SIwave is a power integrity and signals integrity tool. ZoScan is one of the most important tools in SIwave and will be discussed in this article.
ZoScan is a necessary tool to scan large PCB boards with hundreds and thousands of lines, extract the impedance of these lines, and quickly identify any violation. The setup for the Zo Scan tool is so simple.
Figure 1: Zoscan solver 4th icon from the left
SIwave should not be used to build PCBs. While this is possible, it is not the best way to utilize SIwave. SIwave can import the following type of CAD files:
Figure 2: Import dialog box in SIwave
SIwave extracts lots of information from the CAD file, for example, the stackup, the materials, the components, and the nets. The model is ready to be solved.
Any process in SIwave: DC, PI, SI, or radiation starts by selecting a solver. Once a solver has been selected, SIwave generates a dialog box that looks like a form. The user needs to check the form and fill up the missing information.
Here, for example, SIwave populates the dialog box with all the existing structures in the model. I can select some of the lines, or I can solve them all. SIwave uses advanced techniques that can solve all the lines very fast. So I choose to solve them all.
Figure 3: ZoScan dialog box
Notice here that SIwave only selected the traces. Anything classified as a power plane SIwave does not put in the table.
Now in the table, I see all the trace categories, Single, differential, and extended. Make sure to check them all. In the nominal Zo, one will find the number that SIwave expects to calculate. To change many lines, select the rows, then use the entries at the bottom of the table to change them all in one shut.
In addition to the nominal, enter the warning and the violation thresholds. It will help later to identify fast the bad sections. The default numbers are 10% and 20%. The user can change them to any number.
At the bottom, Enter the Frequency for calculation. So SIwave does not calculate the characteristic impedance for all the frequencies, just at one frequency.
Again under the Frequency, SIwave is asking if it has to check also the short lines. Their existence will make it difficult for the user to focus on the long ones. So decide but do not make it zero.
And now we are ready to solve.
- Examining the solution:
- Impedance plot
The first result is the impedance on all lines. Turn off all the nets.
Figure 4: Impedance plot
Zoom in and hover the mouse over any line to see the values at any point. One can also change the scale. Double-click on the scale and modify the scale. Select a log scale if there is a large variation. One can select which layer to display.
If the user is examining the impedance and would like to know which line is this? Activate the trace option in all layers. Now one can see the original nets, zoom in, and identify the net.
- Violations plot
The second information is the warning/violation plot.
Figure 5: Impedance violations
One can zoom in very fast on bad sections—the ones in red, the worst of all, then on the orange ones. One can also have this information in a table.
Figure 6: Violations report
Show all, show only violations, or show only warnings. One can also edit the entries. Just click on Edit Nominal Impedance and Thresholds:
Figure 7: Violations and warning parameters
One can also generate the report and export it.
Figure 8: Violations and warning exported report
So lots of things the user can check and verify fast with the ZoScan.
To modify any trace, then just click on the trace, select the Center Line Edit, then modify the coordinates and the width of each section.
Figure 9: Trace modification
- Debug the solver:
View the profile. This is important when comparing different solutions of the same package. The user may need to use high accuracy option instead of a balance option. In the ZoScan setup dialogbox, choose other options, then select Optimum accuracy. It will take longer, but better results are expected.
Figure 10: Profile report
The user can also look at the simulation profile to see what accuracy was used in the solution:
Figure 11: Solver setup
