UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 29883

9.2iSP3 Timing - Changes in the calculation of Discrete Jitter for the uncertainty equations for PLL2DCM and DCM2PLL

Description

When I do timing analysis, I noticed that the calculation of Discrete Jitter (DJ) for the PLL2DCM and DCM2PLL situations has changed. When did this happen?

Solution

From DCM to PLL

Currently Dj is calculated by {Dj(pll) + Dj(dcm)}. However, PLL is very good at filtering out the DCM jitter, so we will change the Dj equation to only include the Dj from the PLL and to ignore the Dj from the DCM. The "Ref Jitter" input will be inputted to the PLL jitter equation.

From PLL to DCM

DCM will pass any PLL jitter and then add in its own jitter. So we will calculate Dj as Dj(pll)+Dj(dcm). The"Ref Jitter" input will used as an input to the PLL jitter equation.

This problem has been fixed in the latest 9.2i Service Pack available at:

http://www.xilinx.com/xlnx/xil_sw_updates_home.jsp

The first service pack containing the fix is 9.2i Service Pack 4.

AR# 29883
Date Created 12/06/2007
Last Updated 01/18/2010
Status Archive
Type General Article