Intel® Stratix® 10 High-Speed LVDS I/O User Guide

ID 683792
Date 7/13/2021
Public

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3.2.4.1. RSKM Equation

The RSKM equation expresses the relationship between RSKM, TCCS, and SW.
Figure 29. RSKM Equation


Conventions used for the equation:

  • RSKM—the timing margin between the clock input of the receiver and the data input sampling window, and the jitter induced from core noise and I/O switching noise.
  • Time unit interval (TUI)—time period of the serial data.
  • SW—the period of time that the input data must be stable to ensure that the LVDS receiver samples the data successfully. The SW is a device property and varies according to device speed grade.
  • TCCS—the timing difference between the fastest and the slowest output edges across channels driven by the same PLL. The TCCS measurement includes the tCO variation, clock, and clock skew.
Note: If there is additional board channel-to-channel skew, consider the total receiver channel-to-channel skew (RCCS) instead of TCCS. .

You must calculate the RSKM value, based on the data rate and device, to determine if the LVDS receiver can sample the data:

  • A positive RSKM value, after deducting transmitter jitter, indicates that the LVDS receiver can sample the data properly.
  • A negative RSKM value, after deducting transmitter jitter, indicates that the LVDS receiver cannot sample the data properly.
Figure 30. Differential High-Speed Timing Diagram and Timing Budget for Non-DPA Mode This figure shows the relationship between the RSKM, TCCS, and the SW of the receiver.


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