3 Replies Latest reply on Jan 9, 2017 5:30 PM by chris_balcom

    Connectivity Info (net name) from layout spice netlist (generated by calibre LVS)

    anandmohancec@gmail.com

      Hi,

       

      I have a layout which has some device with respect to schematic and also some dummy devices that are not in schematic.

      I have generated the spice netlist for layout by running LVS.

      I am making a skill program and For the input, I need the connectivity information of all the devices.

       

      The issue is,

              All the dummy devices has no information about the terminal name (net name) based on the connectivity.

      But all the active devices has the connectivity information in the order of DGSB (Drain Gate Source Bulk).

       

      Please tell me how to get the connectivity information from the spice netlist ?? or

      Is there any switch that I need to enable while running calibre LVS?

       

      Thanks in advance

       

      Regards,

      Satheesh

        • 1. Re: Connectivity Info (net name) from layout spice netlist (generated by calibre LVS)
          chris_balcom

          I would expect the connectivity information for the dummy devices to exist in the netlist extracted from layout. If the dummy devices are connected to ground, they should appear in the netlist extracted from layout as connected to ground. If floating, then that should be the way they appear in the netlist too (with numeric ID's instead of net names usually)

           

          Is it possible that you're looking at a "transformed" version of the layout netlist where the dummy devices were filtered away before comparison so that they could be ignored during LVS comparison?

           

          Sometimes dummy devices are represented on the schematic and they can be checked during LVS instead of ignored.

          • 2. Re: Connectivity Info (net name) from layout spice netlist (generated by calibre LVS)
            anandmohancec@gmail.com

            Hi Chris, thank you for your reply.

             

            I can see the dummy devices in the spice netlist along with the active devices.

            BUt the issue I am facing is, I am not able to identify the connectivity information of drain(D),gate(G),source(S),bulk(B) terminals from netlist

            ie the order in which D,G,S,B has been connected in layout

             

            for example: a)if all 4 terminals are connected to VSS, only VSS is appearing

                                 b)if one terminals is connected to VSS and remaining 3 terminal to another pin(say OUT), then only VSS & OUT will be in the spice netlist, but how can I identify whether D,G,S or B is connected to these nets?

             

            These dummy devices are not in the schematic.

            As you told, the dummy devices are not filtered away since I can see those instance name and bBox in the spice netlist.

             

            Regards,

            Satheesh

            • 3. Re: Connectivity Info (net name) from layout spice netlist (generated by calibre LVS)
              chris_balcom

              The devices won't be filtered from the original netlist extracted from layout such as with calibre -spice. The filtering takes place during LVS comparison so the effect will only be seen in a netlist created after transformation such as with LVS WRITE LAYOUT NETLIST or maybe a netlist created with the CCI Query Server capabilities.

               

              If the first character of the line for the spare device in the netlist begins with the letter "M" then the pin order will be D, G, S, B but the S and D are usually swappable so it might be impossible to tell from the netlist alone which net corresponds to S/D vs D/S in the layout. you might need RVE to visually show exactly which order the nets are connected to the S/D pins if there are two different nets for those pins.

               

              If the first character of the line in the netlist for the device is "X" then you can look at the field of that line near the end showing the name of the called subckt (before the $T and $X, $Y properties). Once you have that name you can go to the "subcircuit description" line for that device and see the order of the D/G/S/B/etc pins there and use that order to understand which nets were connecting to those pins in the "subcircuit call" line that began with "X". the S/D pin swapping is still likely to be a consideration for this type of device too, so you may need to keep that in mind as before.