Hi,
I am designing a simple high Q 16M XTAL + INV oscillator in MMSIM 14.10.576 (I think this is the latest version?) using PSS with the shooting engine. The reason I went for the shooting engine rather than the hb is that there is a significant amnount of distortion in the waveforms. On top of that I found that the hb engine gives convergence problems in some of my corners (typically 2 or 3 of my 22 corners will fall over). These errors can be fixed by tightening reltol and vabstol as recommended in the SpectreRF documentation, however, doing so will make other corners not converge!
Therefore I switched to the shooting engine which I was hoping would give me reliable results over all coners. Unluckily, I find even though the simulation always converge, I get strange results 1 corner (very low amplitude steady state). Changing simulation engine parameters will not help, the results will always be very similar. I checked the behaviour of the design in that particular corner with a transient noise simulation and the oscillator reaches the expected steady state with a normal amplitude. What it is more when I use the hb engine in that corner the results are the right one :s
So I guess my questions are:
- Any insight in why the shooting engine is giving the wrong steady state solution? What can I tweak to improve solution accuracy?
- Is there any way to rerun a set of corners in which several BUT not all the analysis in a test have failed AND add the results together to the corners Job? I know it is possible to rerun erroneous corners but in order to be able to do so all the analysis should have failed. So far I am putting a note to the corners Job but it is messy
Many thanks!
Alberto