[SI-LIST] Re: 0306 Capacitors
- From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <weirsp@xxxxxxxxxx>, <leeritchey@xxxxxxxxxxxxx>,<Farah.Haddadin@xxxxxxxxx>,"Ken Patterson" <pattken@xxxxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 11 Mar 2004 21:19:36 -0500
Steve,
Eight and 10-terminal capacitors are also available from multiple
sources, not only from AVX. Also, similar to the IDC parts, there are
capacitor arrays available in four and eight terminal packages, which offer
inductances only slightly higher than IDC parts' inductances.
You are correct that even if the capacitance was different, the
important parameter is inductance. To Lee's point: these measured curves
dont really show apples to apples comparison, because each via pattern
is different. However, given the fact that the terminal geometry of these
capacitors are also different, they cant even have the same via pattern.
And this could show the strength of the X2Y capacitor in this application.
The fact that one of the terminals is in the middle of the body, lends
itself
very well to via placements with small loop size. While the
field-cancellation
mechanism of the X2Y capacitor may be accessible mostly in
differential connections, when hooked up to planes in single-ended manner,
the terminal arrangement of the part appears to be its strength.
Regards,
Istvan
----- Original Message -----
From: "steve weir" <weirsp@xxxxxxxxxx>
To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>; "Ken Patterson"
<pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Thursday, March 11, 2004 8:18 PM
Subject: [SI-LIST] Re: 0306 Capacitors
> Lee, there is no sleight of hand here. First, a 56nF X2Y is really a
112nF
> part. X2Y parts are rated on the circuit one capacitance. A 56nF X2Y has
> two 56nF caps in it, so in a circuit two configuration the capacitance is
> 112nF. This is easily seen by the fact that the capacitive portion of the
> plots line up directly with the 100nF conventional capacitors.
>
> Second, inductance is determined by the capacitor body design, not the
> capacitance. We can take virtually any 0603 capacitor and get the same
> inductive line. Once we get significantly past the SRF the insertion loss
> is equal for all. Similarly for the X2Y, IDC etc. The IDC 0.47 is what
> was available in stock. The device still demonstrates very good ESL, but
> it is impaired by the via pattern. I have a new via pattern that we are
> testing that should improve it somewhat. Whether the pattern will pull
the
> IDC below the X2Y plot or not remains to be seen.
>
> These tests show the real behavior with the capacitors attached to a plane
> without using a plane so large that the anti-resonant peak interferes with
> measurements well beyond 100MHz. The tests correlate to models very, very
> well. The predicted performance of capacitors came out within 1dB of
> models made before the tests were run. If we build a big board, there is
> not going to be any change in the relative results. If you disagree with
> this, please indicate the science that would support such an idea.
>
> X2Y's are licensed to five manufacturers at present. IDC's are an AVX
only
> option.
>
> No, I fundamentally disagree with your claim about capacitive SRF. What
> matters is insertion loss. The SRF determines where that loss bottoms
out,
> and Q determines how steep the peak inflection is. Significantly above
the
> SRF, which will be well below 30MHz for any large capacitance versus case
> style we care to choose we will be well past the SRF, and impedance and
> therefore insertion loss is determined by the mounted ESL. This is a
point
> you can find in your own book in the chapters written by John Zasio.
>
> If you prefer milliohms it is a simple translation of:
>
> 0 dB 25 ohms
> -20dB 2.5 ohms
> -40dB 0.25 ohms
> -60dB 0.025 ohms
>
> Again this you will find in your own book. We reported dB because that is
> exactly what the tests report.
>
> Regards,
>
>
> Steve.
> At 08:51 AM 3/11/2004 -0800, Lee Ritchey wrote:
> >Steve,
> >
> >Looked at the data from X2Y. Most of the tests use two different values
of
> >capacitor, the value used for the X2Y making it look better. (IDC 470
nF,
> >X2Y 56 nF) (0612 100 nF, X2Y 56 nF) I could get the same results with
the
> >same skewed tests. Sadly, this is a common problem with vendor furnished
> >data. Remember Getek?
> >
> >I was really interested in tests you have personally made that
demonstrate
> >true A-B comparisons on a PCB that is representative of a real power
> >subsystem, as we have done. What I mean by that is examine impedance vs.
> >frequency for a PCB with enough plane capacitance to support the
switching
> >transients seen when driving data buses, etc. When you do that, you are
> >going to come to the same conclusions that we did- not worth the extra
> >resources and not worth forcing your manufacturer to use a single sourced
> >part.
> >
> > Remember, what counts is the frequency at which the capacitor is
series
> >resonant and that is a combination of the value of C and total ESL. For
> >all of the examples shown it is less than 30 MHz. Switching harmonics
> >usually start abouve 100 MHz.
> >
> >Final comment on the data is the vertical scale is in db. It would be of
> >far greater value if it were in milliohms. Then we could tell more about
> >what these capacitors do for us in the power subsystem.
