How to reduce/eliminate PSS convergence errors?

[iVenky]

Hi,

I am running PSS on Cadence Virtuoso for a wide-range Quadrature VCO. I am facing convergence issues sometimes. Sometimes it works. Do you know the reason behind these convergence issues and how to reduce/solve those?

 

[BradtheRad]

* Some simulators insist that there be at least one 0V ground icon in your schematic.'

* Sometimes it helps to add a high-ohm resistor, at any node that the simulator might have trouble with. Tie it to a supply rail, or 0V ground.

* Capacitors and inductors should have a low-ohm resistor inline, to ensure the simulator can calculate a time constant for them, regardless of neighboring components.

 

[pancho_hideboo]

I am running PSS on Cadence Virtuoso for a wide-range Quadrature VCO.
I am facing convergence issues sometimes.
Sometimes it works.
Do you know the reason behind these convergence issues and how to reduce/solve those?

Show me log file.

Can your QVCO satisfy oscillation condition surely ?
Did you confirm initial transient results ?

https://www.edaboard.com/threads/346180/#6

 

[dick_freebird]

PSS requires that you truly have a stable and on-period
solution. If (for example) your tune voltage is still creeping,
is that then true? Maybe the trouble lies with your initial
conditions.

 

[iVenky]

Is it possible for the oscillator to oscillate in transient sim but not in pss sim? It's oscillating in transient sim and I have given enough tstab for the pss sim.

- - - Updated - - -

Show me log file.

Can your QVCO satisfy oscillation condition surely ?
Did you confirm initial transient results ?

https://www.edaboard.com/threads/346180/#6

I will include the log file when I face an error once again. Thanks for your help!