EM Simulator Tackles Power Design Challenges

Jul 18, 2007 4:31 PM
By Mark Valentine, Technical Editor, Power Electronics Technology

Enabling designers to quickly converge on pc board layouts compliant to design targets, including those for EMI and power integrity, Ansoft has released version 3.5 of its SIwave tool. This latest release features a fast and efficient finite-element-based dc solver optimized for extraction of power rail geometry in complex low-voltage/high-current pc boards and packages. The tool thus provides a major benefit to power designers by jointly checking for electromagnetic (EM) issues (such as EMI compliance) and power-integrity issues (such as decoupling-capacitor placement; see the Figure) in parallel, a process that otherwise would involve multiple iterations between separate simulation engines.

According to Sergey Polstyanko, manager of signal integrity research and development at Ansoft, the focus of the tool is on pc board design. However, it can model and probe all interconnections between electronic elements mounted on the board, including the bond wires and lead frames of complex ASICs. This enables the tool to apply precise modeling and analysis to regions of the system that might otherwise be overlooked.

Engineers can also view voltage and current distributions in all relevant parts of the pc board besides the traces, such as bond wires and vias. Furthermore, voltage drop and current flow information can be presented in tabular format for external sources, vias, bond wires and voltage probes, allowing engineers to quickly identify design rule violations.

While the tool is particularly well suited for addressing the emerging challenges of cellular handset design, its modeling capabilities can be applied to the pc board layout of any system, including dedicated power supplies. Polstyanko states that no upper limits have been observed on parameters that can be applied to the modeling, so both low-power portable and high-power stationary designs can be accurately analyzed by the tool.

The impact that a given pc board layout has on circuit functionality can also be examined by integrating to other tools. For example, SIwave can perform EM modeling on a passive network connected to the input or output of an IC, and then extract frequency-domain parameters for that network. These parameters can then be applied to Ansoft’s Nexxim circuit simulation tool to observe its effect on circuit operation, all within a unified environment.

"SIwave is a key technology for enabling the new era of mixed-signal electronics design driven by form-factor, functionality and integration," said Dr. Zoltan Cendes, chairman and chief technology officer of Ansoft. "Extreme integration in wireless handheld devices, for example, creates new challenges for RF performance, system signal integrity, system-level EMI, low power and communications reliability. SIwave, combined with HFSS, Nexxim and DesignerSI [design tools], form a system design platform capable of addressing these challenges."

Figure. SIwave’s resonant mode solver and advanced post-processing capabilities allow users to quickly identify regions on pc boards requiring decoupling capacitors.

Though not supported at present, there are plans to link later versions of SIwave to another solver, ePhysics. This would enable power designers to optimize temperature and heat flow in parallel with the EM and power-integrity optimization presently supported.

There have also been requests to extend the capabilities of the SIwave tool to the die level, as the tool is on the threshold of doing this with its support of bond wire and lead-frame monitoring.

To learn more about this tool, or to provide feedback on additional desired capabilities, please email Mark Ravenstahl of Ansoft (mravenstahl@ansoft.com).