16 DESIGN007 MAGAZINE I MARCH 2018
power integrity utility technology, the Allegro
PowerTree™ tool. This utility enables a new
ecosystem of PI analysis to be shared between
schematic designer, layout designer and PI
expert. We want to truly automate the PI
methodology in which all three of these users
can contribute to PDN analysis that ultimately
yields an optimized design within budget and
schedule.
Dack: Tell us about the PowerTree tool and how
it handles PI.
Chitwood: The objective is the ability to auto-
mate both DC and AC simulation setups and
make things that used to be quite compli-
cated now be extremely simple. For instance,
a power domain on a large server board might
be incredibly complex with dozens of net
names associated with it. And these net names
are not always human-readable, as in they are
automatically generated and just random text
strings. Obviously, a human doesn't want to
track those names. The PowerTree tool auto-
matically identifies all the DC nets from source
to all loads. Components are automatically
identified, such as any filter inductors, resis-
tors, capacitors, their models are automatically
assigned. Pass/fail constraints are automati-
cally applied, such as per-pin voltage drop and
target impedance. The simulations can literally
be push-button automatic.
Dack: Wow. Sounds simple.
Chitwood: Yes, it is and from both a DC and
an AC perspective. I'm sure you know that
Cadence is famous for constraint-driven rout-
ing from a signal integrity perspective. We
wanted to do the same thing from a power
integrity perspective. We have many types of
DC constraints and AC target impedance con-
straints. As long as these constraints are pro-
vided, PCB designers can have guaranteed cor-
rect power delivery from schematic all the way
through the design cycle to board sign-off.
Finally, I will mention that we have an IC
vendor here at DesignCon presenting this
flow about how they are now providing target
impedance to their PCB customers. We want to
proliferate this methodology so that the rest of
the industry can benefit from this flow.
Dack: Well, very good information, Sam.
Thanks so much for your time today.
Chitwood: Thank you, Kelly. DESIGN007
Additional Reading:
1. Sigrity Tech Tips.
2. How Your PCB Design Team Can Become
Your PI Dream Team.
3. How a Team-Based Approach to PCB PI
Analysis Yields Better Results.
4. Sigrity PowerDC Technology.
