Although its true that too large a drive might kill the xtal, that is not usually the determinator of max drive current in a precision oscillator xtal. A key issue is ageing. Excessive overdrive makes the xtal frequency drift over time. A second issue is the creation of anomalous frequency variations over temperature that can't easily be compensated out.
An, arguable, more convenient alternative to setting node initial conditions to speed startup is to simple set the initial inductor current of the xtal inducter e.g. to form a line:
LXTAL 1 2 1m ic=1.5ma
In SuperSpice, you just set it in the inductor setup dialog.
In standard spice you also need to set UIC (use initial conditions). not sure how LTSPice handles this.
To get an accurate value requires running a sweep of initial values to find the correct value, typically running a deQed circuit to speed up that evaluation. What looks like a steady state amplitude, isn't. It still takes the time associated with its c1/L to stabilise.
Yes.
It is indeed an excellent example of a mathematically chaotic system. The fact that a simulation will repeat itself exactly, with the same data does not make the system non chaotic. Indeed, the predictability of the apparent randomness is, arguable, the key feature of chaotic systems. The classic example being the rediscovery of chaos theory when Edward Lorenz noted a difference in results for what he initially thought was an identical simulation.
Oh dear... "Don't believe just because a computer was involved" includes "be careful about the data" . Data is what drives a computer
The models are never 100% accurate, and neither is the simulator, even if the models were 100% accurate. Spice, now get this, has a reltol, vntol, chgtol and an abstol, additionally it has a gmin. These create errors... Now....
In order to simulate high Q xtal oscillators (c1=0.3fF), especially embedded into larger circuits one might well need to put a clamp across the inductor. This is because operating voltages across the the inductor may be 100kV, and whilst searching for the solution, the iterator might start generating voltages of 1000s of MV. If not clamped, the large span of voltages can cause convergence failure. Typically numbers need to be restricted to about
12-13 digit spans.A two diode series clamp using a spice default gmin=1p across the inductor will totally collapse the phase response so that the system won't oscillate. Reducing gmin can cause convergence failure for other parts of the circuit.
1 Tohms is too low a resistance!The point here, is that the simulator itself has limitations independent of the accuracy of the models that can cause it to fail. Its not just the models that cause accuracy problems.
-- Kevin Aylward