Well said.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Smith, Larry
Sent: Tuesday, March 22, 2016 12:59 PM
To: scott@xxxxxxxxxxxxx; Sebastian Garcia <sg-listas@xxxxxxxxxxxx>
Cc: SI-LIST <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Hi Scott - I need to comment on this one. There are some subtleties that will
help us envision the inductance mechanisms for decoupling capacitors.
For horizontal structures (i.e. power planes and MLCC capacitors) we should
think of inductance in terms of the "number of squares" for the material. The
standard geometry capacitors have about 2 squares. Common sizes are 0201,
0402, 0603, 0805, 1206, etc. They are all twice as long as they are wide and
contribute about 2 squares of inductance. The current path is through the
capacitor and the return current path is somewhere on the board. BTW, this
works for ESR also. The horizontal contribution to both inductance and
resistance goes as the number of squares.
But horizontal is not the whole story. Current must go vertical in the
capacitor as well as horizontal. The larger capacitors tend to be taller and
some of the current has to go farther away from the return path on the board,
therefor larger size capacitors have somewhat larger inductance. The increase
in capacitor inductance with size is not as much as you might think because of
the "number of squares" argument.
The X2Y capacitors really do have fewer squares. They have a Vss terminal in
the middle of the cap structure and Vdd terminals on the two ends (these can be
reversed if you want). This separates the cap into two portions (two squares)
which are in parallel, effectively making 1/2 square. This should be compared
to the 2 squares of a standard geometry cap. BTW, reverse geometry caps (
0204, 0306, etc) are 1 square long and 2 squares wide, also resulting in 1/2
square. They are on par with X2Y caps in terms of the intrinsic inductance
associated with the cap body.
As you and other SI-list posters have pointed out, it is really all about the
vias. In many circumstances, the via loop inductance dominates and so the
intrinsic inductance associated with the cap body becomes insignificant. This
is often the case in server boards that tend to have through-hole vias. But in
the mobile space where microvias are the rule rather than the exception, the
board mounting inductance becomes small making the intrinsic capacitor
inductance a relatively bigger part of the problem. This is where alternative
cap geometries (X2Y, 3 terminal, reverse geometry) can really pay off. You
have to earn the right to use low inductance capacitors by having low
inductance mounting structures.
Regards,
Larry Smith
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Scott McMorrow
Sent: Monday, March 21, 2016 8:56 PM
To: Sebastian Garcia <sg-listas@xxxxxxxxxxxx>
Cc: SI-LIST <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
sebastian,
This is just physics. An 0201 capacitor is half the physical size of an 0402.
The loop area through the capacitor is half the loop area of an 0402 capacitor.
Therefore, the capacitor contribution to bypass inductance for an 0201
capacitor is one half of an 0402.
Loop inductance below the capacitor will depend on the via configuration used
to connect to the power and ground planes, along with the placement of the
planes on the z-axis. I can engineer pretty much any inductance you want with
enough vias and optimized spacing. The capacitor has absolutely nothing to do
with what happens inside the board.
When the vias dominate inductance ... you need more vias, or better placement
of the planes and capacitors with respect to the load. No capacitor fixes that
problem.
What an X2Y capacitor does do is to have some amount of mutual inductance
cancellation near the capacitor terminals, which does lower inductance above
the plane, but, the biggest benefit of the X2Y capacitor is the terminal
configuration, which facilitates the use of 6 vias in a nearly minimum energy
configuration that is low inductance.
Scott McMorrow
R&D Consultant
Teraspeed Consulting - A Division of Samtec
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com
On Mon, Mar 21, 2016 at 4:01 PM, Sebastian Garcia <sg-listas@xxxxxxxxxxxx>
wrote:
Dave, the post you linked is technically enlightening.
Scott: Could you recommend a doc reference about more recent tests
with
0201 caps?
Best regards,
Sebas.
David Anthony wrote:
No disparaging comments here, just a clean Engineering discussionwith
about inductance and John's results:
https://www.freelists.org/post/si-list/6-layers-stackup,31
-Dave
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Lee Ritchey
Sent: Monday, March 14, 2016 1:00 PM
To: sg-listas@xxxxxxxxxxxx; 'SI-LIST'
Cc: John Zasio
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Todd,
Well said.
As to the tests that John Zasio did, they were done on a 16 layer
PCB
plane capacitance designed into it as one would do for a high03/14/16
performance design.
The testing was done as one would do to see how the PDS impedance
looks with either of the two capacitors connected. The results show
that, in this configuration, there is little difference with respect
to PDS performance.
From a PDS point of view, they don't offer anything more than an
0402 as you point out.
It has been a long time since I looked at the way Steve did his tests.
I'll have another look and see if I can find how he gets different
answers.
