[SI-LIST] Re: Decoupling Using 3-Terminal Capacitor
- From: Himanshu Arora <ha324005@xxxxxxxxx>
- To: Larry Miller <ldmiller@xxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Tue, 31 May 2005 16:54:19 -0700 (PDT)
Hi Larry,
Thanks for your response. Originally I also thought
the both the series and parallel arrangements are the
same---prallel.
But after thinking through it with other designer I
came to the conclusion that the way to think about
these feedthrough caps is the S12 parameter....For
series arrangement S12 (between node A and VDDA) is
going to be better than the parallel arrangement case.
In other words there is going to less high frequency
noise at node A in series arrangement.
Analogy is that people always cascade the filters in
series...not sure if the parallel connection of
filters is done...!!
It is also likely that my above thinking is wrong....
Figure is attached in the text file.
Sincerely
Himanshu Arora
--- Larry Miller <ldmiller@xxxxxxx> wrote:
> ???
>
> Your "Series" and "Parallel" connections are both
> the same-- parallel.
>
> Larry Miller
>
> On May 31, 2005, at 4:13 PM, Himanshu Arora wrote:
>
> > Hello Tom,
> > Thanks for your valuable inputs. I thought about
> > connecting the 3-terminal caps in series or in
> > parallel.
> >
> > Series and parallel arrangement is shown in the
> > attached text file.
> >
> > Out of these two arrangements I think it is better
> to
> > have the series arrangement. COnnecting them in
> series
> > is like cascading filters. Further, the series
> > arrangement should offer higher reverse isolation
> than
> > the parallel arranagement.
> >
> > Sincerely
> >
> > Himanshu Arora
> >
> >
> > --- Tom Dagostino <tom@xxxxxxxxxxxxx> wrote:
> >
> >> You might want to think about parallel and series
> >> circuits. In parallel
> >> circuits the total impedance is less than putting
> >> the same two impedances in
> >> series. And, yes, yes, I know there are
> resonance
> >> issues that will make
> >> that not a general case.
> >>
> >> -----Original Message-----
> >> From: si-list-bounce@xxxxxxxxxxxxx
> >> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of
> >> Himanshu Arora
> >> Sent: Tuesday, May 31, 2005 2:45 PM
> >> To: si-list@xxxxxxxxxxxxx
> >> Subject: [SI-LIST] Decoupling Using 3-Terminal
> >> Capacitor
> >>
> >>
> >> Hello,
> >> I am making a prototype PCB where in there are
> >> multiple VDDs.
> >>
> >> The Power Supply filter network looks somewhat
> like
> >> the one shown in the figure attached in text
> file.
> >> Instead of 2 terminal caps I plan to use the
> >> 3-terminal cap. The 3-terminal caps are from
> Murata.
> >>
> >> The reason of using 3-terminal caps against
> >> 2-terminal
> >> Multi-layer-ceramic caps is that they offer lower
> >> ESR
> >> at SRF, their lead inductance is lower and their
> SRF
> >> is higher for the comparable cermic cap in value
> and
> >> case size. The reason I am connecting the two
> >> 3-terminal caps in series is to offer a lower
> >> impedance across a wide range of frequencies.
> >>
> >> I would like to have your views and inputs for
> the
> >> above arrangement. Thanks.
> >>
> >> Sincerely
> >>
> >> Himanshu
> >>
> >>
> >>
> >> __________________________________
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> >>
> >> -- Attached file included as plaintext by Ecartis
> --
> >> -- File: 3tcap.txt
> >> -- Desc: 2302733855-3tcap.txt
> >>
> >>
> >> VDD C1 C2
> >> ---- ----
> >>
> >>
> >>
> >
>
|--------Ferrite------------------------------------VDDA
> >
> >> | ---- ----
> >> | | |
> >> | | |
> >> | GND GND
> >> |
> >> | ---- ----
> >>
> >>
> >>
> >
>
|--------Ferrite------------------------------------VDDD
> >
> >> | ---- ----
> >> | | |
> >> | | |
> >> GND GND
> >>
> >>
> >> C2 = 2200pF (NFM21CC222R1H3)
> >> C1 = 1uF (NFM21PC105B1A3)
> >>
> >>
> >>
> >
>
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-- Attached file included as plaintext by Ecartis --
-- File: 3tcap.txt
-- Desc: 2302733855-3tcap.txt
SERIES ARRANGEMENT of C1 and C2
VDD C1 C2
A ---- B ----
|--------Ferrite------------------------------------VDDA
| ---- ----
| | |
| | |
| GND GND
|
| ---- ----
|--------Ferrite------------------------------------VDDD
| ---- ----
| | |
| | |
GND GND
C2 = 2200pF (NFM21CC222R1H3)
C1 = 1uF (NFM21PC105B1A3)
********************************************************************
PARALLEL ARRANGEMENT of C1 and C2
GND
|
| C1
----
---------------
| ---- |
| |
VDD | C2 |
A | ---- |
|--------Ferrite------------------------------------VDDA
| ----
| |
| |
| GND
|
------------------------------------------------------------------
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