Table of Contents
Advertisement
• For testability, route the TX and RX pairs for a given port on the same layer and close to each other to
help ensure that the pairs share similar signaling characteristics. If the groups of traces are similar, a
measure of RX pair layout quality can be approximated by using the results from actively testing the TX
pair's signal quality.
• Length matching rules are required on SATA differential signals for optimum timing margins, preventing
common-mode signals and EMI.Each net within a differentialpair should be length matched on a
segment-by-segment basis at the point of discontinuity. Total length mismatch must not be more than
20 mils (0.508 mm). Examples of segments might include breakout areas, routes running between two
vias, routes between an AC coupling capacitor and a connector pin, etc. The points of discontinuity
would be the via, the capacitor pad, or the connector pin.Matching of TX and RX within the same port
and between SATA TX and RX pairs from differential ports is not required. When length matching
compensation occurs, it should be made as close as possible to the point where the variation occurs.
• DO NOT serpentine to match RX and TX traces; there is NO requirement to match RX and TX traces.
In addition, DO NOT serpentine to meet minimum length guidelines on RX and TX traces.
• Recommend keeping SATA traces 20 mils (0.508 mm) from any vias on the motherboard whenever
possible.
８４
Advertisement
Table of Contents
