[SI-LIST] Re: Split gnd planes - for/against? - Thanks!

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Lakshmi Narayanan Sowrirajan, TLS-Chennai wrote:
> Hi Steve,
>
>       Where can I download this student version, can you please help
> me on this..?
>
> Thanks & Regards
> Lakshminarayanan.S
> 9840250902
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of steve weir
> Sent: Friday, April 10, 2009 9:23 AM
> To: simsonl@xxxxxxxxxxxxxx
> Cc: Tony Luan; Sol Tatlow; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Split gnd planes - for/against? - Thanks!
>
> 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 
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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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