Stats

  • Locked Locked
  • Replies 2
  • Subscribers 125
  • Views 13463
  • 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

Spectre: TRAN results slightly differ according to which outputs are saved

dontpanic

Hi! I noticed in the TRAN simulation of a 4GHz clock buffer that the calculated jitter at the output differs slightly depending on which outputs are saved. If I choose to save nothing but the output clock, I get ~17fs; if I save also a drain current of one of the devices in a diff pair in the DUT, I get ~18fs, and saving the currents of both devices gives ~19fs.

I double-checked the netlists produced in all cases, and indeed the only differences are the "save" statements.

What could be causing this? Reducing the maxstep from 1ps to 0.1ps seems to solve the problem, but I was expecting that for a given maxstep the results should be consistent irrespective to the outputs saved, shouldn't them?

I'm using Spectre 17.1.0.307.isr6 64b

Thanks and regards, Jorge.

Parents
  • Andrew Beckett

    Hi Jorge,

    Could you contact customer support over this? My guess is that the addition of the current saving is causing an iprobe to be inserted in the circuit (inside the simulator) which alters the matrix and means you are getting a slightly different solution. I would expect that the solution is still within the simulator tolerances, but I can't really be sure without us seeing the example in more detail.

    Regards,

    Andrew.

  • dontpanic
    in reply to Andrew Beckett

    OK Andrew, I'll file a case to have this checked further!

    Thanks and regards, Jorge.

Reply
  • dontpanic
    in reply to Andrew Beckett

    OK Andrew, I'll file a case to have this checked further!

    Thanks and regards, Jorge.

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.