SIwave: Unleash the Power of the PI Solver

SIwave: Unleash the power of the PI solver (SD) Hi, today we will be talking about the PI solver inside SIwave. We need to perform power integrity if one die or chip on the board withdraws variable current, such as drivers and power amplifiers.

Most basic chips withdraw variable current, which contains a DC value and a spectrum of frequencies. Consequently, we need to understand the response of the power distribution network (PDN) along the spectrum. You start working with SIwave by uploading a .cad file.

Do not try to build your PCP using SIwave; although you can, it's not the right way to use it. You can upload the file using any of the forms shown in the table. Before you start using SIwave, it's highly recommended that you go through your schematic and study it well.

It will save you lots of time. We have a PCB board with many power planes and chips. When you select them all and solve them together, nothing prevents you from doing that. However, we will focus on only one of them.

We will put all power planes in red because SIwave solves and reads them in a different way when solving for power integrity. The next few minutes are for people who are new to PI analysis and PI tools like SIwave. SIwave understands the language of nets when it uploads any structure.

It looks for nets and what we call single nets. Single nets are electrically connected structures without the use of any external component. Single nets cannot be disconnected. When you want to analyze a power plane, you need to identify its nets.

It could have just one net or many nets, like the one you see here. If there are many, they should be connected using resistors, inductors, or capacitors, or what we call passive components. This will construct what we call a passive link.

If integrated or discrete components exist along the path, SIwave will treat the passive links separately. SIwave is a linear numerical tool that solves only passive links. This is important for you to understand because it changes the way you read the schematic when you read the schematic.

You look for all the passive links in the power planes and document them. After solving the model, if you have something like this with passive links, you can take the results and cascade the different passive links of a power plane using a circuit tube.

Circuit tube is available also with SIwave and comes for free with SIwave. Now, if you want to analyze a net or a passive link and then see any other links of the Ethernet line, you can use it in totality. This is useful for limited communication in series.

When you upload SI Wave from an ECAD, SI Wave uploads all kinds of information from your CAD file, including the stack-up, layers, material, thicknesses, components, and connections between the different structures. The only thing missing to be able to solve a problem is to assign ports.

To assign ports, click this button and get the introductory panel. Click on PI for a PI analysis. SI Wave starts by selecting the solver you want to use. Once you select the solver, SI Wave opens a dialog box with as much information as possible.

It expects you to review the assumptions it made and fill up whatever is missing. SI Wave presents a list of all the nets that exist in the board, whether they are power planes or even RF lines or control lines or anything. You can select a power plane to solve.

To assign ports, SI Wave populates this section with all the connections to the components, whether they are passive or non-passive components. You can hide what we call parallel components, the RLC, using this button, and you are left with the ones that are in series or integrated components.

For our case, we have a power plane with a couple of integrated components. We are interested in analyzing the connection between the voltage regulator and the CPU. So we put a port at the CPU and a port at the voltage regulator.

You can save your setup specifically if you have so many power planes or passive links. This is useful when you upload the same model later on. Now, we do configuration. Configuration simply means assigning ports and the necessary setup to start the problem.

SI Wave goes through the nets, checks them in a physical way, and makes sure there are no violations in terms of nets joined or disjoined. Once you are done, you go to simulate. You are ready to simulate. As simple as that. That's how easy it is to use SI Wave. Now, let's talk about the results.

The first result we got from doing SI analysis is the S parameters, which gave us the return loss, insertion loss, and crosstalk. You can select to see them all or display one at a time. The S parameters are normalized to 0.1 ohm. However, we don't know what's the impedance of our power planes.

Consequently, we know that these results are not reliable. You cannot trust them. Because you have to normalize the port to the right impedance that matches your power plane.

To make sure that the power planes' return loss is extremely good, like minus 40 or minus 50 across the band of interest, you can use the Z parameters. The Z matrix is simply the Z matrix extracted. Now, the Z matrix is the Z matrix extracted.

The Z parameter looks at the impedance of the power plane itself. We focus mainly on the Z11 and Z2, which represent the real impedance of the power planes. That impedance is what is going to affect the drop in the voltage due to the change in the current.

Once you get the best possible return loss, you can tell that the crosstalk results can be trusted. You can also do sensitivity analysis. This allows you to see how sensitive your parameters, whether S parameters or Z parameters, are to the change in the impedance of the components.

You can calculate the sensitivity of the S parameters or the Z parameters with respect to these numbers. Then, when you solve the problem, you can activate the sensitivity tab and launch.

You will get a plot of the Z parameters with respect to C11 and C 12. You can look at the slope, which gives you an idea of how sensitive your Z parameters are to C11 and C 12. You can turn off one of them or look at one of them. You can look at it and study the components one by one.

And that's how you can tell if your parameters are sensitive or not to these components. You can also calculate the equivalent circuit of your power plane. Practically, you can compute the equivalent RLGC subcircuit.

You can do that only for the case where you have no equivalent circuit of the VRM attached to your circuit. You can export RLGC subcircuit in a different way, using different formats, depending on where you're going to use your file. When you finish solving a model, you can check the mesh.

Sometimes it's good to verify the mesh. You can also verify the profile, which gives you more information about how much triangles have been used in each section. You can also verify the simulation properties.

Simply, you can select this option and review the setup that you did in order to produce this result. You can export your model to an IBIS file or a Sentinel SSO netlist. These files are useful for other applications.

Finally, you can export the result to S Utility, which allows you to do quite nice stuff with your data. These are the things that you will be able to do through SI Wave PI analysis. Thank you. A record posted today.