Re: gEDA-user: pcb, howto partition power planes?

[Eric Winsor <eric@xxxxxxxxx>]

Steve,

I don't see these other attempts.

Eric Winsor

Steve Meier wrote:
> Dave,
>
> No I struggled three times to get usable url's so go down a couple more
> of my attempts and then you will have to take the line breaks out of the
> ultra long url but you can get there.
>
> Steve Meier
>
>
> On Thu, 2008-10-30 at 16:29 -0400, Dave McGuire wrote:
>   
>> I don't see any URLs in there..
>>
>>           -Dave
>>
>> On Oct 29, 2008, at 6:08 PM, Steve Meier wrote:
>>     
>>> I went looking to see if the Analog Device book was available
>>> electronically. Here are the links.
>>>
>>>
>>> Steve Meier
>>>
>>>
>>> High Speed System Applications Table of Contents
>>>
>>>
>>>
>>> High Speed System Applications Section 1: High Speed Data Conversion
>>> Overview
>>>
>>>
>>>
>>> High Speed System Applications Section 2: Optimizing Data Converter
>>> Interfaces
>>>
>>>
>>>
>>> High Speed System Applications Section 3: DAC, DDS, PLL's, and Clock
>>> Distribution
>>>
>>>
>>>
>>>
>>> High Speed System Applications Section 4: PC Board Layout and Design
>>> Tools
>>>
>>>
>>>
>>> On Tue, 2008-10-28 at 13:44 -0700, Steve Meier wrote:
>>>       
>>>> I won't argue this point. I will refer every one to an Analog Device
>>>> publication "High Speed System Applications" copyright 2006 ISBN-10:
>>>> 1-56619-909-3  or ISBN-13: 978-1-56619-909-4
>>>>
>>>> In particular if you get a copy of this book (and they gave me mine)
>>>> look at pages 4.15 and 4.16
>>>>
>>>> There AD recommends connecting both of the A/D grounds "digital" and
>>>> "analog" to the analog ground plane "this is because it causes less
>>>> problems for the relatively small amount of digital return current  
>>>> to be
>>>> returned through the analog ground than it would to connect the
>>>> converter to the much noisy digital ground.
>>>>
>>>> There is a lot more talked about then just that one blurb.
>>>>
>>>> Steve Meier
>>>>
>>>>
>>>>
>>>> On Tue, 2008-10-28 at 11:22 -0700, Joerg wrote:
>>>>         
>>>>> Stefan Salewski wrote:
>>>>>           
>>>>>> Sometimes it is necessary/recommended to partition (separate)  
>>>>>> power or
>>>>>> ground planes, i.e. for ADC or DC/DC-Converters, see page 16 and  
>>>>>> 17 in
>>>>>>
>>>>>> http://focus.ti.com/lit/ug/slwu028c/slwu028c.pdf
>>>>>>
>>>>>> We can do this in pcb program with (adjoining) polygons.
>>>>>> Disadvantage is, that if we change the size of one of the  
>>>>>> polygons we
>>>>>> have to manually adjust the other sizes. A other method may be  
>>>>>> so divide
>>>>>> a large polygon by copper clearing traces (with trace width zero).
>>>>>>
>>>>>> This is related to my question from
>>>>>>
>>>>>> http://archives.seul.org/geda/user/Sep-2008/msg00387.html
>>>>>>
>>>>>> but not identical.
>>>>>>
>>>>>> What is the best way to handle this?
>>>>>>
>>>>>>             
>>>>> I can't speak to that but just one word of caution: In my 20+  
>>>>> years in
>>>>> engineering I have yet to see one case where splitting a ground  
>>>>> plane
>>>>> under high-speed ADCs has worked. Regardless of what application  
>>>>> notes
>>>>> say. Usually it didn't work, lots of noise. Or it kind of worked but
>>>>> fell apart the instant somebody whipped out a GSM cell phone or  
>>>>> BlackBerry.
>>>>>
>>>>> Myself, I never spilt a ground place. OTOH the industry practice of
>>>>> splitting planes is providing part of my income :-)
>>>>>
>>>>> The only time I split is where required for safety, for example  
>>>>> patient
>>>>> isolation per 60601 (ECG, ultrasound etc.).
>>>>>
>>>>>           
>>>>
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>>>>         
>>>
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>>     
>
>
>
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