How to Accelerate the Analog Design Verification Flow

Report
How to Accelerate the Analog
Design Verification Flow
Itai Yarom
Senior Verification Expert
Synopsys
Where do we have analog blocks?
• A common SoC chip uses
many IP’s
– Like: USB, HDMI, etc.
• Each IP uses one or
more analog blocks
• A certain analog block
can be used in different
IP’s
– Therefore, we can have the
same analog block but with
different configuration
2
How good is verification flow
for analog blocks?
• We want to find
bugs as early
as possible
– Can we use
the vast
knowledge we
have from logic
verification
world?
3
Goals
• Provide robust analog verification flow
Agenda
• Analog designs verification challenges
• Alternative verification flow
• Results & Summary
4
Example: 3GHz ADPLL
ADPLL Block diagram
Reference : IEEE ISSCC 2012
Is this a bug?
• The process of
analyzing the results
is complex
– Done at post
simulation time
• Reduces the
variations checked
6
Analog vs. Digital simulation
Proposed Solution:
SystemVerilog Associative Arrays
• Capture the signal values
into an associative array
• Perform the analysis as
part of the testbench
during the simulation
• Benefits:
– Faster runtime (x100
speedup)
– Can run test hundreds of
characteristics vs. tens
before
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An Example: Jitter
• Using SystemVerilog associative array
– Jitter analysis is possible during simulation
Analog Style Analysis in VCS
• Using SystemVerilog associative array enable
to perform analysis on the analog data at the
end of the simulation
10
Mixed signal ‘regression’ flow
• The automatic
evaluation as part
of the testbench
enable to test
more complex
scenarios
– A scenarios is a
random
combination of the
parameters to be
checked
Results of ADPLL Jitter
• The ‘regression’
flow enable to
tests over 200
combinations of
parameters
– A much more
robust testing
– X100 runtime
improvement
– A significant
better QA quality
New flow:
Discovery-AMS
+ regression
Full spice
Quality improvement
QA Coverage
Effort - Manual, Sim Time, IT resources
Parameter
Full
spice
Regression w/
Discovery-AMS
Sim Time for
15us
>100 h
1h
Number of
Tests runs
Up to 5
Over 200
Post
10 min
Analysis time per test
none
12
Summary
• There are many analog block in typical SoC
design
• The verification process of analog blocks can
be improved
• We used SystemVerilog associative arrays to
enalbe in-sim analysis
– Significant runtime and quality improvement
• This flow is being adopted in the industry
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How to Accelerate the Analog
Design Verification Flow
Itai Yarom, Senior Verification Expert, Synopsys
Thanks to Gabi Glasser for his contribution to this work
Abstract
In this article we propose a method for simplifying analysis and
increasing coverage during mixed signal simulations.
Many checks in a simulation test bench can be implemented by relating
to the value of a signal within a narrow window of time. When the
intention is to analyze analog signals, the measurements are done many
times on long vectors (e.g. RMS). This type of analysis cannot be
implemented within the digital test-bench and is done using post
processing methods.
The method proposed here is to take advantage of SystemVerilog
capabilities, which enable defining a hash (associative) array with
unlimited size. During the simulation, vectors are created for required
signals, allowing them to be analyzed within the test-bench along or at
the end of the simulation, without need to save these signals into a file.
The simplification of the analog style analysis paves the road to
massive mixed signal simulation (i.e. regression testing).
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