[SI-LIST] Re: 6 layers stackup

Tom

Well, although Lee pro ports to be measuring the bulldozer (PCB), the 
article by John Zasio compares two different passengers (capacitors) 
using a flawed test vehicle.  Because of this, the conclusion is dead wrong.

Scott

Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax

http://www.teraspeed.com

Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC



Tom Biggs wrote:
> You can take the bulldozer analogy two ways. It depends on whether you
> care about the weight of the bulldozer with passengers, or just the
> weight of the passengers.
>
> Steve's test fixture was geared toward 'weighing the passengers'. Lee's
> was toward 'weighing the bulldozer'. So they each served their purpose.
> His whole point was that the vias going down 50 mils on a board are
> going to swamp out the advantages of low inductance caps. His test
> fixture, by design, had vias that go down 50mils. I'm sure he'd agree
> that this would be a bad fixture for measuring the cap itself, which was
> not his goal.
>
> The appropriate land pattern to use for the low-inductance caps is a
> separate issue. I'd be curious to see Lee's board with Steve's land
> pattern.
>
>     -tom
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Muranyi, Arpad
> Sent: Tuesday, February 26, 2008 1:31 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: [!! SPAM] Re: 6 layers stackup
>
> Can't resist to illustrate this with an example:
>
> If you want to compare the weight of an ant and a cricket and you put
> them on top of the same bulldozer, you will not see much difference in
> their weight...
>
> Arpad
> ------------------------------------------------------------------------
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Lee Ritchey
> Sent: Tuesday, February 26, 2008 11:16 AM
> To: Charles Grasso; Scott McMorrow
> Cc: Steve Weir; QU Perry; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: [!! SPAM] Re: 6 layers stackup
>
> What does the test vehicle have to do with it?  Both capacitors are
> seeing
> the same stackup.  It's apples and apples.   Why 26 layers?  Lots of
> PCBs
> have 26 layers, pretty much all of them in terabit routers.  This PCB
> was used to test may things besides these two capacitors.
>
> What is being presented is the difference between the two capacitors
> under the same set of test conditions and it is not much.
>
> There are two sets of tests.  One with the capacitors connected to the
> first two planes inside the PCB, which is the lowest added inductance
> and the other is with the capacitors attached to two planes further down
> in the PCB.
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
>                 http://www.si-list.net
>
> List archives are viewable at:    =20
>               http://www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>  =20
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
>                 http://www.si-list.net
>
> List archives are viewable at:     
>               http://www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>   
>
>
>   
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: