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Tool analyzes combined effects of crosstalk and dynamic power
By Michael Santarini, Senior Editor -- EDN, 6/8/2005
Apache Design Solutions has introduced a new tool that analyzes how crosstalk and dynamic power combine to impact the timing on an IC's critical paths and clock tree.
To date, Apache has focused on dynamic-power analysis. But with the new PsiWinder tool, the company is adding dynamic-crosstalk analysis to its portfolio.
Traditional tools try to decouple or isolate crosstalk effects from dynamic-power effects, and vice versa, to accurately analyze each effect's impact on timing, said Andrew Yang, the company's president and CEO. But at the 90- and 65-nm nodes, the noise from power and crosstalk must also be analyzed together. "It's simply becoming harder to determine one noise from the other, and you have to account for their combined impact on timing," Yang said.
Traditional tools fall short in noise analysis because they use static-timing-analysis data—Veff supply rails—that are too general and do not accurately account for the combined effect of crosstalk and dynamic power on timing.
A play on "sidewinder," PsiWinder aims to help designers get a truer read on how crosstalk and dynamic power are teaming up to impact timing. The tool, Yang said, is not based on a static-timing-analysis approach; rather it has a Spice-based crosstalk-analysis engine under the hood. Digital-IC designers typically don't want to deal with Spice, so the company has made the Spice engine invisible to users, he said.
The Spice engine allows the tool to take readings from actual Vdd waveforms rather than from Veff supply rails, which ensures the analysis is "Spice" accurate, Yang claims. The tool also uses a real fanout-transistor load rather than the Ceff capacitance load approximation used by static tools.
Apache intends for designers to employ PsiWinder post-routing and directly after the company's RedHawk-SDL RLC extraction and dynamic-analysis tool. Users feed PsiWinder power and ground-noise data and waveforms from RedHawk-SDL and a timing report from PrimeTime SI. The tool uses the PrimeTime report to identify the critical paths. Yang said the tool will typically pick the top 1000 critical paths from the report and analyze them at a rate of roughly 10 minutes per path with a 20-processor configuration.
"We'll take the top 1000 critical paths from PrimeTime, inject the Spice Vdd/Vss waveform, along with crosstalk-noise analysis built into PsiWinder, and then run parallel Spice jobs for those critical paths," Yang said. "We can turn around 1000 critical paths overnight."
The tool is speedy because it performs a pre-simulation to identify aggressor and victim nets to determine the coupling network, the networks' drivers and receivers, and their power and ground supplies. The tool does simulations of worst- and best-case coupling delay, aggressor vector sensitization, and alignment timing window filtering. It also supports full and partial window-timing overlap to account for situations when two aggressor nets are attacking a victim at once, or where two aggressors attack close together but don't overlap in their attack of the victim net.
For clock-network analysis, the tool provides combined Vdd/Vss impact on skew, insertion delay, and jitter, outputting an SDF file for a loopback to PrimeTime. For critical-path analysis, the tool outputs data on the impact of combined Vdd/Vss on setup-and-hold violations and produces a report for PrimeTime.
PsiWinder costs $150,000 for a yearly subscription. Each license includes 10 integrated Nspice engines for distributed simulation of multiple critical paths, with LSF and Sun Grid support.
