Stats

  • Locked Locked
  • Replies 8
  • Subscribers 90
  • Views 19817
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Peak and average IR drop analysis mode

archive

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
Parents

  • FE's peak IR drop analysis is pseudo dynamic analysis. It uses transition time to calculate instaneous current for IR drop analysis, but it does not consider C effect. It reports the worst IR drop at each wire/instance. The peak worst IR drop is much larger than what is reported in the average mode since transition time is much smaller than the clock cycle.

    To optimize power structure, use the average mode. To reduce peak IR drop, sizing up the power wires won't do the job unless power consumption is small. In this case, decap is needed and VSDG can be used to perform the dynamic IR drop analysis.


    Originally posted in cdnusers.org by elvis
Reply

  • FE's peak IR drop analysis is pseudo dynamic analysis. It uses transition time to calculate instaneous current for IR drop analysis, but it does not consider C effect. It reports the worst IR drop at each wire/instance. The peak worst IR drop is much larger than what is reported in the average mode since transition time is much smaller than the clock cycle.

    To optimize power structure, use the average mode. To reduce peak IR drop, sizing up the power wires won't do the job unless power consumption is small. In this case, decap is needed and VSDG can be used to perform the dynamic IR drop analysis.


    Originally posted in cdnusers.org by elvis
Children
No Data

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.