[SI-LIST] Re: CHGND connection in DVI connector
- From: steve weir <weirsi@xxxxxxxxxx>
- To: qantrix <qantrix@xxxxxxxxx>
- Date: Tue, 04 May 2010 08:25:42 -0700
My pet peeve: People who repost private correspondence in public. I
marked up your drawing with instructions in the private mail.
Steve.
qantrix wrote:
> Steve,
>
> you mean direct connection or through caps/resistors?
>
>
>
> 2010/5/4 steve weir <weirsi@xxxxxxxxxx>:
>
>> Bill I recommend against the the second drawing. Please see the attached.
>>
>> Best Regards,
>>
>>
>> Steve.
>> wjcsongr@xxxxxxxxxxxxxxxxxxx wrote:
>>
>>> The second image shows the DVI signals crossing under the split in the
>>> ground planes...why wouldn't I be concerned about that Steve?
>>>
>>> Regards,
>>>
>>> Bill
>>>
>>> William Csongradi
>>> Senior Electrical Engineer
>>> Rockwell Collins Heads Down Display Center
>>> 319-295-7884
>>>
>>> Mailing Address
>>> Rockwell Collins
>>> 400 Collins Road NE
>>> MS 105-167
>>> Cedar Rapids, Iowa 52498-0001
>>>
>>>
>>>
>>>
>>> *qantrix <qantrix@xxxxxxxxx>*
>>> Sent by: si-list-bounce@xxxxxxxxxxxxx
>>>
>>> 05/04/2010 08:15 AM
>>>
>>>
>>> To
>>> si-list@xxxxxxxxxxxxx
>>> cc
>>>
>>> Subject
>>> [SI-LIST] Re: CHGND connection in DVI connector
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> Steve,
>>>
>>> http://img504.imageshack.us/i/currentdesign.png/
>>> you can find current design. data(diff.pairs) shield connected to sgnd.
>>>
>>> suggested design see here
>>> http://img266.imageshack.us/i/suggested.png/
>>>
>>> As you can see ch_gnd will cover all area of dvi connector and pins of
>>> data pairs shield connected to ch_gnd.
>>> diff.pairs will pass under separation between planes.
>>>
>>> Idea make it like this seems like bad.
>>>
>>> But it's possible to connect pairs shield to ch_gnd without creating
>>> slot under pairs and cable will have only quite ch_gnd shield for each
>>> pair and not dirty sgnd. Question is - does this shield carrying
>>> return currents ? How it will work from EMC point ?
>>>
>>>
>>>
>>> 2010/5/4 steve weir <weirsi@xxxxxxxxxx>:
>>>
>>>> Is there a reason you want to isolate signal common from chassis?
>>>> Common
>>>> practice is to join the two near the chassis boundary. If you attempt
>>>> to
>>>> isolate them, you will have lots of capacitive sneak paths. If they are
>>>> joined you will not have a CM discontinuity issue.
>>>>
>>>> Steve.
>>>>
>>>> qantrix wrote:
>>>>
>>>>> I have question about CHGND connection in DVI connector/cable.
>>>>> There is two kind of shields - one - is shield for data/clock pair;
>>>>> second - whole cable shield.
>>>>> http://en.wikipedia.org/wiki/Digital_Visual_Interface
>>>>>
>>>>> We had some EMC consultation - was suggested to connect internal pairs
>>>>> shield to chgnd.
>>>>> on pcb make polygone chgnd that cover area up to end of dvi connector.
>>>>> So diff.pairs will run under slot of gnd.separation.
>>>>>
>>>>> Question is - how should be connected internal shields in DVI
>>>>> conenctor - to sgnd or to chgnd?
>>>>>
>>>>> diff. pairs running on the slot - seems like bad idea?
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>>>> --
>>>> Steve Weir
>>>> IPBLOX, LLC 150 N. Center St. #211
>>>> Reno, NV 89501 www.ipblox.com
>>>>
>>>> (775) 299-4236 Business
>>>> (866) 675-4630 Toll-free
>>>> (707) 780-1951 Fax
>>>>
>>>>
>>>>
>>>>
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>> --
>> Steve Weir
>> IPBLOX, LLC 150 N. Center St. #211
>> Reno, NV 89501 www.ipblox.com
>>
>> (775) 299-4236 Business
>> (866) 675-4630 Toll-free
>> (707) 780-1951 Fax
>>
>>
>>
>>
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--
Steve Weir
IPBLOX, LLC
150 N. Center St. #211
Reno, NV 89501
www.ipblox.com
(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax
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