Analog designers ‘need to use digital tools’
It’s not the easiest job in the world to tell analog designers they should consider digital tools, but it is something that Tom Beckley, senior vice president of R&D for custom ICs at Cadence Design Systems, emphasized in his keynote at CDNLive EMEA today.
A lot of responses from analog designers are that he should get his group to spend more time on getting Spice to run faster. At the same time as recommending that analog engineers start to consider crossing the Rubicon into the world of digital simulation, Beckley wanted to reassure the engineers who just want a faster Spice that a faster Spice is indeed on the way.
“We are working feverishly on a next-generation fast Spice,” Beckley claimed, that will probably start to see a rollout in the second half of the year.
The problem with many designs that need Spice simulation is simply that they are too big. Beckley said analog engineers should consider “real-number modelling rather than going to Spice” to simulate some mixed-signal designs, particularly those of the big-D/little-A variety.
“Real-number modelling has been around for a long time in the digital languages,” Beckley explained. “And it opens up the option of using assertions for mixed-signal simulation. But it has languished for the most part.”
It has taken off a little in the past couple of years, Beckley claimed, describing work at Texas Instruments to use it. “The results are stunning: a 300 times improvement in performance if you can move out of Spice and into real-number modelling and event-driven analysis.”
No-one is going to model an RF amplifier using the real-value support of a digital simulator but, as a 2009 white paper from Cadence pointed out, the accuracy of a discrete, real number-based model is probably enough to satisfy a pin-connectivity test that might need a large number of simulation cycles to test the various events and states that the target chip may face.
Learning the digital tools is not the only problem. “A lot of you work in the Virtuoso cockpit,” he conceded. So, the company is working to bring greater support for the digital tools into Virtuoso itself so that it is easier to compare results from different simulation modes and control verification runs that use the digital tools. Some of this work is already ready, such as the amsDMV tool developed by Cadence’s operation in Livingston, Scotland.
“Cadence has brought a lot of digital functionality to your analog cockpit,” said Beckley.
Beckley said the key to the upcoming fast Spice tool lies in a number of senior engineers who joined Cadence recently – namely four of the team that formed Nassda. He said the next-generation fast Spice engine and the tools around it represent “a big focus area for us”.