Lee
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Sebastian Garcia
Sent: Monday, March 14, 2016 9:23 AM
To: SI-LIST <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Well said, Todd. No more black magic, please, just well done Engineering.
Without solid engineering documents describing repeatable tests, it
turns to be a battle of professional egos spiced with commercial interests.
Sebas.
Todd Hubing wrote:
I think what Sebastian and others would like to see is a paperconfiguration.
describing the board and the measurements that were made. The slide
presentations on the website are interesting, but they do not
describe the board stackup or the measurements that were made to
justify the conclusions. In fact, in the 10 years since this work
was done, it has been effectively demonstrated that the conclusions
related to capacitor ratio and via ratio are not justified. The
impedance of the board in this study was not significantly affected
by the connection inductance of the decoupling capacitors above
about 200 MHz. Also, the extra vias on the 0402 capacitors have
relatively little effect on the mounting inductance and do not
represent a typical or recommended mounting
I don't mean to disparage Steve's work or X2Y capacitors. I talkedthan to say "always" or "never"
to Steve when he exhibited this at the IEEE EMC Symposium. His
board does a great job of presenting X2Y capacitors in a favorable
light, which is exactly what it was designed to do. It's actually a
very clever design.
Also, the X2Y capacitors themselves represent a well thought-out
design with many useful applications.
My point is that an optimum decoupling strategy depends on many
factors including the board stackup, active device requirements and
the intended application. 0402 MLCC capacitors do an excellent job
of high-frequency decoupling in most situations if they are
properly configured for the given application. If lower inductance
is called for, there are other options including embedded
capacitance, IDC capacitors, and 0201 capacitors. I have not seen
an application where X2Y capacitors, are the best option for power bus
decoupling.
Nevertheless, I've been in this business long enough that I know
better
and I would be very interested to review any published paper thatwebsite:
describes measurements and/or simulations on this topic.
Todd
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of David Anthony
Sent: Sunday, March 13, 2016 11:24 PM
To: tom@xxxxxxxxxxxxxxxxx; sg-listas@xxxxxxxxxxxx
Cc: 'SI-LIST' <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Sebastian, the design papers Tom referenced showing system
measurements by Steve can be found here:
http://www.x2y.com/bypass.htm#examples
Dave Anthony
X2Y
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Tom Dagostino
Sent: Sunday, March 13, 2016 10:52 PM
To: sg-listas@xxxxxxxxxxxx
Cc: SI-LIST
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Sebastian. I'm traveling right now and don't have access to those
archives. But look at the work by Steve on the X2Y web page. I
think you will find what you are looking for there.
Tom Dagostino
Teraspeed LabsOn Mar 13, 2016 8:13 PM, Sebastian Garcia
<sg-listas@xxxxxxxxxxxx> wrote:
Tom,
Could you shed some light on this, providing the specific Steve
Weir's documents you mention, please?
Best regards,
Sebas.
Sebastian Garcia
Slabs Electronics
Buenos Aires - Argentina
+54 911 3865 1770
Tom Dagostino wrote:
Joelinformation?
The layout I saw and Steve Weir commented on had the vias so
far away from the capacitor that the measured inductance was
dominated by circuit board traces. Steve fitted about 8 proper
layouts within the confines of the layout that Lee mentioned.
I asked Lee about this and he said the layout was something he
found on the X2Y web site I think it was in about 2007.
Since then X2Y has updated the layout and the Work Steve Weir
did has shown that with fewer X2Y caps the power supply noise
was lower compared to 0402 caps. This was shown with two
layouts of FPGAs running the same code and differing only in the caps
used.
My issue here is the dragging out of data that does not
represent current recommended applications as proof anything.
I think I still have one of Steve's boards. His method was well
documented with measurements. He set up unused I/O cells high
and low and attached SMAs to them for ease of measurement. So
he showed the supply as the chip saw it.
Regards
Tom Dagostino
Tom Dagostino
Teraspeed LabsOn Mar 13, 2016 11:42 AM, Todd Hubing
<hubing@xxxxxxxxxxx>
wrote:
I wouldn't characterize the Zasio paper as bad information. It
is a rare (on this mail list) example of someone supporting an
argument with actual data from a test described well enough
that anyone else could repeat it. Yuriy Shlepnev's app
note is another example of this. Both of these studies
demonstrate that, for the configurations evaluated, two
0402 capacitors are probably a better choice than an X2Y cap.
Of course, it is possible to come up with configurations or
test criteria that favor the X2Y also.
For printed circuit board decoupling, the X2Y via configuration
is not optimum. The two capacitors share a pair of ground vias
that must be relatively close to each other. If the power
planes are more than about
0.5 mm from the board surface, an IDC capacitor or a pair of
two-terminal capacitors can achieve better flux cancelation by
alternating closely spaced power and ground vias. That said, if
you're REALLY concerned about high-frequency decoupling, take
Scott McMorrow's advice and use 0201 caps.