> >
> >Lee
> >
> >
> > > [Original Message]
> > > From: steve weir <weirsp@xxxxxxxxxx>
> > > To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>; Ken
Patterson
> ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > Date: 3/10/2004 3:17:18 PM
> > > Subject: Re: [SI-LIST] Re: 0306 Capacitors
> > >
> > > Lee, the file is available on X2Y's web site, but I have attached it
here
> > > as well. I spoke with Dave Anthony, dave@xxxxxxx and he will be happy
to
> > > supply you with one of the test boards if you like.
> > >
> > >
> > > Regards,
> > >
> > >
> > > Steve.
> > > At 01:50 PM 3/10/2004 -0800, Lee Ritchey wrote:
> > > >Steve,
> > > >
> > > >How about sharing the actual test results with us?
> > > >
> > > >Lee
> > > >
> > > >
> > > > > [Original Message]
> > > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > > To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>; Ken
> >Patterson
> > > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > > Date: 3/10/2004 10:44:23 AM
> > > > > Subject: [SI-LIST] Re: 0306 Capacitors
> > > > >
> > > > > Lee, It is all in the coefficients. There is no magic here. I
have
> >the
> > > > > data carefully taken at the planes themselves and it does show
> >dramatic,
> > > >as
> > > > > in 3:1 improvement at the planes using X2Y versus 0603. All the
data
> >I
> > > > > have, does in fact correlate well to what you have published.
While
> >that
> > > > > may seem a contradiction, it is not.
> > > > >
> > > > > What we are dealing with is a simple 1/( M + N ) equation for
> >admittance
> > > > > where M is the ESL of the discrete device and N is the partial
> >inductance
> > > > > of the mounting structure and the planes themselves. As I
suggested a
> > > > > month or two ago, if we take a graphical view of this to gain
> >intuition,
> > > >we
> > > > > can simply hold M or N constant and plot against the other. It is
> >easy
> > > >to
> > > > > confirm that if M >> N, then reductions to N offer little help and
> > > > > vice-versa. When dealing with ordinary capacitors with ESLs of
> > > >450-500pH,
> > > > > that means that reducing the attachment inductance from values
much
> >below
> > > > > 1nH show rapidly diminishing returns. A good two via mount on a
four
> > > > > layer 0.062 board yields total inductance of just about 1200pH.
Here
> >the
> > > > > attachment inductance is not too much bigger than the ESL of the
> >device,
> > > > > and as you have experience with, dropping the attachment
inductance
> >by a
> > > > > factor of two only improves the total inductance by less than 1/3
to
> > > >about
> > > > > 850pH, while doubling the number of holes that we have to drill.
So,
> >we
> > > > > are only able to exchange primarily parts placement costs against
> >drill
> > > >holes.
> > > > >
> > > > > However, when we take an ESL on the order of 120pH, that picture
> >changes
> > > > > completely. Now, the mounting inductance of 700-750pH is very
> >dominant,
> > > > > and there are substantial gains to be had by reducing same. So,
for
> > > > > example by using a properly designed six via mount for the X2Y,
the
> >total
> > > > > mounted inductance drops to 300-400pH depending on just how
aggressive
> > > >you
> > > > > want to get with the vias. I have test boards you can measure in
your
> > > >own
> > > > > facilities with repeatable values under 300pH. That is a 75%
> >reduction
> > > >in
> > > > > parts count, and a 25% reduction in total vias to achieve the same
> >high
> > > > > frequency impedance AS SEEN AT THE PLANES.
> > > > >
> > > > > Regards,
> > > > >
> > > > >
> > > > > Steve.
> > > > >
> > > > >
> > > > >
> > > > > At 09:01 AM 3/10/2004 -0800, Lee Ritchey wrote:
> > > > > >Steve,
> > > > > >
> > > > > >I have similar tests that show the inductance reduction and I
agree.
> > > >What
> > > > > >counts is the effect the mounted capacitor has on the impedance
of
> >the
> > > > > >power system. When this test is done, the lowering of the
overall
> > > > > >inductance is visible as a shift to a higher frequency of the
series
> > > > > >resonance as well as the parallel resonance between the capacitor
> > > >parasitic
> > > > > >inductance and the plane capacitance.. However, in almost all
cases
> >this
> > > > > >shift is not large enough to warrant the extra cost of the vias
or
> >the
> > > >more
> > > > > >expensive capacitors.
> > > > > >
> > > > > >I hate to mention books, but we have published this data. I'll
post
> >it
> > > >on
> > > > > >my web site. UMR has done similar tests and published the
results
> >in the
> > > > > >IEEE proceedings on EMC.
> > > > > >
> > > > > >Lee
> > > > > >
> > > > > >
> > > > > > > [Original Message]
> > > > > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > > > > To: <leeritchey@xxxxxxxxxxxxx>; <Farah.Haddadin@xxxxxxxxx>;
Ken
> > > >Patterson
> > > > > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > > > > Date: 3/9/2004 10:00:18 AM
> > > > > > > Subject: RE: [SI-LIST] Re: 0306 Capacitors
> > > > > > >
> > > > > > > Lee, I have a whole lot of test data that shows big
differences
> > > >between
> > > > > > > normal 0603's, with 2 and four via patterns as well as reverse
> > > >geometry
> > > > > > > caps versus X2Y's.
