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https://designers-guide.org/forum/YaBB.pl Other CAD Tools >> Unmet Needs in Analog CAD >> Sensitivity-driven design https://designers-guide.org/forum/YaBB.pl?num=1121619087 Message started by Ken Kundert on Jul 17th, 2005, 9:51am |
Title: Sensitivity-driven design Post by Ken Kundert on Jul 17th, 2005, 9:51am In http://www.designers-guide.org/Forum/?board=circuit;action=display;num=1100690630 Stephan suggests that the simulator should be able to perform a sensitivity analysis to determine which nodes are most sensitive to layout parasitics. That seems like a very useful little feature than none of the vendors offer. -Ken |
Title: Re: Sensitivity-driven design Post by sheldon on Sep 23rd, 2005, 9:50am Ken, Could you clarify the type of sensitivity you are looking for? For example, Virtuoso's VAVO/VAEO give you the sensitivity to parastic resistance, IR drop, and the sensitivity to electromigration failure, em analysis. Were you looking for sensitivity of circuit performance to layout parasitics? Best Regards, Sheldon |
Title: Re: Sensitivity-driven design Post by Ken Kundert on Sep 23rd, 2005, 10:56pm Nice. But VAVO/VAEO? It sounds more like a 70's rock band than a CAD tool. are we not men? we are VAVO! are we not men? V-A-E-O -Ken |
Title: Re: Sensitivity-driven design Post by Andrew Beckett on Sep 24th, 2005, 3:27am And strictly speaking VAVO/VAEO don't tell you the sensitivity to the IR drop/EM issues. They allow you to analyse the circuit and find out what the IR drop is at various nodes in the circuit, or find EM failures. Not quite the same thing as seeing a sensitivity (IMHO). Still pretty useful though! I liked Ken's views on the names though! They're just acronyms, because as engineers we don't like long marketing type names. They actually stand for: Virtuoso Analog Voltagestorm Option Virtuoso Analog Electronstorm Option Rather boring really. I preferred the rock bands ;) Andrew. |
Title: Re: Sensitivity-driven design Post by sheldon on Oct 3rd, 2005, 5:35am Andrew, Guess it is a matter of perspective. Since the tool provides IR drops plotted on the "extracted" layout, effectively, it provides you the sensitive regions in the layout. If you always follow good design practices, differential signal paths, star grounds, routing bias currents, etc, then the regions with noisy power supplies are most likely regions where there are supply noise issues. Back to the original question, there was a technology from OpMaxx --> Fluence --> IMS --> Credence called DesignMaxx that calculated the sensitivities of the circuit matrix using the adjoint matrix. This technology would allow you to quickly calculate the sensitivities of the output to the nodes in the circuit. However, aren't there some issues with this approach? For example, do all parameters have the same sensitivity to layout parasitics? Or do you need to do a sensitivity analysis for each design parameter? How are you going to capture and use the layout constraints, particularly, if the each parameter is sensitive to the parasitics at different nodes? To look at the problem the other way around, why aren't there tools for analog virtual prototyping? Doesn't it make more sense to concurrently design the circuit and the layout? Maybe it is just me but it seems like the best solution to this problem is to be proactive, i.e., use analog virtual prototyping. Best Regards, Sheldon P.S. For more information on the DesignMaxx approach, see IEEExplore and search for limsoft, that was the name of the Analog BIST tool DesignMaxx was integrated into. |
Title: Re: Sensitivity-driven design Post by weber8722 on Nov 18th, 2011, 1:16am Hi again Ken Kundert wrote on Jul 17th, 2005, 9:51am:
I think in RF design or general analog design it would be good to see how much e.g. the gain at a certain frequency changes (or phase-margin or S12, etc.) from the presence of a parasitic C (or R or L) on a specific net. In Cadence Parasitic-Aware Design flow there is the option to sweep parasitics, but only globally. Recently we made a 5GHz LNA design, and the performance changed dramatically in RLC extracted view! So a designer need to find out, in which parts of the design the routing has the most impact. Bye Stephan |
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