| Impedance | ||
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It is vital that design tools accurately
predict the nominal characteristic impedance of your traces. There is
generally a large tolerance on the finished trace impedance, +10%
is common. However, the purpose of this tolerance is to allow
manufacturing processes to achieve an acceptable yield, it is not
there to allow for approximations during the design phase! |
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| Most PCB manufacturers use the 'Polar' tools for calculating controlled impedances. To create as few DFM issues as possible, it is important that your layout and simulation tools agree with the Polar impedance results. We compared three design tools and a popular mathematical formula with the Polar Si8000 field solver to see how closely the results correlate. The tools used and corresponding results are shown below. | ||
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Polar Instruments Ltd Si8000 v5.0.0 | |
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Cadence Inc Allegro PCB SI 610 v15.2 | |
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Mentor Graphics Inc HyperLynx BoardSim v7.0 | |
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Agilent Technologies AppCAD v3.0.2 | |
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Formula | |
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The Conclusion
In this stripline example the Allegro field solver correlates with Polar Si8000 to within fractions of a percent, the red and yellow curves in the graph above are virtually coincident. This level of accuracy ensures that representative trace models are generated for board-level simulations and allows our layout designers to reliably predict the nominal trace impedances in your design.
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| Advanced Layout Solutions Ltd offers the complete PCB design solution. | ||
| +44 (0) 118 971 1930 | ||
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