> > > > > > >
> > > > > > > On a four layer board where the differences will be the least
due
> >to
> > > >the
> > > > > > > dominance of via inductance, we go from about 1200pH for an
0603
> >with
> > > > > > > 0.050 spaced side mount via's, one per pad, to 850pH with four
> >vias
> > > > > >total,
> > > > > > > to under 300pH with X2Y 0603 and a optimized via pattern. A
4:1
> > > > > >reduction
> > > > > > > in parts count saves a lot of money.
> > > > > > >
> > > > > > > Nothing is free, the via pattern isn't as friendly as that
> >convenient
> > > > > > > 0.050" spacing, but the total number of vias needed in the
board
> >to
> > > >yield
> > > > > > > an impedance at say 100MHz also comes down considerably versus
> >normal
> > > >or
> > > > > > > reverse geometry 0603s.
> > > > > > >
> > > > > > > Steve.
> > > > > > >
> > > > > > > At 09:29 AM 3/9/2004 -0800, Lee Ritchey wrote:
> > > > > > > >Farah,
> > > > > > > >
> > > > > > > >By the time you add in the inductance of the mounting
inductance
> >for
> > > >your
> > > > > > > >PCB, the lower inductance you get with this uncommon shaped
> > > >capacitor is
> > > > > > > >not worth it. Stick with 0603 and use via mounting pads on
the
> > > >sides of
> > > > > > > >the capacitor rather than the end and you get the best
compromise
> > > >between
> > > > > > > >cost, PCB space and performance. Using multiple vias does
> >reduce the
> > > > > > > >mounting inductance some, but is not worth the cost in terms
of
> >PCB
> > > >space
> > > > > > > >and drilling costs. We've made many controlled tests to
> >establish
> > > >this.
> > > > > > > >
> > > > > > > >Lee
> > > > > > > >
> > > > > > > >
> > > > > > > > > [Original Message]
> > > > > > > > > From: steve weir <weirsp@xxxxxxxxxx>
> > > > > > > > > To: <Farah.Haddadin@xxxxxxxxx>; Ken Patterson
> > > > > > > ><pattken@xxxxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > > > > > > > > Date: 3/9/2004 6:27:44 AM
> > > > > > > > > Subject: [SI-LIST] Re: 0306 Capacitors
> > > > > > > > >
> > > > > > > > > Farah,
> > > > > > > > >
> > > > > > > > > I believe Murata does make 0306's, but you will get lower
> > > >inductance
> > > > > >at a
> > > > > > > > > much lower price from an 0603 X2Y. The only caveat is
that
> >you
> > > >are
> > > > > > > > > presently limited to 200nF in the X2Y, whereas an 0306 in
X5R
> >can
> > > > > >support
> > > > > > > > > larger values. Unmounted an 0306 is about 190-200pH,
whereas
> >an
> > > >0603
> > > > > >X2Y
> > > > > > > > > is about 120pH.
> > > > > > > > >
> > > > > > > > > Regards,
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Steve.
> > > > > > > > > At 08:16 AM 3/9/2004 -0600, Haddadin, Farah wrote:
> > > > > > > > >
> > > > > > > > > >I tried AVX... They don't make 0306 caps, although their
data
> > > >sheets
> > > > > > > > > >indicate that they do.
> > > > > > > > > >
> > > > > > > > > >Thanks,
> > > > > > > > > >Farah
> > > > > > > > > >
> > > > > > > > > >-----Original Message-----
> > > > > > > > > >From: Ken Patterson
[mailto:pattken@xxxxxxxxxxxxxxxxxx]=20
> > > > > > > > > >Sent: Tuesday, March 09, 2004 8:16 AM
> > > > > > > > > >To: Haddadin, Farah; si-list@xxxxxxxxxxxxx
> > > > > > > > > >Subject: RE: [SI-LIST] 0306 Capacitors
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >Try AVX. They make a line of reverse aspect caps.
> > > > > > > > > >
> > > > > > > > > >Regards,
> > > > > > > > > >
> > > > > > > > > >Ken
> > > > > > > > > >
> > > > > > > > > >-----Original Message-----
> > > > > > > > > >From: Haddadin, Farah [mailto:Farah.Haddadin@xxxxxxxxx]
> > > > > > > > > >Sent: Tuesday, March 09, 2004 9:11 AM
> > > > > > > > > >To: si-list@xxxxxxxxxxxxx
> > > > > > > > > >Subject: [SI-LIST] 0306 Capacitors
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >Experts,
> > > > > > > > > >
> > > > > > > > > >Does anybody know vendors that can produce 0306 ceramic
> > > >capacitors?
> > > > > > > > > >
> > > > > > > > > >Thanks,
> > > > > > > > > >Farah
> > > > > > > > >
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