SIwave: Unleash the Power of the DC IR Solver
In this video, we discuss the power integrity and signal integrity capabilities of SIwave, focusing on the DC IR solver. This tool is particularly useful when analyzing PCBs where all dies carry a constant current, such as in TIAs, power amplifiers, and drivers. If a die carries variable current, a DC plus PI analysis is required.
Key Features of SIwave
- Calculates voltage drop in power planes and voltage rise in ground planes.
- Analyzes current distribution and detects overloading in vias.
- Identifies potential ESD issues and other defects.
SIwave should not be used to build PCBs, although it can import files and extract information such as stack-up, materials, components, and nets. The main task in SIwave is assigning ports before starting the analysis.
Understanding Nets and Links
SIwave defines a single net as an electrically connected structure without external components. A single net can span multiple layers but cannot be electrically disconnected. To analyze a power plane, identify its nets, which may be connected using resistors or inductors to form passive links. Integrated discrete components along the path are treated as independent links.
Setting Up the Analysis
- Select a passive link, such as a 1.2V line.
- Specify the location of the power plane, source, and probe (ports).
- Set the voltage at the VRM output and the current withdrawn by the loads (e.g., CPU).
- Configure simulation, validate setup, and launch the solver.
SIwave generates a dialog box with a list of power planes, distinguishing them by color (red for power planes, black for RF and control lines). Assign ports for each passive link and save the setup for future use if necessary.
Analyzing Results
After solving, examine the results in the following areas:
- Voltage Distribution: Check for smooth transitions in voltage across power planes. Examine both VCC and ground planes for voltage rise.
- Current Distribution: Analyze current amplitude and direction to identify bottlenecks and potential ESD issues.
- Via Density: Ensure vias are not overloaded by checking current density. Increase via count if necessary.
Advanced Features
- Export power trees and SPICE netlists for further analysis.
- Use Icepak for thermal analysis by converting power distribution into temperature distribution.
- Calculate MTTF (Median Time to Failure) using power distribution data.
Conclusion
SIwave provides comprehensive tools for analyzing DC IR solutions, including displaying and exporting data in various formats. It is essential for PCB designers to utilize these features to ensure robust and reliable designs.
SI wave: Unleash the power of the DC IR solver (SD) SI wave is a power integrity and signal integrity tool. One of its power integrity solvers, DCI, is discussed in this video.
DCI is used only when all the dies in a PCB or the ones that you want to analyze are carrying a fixed amount of current, like TIAs, power amplifiers, drivers, and many other kinds of dies. If one of the dies is carrying variable current, you need to do DC plus PI.
The solver calculates the voltage drop in any power plane, voltage rise in the ground plane, current distribution, current in each Via, detects overloading in any Via, detects any massive current accumulations, identifies the location of potential ESD issues, and many other defects.
SI wave should not be used to build PCBs, but it can import files and extract stack up, material, components, and nets. What's missing is assigning ports. Before using SI wave, it is highly recommended that the user reads the electrical schematic well. SI wave understands the language of nets.
When a board is imported, SI wave immediately starts looking for single nets. Any single net is an electrically connected structure without the use of any external component. A single net could occupy many layers but cannot be electrically disconnected.
To analyze a power plane, one needs to identify its nets. It could have just one net and it could have many nets. If there are many nets, they should be connected using resistors or inductors, and that will construct what we call a passive link.
If integrated discrete components exist along the path, SI wave will treat each side of the integrated component as an independent link. These are independent links and should be treated as two different structures.
When using SI wave, you can solve one net, one passive link, many passive links in a power plane, or many power planes at once. However, you cannot solve one power plane with an integrated circuit in between. When using the DC parameters, you need to select a solver.
Once a solver has been selected, SI wave generates a dialog box for you. Think about this dialog box as a form where SI Wave will fill up this form with all the information that it was able to extract from the file. For the DC, when you click the DC solver, you will get a dialog box.
You need to select the power planes and specify the location of the power plane, source, and probe, which is practically specifying the location of the ports. You are ready to solve once you know the voltage and current at the load.
If you have many power planes, you can select them one by one and assign ports. It is recommended to save the setup if you have many nets and spend some time doing the setup. This will allow you to load the setup again if you upload the same structure after certain modification.
Once you have configured the simulation, you can validate it. This will look at your nets to make sure that they are all as per the configuration that you have set up. The results panel will provide a plot of the currents and the voltage. You can select what you want to see in the table.
The voltage on the VCC is important. You should look for a smooth transition of the voltage and small changes in large power planes. Any significant delta means lots of power is being dissipated in the wrong way. The voltage of the power planes is also important.
You need to worry about the voltage rise in the ground. To do this, you need to activate the right layer and examine your ground. The current distribution inside your power plane is the third most important information. You can activate the current distribution and look at the region of the VCC.
This will provide you information about the amplitude of the current as well as the direction of the current. Any concentration of currents will show up in red and must be examined by the user. If it turns out that the section is narrow, one needs to find a way to widen it.
The most important thing from the analysis of the DC is the via density. This is the current density of the current flowing in the vias. To see the via density, you need to display element data. SI-wave will populate this dialogue box for you.
If any via carries too much current, the probability of a PCB failure becomes very high. SI wave can identify sections with voltages greater than or less than certain value. It can also find regions with current density above certain value.
These things can be used to examine your board section by section and make sure that there is nothing, no weaknesses within your structure, within your design. You can also look at the voltage probes. If you used any voltage probe, you will be able to see the voltage value at that location.
The last thing you can see from this table is the power distribution. This information is important for thermal analysis. From these values of the power density and the current and the voltage, you can also calculate the current and the voltage. You can also calculate the loop resistance.
SI wave allows you to export things. It can export a power tree, which is a flow chart that summarizes everything in one place in a graphical way. It can also export SPICE netlists. After solving the problem, you should check for refinement statistics.
This will tell you about the convergence and the profile. The profile will give you information about the mesh used in each section and the time it took to solve the problem. You can also look at the simulation properties.
This will take you back to your setup and is important if you are reviewing the results after many months or years and are not sure how these results were produced.
