Promising a new approach to fast Spice simulation, Synopsys Inc. this week will introduce Discovery AMS 2007, a group of solutions that includes the XA simulation technology option for the NanoSim and HSim fast Spice simulators. The new release also promises tighter integration with the digital VCS verification simulator and a unified mixed-signal debugging environment.
Discovery AMS includes NanoSim, Synopsys' original fast Spice simulator; HSim, a fast Spice simulator that Synopsys acquired along with Nassda Corp.; HSpice, a full Spice simulator; and VCS, a digital Verilog simulator. Discovery AMS is not a bundle; customers can pick the components they want. XA is an option for either HSim or NanoSim.
XA promises a new level of performance and accuracy for fast Spice simulation, along with user control over performance and accuracy through one of seven "modes." It also eliminates the setup and tuning requirements of today's fast Spice simulators, Synopsys said.
XA was built on top of a full Spice engine. Synopsys (Mountain View, Calif.) expects most of XA's usage to be in modes three to six. Here, said Jeffrey Ying, director of marketing for mixed-signal simulation products at Synopsys, performance is about five times faster than typical fast Spice simulation and 50 times faster than Spice, with only a 1 percent loss in accuracy compared with full Spice.
According to a comparison by Synopsys, a switching regulator that took 24 hours to simulate in Spice and 4.1 hours in fast Spice ran in 48 minutes using XA. A charge pump that took 13 hours in Spice and four hours in fast Spice simulations ran in three minutes using XA. A phase-lock loop that Spice couldn't handle ran in 24 days in fast Spice and 2.5 days in XA. These comparisons used modes four and five, Ying said.
Moreover, said Ying, traditional fast Spice requires setup commands and configuration files, none of which exist in XA. "You can get to within 1 percent of Spice accuracy almost effortlessly," he said. "You may be able to tune fast Spice to that level of accuracy, but it will take a lot of effort and a lot of commands."
XA is a full-fledged simulator, but Synopsys is not selling it as a standalone product. That's because it doesn't have all the capabilities designers have come to expect from fast Spice products, Ying said. For example, it lacks the IR drop and electromagnetic simulation capabilities of HSim and the cosimulation capabilities of NanoSim.
XA is also not a replacement for HSpice. XA runs only in the time domain, Ying noted. XA uses the HSpice model evaluation engine, however, and runs HSpice netlists, he said.
Two technologies--partitioning and multirate design--give XA an edge in fast Spice mode. Fast Spice simulators generally partition designs so they don't have to solve the matrix for the entire design. XA provides a "dynamic" partitioning approach that recognizes the mode of operation for the circuit and decides how to partition it on the fly.
Synopsys literature states that XA is particularly well-suited for nonideal power supplies, phase-lock-loop lock times and switched capacitor circuits. But despite its broad range of uses, "I wouldn't guarantee 50x performance across the board," Ying said.
Also with Discovery AMS 2007, HSim and NanoSim are more tightly integrated with VCS. Previously, said Ying, the integration was through the Verilog programming language interface. With the new release, it's a direct kernel-based integration, resulting in one process and one executable. The two advantages are performance and flexibility, Ying said.
Finally, while previous releases of Discovery AMS had separate analog and digital waveform displays, the new release has a single debugging environment so users don't have to switch back and forth.
Discovery AMS 2007.03 is available immediately. The NanoSim, HSim and XA options start at $75,000.
See related image
