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 Regarding spare cells 

Last post Thu, Jul 19 2012 8:19 AM by Scrivner. 2 replies.
Started by Ganga111AtFPS 18 Jul 2012 02:08 AM. Topic has 2 replies and 1552 views
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  • Wed, Jul 18 2012 2:08 AM

    • Ganga111AtFPS
    • Top 500 Contributor
    • Joined on Fri, Jun 29 2012
    • Hyderabad, Andhra Pradesh
    • Posts 21
    • Points 545
    Regarding spare cells Reply

    HI,

    After routing at the stage of filler cells adding to the design::

    can we add all spare cells in the design instead of filler cells. ofcourse filler cells will be used for N-well continuity between standard cells.

    But why dont we use spare cells instead of fillers..

    While fabricating the chip the fabricator should fabricate the spare cells(at transistor level) like std cells at that time also we'l have N-well continuity, then why dont we prefer spares instead fillers??

    What will be the draw back if we use spares in empty places of design??

    Can some one please explain....

     

    Regards,

    Gangadhar

    • Post Points: 35
  • Wed, Jul 18 2012 6:29 AM

    • fitz
    • Top 150 Contributor
    • Joined on Wed, Aug 4 2010
    • Kanata, Ontario
    • Posts 56
    • Points 745
    Re: Regarding spare cells Reply

    Leakage current, compare the leakage current on a filler vs. standard cell. The lower tech nodes tend to fill first with large decoupling caps then the smaller filler cells.

    Shawn 

    • Post Points: 5
  • Thu, Jul 19 2012 8:19 AM

    • Scrivner
    • Top 100 Contributor
    • Joined on Thu, Oct 9 2008
    • Ridgeland, MS
    • Posts 75
    • Points 1,475
    Re: Regarding spare cells Reply

     Using standard cells in place of fillers may also cause some extra routing congestion because the inputs of each spare cell will need to be routed to ground.

    Also, note that decap cells have power leakage as well.

    • Post Points: 5
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Started by Ganga111AtFPS at 18 Jul 2012 02:08 AM. Topic has 2 replies.