SIwave: Everything you need to know about the Crosstalk Scan
SIwave is a power integrity and signal integrity tool. One of the most essential features in SIwave is the Crosstalk Scan, which is the focus of this video. Other features such as the Impedance Scan and TDR Wizard are covered in separate videos. The Impedance Scan highlights defects in traces and grounds by calculating the impedance on each trace. The TDR Wizard identifies discontinuities or defects in transitions on all traces.
Crosstalk Scan Overview
The Crosstalk Scan identifies defects in transitions, grounding, and vias around traces. It highlights areas where traces are not well isolated. While SIwave can be used to build PCBs, it is not the optimal use of the tool. SIwave can import models in various formats such as ADB, IPC, DB++, DXF, and GDS. Upon uploading a file, SIwave extracts information from the CAD file, including stack-up, materials, components, and nets, preparing the model for simulation.
Simulation Setup
- Select the Crosstalk option in the simulation menu.
- Choose the frequency domain for analysis.
- Select a solver: DC, signal integrity, or radiation.
- Fill in the dialog box with existing traces in the model. You can choose to solve all lines or select specific ones.
- Specify limits, warning, and violation percentages to identify weak areas during post-processing.
Understanding Crosstalk
Crosstalk can be categorized into two types:
- Far-End Crosstalk: Travels in the same direction as wave propagation, with contributions arriving simultaneously at the far-end port of the victim.
- Near-End Crosstalk: Requires wave direction reversal, causing contributions to arrive at different times at the near-end port.
The SYZ solver calculates the total crosstalk seen from other traces' ports when a sinusoidal signal is injected into the aggressor trace. The terms KNEXT and KFEX relate to mutual coupling and inductance, providing insights into amplitude and maximum amplitude at each point.
Solver Options
SIwave offers three solver options for accuracy:
- Optimum Speed
- Balanced
- Optimum Accuracy
Start with the balanced option and adjust based on solution speed and model size. Advanced options allow control over meshing, frequency, crosstalk threshold, and coupled lines.
Temperature and Multi-Processing
You can select a temperature that affects trace conductivity and import temperature distribution from iSPEC. Multi-processing options include selecting cores, memory percentage, and specifying local host and port numbers.
Simulation and Results
- Select power planes and traces for simulation.
- Choose a frequency point, such as 10 GHz, and launch the solver.
- Display crosstalk results, focusing on near-end or far-end crosstalk.
- Identify weak areas by zooming into red spots and modifying traces to improve crosstalk.
Time Domain Analysis
The time domain analysis is similar to TDR, requiring specification of rising time, driver, and receiver. Unlike frequency domain, it shows crosstalk from all traces. You can plot multiple curves for comparison and identify worst crosstalk locations.
Advanced Features
SIwave allows plotting of coupled structures, creating reports, and analyzing simulation profiles. The tool provides a comprehensive understanding of model behavior, enabling efficient modifications and improvements.
For further exploration, SIwave offers options like the SYZ solver, crosstalk frequency domain, time domain, and TDR wizard, enhancing the designer's ability to optimize models.
SI Wave: Everything you need to know about the Crosstalk Scan (HD version) SI Wave is a power integrity and signal integrity tool. The Cross Talk Scan is one of the most essential tools in SI Wave and it's the subject of this video. Impedance Scan was explained in another video.
The Impedance Scan highlights defects in the traces and grounds. It calculates the impedance on each trace. The TDR Wizard, discussed in another video, identifies discontinuities or any defects in the transitions on all the traces.
The Cross Talk Scan, which is the subject of today's video, identifies the defects in the transitions and grounds. It highlights areas where the traces are not well isolated. SI Wave should not be used to build PCBs, but it can import various models such as ADB, IPC, or DXF, GDS.
When SI Wave uploads the file, it extracts lots of information from the CAD file, such as the stack-up, materials, components, and nets. The model is then ready to be solved. To start a simulation in SI Wave, select the Crosstalk option and choose the frequency domain.
