[SI-LIST] Re: Parallel resonance (anti-resonance) on power distribution system and Full impedance compensation concept
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Rodrigo Rodriguez <coco.roro@xxxxxxxxxxx>
- Date: Sat, 10 Apr 2010 04:36:24 -0700
That term appears in Mezhiba, Friedman "Power Distribution Networks in
High Speed Integrated Circuits". As used in that book, it refers to
tuned compensation networks in order to damp out PDN resonances. In
effect, all multipole networks (FDTIM in Altera parlance) do this to
some degree although in more of a whack-a-mole fashion. Sigrity's
Optimize PI(tm) product will calculate the capacitor network for you.
The Cadence Allegro PI(tm) and Mentor Hyperlynx PI(tm)tools will both
evaluate a capacitor network of your specification.
In order to perform the kind of compensation that Mezhiba and Friedman
talk about, the tricky part is finding capacitors with the combination
of ESR and capacitance that you want. As frequency goes up this becomes
tougher and tougher. You are very unlikely to find the values you want
right off the shelf, forcing compromise. If you pick a capacitor and
the mounted SRF lands in the wrong place due to tolerances, and/or the
capacitor Q is too high, then you will take one peak and turn it into
two or more peaks. Since inductance directly contributes to Q, as in
all other things PDN, inductance is the primary enemy here. The lower
the mounted inductance of the cap compared to the ESR the easier it will
be to realize an effective compensation network. Because they have very
low mounted inductance and are available over a wide value range, X2Y(r)
caps are particularly good for this kind of duty. There is an example
on the X2Y(r) website where one capacitor compensated out a resonance at
about 600MHz very nicely contributing to dramatically improved SerDes
jitter:
http://www.x2y.com/bypass/method/altera_bypass.pdf
Steve.
Rodrigo Rodriguez wrote:
> Hello,
>
>
>
> >From what I read, the concept of "Full Impedance compensation" applied to
> >power distribution system with decoupling capacitors sounds an interest
> >concept to achieve the target impedance over the wide frequency range of a
> >power distribution network with a damped or fully compensated impedance
> >which eliminates the anti-resonant peaks due to parallel RLC tank formed by
> >the decoupling capacitors.
>
>
>
> I would like your guidance on recommended source of information about the
> concept of Full Impedance Compensation applied on Power Distribution System
> for the reduction of the impedance (damped anti-resonant impedance).
>
>
>
> - Has this concept being applied to real applications?
>
> - Is this concept used on comercially available SI simulation tools?
>
>
>
> Thanks.
>
>
>
> Rodrigo
>
>
>
>
>
>
>
>
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--
Steve Weir
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