[SI-LIST] Re: Split gnd planes - for/against? - Thanks!
- From: steve weir <weirsi@xxxxxxxxxx>
- To: simsonl@xxxxxxxxxxxxxx
- Date: Thu, 09 Apr 2009 20:53:20 -0700
Larry, yes it did come with the ChipQuake software. ChipQuake is
focused on the IC and while it does allow specifying the PCB bypass
network and package power / ground connections it doesn't not have that
facility. For small problems you could can model in the student version
of Sphinx.
Steve.
simsonl@xxxxxxxxxxxxxx wrote:
> Steve,
>
> The book you mentioned in an earlier post, "Noise Coupling in Integrated
> Circuits", is on amazon.com bundled with a simulation software. Did you get
> yours with that software and can it simulate multiple (split) power/ground
> planes?
>
> Thanks
> Larry
>
>
> ---- steve weir <weirsi@xxxxxxxxxx> wrote:
>
>> Tony usually that is the right decision. However, there are cases when
>> a package will not fit and still provide adequate isolation between
>> circuits without implementing a split. These don't happen in digital
>> designs running one signaling level.
>>
>> But suppose that you have a big digital bus switching 5A / ns that is
>> 0.25" away from some analog circuit that is sensitive to 10uV noise. Do
>> you think the 0.25" separation will be enough? If you cannot change the
>> placement to put the analog circuitry further away, what will you do?
>>
>> Steve.
>>
>> Tony Luan wrote:
>>
>>> Hi Sol,
>>>
>>> I think to split GND plane is not a good idea.
>>> For any high frequency noise, GND and power plane are playing completely
>>> equivalent role. How can a high frequency noise tell which plane is GND?
>>> Which plane is power? Why not split power plane instead and keep a solid
>>> complete GND plane, because in package or PCB, we have tons of power
>>> rails and power islands already.
>>> The biggest disadvantage to split GND plane I saw is that it increases
>>> routing difficulty when try to avoid high speed signal, clock, parallel
>>> bus across those gaps on GND plane.
>>>
>>> Thanks
>>> Tony
>>> -----Original Message-----
>>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>>> On Behalf Of Sol Tatlow
>>> Sent: Thursday, April 09, 2009 4:58 AM
>>> To: si-list@xxxxxxxxxxxxx
>>> Subject: [SI-LIST] Re: Split gnd planes - for/against? - Thanks!
>>>
>>> One last mail to put this thread 'to bed'...
>>>
>>> Thanks to everyone who took the time to reply, particularly to
>>> those who actually gave me what I asked for, those reluctant beasts,
>>> the real-life examples - it's great that you're willing to so fully
>>> participate in such a discussion. After all, theory is great;
>>> coupled with real-life examples it's even better.
>>>
>>> Of course, the specific examples can't be applied 1:1 to any other
>>> design, as has been said 'x' times, but I, for one, am nevertheless
>>> wiser for the experiences that have been shared... I believe I'm a
>>> good engineer, but won't stop learning 'till the day I die.
>>>
>>> It was also good to see that I am not the only one suffering at the
>>> hands of less-than-perfect datasheets and the implementation of
>>> often contradictoray 'hints' :) - regardless of simulation results
>>> and past experiences, it's not always easy when it comes to
>>> persuading a customer, who is still convinced that app notes are
>>> written by all-knowing beings, to 'do the right thing'.
>>>
>>> Sol
>>>
>>>
>>>
>> --
>> Steve Weir
>> Teraspeed Consulting Group LLC
>> 121 North River Drive
>> Narragansett, RI 02882
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>
>
>
--
Steve Weir
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
California office
(866) 675-4630 Business
(707) 780-1951 Fax
Main office
(401) 284-1827 Business
(401) 284-1840 Fax
Oregon office
(503) 430-1065 Business
(503) 430-1285 Fax
http://www.teraspeed.com
This e-mail contains proprietary and confidential intellectual property of
Teraspeed Consulting Group LLC
------------------------------------------------------------------------------------------------------
Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC
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