COM Express® Carrier Design Guide Guidelines for designing COM Express® Carrier Boards December 6, 2013 Rev. 2.0 This design guide is not a specification. It contains additional detail information but does not replace the PICMG COM Express® (COM.0) specification. For complete guidelines on the design of COM Express® compliant Carrier Boards and systems, refer also to the full specification – do not use this design guide as the only reference for any design decisions. This design guide is to be used in conjunction with COM.0 R2.1. PICMG® COM Express® Carrier Board Design Guide Rev. 2.0 / December 6, 2013 1/218 © Copyright 2013, PCI Industrial Computer Manufacturers Group. The attention of adopters is directed to the possibility that compliance with or adoption of PICMG® specifications may require use of an invention covered by patent rights. 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PICMG® COM Express® Carrier Board Design Guide Rev. 2.0 / December 6, 2013 2/218 Contents 1. Preface..................................................................................................................................8 1.1. About This Document...........................................................................................................8 1.2. Intended Audience................................................................................................................8 1.3. No special word usage.........................................................................................................8 1.4. No statements of compliance..............................................................................................8 1.5. Correctness Disclaimer........................................................................................................8 1.6. Name and logo usage...........................................................................................................9 1.7. Intellectual property............................................................................................................10 1.8. Acronyms, Abbreviations and Definitions Used...............................................................11 1.9. Signal Table Terminology...................................................................................................14 1.10. Schematic Conventions......................................................................................................15 2. COM Express Interfaces....................................................................................................16 2.1. COM Express Signals.........................................................................................................16 2.1.1. Connector Pin-out Comparison.......................................................................................20 2.2. PCIe General Introduction..................................................................................................30 2.2.1. COM Express A-B Connector and C-D Connector PCIe Groups....................................30 2.3. General Purpose PCIe Lanes.............................................................................................31 2.3.1. General Purpose PCIe Signal Definitions.......................................................................31 2.3.2. PCI Express Lane Configurations – Per COM Express Spec.........................................32 2.3.3. PCI Express Lane Configurations – Module and Chipset Dependencies.......................32 2.3.4. Device Up / Device Down and PCIe Rx / Tx Coupling Capacitors..................................33 2.3.5. Schematic Examples.......................................................................................................34 2.3.6. PCI Express Routing Considerations..............................................................................47 2.4. PEG (PCI Express Graphics)..............................................................................................48 2.4.1. Signal Definitions.............................................................................................................48 2.4.2. PEG Configuration...........................................................................................................49 2.4.3. Reference Schematics.....................................................................................................52 2.4.4. Routing Considerations...................................................................................................53 2.5. Digital Display Interfaces....................................................................................................55 2.5.1. DisplayPort / HDMI / DVI ................................................................................................55 2.5.2. SDVO...............................................................................................................................61 2.6. Mobile PCI Express Module (MXM)....................................................................................66 2.6.1. Signal Definitions.............................................................................................................66 2.6.2. Reference Schematics.....................................................................................................68 2.6.3. Routing Considerations...................................................................................................69 2.7. LAN.......................................................................................................................................70 2.7.1. Signal Definitions.............................................................................................................70 2.7.2. Reference Schematics.....................................................................................................73 2.7.3. Routing Considerations...................................................................................................75 2.8. USB Ports............................................................................................................................76 2.8.1. Signal Definitions.............................................................................................................76 2.8.2. Reference Schematics.....................................................................................................77 2.8.3. Avoiding Back-driving Problems......................................................................................80 PICMG® COM Express® Carrier Board Design Guide Rev. 2.0 / December 6, 2013 3/218 2.8.4. Routing Considerations...................................................................................................80 2.9. USB 3.0................................................................................................................................81 2.9.1. Signal Definitions.............................................................................................................81 2.9.2. Reference Schematics.....................................................................................................84