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DFF Hold/setup and jitter

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mouzid

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Hello edaborders,

I have two questions about jitter and dffs working condition.
1- If a dff has a hold time of 60 ns setup time of 70ns. Can it work with a clock signal with a 30 ps peak to peak jitter ?

2- If two dffs (like discribed above) are such that each one is synched with a clock. The two clocks are synchronous and have 30 ps peak to peak jitter. Suppose there is no delay in signal propagation. Is that case equivalent to the case where the two dffs are synched with the same clock signal that has a 60 ps peak to peak jitter of 30 ps peak to peak jitter ?

Thanks.
 

1. Depends on the frequency, no?
 

    mouzid

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jbeniston said:
1. Depends on the frequency, no?

Sure !
I'm sorry to forget to say that the dffs are able to work well with a perfect (no jittered) 2 GHz clock signal.

What if this clock is jittered as discribed ?

Feel free to participate ! :D
 

It depends how much slack there is. If there is 0 slack at 2GHz, then you add 30ps jitter, you will get violations. However, if there is 50ps slack, and only 30ps jitter, then it will be fine.
 

jbeniston said:
It depends how much slack there is. If there is 0 slack at 2GHz, then you add 30ps jitter, you will get violations. However, if there is 50ps slack, and only 30ps jitter, then it will be fine.

As far as I know, slack is related to synthesis constraints. My dff is designed at transistor level. I characterized them and determined hold/setup time by simulation.
 

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