eldo_user

Setting Up An Analysis
Transient Noise Analysis
signal to deviate from its nominal trajectory (phase shift). The consequence is that this
method can suffer from convergence problems or inaccuracy in some applications, such
as those having very non-linear circuits, where noise is not just a perturbation of the
nominal simulation. When convergence is affected a warning is reported, advising you
to use the alternative method by setting the MRUN flag. This method may not be
appropriate for PLLs or Sigma-Delta converter applications. By default, this method is
deactivated when NBRUN=1.
Related Topics
Tip
See “.NOISETRAN” in the Eldo Reference Manual.
Specifying .NOISETRAN Parameters
Transient Noise Analysis Results
Specifying .NOISETRAN Parameters
The .NOISETRAN command is used to control the transient noise analysis of a circuit and must
be used in conjunction with a transient analysis (.TRAN).
Tip
For full description of the .NOISETRAN command and its syntax, refer to “.NOISETRAN”
in the Eldo Reference Manual.
The most important parameters are:
• FMIN and FMAX define the range of the noise frequency band (same function as
FSTART and FSTOP in AC noise analysis). This frequency range may sometimes not
correspond to the noise frequency band at the output of the circuit. For instance, the
band (FMIN, FMAX) does not correspond to the output noise frequency band in the
case of filters, oscillators and mixers that exhibit frequency conversion.
• NBRUN defines the number of noise simulations to perform (those which include the
noise sources). This parameter defines the accuracy of the noise analysis. Care must be
taken when setting the NBRUN parameter as it strongly influences the CPU time used
by the simulation. This parameter is ignored when NONOM is specified to suppress the
nominal simulation; a single noisy run is performed and a warning generated.
• Other options are available for more advanced and more efficient use of the command.
Note
The .NOISETRAN command cannot be used in a netlist together with Monte Carlo
analysis (.MC), except for the specific case of a single run Monte Carlo analysis
specified with the IRUN parameter.
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Eldo® User's Manual, 15.3