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length matching

Yuva09

What is Dynamic and static length matching? with respect to Relative propagation delay and total length match 

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    Introducing a phase shift between the two legs of a differential pair changes the timing of the signal at the crossing point at the receiver. If the phases are left mismatched for a long time, the common mode voltage is generated, causing certain EMI issues.

    Therefore, for high-speed signals, designers tend to match the lines as soon as the mismatch occurs.

    To achieve this, Allegro PCB Editor uses “dynamic phase matching” in which the phase is checked as you route.

    While static phase matching is also an option available in Allegro PCB Editor, in this type, the check is at the end of routing. PCB engineers tend to correct any issue by matching the length of one leg at one end, by comparing it with the other leg.

    In these cases, the velocities of the common mode and differential mode signals are different, as is the loss between the differential and common modes. If the mode conversion is low, the amount of deterministic jitter is small too.

    You can find more about this in the following article:
    Article (20491912) Title: Impact of static and dynamic phase matching for differential pairs in serial link designs
    URL: support.cadence.com/.../ArticleAttachmentPortal

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