Joel
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? 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 information?
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 instructions given by the vendor.
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 website:
- 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
measurements.
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 practices.
On Fri, Mar 11, 2016 at 9:50 AM, Grasso, Charles <
Charles.Grasso@xxxxxxxxxxxx> wrote:
Hello,Scott's recent input on this re:
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 anyone became concerned about PDN performance.
Anyway, Steve and I were in agreement that they worked well enough
but that the layout and placement were absolutely critical which
agrees with
spreading inductance and placement distance. If it matters, we hadhelps.
the test boards micro-sectioned after the fact to make absolutely
sure that we made no assumptions about mounting dimensional parameters.
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 practice.
It was heresy back then. BTW, as you might guess, the 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
'poor'
Michael E. Vrbanac
EMC Forensics, President
On 03/11/2016 10:00 AM, David Anthony wrote:
Lee, the vendors dimensionally detail land pad 'recommendations'X2Y, but stay away from dimensioning specific via layouts. Scroll
for
down to Johanson's 'PCB mounting' tab at this link:
http://www.johansondielectrics.com/x2y-filter-decoupling-capacitor ;in the PDN Bypass applications section, notice the 'recommended' and
s#
pcb
Below the land pad dimensions, Johanson shows 'stick' figure via
layouts
layout depictions, no dimensions. If any vendor sent you, or youpreached:
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%20East%20200 ;
Bypass Capacitor Inductance, Data Sheet Simplicity to Practical
Reality
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 Steve. IT
The board layout complied exactly with what was specified by the
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 Anderson'
To: leeritchey@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; 'Ray Anderson' <raya@xxxxxxxxxx>;
< ray.anderson@xxxxxxxxxx>
Subject: [SI-LIST] Re: X2Y equivalent circuit modelwas incorrect.
Lee you know that board was not the optimal layout. Steve told
you it
Tom Dagostinoleeritchey@xxxxxxxxxxxxx> wrote:
Tom Dagostino
Teraspeed LabsOn Mar 9, 2016 8:30 AM, Lee Ritchey <
03/11/16We 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 Anderson'
<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-attachments immediately.
Johanson Dielectrics has downloadable spice models available
from this web
page:
http://www.johansondielectrics.com/x2y-filter-decoupling-capacit ;
or
s
download link:
http://www.johansondielectrics.com/downloads/JDI_X2Y_H-Spice_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 OK).
-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
http://www.x2y.com/bypass/X2Y%20Equivalent%20Circuit%20for%20Models. ;
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 for?
thanks in advance
Regards
Cristian
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