Any process in SI Wave, whether it's for DC, signal integrity, or radiation, starts by selecting a solver. Once a solver has been chosen, the solver is ready to be used to create a new model. SI Wave generates a dialog box that looks like a form.
The user needs to check the form and fill in the missing information. For example, SI Wave populates the dialog box with all the existing traces in the model. One can select some of the lines or solve all of them. SI Wave uses advanced techniques that can solve all the lines very fast.
Next, specify the limits for each trace. These numbers help to zoom in on the bad and worst areas later on in the post-process. Before proceeding, it's important to understand the meaning of the terms Fixed and Next.
The Fixed term in SI Wave is modified to include the length over the rising time, TR, the rising time. This is a more detailed explanation of the terms KNEXT and KFEX. With these terms, one can calculate the VNEXT and VFEX from the parameters.
Use the other solver options button to decide on the accuracy of your solution. Three options are available: optimum speed, balance, or optimum accuracy. Start with the balanced one. There are more advanced options in the Signal Integrity and Power Integrity advanced tab.
If the custom button is activated, one can use the Signal Integrity, Power Integrity advanced tab to have access to more options and more capabilities within SiWave. One can control the meshing and force the solver to mesh at a specific frequency for the crosstalk scan.
The user can also choose between the two or change the crosstalk threshold and the maximum number of coupled lines. Click on the temperature button to select another temperature that will affect the conductivity of the traces. One can import the temperature distribution from iSpec to the model.
In the multi-processing tab, select the number of cores, the percentage of your memory, whether you have a pool or a pack, of course, the local host and the port number if you need to specify them. Before launching the solver, select a name and specify the transmission lines to simulate.
One can select them all or select a portion of them. After launching the solver, one can look at the results. The first thing to see is the display of the crosstalk. One can show near field or the far end along each path of all the traces that were selected.
The proper way to use these graphs is to first look at the SYZ solver results and look for the traces with the worst possible crosstalk. Then, zoom in on the areas where you have red spots instead of blue. These areas are weak areas. Start modifying and improving things around these areas.
One can also zoom in on any trace while trying to improve the traces or trying to improve the cross. And see which trace is having a problem. One can modify them, add more vectors, delete some of them, or move them away from each other.
The data is being modified, and one can see that the data is being modified. One can also look at the violation. Studying these numbers is very good, but sometimes it's very hard to tell if there are weak points very fast. Especially when you have tens and tens of these traces.
So, what you can do is ask the system to zoom in on the areas that are violating and those who are having a warning. The values that you had in mind for the Next or Fixed don't match, and the delta is higher than a certain percentage.
SI Wave detects which sections of the trace cannot be considered single but rather coupled to other lines. If the cross-talk results show that anything is red, it means SI Wave cannot consider them singles. The coupling between them is too high to be considered singles.
One can create a report and publish it. The profile gives information about how much mesh was used, the CPU used, the memory, and the time it took to solve the problem. In addition to the frequency domain, we also have the time domain.
Again, as you can see, the moment you click the solver, you get a dialog box with all the traces, and you just need to select some of them to be analyzed. The time domain shows the crosstalk from all the other traces.
If you select any one of these bars, it will immediately show you the far end of the line. And you can see the values, exactly like as if you are doing a TDR. From these curves, you can tell the location of the worst possible crosstalk. Then, you can zoom in on this area in your model and fix it.
It's a different way of looking things. In addition to having bars, you can also plot things on the traces. You can display things on the traces, exactly like we did with the frequency domain solve. You can also plot the coupled structures.
These are the lines that SI Wave cannot treat them as single lines. The coupling between them is so high that they are considered coupled lines, not single lines. You can look at the profile and the simulation properties. And there, you will be able to remind yourself with the setup you did.
What is the rising time, the location of the driver, the amplitude of the signal, and all of this setup. SI Wave is a very useful tool for studying the cross talk. The designer will have a better understanding of what is going on inside his model.
He will be able to zoom in on weak sections very fast and modify them and improve them in an efficient way.
