Wednesday, February 08, 2012     Register | Login | Search | Contact Us
     
   
     
     

Many of you already received communications about the move of the Cadence user community into cadence.com. And many of you have already joined, with over 4000 registrations in the first two weeks.

The new Cadence Community enhances the ability of Cadence users to connect and collaborate. In addition to moving the community into cadence.com -- enabling single sign-on for community, Sourcelink and Cadence events -- the new site is organized around nine technology segments, giving you easy access to product information, training, forums and blogs. Some of the new features include:
  • Ability to respond to posts via e-mail
  • Technology-specific blogs
  • Latest Web 2.0 social networking capabilities
  • Public profile options
  • Private messaging
  • Friends lists
Visit the new Cadence Community today at www.cadence.com/community and join the discussions!

Registration note: Due to the scope of the enhancements and the new SSO registration system, we were not able to migrate existing cdnusers.org member accounts. So new registrations are required, but this enables a broader set of functionality we think you'll enjoy.

Forum note: Under the guidance of forum moderators, we have taken the 20+ cdnusers.org forums and consolidated them into 11 forums on the new site. Posts have been brought over so you can leverage that posting history. CDNusers forums will be set to read only starting 7/30, and cdnusers.org will be redirected to the new community on 8/4.

Best regards,
Mike and Tom

Michael A. Catrambone - Steering Committee Chairman
Distinguished Engineer
PCB/Mechanical
UTStarcom, Inc.

Tom Diederich
Cadence Community Manager
Home
Forums
Forums > Custom IC > Custom IC Electrical Design

Subject: schematic and symbol pcells?
Posting to forums is available to community members only.
Login or Register
Rate this topic:
   
Author Messages
m27315
Posts: 24
Online: User is Offline
5/10/2006 3:51 PM  
For analog design, I have not seen too many people make use of pcells for schematics or symbols.

Are you using pcells for schematics or pcells, especially for analog design?  If so, what is the basic function of the pcell?  Why did you choose a pcell instead of a static cell?

Thanks!
adbeckett
Posts: 248
Online: User is Offline
5/10/2006 10:37 PM  
I have created both schematic and symbol pcells. Some examples:

I have a transistor symbol which can either be a 3 or 4 terminal mosfet, controlled by a property on the pcell. If the user chooses 3 terminals, then the 4th terminal is found via an inherited connection terminal on the stopping (e.g. spectre) view - but they don't need to wire it up. If the user chooses 4 terminals then all 4 terminals are present on the symbol.

Another example is a component for driving a bus with a constant value. This has parameters for the value and the bus width. This is implemented with both a schematic and a symbol pcell. The symbol pcell merely changes the terminal/pin to be a bus with variable width; the schematic pcell instantiates a variable number (depending on the bus width parameter) of "cds_thru" components to create connections from either a high input or a low input to the particular bit of the bus - which connection is made depends on the value parameter of the pcell.

Another schematic pcell is for a series-connected resistor. I wanted a resistor with an "s-factor", so that the voltage dependency on a number of series connected resistors could be modelled properly (there are other ways of solving this, but this was more of an illustration). So it divides the resistor value by the s-factor, and places s resistors with that divided value, connected in series.

That's some simple examples of what they can be useful for.

Note with schematic pcells there's no need to create the graphical representation of the schematic - just the connectivity information will do.

Regards,

Andrew.
stevea
Posts: 1
Online: User is Offline
7/27/2006 2:54 AM  
In a previous life, we were working with a process which was yet to be fully qualified, and for which there were no PDKs, so I wrote the pCells for layout and schematics. Using common code between the schematic symbol and layout views allowed me to know the exact dimensions of the component given appropriate parameters (FET width and length, resistor value, capacitor value), from which parasitic effects could be determined and annotated onto the device for netlisting (via CDF parameters) eg. FET AS/AD/PS/PD, resistor parasitic cap, capacitor bottom plate cap, etc. We had very good agreement between schematic simulation and RCX extracted simulation (and final silicon) at and above 6GHz, and our design cycles were tighter because we didn't need to go around the RCX loop as often. With proper parameterized spectre/spice models, or a decent PDK, you don't need to do this. But if you want to work outside those models, nothing beats it. cheers, -steve
Posting to forums is available to community members only.
Login or Register
Forums > Custom IC > Custom IC Electrical Design > schematic and symbol pcells?


ActiveForums 3.6
     
Copyright 2006 Cadence Design Systems, Inc.