Simulating a circuit which is partly extracted and partly schematic

Discussion in 'Cadence' started by praveen thomas, Oct 30, 2003.

  1. gurus,
    In my mixed signal design, I use integrated inductors in my
    analog part. Is it possible to extract inductors ?

    If not,
    I have a model for the inductors in schematic. So while simulating the
    circuit in Cadence Hspice, can i have the other portion of my circuit
    extracted while keeping the inductors in schematic itself.

    if the above is possible, what are the steps to do it?

    thanks for your patience,
    K. Praveen
    praveen thomas, Oct 30, 2003
  2. Hi,

    In Assura 3.1 it is possible to extract Inductors
    with the commands 'centerTapINDPackge' or 'spiralINDPackage'.

    In Assura 2.0 or Diva it is also possible to work around it.
    The example is for Assura 2.0

    use the extractDevice command to extract your inductor e.g

    ;; differential inductor metal 8 tap
    ;; recognition layer diffInd8

    m8IndOut( "PLUS" "MINUS" ) m8IndTap( "TAP" )
    cellView( "ldiffm8 ivpcell refLib" )

    ;; saveProperty( diffInd8 "trun" "5" )

    For the parameters it is a little bit tricky and it works
    only if you have fixed values for your model. Either you use
    a model which can not vary the parameters, then
    'cellView( "ldiffm8 ivpcell refLib" )' points to the inductor
    cell and the extracted cell view will contain the 'ivpcell'
    for the cell and in the netlist there will be the same model as
    you us in the schematic with the default values for the parameters
    or you save defined parameter value with the 'saveProperty' command.

    It might be also possible to use 'measureParameter' and
    'calculateParameter' parameter to get the exact inductor parameters you
    want, for a model which can vary the parameters,
    but this I believe is not that easy for an inductor.

    In any case the inductor has to be recognized by the extraction
    which means you have to have an extract command for the inductor
    in you extract rule file.

    Regards Bernd
    Bernd Fischer, Oct 30, 2003
  3. praveen thomas

    S. Badel Guest

    yes it's possible to use the schematic models.

    the problem is, your extractor won't recognize the
    inductors and hence, won't create components for them
    in the extracted view (they will be treated as 'wires').

    what you should do then is create a cell for each inductor
    with one layout view and one schematic view.
    in the layout view put the layout, and in the schematic
    view add one inductance component.

    ok, next, on the layout view add a property to your cell
    called ivCellType and set its value to "macro".
    this will tell the extractor (provided you use diva)
    not to flatten the cell. your extracted view will
    know contain one cell for each inductor.

    now what's gonna happen during netlisting : the netlister,
    when it will encounter one of your inductor cells, will
    try to find a alternate view for it. the only one it will find
    will be the schematic view (be sure to have schematic
    in your switch/stop view lists), in which it will find an
    instance of an inductor, which can be netlisted.

    i guess it should work this way.

    S. Badel, Oct 30, 2003
  4. hey thanks bernd for your kind reply.

    but i don't have access to Assura, so i'm not fimilar with the
    commands you give.
    is there other way to do it in analog artist itself.

    otherwise can i modify the netlist generated after extraction, so that
    the part which discribes the inductors, replaced with that of the
    schematic model i have for the inductor.

    in that case what should be my steps.please guide me

    thanks for your help,

    K. Praveen.
    praveen thomas, Oct 30, 2003
  5. Hi,

    I believe Stephane's reply shows the better approach for your
    For details refer to the Diva docs for 'Macro Cell' extraction.

    Regards Bernd
    Bernd Fischer, Oct 31, 2003
  6. hey thanks stephane and bernd for your kind guidance.

    I'm trying stephane's way of do it.
    I also came to know recently that using Hierarchy editor we can
    simulate these type of combined shematic and extracted views of the
    same design. for which we have create a view name called "config" for
    the top level cell we want to simulate.

    Thanks for your help,
    K. Praveen.
    praveen thomas, Nov 1, 2003
  7. that's right, you create a config view and
    you can choose which view will be used
    for each cell, kinda override the switch/
    stop view lists.
    if you're doing this you'll have to select the
    config view of the top cell as design
    in analog artist.
    anyway, this wouldn't solve your extracting
    problem. as long as you don't have extract
    rules for inductances, the extracter will
    skip them. that would mean you could
    only simulate schematic.

    give us feedback, praveen.

    Stéphane Badel, Nov 1, 2003
  8. yes, without extraction rules, we can simulate only the extracted
    other part of the circuits keeping inductor model in schematic.

    another way is that, Extract with the inductor in the layout and
    generate a netlist with analog artist, then use some inductor
    modelling sofware like ASITIC or SISP and get a extracted netlist from
    them only for the inductor.

    then identify where in your analog artist netlist the inductor is,
    replace that one with that of the special software netlist and run it.

    i haven't tried this one, but i don't think this too will be that

    K. Praveen.
    praveen thomas, Nov 3, 2003
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