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Cadence and Zuken update PCB flows

Posted: 02 May 2003 ?? ?Print Version ?Bookmark and Share

Keywords:cadstar 3d? verification module? cadstar 6.0? pcb? xr?

Cadence Design Systems Inc. and Zuken Ltd demonstrated developments to their respective design environments at the PCB West design conference.

Cadence showed increased automation of its flow for designers implementing differential signaling on high-speed PCB designs. Zuken exhibited an updated version of its CadStar 3D verification module that allows complex board outlines to be directly imported and exported from mechanical-CAD tools and transferred to the CadStar 6.0 PCB design tool suite. Zuken also showcased a new rules-by-area option for its PR Editor XR place-and-route tool.

As nanometer-scale ICs become more common, the use of differential signaling in PCB has increased to accommodate the communications between ICs running multiGb data rates, said Keith Felton, product marketing director for Cadence's PCB and IC-packaging group.

Differential signaling is a method of sending the same piece of information, both inverted and non-inverted, over two traces from a differential driver over two traces to a differential receiver. Differential signals allow for lower voltage swings, resulting in faster circuits, reduced power consumption, and reduced EMI.

To date, Felton said, the implementation of differential signals on a PCB has required engineers to perform many iterations between design and analysis to get the signals to work without interference from - and without interfering with - other components or traces.

At last year's PCB West, Cadence began its work on supporting differential pairs by introducing simulation support and topology exploration. This year, the company has automated the flow by tying the analysis closely to design and implementation tools.

"Up to now, every vendor, including Cadence, has had some physical differential-pair capabilities: People could specify an arbitrary spacing between two signals, and then the system would implement that spacing," said Felton. "The spacing, however, was driven by rules of thumb and not simulation, so there was no control over differential impedance of the signal or phasing of the signal."

But arbitrary rules of thumb can be overly conservative or may even cause more problems to nearby traces or components, Felton said. Cadence now offers engineers a simulation-driven environment in which designers use simulation to derive an optimal rules set that is captured within SpecctraQuest's Constraint Manager utility, Felton said.

Saving development time "engineers can now figure out, through simulation and what-if analysis, what the optimal environment is for that signal to operate," said Felton. The environment "looks at impedance, phase matching and captures the electrical constraints for the rest of the design and implementation flow." That eliminates multiple iterations between design and analysis and saves overall development time, he said.

To implement the flow, Cadence has upgraded many of the tools in its PCB development suite. Beyond adding differential-signal rules to the SpecctraQuest SI analysis tool, the company has added custom stimulus and custom measurement capabilities that let users measure common-mode offset from die pads inside an IC package. That increases user understanding of the influence of the package on the performance of differential signals, according to Cadence.

The company also included an interactive push/shove routing capability to the Allegro layout tool. An interactive feedback feature in place during the layout phase warns the user if rules are being violated and if the layout of the differential pair interferes with other traces or components.

Cadence has also added to Allegro a feature that allows differential-signal pairs to be routed as a single entity. The tool gives feedback during layout, displaying information on phase or delay control and suggesting options to use various via patterns.

To use the differential-signal capability, users also need a SpecctraQuest Signal Integrity Expert.

Also at PCB West, Zuken showed the latest version of its CadStar 3D verification module and a new rules-by-area option for PR Editor XR.

The CadStar 3D tool links the 2D PCB world with the 3D mechanical-CAD world and has a design rule check capability to CadStar 3D version 4.2 that identifies areas where collisions may occur between objects on a PCB or between the board and its enclosure.

- Michael Santarini

EE Times

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