 0 Equation - MDNEXTCable() =.. log 0 ( ) db or 0.0 GHz b GHz b MDNEXTCable. GT/s,.0 GT/s, and.0 GT/s: is the minimum mated cable assembly MDNEXT loss, in db Equation - MDFEXTCable() = log 0 ( ) db or 0.0 GHz b GHz b MDFEXTCable is the minimum mated cable assembly MDFEXT loss, in db Acceptable Region Figure -: Minimum Mated Cable Assembly MDNEXT Loss and MDFEXT Loss

9 0... Lane-to-Lane Skew The time delay across a cable assembly at any point is measured using zero crossings o dierential voltage o the compliance pattern, while simultaneously transmitting on all physical Lanes. The compliance pattern is deined in the PCI Express Base Speciication. The skew or a mated cable assembly is quantiied as the dierence between the longest and shortest time delays measured or a given assembly. The maximum skew permitted or. GT/s,.0 GT/s, and.0 GT/s OCuLink cable assemblies in 0.ns.... Within-Lane Skew Maximum within-lane skew is not speciied in this speciication in the time domain. Within-Lane skew is instead controlled in the requency domain by means o the restrictions on dierential-to-common mode return loss and dierential-to-common mode conversion loss minus insertion loss.