Improve Power Integrity Analysis by Incorporating Spice and S-Parameter Models

November 5, 2020 Jared Hansen

Ensuring the desired voltage and current are reaching ICs is paramount. Most designers implement a voltage regulator module (VRM) to maintain a consistent supply. This network of VRM to IC is commonly called the power distribution network (PDN). Understanding the entire PDN is important throughout the power integrity (PI) analysis. Ansys tools, specifically SIwave is already well known for its PI simulation. Things such as optimization of decoupling capacitors, SYZ extraction for the PDN, and resonant modes are great tools for fully understanding the PDN on your PCB. For many customers simple inductor and capacitor values do not provide enough detail to drive accurate results. The good news for Ansys users is that the tool houses multiple capabilities to integrate spice models, including a large library of vendor models as well as tools for adding spice models.

Below is the Vendor Component Management tool. Within this tool, users can assign vendor supplied models to their capacitors and inductors.

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Major vendors include Kemet, TDK, Murata, and many others to create a library with more than 10,000 different components. As shown below these components include more accurate models than just a passive component value, they include the ESL and ESR values to increase accuracy.

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Not seeing your part number in the library? Don’t worry, users can create models using s-parameter data created by the manufacturer. SIwave can import SNP files into the library to create new components. Using the tool found in the image below, users can input information to create a new component that can be searched using the library found above.

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Filling in this information allows the user to add new models to the library with some additional flexibility to take both series and shunt type SNP files.

What if you are unable to find an SNP file but you have a Spice model? SIwave can handle many spice models as well. Using the RLC spice model setup tool, users can import and assign spice models to their part numbers.

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Using this tool, users can quickly assign identical part numbers to the same spice model, allowing for quick incorporation of the spice model and getting them ready for simulation. Users can quickly turn on and off spice models to perform ‘what if’ studies and determine the change in z-parameters for their PDN.

The S-parameter Vendor Model and the RLC Spice Model tools allow for Ansys SIwave users to increase the accuracy of their PI simulations by including higher fidelity information about their inductor and capacitors. This increased fidelity of the passive models allows for higher accuracy of the z-parameters of the PDN. With this more accurate data, users can then drive decision making analysis using the decoupling capacitor placement optimizer to ensure that their PDN is providing a clean voltage and current signal to their ICs. This of course is all found with Ansys SIwave and as a tool helps designers make design decisions with confidence through high fidelity models and world class simulation.

About the Author

Jared Hansen

Manager, Electronics Engineering Solutions

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