[SI-LIST] Re: Power Plane resonance analysis
- From: Ihsan Erdin <erdinih@xxxxxxxxx>
- To: steve weir <weirsi@xxxxxxxxxx>
- Date: Fri, 28 Aug 2009 07:14:16 -0400
... I mean: c0/sqrt(eR)
On Fri, Aug 28, 2009 at 7:11 AM, Ihsan Erdin<erdinih@xxxxxxxxx> wrote:
> That's correct. A parallel plate power/ground plane pair is basically
> a nonuniform transmission line for which both C and L are
> area-dependent. The phase velocity is simply c0/eR for an ideal
> component between those two planes. In actual case, however, the
> mounting inductance of the component may vary the velocity
> significantly.
>
> Regards.
>
> Ihsan
>
> On Thu, Aug 27, 2009 at 6:38 PM, steve weir<weirsi@xxxxxxxxxx> wrote:
>> Propagation velocity depends only on eR.
>>
>> Steve.
>> Aleksandr Oysgelt wrote:
>>> How do you figure out propagation delay through planes? Is it sqrt(L/C) so
>>> L is about 32pH/mil of separation (sheet inductance) but what is C (which is
>>> area dependent - no concept of "sheet capacitance")?
>>> Thank you
>>> Aleks
>>>
>>> On Thu, Aug 27, 2009 at 5:25 AM, Istvan Novak <istvan.novak@xxxxxxx> wrote:
>>>
>>>
>>>> Hi San,
>>>>
>>>> If you have the good luck to have rectangular plane shapes, you can
>>>> simply calculate the
>>>> modal resonance peak frequencies from the propagation delay along each
>>>> of the two sides
>>>> of the rectangle. 1/(2*tpd) gives you the lowest resonance peak, and
>>>> you will get all of
>>>> the harmonics, so it becomes a double infinite series. On typical PCB
>>>> dimensions today,
>>>> the first five or ten resonance peaks matter in self impedance; the
>>>> higher-order modes
>>>> will tend to blend together into an inductive slope.
>>>>
>>>> For more complex shapes the modal resonance frequencies need to be
>>>> calculated by
>>>> an appropriate software. You can go from simple and low-cost tools like
>>>> EZPlane
>>>> (http://www.ems-plus.com/ezpowerplane.html) to more sophisticated tools
>>>> like
>>>> Sphinx (http://www.e-systemdesign.com/products.aspx) to high-end tools
>>>> such
>>>> as Ansoft SiWave or HFSS. For HFSS and correlation on power planes, you
>>>> can
>>>> check out the Unofficial HFSS User forum (http://www.hfss-forum.com/).
>>>>
>>>> To make sure that resonances do not create a problem, best and cheapest
>>>> defense
>>>> is to make sure you dont excite them. You can do this by creating a
>>>> stackup to
>>>> minimize signal-return currents going through unrelated power-ground
>>>> cavities.
>>>> To reduce the resonances themselves, you can either sprinkle the planes
>>>> with many
>>>> capacitors, match the planes or use thin laminates, or a combination of
>>>> these. If
>>>> you sprinkle the planes in the old-fashioned brute-force manner, you
>>>> could use the
>>>> same capacitance value, say 0.1uF or 1uF. Key is minimizing the inductance
>>>> in the capacitor connections because with the cumulative inductance of
>>>> all capacitors
>>>> on the plane you want to stay below a couple of percents of the plane's
>>>> inductance.
>>>> You can read more on these design options at
>>>> http://www.electrical-integrity.com/,
>>>> go to Paper download. In the Tool download section you can also find
>>>> simple
>>>> illustration tools for plane resonances.
>>>>
>>>> For measurement options, you can look at the paper "Frequency Domain Power
>>>> Distribution Measurements - An Overview" from DesignCon 2003 East, Boston,
>>>> MA, June 23-25, 2003. You will find it at the site above. For more
>>>> details and
>>>> tips, you can look at the book Frequency-Domain Characterization of Power
>>>> Distribution Networks, Artech House, 2007.
>>>>
>>>> Regards,
>>>>
>>>> Istvan Novak
>>>> SUN Microsystems
>>>>
>>>>
>>>>
>>>> Sandhya I. M. wrote:
>>>>
>>>>> Hi SI experts,
>>>>>
>>>>> If any one can help me in doing PCB Power Plane resonance analysis by
>>>>> sharing documents or by explaining how it occurs.
>>>>>
>>>>> What are the causes of PCB Power Plane resonance analysis
>>>>> How can we measure resonant frequency
>>>>> How decoupling caps helps in suppressing resoinance in planes.
>>>>> What are the factors we should consider while doing resonance analysis.
>>>>>
>>>>> Thank you
>>>>>
>>>>> Regards
>>>>> san
>>>>>
>>>>>
>>>>>
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>>>
>>>
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>>
>>
>> --
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