Electrical Analysis Constraints for SI Analysis

From the menu bar, click Analysis > Signal Integrity > Electrical Analysis Constraints. The Electrical Analysis Constraints dialog opens. The Electrical Analysis Constraints dialog shows editable versatile control parameters which influence the simulation/analysis results for crosstalk, network, electromagnetic field, eye-diagram, and SPICE.

EM Solver Run Control Parameters

EM solver run control parameters control running built-in 2-D and 3-D electromagnetic full-wave field solvers. Various numerical analysis schemes such as finite-element and moment methods are employed for the EM solvers. The run control parameters include the lower and upper bounds of frequency points, number of frequency points for output, and frequency sweep type (linear or quadratic).

  • Lower/Upper bound of frequency points (MHz): Specify the frequency ranges for electromagnetic field simulation.
  • Number of frequency points for output: Specify the desired output saving frequencies.
  • Frequency sweep type: Quadratic, Linear.
    • Number of frequency points for output: Specify the number of frequency point for output.
    • Power/Ground plane modeling:
      • Ideal: During analysis, the Power/Ground Plane specified in the layer stackup is regarded as an ideal infinite plane and analyzed.
      • Real: When performing the analysis, it does not refer to the plane information specified in the PCB layer stackup, but searches for the reference plane by using the Net Type information set in Properties/Nets. In transmission line modeling, the reference plane reflects the real shape, not the ideal plane.
    • Consider co-planar coupling with grounds: Include nearby ground traces and planes in the same layer in trace parasitic models for network and net topology analyses.

Waveform/Eye Diagram Analysis Parameters

  • Number of random pulses: Means the number of random pulses excited to the simulating net during the eye diagram analysis.
  • Bit pattern style: Select the numerical method among random, ABS (Artificial Bit Stream) and PRBS (Pseudo Random Bit Stream) for generating the bit sequences. ABS (Artificial Bit Stream) is a method designed to provide a large pattern of bits to show worst case signal transmission quality of the net that would quickly converge the eye diagram. PRBS (Pseudo Random Bit Stream) is the mostly common method deemed as an industry standard.
  • Bit pattern length – if bit pattern style is ABS or PRBS, choose the bit pattern length here.
  • Using the Random bit pattern, state of each bit of bit stream is randomly selected. ABS (Arbitrary (Random) Bit Stream) is a popular random bit stream used to generate eye diagrams. The ABS pattern is designed to provide a large random pattern of bits that would quickly converge to the eye diagram showing worst case tolerances. PRBS (Pseudo-Random Bit Sequence) is another popular bit stream style generating random-like bit sequence created from a specified pattern length. For example, when 2^7 is selected for the pattern length, 127 (2^7-1) unique data words are assembled according to the sequence.

Default Device Models

You can specify default linear model to the parts which does not have simulation model.
  • Linear driver model: shows the default driver model.
  • Linear receiver model: shows the default receiver model.

Crosstalk Analysis Parameters

To extract the coupling parasitic elements and configure the SPICE netlist for the coupled nets, Crosstalk Analysis Parameters should be defined properly which will be involved to calculate the total coupling lengths for all nets included in the PCB by PollEx SI.
  • Max trace coupling distance (MM): The trace segments are located closely within less than this distance will be deemed as coupled by PollEx SI. During finding coupling, PollEx SI find the traces within given distance from selected pivot net (trace).
  • Max number of adjacent signal layers to couple: Coupling distance will be checked not for the neighboring nets running in the same layer where pivot net is running. But also done for the nets running over specified numbers of adjacent layers specified by this parameter which locates above or below to the current layer.
  • Max number of adjacent traces to couple: When there are many coupled nets to a certain pivot net, this parameter limits the maximum number of nets which will be participated in making coupled spice netlist.
  • Max via coupling distance (MM): Specifies the coupling distance between via and pivot trace.

Min parallel length for coupling (MM): Even though two traces are coupled by meeting Max trace coupling distance condition, if the coupled length is shorter than this value, this coupling net segment will be ignored.

Network Analysis Parameters

Network analysis parameters are used to control the frequency-domain analysis for extracting network parameters such as S, Y, and Z parameters. The parameters include the starting and ending frequencies, frequency sweep type (decade or linear), and number of frequency points. The network parameters are calculated at the user-defined number of frequency points when linear frequency sweep is employed. However, when decade frequency sweep is employed, the number of frequency points is assigned to each decade within the frequency range.
  • Starting/Ending frequency (MHz): Denotes the starting and ending frequencies during the network parameters extraction.
  • Frequency sweep type: Specifies the type of frequency variation. Linear or decade should be one of them.

Number of frequency points for sweep type: Denotes the number of observing points of frequency between starting and ending frequencies.

SPICE Run Control Parameters

You can specify the HyperSPICE’s simulation control parameters which will affect the simulation time, accuracy and convergence characteristics.
Parameter Description
ABSTOL Reset the absolute current error tolerance of the program. The default value is 1 Nano-ampere.
CHGTOL Resets the charge tolerance of the program. The default value is 1.0e-14.
GMIN Resets the value of GMIN, the minimum conductance allowed by the program. The default value is 1.0e-12.
VNTOL Sets the absolute voltage error tolerance of the program. The default value is 10 micro-volt.
ITL4 Reset the transient analysis time-point iteration limit. The default is 10.
METHOD Sets the numerical integration method used by SPICE. Possible name is TRAP (or Trapezoidal) or BE (or Backward-Euler). The default is TRAP.
RELTOL Set the relative error tolerance of the program. The default is 0.005 (0.5%).
TRTOL Set the transient error tolerance. The default is 7.0. This parameter is an estimate of the factor by which SPICE overestimates the actual truncation error.
Simulation Temperature(C) Sets the temperature of simulation. Default value is 25.