[SI-LIST] Re: Power Integrity Question
- From: steve weir <weirsi@xxxxxxxxxx>
- To: "Peterson, James F (EHCOE)" <james.f.peterson@xxxxxxxxxxxxx>
- Date: Thu, 06 Nov 2008 05:51:22 -0800
They're in their catalog. I haven't seen any though.
Steve
Peterson, James F (EHCOE) wrote:
> (follow-up to Steve's comments on Q)
>
> Whatever happened to the technique that TDK came up with a couple years
> back where they were purposely increasing a capacitor's ESR to reduce Q
> (and thus the large peaks mentioned in this thread)?
>
> I remember seeing it a few DesignCons ago - it seemed like such a great
> idea...
>
> Jim.
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of steve weir
> Sent: Thursday, November 06, 2008 8:07 AM
> To: Avtaar Singh
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Power Integrity Question
>
> The simulators are reporting correctly. Your understanding of physics
> theory ( actually Calculus ) is incorrect. A convenient way to think
> about the impedance anywhere is as a result of the characteristic
> impedance and the Q. In the original case, the impedance significantly
> away from the original pole approximates the characteristic impedance.
> At each of the two peaks, when the impedance is reactive, Q > 1, and the
>
> peak impedance is substantially greater than the characteristic
> impedance. Therefore if you've got peaks at all the impedance will
> always be above the original curve surrounding each one.
>
> Steve.
> Avtaar Singh wrote:
>
>> Dear All:
>> I have a very basic Power Integrity question.
>>
>> Lets say a Power Delivery Network (PDN) has an impedance peak at
>>
> 100MHz. I
>
>> add a capacitor that dips the impedance exactly at 100 MHz, and
>>
> creates 2
>
>> smaller peaks at, lets say, 20 MHz and 250 MHz. According to the
>>
> theories of
>
>> Physics, these peaks should have their impedance value little bit
>>
> lesser
>
>> than the impedance value of the PDN, at those 2 frequency points,
>>
> before
>
>> this capacitor was added. But we do not always see that in simulation
>>
> tools.
>
>> Sometimes we see that the 2 peaks that are formed have higher
>>
> impedance than
>
>> the impedance that existed at those frequency points before this last
>> capacitor was added. This seems weird to me, because even though the
>>
> ESR of
>
>> the caps should decide how sharp or blunt the Z peaks are, but an
>>
> added Z in
>
>> parallel should always mean lesser impedance rather than more
>>
> impedance. Can
>
>> someone please explain this paradox?
>>
>> Thanks for the kind guidance.
>>
>> Regards,
>> Avtaar Singh
>>
>>
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>
>
>
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