Cadence and Agilent ADS RFIC Design Tutorial

T.P. Weldon
Copyright 2010


Overview

This is a simple tutorial for using Agilent ADS, Cadence, and our custom libraries to design RFIC's.  The libraries will greatly simplify your effort.

In the following, you will be supplied with a Cadence library of IC layout components along with a companion schematic/simulation library for Agilent ADS.  Using these two libraries will save you many hours of time.  If you design a circuit using these library components, you will be able to place all of your integrated circuit components in 5 minutes, automatically.  After component placement, you will only need to wire the components together.


Preliminary tips and notes:
  • Save yourself from wasting many hours: Use our custom Cadence library along with the companions Agilent ADS library
  • Use subcircuits wherever  you intend to repeatedly use a circuit.  In this way, you will only have to do the layout once.
  • If you plan to use an inductor, read section 8 below for workarounds.
  • In naming your files, avoid the use of hyphens,  use undercscores instead.
  • There should be only one ground in the entire design, at the top level connected to pin 30 of the padframe.  There should be no ground in any subcircuit, use a pin with a name such as "mysubcktgnd" in any subcircuit.
  • Do not name any subcircuit pins "vdd" or "gnd", since these are reserved system names/keywords.  Instead, give your subcircuit pins names such as "abcAmpGnd" and "abcAmpVdd."
  • All pins should be "InputOutput" type.  Avoid using "Input" or "Output" type pins.
  • You must copy the BSIM3 models into your test/simmulation schematics from the tpw-IFamp-sub-transTest schematic provided in the ADS library.
  • Use the standard component values in the libraries.  For example,  you need a 250 ohm resistor and it is not in the library, use two 500 ohm resistors in parallel.  Only in extreme circumstances should you consider using custom components.  Ask the instructor before you use any custom components.<>
  • Do not forget to add the "ptap" substrate contacts at your pin30 ground pin.  These are needed to ground the substrate of your integrated circuit. 


  • 1. Download and install the Agilent ADS library

    Use this Agilent ADS library for entering schematics for all circuits that will be fabricated on your integrated circuits. 
    In your schematics, only use the components included in the following library.

    To minimize problems and confusion with prior projects,
    you may want to move all old ADS projects and folders to a folder named "old."

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    2. Download and install the Cadence library


    Use this Cadence library for entering layouts for all circuits that will be fabricated on your integrated circuits.   Each component in the Cadence library corresponds to a component in the ADS library, and will be automatically created without you needing to enter every component layout by hand.
    In your layouts, only use the components included in the following library.

    !!! STRONGLY RECOMMENDED: !!!
    To minimize problems and confusion with prior projects,
    you may want to move all old Cadence projects, libraries, and folders to a folder named "cadence/NCSU/old"
    and open Cadence and run MenuBar::File::DeleteLibrary to remove the old libraries from the LibraryManager list.

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    3. Example schematic and simulation using the library

    The schematic created in this section will later be exported for layout in Cadence.
    In your schematics, only use components from the Agilent ADS library that was installed in Section 1 above.
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    4. Exporting your ADS schematic to IFF format  for layout


    The schematic created in Section 3 will be exported for layout in Cadence.
    Make sure that your ADS project directory "xyz"_ami05_Fall2010_prj and Cadence directoriy have the same name before proceeding.
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    5. Importing your ADS schematic IFF file to Cadence  for layout

    The IFF file created in Section 4 will be imported for layout in Cadence.
    Make sure that your ADS project directory "xyz"_ami05_Fall2010_prj and Cadence directory have the same name before proceeding.
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    6. Schematic-driven layout in Cadence 

    The IFF file created in Section 4 will be imported for layout in Cadence.
    Make sure that your ADS project directory "xyz"_ami05_Fall2010_prj and Cadence directory have the same name before proceeding.
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    7. Exporting your design in cif format for MOSIS fabrication

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    8. Inductors


    9. Other workarounds and tips



    10. Other helpful websites

  • http://www.eda.ncsu.edu/wiki/NCSU_EDA_Wiki
  • http://www.eda.ncsu.edu/wiki/NCSU_CDK
  • http://www.eda.ncsu.edu/wiki/NCSU_CDK_download
  • http://www.ece.umd.edu/~dilli/research/layout/cadencetutorial/cadencedemo9.html
  • http://www.cadence.com/support/university/ww_usp.aspx
  • http://www.ece.nmsu.edu/vlsi/cadence/CADENCE%20Manual.pdf



  • STOP HERE

    STOP HERE



    The following  methods are not required for our class,
    they are used in full-custorm layout instead of using our library components.


    Exporting ADS Schematics to Cadence

  • DO NOT DO THESE STEPS, IF YOU ALREADY LOADED cadence_ami06partlibFALL07 IN A PREVIOUS LAB
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  • Open the schematic IFamp-sub2-export-iff which only contains the symbol for the circuit as below:
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  • To export the schematic to cadence in iff format, click MenuBar::File::Export in ADS, and export as type iff, as below
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  • Click the MoreOptions button, and check that the options show overwrite iff, and  3 of 4 checkboxes are checked, and default library name should be ami06partlibFALL07, schematicHeriarchy includes currrent design, projects, and NO library parts (the library parts are already in ami06partlibFALL07). The options should appear as below:
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  • After exporting the iff file, it should be somewhere in your ADS directory tree, typically the same directory as the schematic. Copy this file to your cadence/NCSU directory.
  • Before running cadence icfb to import the iff file, you must first have this line somewhere in your .cdsinit file: load("/afs/uncc.edu/coe/unix/opt/ads2006/links/tools/iff/cadence/composer/mdsinit.il")
  • Run Cadence, and you should see the IFF->importIff option in the icfb menu-bar (in the icfb text-window not the icfb file window). Click the IFF menu bar button, select the iff file to be imported as below.
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  •  Check/activate the three "do not" buttons, and click OK to convert. In the pop-up, attach to existing techfile, attach to the proper library (ami06), as illustrated in the three panes below:.
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  • If all goes well, you should be see the new library cadenceExample1_prj in Cadence along with the library cell IFamp-sub2-export-iff as shown below.

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  •  In Cadence, open the schematic of your top-level Cell IFamp-sub2-export-iff as shown below

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  • In Cadence, open the schematic of your next-level Cell IFamp-sub2 as shown below

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  • After you open the schematic, check the cellview: MenuBar::Check::Cellview.  Hopefully, no errors. 

  • To check the warnings, MenuBar::Check::FindMarker and double-click any warnings in the pop-up

  •  Also remove power supplies and any ADS-specifice items such as variables, harmonic balance boxes, transistor models, power supplies, etc.

  • Next create the layout cellview by selecting the low-level cell IFamp-sub2 in Cadence LibraryManager andMenuBar::File::New::CellView.  And choose Tool=Virtuoso as below:
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    Copyright © 2010 T. Weldon