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Setting Up An Analysis
Transient Noise Analysis
Run the simulation with the default accuracy up to 2.9μ, then tighten the tolerance
(VNTOL and RELTOL set to 1e-6).
The plot of the VCO control node is shown in Figure 6-18 (blue curve). It shows the
steady-state being reached at about 4μs.
Figure 6-18. VCO Control Node - Steady State Reached
2. The following commands restart a transient noise analysis from the previously saved
steady-state, and plot the output of the PLL circuit.
.tran 0 100u
.noisetran fmin=0 fmax=2GigaHz tstart=6u nbrun=1 mrun nonom
.plot tran V(CP_VCNT)
.plot tran V(VCO_OUT)
.restart pll.sav
The following actions are performed:
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Run a transient noise analysis on the PLL circuit up to 100μs, starting from the
steady-state store in the pll.sav file at 6μs. Noise sources are specified between 0 and
2GHz.
One noisy run is performed, without nominal simulation, in an MRUN
configuration.
Two simulation plots are requested: The VCO control node and the PLL output
node.
Eldo® User's Manual, 15.3 261