Calibre Calibre PEX Series - Episode 2: Calibre xL for Inductance Extraction

Q&A  
 
Note: 
1. Thank you all for the questions during the webinar! Below is the transcript of the questions and answers.
2. If more support is needed for any of the issues you are facing, please open a support case at  https://support.sw.siemens.com/en-US/support-case/open 

Q: How much accuracy results can Calibre xL tool guarantee?

A: Calibre xL tool is designed to deliver highly accurate results, but the precision of these results can be influenced by various factors such as the operating frequency, design structure, and reference setup. In our experience, as highlighted in the presentation on slide 5, we have observed a high degree of accuracy in correlation with full-wave solvers, maintaining reliability up to frequencies as high as 50 GHz. 

 

Q: What is the highest frequency that we can specify in calibre xL?

A: Typically, users run Calibre xL at frequencies up to 60 GHz. While there is no specific frequency limitation, other factors such as design structure, dimensions, and process node can also significantly impact the run. Therefore, while high frequencies are achievable, overall performance depends on a combination of these elements. 

 

Q: What frequency value can be used for RF designs?

A: The appropriate frequency value for RF designs depends on the operating frequency of the specific design and the requirements of the target application. The frequency should be selected to match the actual operating conditions to ensure accurate simulation and extraction results.

 

Q: When I run loop, the inductance of my power/Gnd nets are not extracted?

A: Calibre xL is based on a loop formalism, so the extracted R-L values correspond to loop geometries formed by a signal net path and the nearby power/ground network. The power/ground network serves as the return path for the current of the signal net.

users have the options to either include power or ground nets or both of them as return paths for the signal currents, therefore, the power or ground nets are actually extracted by default in a normal xL run. In terms of netlisting, the extracted loop values will only appear as parasitics associated with the signal net. There will be no inductance values reported for the power/ground nets, since their contribution has been already lumped into the loop values associated with the signal parasitics. This way a more compact parasitic netlist is generated at the end without any implications in the final accuracy, for example for timing analysis. If a user wishes to have power/ground nets netlisted, which could cause the netlist size to expand drastically for large power grids, then this could be done by treating them as regular signal nets for the xL runs. This means that they should not have been assigned as return paths for other signals through the “PEX POWER netname” or “PEX GROUND netname” commands.

 

Q: Can I run Inductance without resistance?

A: Extracted resistors is a pre-requisite for self-inductance.

 

Q: Should I expect my Resistance values to change when I run with and without inductance?

A: When running xL, xRC/xACT removes the R that was calculated, and replaces it with a frequency dependent R and L, or with the broadband model. The caps stay the same.

R is also expected to change according to the specified frequency

 

Q: What happens if I specify the tool to filter on a specific wire length, and all the wires in my design do not fit the criteria?

A: There will be no L parasitic in the extracted netlist. The log will also highlight this. It will report that there nothing to be processed for inductance extraction

 

Q: How Can I extract mutual inductance?

In PEEC mode the mutual inductance is extracted and netlisted even if it has not explicitly been specified.

 

Q: What does set the INDUCTANCE Range to 0 mean?

The Inductance Range specifies how far to search from a given net segment for the return paths to include in self-impedance calculations. If you set this option to 0, you basically tell Calibre xL to search the extent of the chip for return paths to include in self impedance calculations.

 

Q: Why does the Resistance values increase with the frequency increase?

A: This is due to the Skin effect that was explained in the Webinar. At DRC/Low frequencies, the current is distributed homogenously across the conductor's cross section. At sufficiently high frequencies, current may be “crowded” at the outer surface of the conductor -> R increases .. This decreases the effective value of the loop inductance since a decrease in magnetic field within the line core, reduces the effective area of the current loop and decreases the internal inductance

 

Q: Is there an SVRF that enables Skin effect?

A: If you are running 2017.4 version or later, the Skin effect is considered by default in Calibre xL

 

Q: Will this testcase be available after the Webinar to try the different Calibre xL capabilities?

A: Yes, we have included a support kit in the resources, which is a KB article that contains a package with a testcase to try the different options on. There you go the link: https://support.sw.siemens.com/en-US/product/852852053/knowledge-base/KB000132689_EN_US

 

Q: Is there an additional license needed for running Calibre xL?

A: At a minimum, you must have a Calibre xL license. Depending on the specific operations you intend to perform, additional licenses may be required. Please note that there are no substitute licenses available.

 

Q: To what extent can Calibre xL replace 2.5D/3D simulators such as EMX or HFSS?

A: Calibre xL is not a full wave solver. It is an inductance field solver which can run on top of Calibre xRC, xACT or xACT3D for resistance and capacitance.