Stats

  • Locked Locked
  • Replies 1
  • Subscribers 125
  • Views 12997
  • 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

matching constraint in extracted view simulation

PBWU

In IC6, device matching constraints are stored as constraint views of a cell. While it works OK with schematic pre-layout monte-carlo simulation, where the constraint views are effective clearly. However, when replacing the cells with PEX extracted views, the same monte-carlo simulation gives different results of matching performance. I think it is because that the constraint views are not connected to the extracted view netlist (instance name change). I wonder if there is a formal method to preserve the constrained instance paths to be exactly the same before and after layout? I realized in IC5, the same issue should exist.  FYI, I am using Calibre PEX.  Thanks. 

Parents
  • Andrew Beckett

    I don't think there's any support for this, although you're clearly not comparing like with like. Typically m-factored devices pre-layout are fully correlated, whereas they aren't post-layout (because each finger is extracted separately, for example).

    In general setting up correlation constraints is not that widely used, because the "mismatch" models from most foundries are actually modelling the remaining local random variation, and are not trying to model systematic effects caused by poor alignment/orientation in the layout - so it's questionable as to the value of setting up correlation coefficients anyway (what should you set the coefficients to, especially when this is not what has been characterised by the foundry). 

    Even if we had implemented some smarts to map devices across to the post layout names (which I don't think we have), it's unlikely that would work with a non-Cadence extractor as there's far less information about the mappings that were performed. 

    Either way, you probably should contact customer support about this.

    Andrew.

Reply
  • Andrew Beckett

    I don't think there's any support for this, although you're clearly not comparing like with like. Typically m-factored devices pre-layout are fully correlated, whereas they aren't post-layout (because each finger is extracted separately, for example).

    In general setting up correlation constraints is not that widely used, because the "mismatch" models from most foundries are actually modelling the remaining local random variation, and are not trying to model systematic effects caused by poor alignment/orientation in the layout - so it's questionable as to the value of setting up correlation coefficients anyway (what should you set the coefficients to, especially when this is not what has been characterised by the foundry). 

    Even if we had implemented some smarts to map devices across to the post layout names (which I don't think we have), it's unlikely that would work with a non-Cadence extractor as there's far less information about the mappings that were performed. 

    Either way, you probably should contact customer support about this.

    Andrew.

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.