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Peak and average IR drop analysis mode

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Hello,

I am not sure about what means peak and average IR drop mode analysis in Encounter. What of these two analysis modes should be considered for power plan optimization?

I have a small block design (5K gates) operating at very low frequency (640 KHz) and there is a big difference between the results of these two analysis modes:

  • worst IR drop average analysis: 9.8035e-05 v

  • worst IR drop peak analysis: 4.3088e-01 v

Is average analysis frequency dependent? But voltage drop is not event dependent and so can cause timing problems also at low frequencies?

Thanks in advance.

 


Originally posted in cdnusers.org by clsantos
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  • Hi Eng Han,

    That is the point! In my case the average power is very low because of very long period. Please, consider figure 1.

    I think there are switching activity only in a period equal to the critical delay within a clock period. The average current and so the IR drop during this critical delay period will be higher than the average IR drop over the entire clock period. So, this higher IR drop during this short period can provoke timing violations.

    Is a good practice to consider a clock period equal the critical delay only to evaluate this effect (not for power estimation)?

    Regards,

    Cristiano.
Reply
  • Hi Eng Han,

    That is the point! In my case the average power is very low because of very long period. Please, consider figure 1.

    I think there are switching activity only in a period equal to the critical delay within a clock period. The average current and so the IR drop during this critical delay period will be higher than the average IR drop over the entire clock period. So, this higher IR drop during this short period can provoke timing violations.

    Is a good practice to consider a clock period equal the critical delay only to evaluate this effect (not for power estimation)?

    Regards,

    Cristiano.
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