Todd
---------------------------------------------------------------
--
Todd H. Hubing
LearnEMC.com
---------------------------------------------------------------
--
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Tom Dagostino
Sent: Saturday, March 12, 2016 7:00 PM
To: leeritchey@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; Charles.Grasso@xxxxxxxxxxxx;
vrbanacm@xxxxxxxxxx; joel@xxxxxxxxxx
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Lee
What was the date was that recommended mounting? Do we
still believe Saturn is the furthest planet from the sun?Â
Has X2Y changed their recommendations since John did his
measurements? Has Steve Weir's work contradicted John's
because Steve used the correct layout? Why are you basing
you argument on known bad
instructions given by the vendor.
Tom Dagostino
Teraspeed LabsOn Mar 12, 2016 2:27 AM, Lee Ritchey
<leeritchey@xxxxxxxxxxxxx> wrote:
On our web site, www.speedingedge.com you can download the
article by John Zasio showing comparison of X2Y to 0402
capacitors mounted on the same test PCB following the
mounting
You can decide for yourself which to use from that data.
This should be the detail that some of you have requested.
Lee Ritchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Joel Brown
Sent: Friday, March 11, 2016 10:05 AM
To: Charles.Grasso@xxxxxxxxxxxx
Cc: vrbanacm@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: X2Y equivalent circuit model
I thought one of the things that make X2Y capacitors lower
inductance is that the current in each terminal flows in
opposite directions causing a cancellation effect. This is
from X2Y
http://www.x2y.com/bypass/X2Y%20Equivalent%20Circuit%20for%20Models.practices.measurements.
  - Low inductance due to cancellation effect
I used them on some boards back when they came out. I can't
say they worked better than 0402 capacitors because I did not
do any detailed
You really need to consider the whole PDN system including
the mounting inductance, spreading inductance, IC package
parasitics, frequency spoectrum of IC switching current, any
decoupling that might be inside the IC package which is often
an unknown. I think this detailed kind of analysis would be
nice to do but is rarely done. IME I have never had a problem
just following good design
anyone became concerned about PDN performance.
On Fri, Mar 11, 2016 at 9:50 AM, Grasso, Charles <
Charles.Grasso@xxxxxxxxxxxx> wrote:
Hello,
Current thinking has it that the PDN performance is only as
good as the first pwb resonance (typically in the few
hundreds of MHZ - I have seen 300 as a commonly used
number) and
that the BGA decoupling is (for the most part) taken care
of by the substrate capacitance.
In other words - it is my understanding that the board
decouplers don't really need to be "high" performers are
the frequencies of interest are (relatively) low.
I'd appreciate the communities thoughts on this.
[Hello Mike - Good to "see" you again!]
Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications
(w) 303-706-5467
(c) 303-204-2974
(t) 3032042974@xxxxxxxxx
(e) charles.grasso@xxxxxxxxxxxx
(e2) chasgrasso@xxxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Michael Vrbanac
Sent: Friday, March 11, 2016 9:42 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: X2Y equivalent circuit model
I agree that Steve had this correct. I had some offline
discussions w/Steve back in that timeframe and between that
and the decoupling capacitor/PDN performance optimization
research studies we did at in my EMC design research lab at
Compaq on this topic back in the early 90's, also
considering "side mounted decoupling capacitors" (yes, that
format was around back then) because we were already seeing
EMC issues long before
'recommendations'parameters.Anyway, Steve and I were in agreement that they worked wellScott's recent input on this re:
enough but that the layout and placement were absolutely
critical which agrees with
spreading inductance and placement distance. If it matters,
we had the test boards micro-sectioned after the fact to
make absolutely sure that we made no assumptions about
mounting dimensional
practice.IIRC, someone on that team later wrote a paper on part of
that study (not all) but I have since forgotten its title
and the name of fe llow who wrote it. Sorry I cannot
remember who but that was back in the days when my head was
handed to me daily for saying what this forum has rightly
understood these days as good engineering
It was heresy back then. BTW, as you might guess, thehelps.
results of that study back then were in good agreement with
most of what has been posted on here as good design
practice for quite some time. I hope that
Michael E. Vrbanac
EMC Forensics, President
On 03/11/2016 10:00 AM, David Anthony wrote:
Lee, the vendors dimensionally detail land pad
SteveAnderson''poor'forX2Y, but stay away from dimensioning specific via layouts.
