( ESNUG 445 Item 11 ) ------------------------------------------- [05/24/05]
Subject: ( SNUG 04 #14 ) User Eval of PT-SI vs. CeltIC for Glitch Analysis
> We use AstroRail and CeltIC. PrimeTime-SI looks like it is gaining share
> and, more importantly, correlating better with SPICE. At some technology
> inflection point (perhaps 90 nm, perhaps smaller), we will want to have a
> tighter integration of SI effects in STA. Exporting timing-windows
> to/from CeltIC is time-consuming, and, more importantly, CeltIC won't
> honour detailed exceptions that PrimeTime does, making its Xtalk
> pessimistic. I think PrimeTime-SI will win in the long run so long as
> people are signing off STA with PrimeTime...
>
> - Andrew Bell of PMC-Sierra, Inc.
From: Ying Gao <ygao=user company=qualcomm spot gone>
Hi, John,
I recently evaluated both PrimeTime-SI and CeltIC in a search for a tool
that could accurately perform glitch analysis on our complex designs. As I
have read a couple of different threads on this topic in ESNUG, I thought
that I would share my experiences with you.
Noise library creation:
CeltIC has an advantage here with its own cell noise characterization
engine that takes in device models, SPICE netlists, and the Synopsys .libs
to generate .cdb noise libraries. We were able to create our libraries in
a few hours. CeltIC achieves this runtime by cutting some of the SPICE
netlists, and according to one of our library engineers, this results in a
loss of accuracy.
PrimeTime-SI has a very demanding noise library characterization requirement
compared to CeltIC. You need to create I-V curves and noise immunity curves
for every timing arc in your library. Everything is simulated in Avanti
HSPICE which is very accurate, but very time consuming. Synopsys provides
an automated noise library generator, but we have a very good library team
that automated this characterization process themselves. We learned from
our previous evaluation of PT-SI for crosstalk delay that the quality of
timing results that you get in PT-SI is directly related to the quality
of your library.
Ease of integration into our flow:
PT-SI has advantage here, because PrimeTime is our golden sign-off timing
engine. So, all we need is just adding several lines of commands to our
existing PT script.
CeltIC is a bolt-on flow that is dependent on PrimeTime for the initial
static timing analysis. Because CeltIC requires moving data in and out of
different tools, we consider it slightly more error prone than the PT-SI
flow. CeltIC does have a CTE flow that allows it to use its own internal
timing engine, but this was not the recommended flow from Cadence during
our evaluation.
Accuracy to SPICE:
We first ran the Synopsys provided noise correlation kit, which consists
of a couple of very simple circuits with each victim net having only one
or two aggressors. Using these testcases with a range of input transition
times, both PT-SI and CeltIC had excellent SPICE correlation. CeltIC
usually had a slight edge.
We then ran PT-SI and CeltIC on a real 0.13 um design with lots of coupling.
Using more complex real design testcase, PT-SI had better SPICE correlation
than CeltIC. It is especially true when a victim net is coupled with many
small couplings.
- Ying Gao
Qualcomm San Diego, CA
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