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Using final conditions as initial conditions with (non) periodic voltage sources

david73

I want to use a final conditions file from one simulation/test as a initial condition/node set for another simulation/test

My test bench has some periodic signals (square waves) and some non-periodic signals (power supply is ramped in the TB)

Regarding periodic signals, what would happen if the first simulation ended on a certain phase, and the second simulation starts at a different phase, but i try to use the final conditions from the first as a initial condition for the second? It seems that would be a problem. Is there any solution to this (besides trying to make the first sim end on the correct phase)? Obviously, with non-periodic signals, this problem is even worse

  • Andrew Beckett

    Initial conditions and nodesets are applied in a similar fashion - but the effects are slightly different. In both cases the voltages in the ic/nodeset file are applied via a series resistance (default 1 ohm, set by the rforce option) - or rather a Norton equivalent but that's not critical here. So doesn't completely force the node, but pulls it towards the voltage (the impedance is to allow other driving signals to work, and to avoid a loop of rigid branches by having voltage sources in parallel). In the case of a nodeset, this is done and when it reaches convergence, the nodesets are removed and it continues trying to converge (so it's likely the effects of a competing nodeset will be nullified). In the case of an initial condition, once converged, it then proceeds with the transient. So what will happen is that if that final condition is based on sources at a different phase or value, the initial condition will conflict with those and so the results may be a little strange until the effect of the initial condition settles out.

    Andrew.

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