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DC after Tran

Pirate King

I followed the instructions from the link 9 years ago but it does not work for me now;

How to simulate DC sweep after TRAN? - Custom IC Design - Cadence Technology Forums - Cadence Community

The tran is required for startup of the circuit.

I sequence the DC after tran and on DC options I set readns=spectre.fc and useprevic=ns or yes

I can see the DC log saying that the file is being read and if I open the file the values make sense but back annotation does not show correct startup voltage nodes

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  • ShawnLogan

    Dear Pirate King,

    Pirate King said:
    I followed the instructions from the link 9 years ago but it does not work for me now;

    From my read of this post and your desire to use the final transient point as the DC node voltages for your DC analysis, the advice was to use "readns" - and I am wondering if perhaps you want to use "readic". In addition, as shown on page 20 and 21 of the application note at URL:

    https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1O0V0000091CAfUAM&pageName=ArticleContent&oMenu=People%20who%20viewed%20this%20also%20viewed

    The DC option "force" must be enabled to use the initial condition file. On page 21 it states:

    "Note: The Spectre simulator ignores Initial Conditions of all types in the DC Operating Point analysis and the AC Operating Point analysis unless the force option is set in the DC and/or AC options forms.

    In all DC solutions, when the force option is set, the node is held to the set value throughout the entire DC analysis. In other words, the Initial Condition defines the node voltage used for the DC analysis."

    I may not have correctly understood your question and need Pirate King, but thought I would add my thoughts.

    Shawn

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  • ShawnLogan

    Dear Pirate King,

    Pirate King said:
    I followed the instructions from the link 9 years ago but it does not work for me now;

    From my read of this post and your desire to use the final transient point as the DC node voltages for your DC analysis, the advice was to use "readns" - and I am wondering if perhaps you want to use "readic". In addition, as shown on page 20 and 21 of the application note at URL:

    https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1O0V0000091CAfUAM&pageName=ArticleContent&oMenu=People%20who%20viewed%20this%20also%20viewed

    The DC option "force" must be enabled to use the initial condition file. On page 21 it states:

    "Note: The Spectre simulator ignores Initial Conditions of all types in the DC Operating Point analysis and the AC Operating Point analysis unless the force option is set in the DC and/or AC options forms.

    In all DC solutions, when the force option is set, the node is held to the set value throughout the entire DC analysis. In other words, the Initial Condition defines the node voltage used for the DC analysis."

    I may not have correctly understood your question and need Pirate King, but thought I would add my thoughts.

    Shawn

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