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# AR# 44228

## Description

What is the equation for the Clock Uncertainty for PLL/DM/MMCM?

## Solution

Following is the equation for DCM Clock Uncertainty:

Clock Uncertainty = ((TSJ^2 + TIJ^2)^1/2 + DJ) / 2 + PE

DCM Discrete Jitter and DCM Phase Error are provided in the speed files for Virtex-4 devices and newer. However, DCM Discrete Jitter and DCM Phase Error are not available in speedprint.

Examples:
INPUT_JITTER [TIJ]: 200ps = 40000ps
SYSTEM_JITTER [TSJ]: 150ps = 22500ps
DCM Discrete Jitter [DJ]: 120ps
DCM Phase Error [PE]: 0ps
Clock Uncertainty: 185ps

Following is the equation for PLL/MMCM Clock Uncertainty:

Clock Uncertainty = ((DJ^2 + TIJ^2)^1/2) / 2 + PE

AR# 44228
Date 12/15/2012
Status Active
Type General Article
Devices
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