Scroll down to Johanson's 'PCB mounting' tab at this link:
http://www.johansondielectrics.com/x2y-filter-decoupling-in the PDN Bypass applications section, notice the
cap
a
citor
s#
pcb
Below the land pad dimensions, Johanson shows 'stick'
figure via layouts
'recommended' and
layout depictions, no dimensions. If any vendor sent you,preached:
or you downloaded a vendor document specifying the poor
layout please send it to me. Steve would not specify that
poor layout as you suggest, these early 2004-05 papers are
just a few examples of the low inductance he
http://www.ipblox.com/pubs/DesignConEast_2005/DesignCon%20E
Bypass Capacitor Inductance, Data Sheet Simplicity to
Practical Reality
ast
%
20200
5%
20TF2_ipb.pdf
On Behalf Of Lee Ritchey
Considerations for Capacitor Selection in FPGA Designs
http://www.x2y.com/publications/decoupling/mar21-05.pdf
-Dave
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
Sent: Friday, March 11, 2016 1:07 AMCharles.Grasso@xxxxxxxxxxxx; 'Ray Anderson'
To: tom@xxxxxxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; 'Ray Anderson';
cristian.gozzi@xxxxxxxxx;
Subject: [SI-LIST] Re: X2Y equivalent circuit modelvendor. I believe that that layout was specified by
The board layout complied exactly with what was specified
by the
Steve. IT looks like what is on his test PCB.
On Behalf Of Tom Dagostino
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
Sent: Wednesday, March 9, 2016 10:19 AMcristian.gozzi@xxxxxxxxx; Charles.Grasso@xxxxxxxxxxxx; 'Ray
To: leeritchey@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; 'Ray Anderson'
<raya@xxxxxxxxxx>;
< ray.anderson@xxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Lee you know that board was not the optimal layout.Â
Anderson'told you itwas incorrect.
Tom Dagostinoleeritchey@xxxxxxxxxxxxx> wrote:
Tom Dagostino
Teraspeed LabsOn Mar 9, 2016 8:30 AM, Lee Ritchey <
We mounted the X2Y capacitors exactly as specified in
the applications notes provided by the vendor.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of ;
Grasso, Charles
Sent: Monday, March 7, 2016 7:46 AM
To: leeritchey@xxxxxxxxxxxxx; cristian.gozzi@xxxxxxxxx;
'Ray
OK).<ray.anderson@xxxxxxxxxx>; si-list@xxxxxxxxxxxxx
Cc: 'Ray Anderson' <raya@xxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Hello Lee - What method is used for a capacitor to
be properly mounted? So, if an X2Y capacitor is properly
mounted the <insert metric here> will not improve?
Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications
(w) 303-706-5467
(c) 303-204-2974
(t) 3032042974@xxxxxxxxx
(e) charles.grasso@xxxxxxxxxxxx
(e2) chasgrasso@xxxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Lee ;
Ritchey
Sent: Saturday, March 05, 2016 5:44 AM
To: cristian.gozzi@xxxxxxxxx; 'Ray Anderson';
si-list@xxxxxxxxxxxxx
Cc: 'Ray Anderson'
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Our tests show that the X2Y capacitor is no better than
a properly mounted
0402 capacitor.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of ;
Cristian Gozzi
Sent: Friday, March 4, 2016 10:57 AM
To: Ray Anderson <ray.anderson@xxxxxxxxxx>;
si-list@xxxxxxxxxxxxx
Cc: Ray Anderson <raya@xxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit model
Thanks
it worked ;-)
Regards
Cristian
Il giorno gio 3 mar 2016 alle ore 10:04 Ray Anderson <
ray.anderson@xxxxxxxxxx> ha scritto:
Cristian-
Johanson Dielectrics has downloadable spice models
available from this web
page:
http://www.johansondielectrics.com/x2y-filter-decouplin
g-c
a
pacit
or
s
download link:
http://www.johansondielectrics.com/downloads/JDI_X2Y_H-
Spi
c
e_Fil
es
.z
ip
They should be usable in ADS using the ADS 'Hspice
Compatibility Component' Wizard. (in fact I just
confirmed that they import
-Ray Anderson
Xilinx Inc.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Cristian Gozzi
Sent: Thursday, March 03, 2016 9:07 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] X2Y equivalent circuit model
Hi Si expert
I was looking for a good circuit model for X2Y
capacitor to be used in my ADS circuit simulation
on internet I found this
------------------------------------------------------------------Â Â Â Â Â Âfor?pd
f
but when I tried to implemented it, something was wrong
The impedance vs freq. shapes on log/log scale does not
seem correct
can someone give to me any feedback or good reference
to look
thanks in advance
Regards
Cristian
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No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.6176 / Virus Database: 4540/11800 - Release Date:
03/12/16
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-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.6176 / Virus Database: 4542/11815 - Release Date:
------------------------------------------------------------------
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