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How to reversely perform transient simulation?

Baiyuzhong

     I have a circuit with serveral transistors and wish to perform backward transient simulation, i.e., for a given final condition for each node, wish to guess/calculte the initial node voltage. Seems that in cadence transient simulation setup it doesn't allow the inital time to be less than the final time. So I'm wondering  anybody know how to do this? Thank you very much.

Parents

  • Well, this is not possible, and I'm sure we wouldn't implement such a capability. For a start, there are too many assumptions that time goes forward, and some components are not modelled via ODE (eg delays, nport, transmission lines). I suspect with a huge amount of work it might be feasible but one big problem would be how you would solve the end point that you are starting from. Right now we can do that with a dc operating point which works by finding a solution with all the capacitances and inductances removed, but for an arbitrary end point that you'd want to go backwards from, you'd have to solve for potentially part charged capacitances and inductances without being able to work out how you got there. I think the elements involving delay would be a problem too. 

    Regardless of this, I seriously doubt it would help you understand anything about convergence.

    So no, you can't do this and there is no prospect of this being implemented.

    Regards,

    Andrew 

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  • Well, this is not possible, and I'm sure we wouldn't implement such a capability. For a start, there are too many assumptions that time goes forward, and some components are not modelled via ODE (eg delays, nport, transmission lines). I suspect with a huge amount of work it might be feasible but one big problem would be how you would solve the end point that you are starting from. Right now we can do that with a dc operating point which works by finding a solution with all the capacitances and inductances removed, but for an arbitrary end point that you'd want to go backwards from, you'd have to solve for potentially part charged capacitances and inductances without being able to work out how you got there. I think the elements involving delay would be a problem too. 

    Regardless of this, I seriously doubt it would help you understand anything about convergence.

    So no, you can't do this and there is no prospect of this being implemented.

    Regards,

    Andrew 

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