vlsi delay calculation

Discussion in 'The Projects Forum' started by mainstreamacademics, Jan 19, 2012.

  1. mainstreamacademics

    Thread Starter New Member

    Jan 19, 2012
    2
    0
    Hello.

    I want to know how delay is calculated for a digital circuit. Most journals/papers state delay values when they are comparing circuits.. how is this done?
     
  2. ifixit

    Distinguished Member

    Nov 20, 2008
    639
    108
    Hi mainstreamacademics,

    I've been through this process a few times, but not for awhile. The answer to your question has a long answer... here is a short one.

    Google: asic delay calculation

    e.g. http://asic-soc.blogspot.com/2008/09/delays-in-asic-design.html

    Synopsis is a company that supplies software to do this on a large scale. Delay information is supplied by the company that will be manufacturing the IC.

    Regards,
    Ifixit
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,035
    3,242
    You can predict it with an analog simulator using accurate models for the IC circuitry, or you can measure the delay in an actual circuit with a high speed oscilloscope.
     
  4. mainstreamacademics

    Thread Starter New Member

    Jan 19, 2012
    2
    0
    Hey guys. Thanks a lot. That really helped. Two questions-

    1) I want to calculate delay for a digital circuit. crutschow.. : Why should i use an analog simulator.. the most accurate way to get delay would be from the layout of the digital circuit, right? is there freeware to do it?

    2) Also, i want to calculate area of a layout design..? how do i do that? any free tools available?
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,035
    3,242
    1) No. How do you calculate the delay from the layout only? It's more than just the propagation delay of the traces. You need the transistor characteristics along with the layout parasitics to put in an analog (Spice) simulator, which then simulates the delay.

    2) If you have tools to do the layout, then from that you can calculate the circuit area. That's very specialized software and I don't know of any free tools for that.
     
  6. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Is it a relatively small circuit, that one of yours? If it contains only a few digital components we might figure something out theoretically. Post your circuit, if you have one.
     
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