188.8.131.52. R-Tiles Features and Capabilities 184.108.40.206. R-Tile Design Layout Examples 220.127.116.11. Landing Pad Cut-out Optimization of AC Coupling Capacitor 18.104.22.168. R-tile HSSI Breakout Routing in BGA Field Area and MCIO connector Pin Area 22.214.171.124. AC Coupling Capacitor Placement Around MCIO Connector 126.96.36.199. PCIe Gen5 Add-in Card Edge Finger Breakout Design Guidelines
188.8.131.52. AC Coupling Capacitor
The layout design of AC coupling capacitors can impact high-speed channel performance.
- Use a 0402 or 0201 size capacitor for a smaller parasitic and smaller footprint.
- Place the AC coupling capacitors at the device end or connector end. Do not place them in the middle of the trace routing.
- Keep the placement of the AC coupling capacitors on the two lines of a differential pair symmetrical, make sure that the fan-in and fan-out routing of the capacitors is symmetric, and make sure the line lengths on both sides of the capacitors are matched.
- Similar to the connector landing pad, optimize the cut-out size under the capacitor pad using a 3D EM simulation tool for your specific stackup and capacitor pad size. Cut the direct, next-layer ground plane of the capacitor pad.
Figure 14. AC Coupling Capacitor Layout
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