Mail Archives: geda-user/2015/07/16/13:34:41
On Jul 16, 2015, at 10:19 AM, John Griessen <john AT ecosensory DOT com> wrote:
> On 07/16/2015 02:37 AM, Roland Lutz wrote:
>> I can currently come up with the following:
>> - managing voltage drop, oscillation, and heat by
>> - keeping trace resistance low and
>> - keeping common trace segments short, and
>> - improving signal quality in differential pairs by minimizing signal
>> run time differences
>>
>> I'm not an electronics engineer, though
>
> The differential pair attribs that can help also include
> 1. smoothness of board material,
> since the waveguide smoothness affects how much mismatch there is and so reflections and in a short
> transmission line in a system, standing wave patterns on the transmission line (differential pair).
> 2. definition and smoothness of the trace width
> so it does not have blips or sharp edges
>
> For some frequencies, (pcb antennas and feed lines), corners matter, so
> 3. min radius spec on a trace edge
>
> 4a. 4b. 4c. Power decoupling caps needed near a pin -- three type ranges
>
> 5. attrib category of keep away by X distance. Add it and a unique name to two nets to keep them apart.
>
>
>
>
>
Yup. It can get quite elaborate. The attributes above are requirements, but then there are also specs derived from layout.
Gschem has the capacity to handle attributes of net segments, but I wonder if this is just too much metadata to burden a schematic with in many cases. DJ¢s database of attributes idea continues to grow on me.
For requirements, I would add that printed circuit traces also have a thermal function. Sometimes you want a net segment to carry away the heat, and sometimes you want one that conducts as little heat as possible.
John Doty Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd AT noqsi DOT com
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