[SI-LIST] Re: 10 Layer Stack-up board/TWR PCB
- From: Doug Smith <doug@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 01 Nov 2011 21:57:18 -0700
The cost of a product stop ship or delayed introduction can be in the
millions of $. I prefer to be conservative and then back off as soon as
things are out and working properly. I see disasters all the time caused
by reducing cost on the first design. If one has a lot of experience
with nearly identical designs (similar circuit boards in similar
enclosures), then one can draw on that to take risks.
A company I used to work for went under (about 1 1/2 years after I left
them) because of a risk that was taken resulting in a stop ship on all
of the company's products that lasted a whole quarter. It was a signal
integrity issue. The company survived the incident but the lost cash set
the stage for later problems.
BTW, using a magnetic field probe I made from a paperclip, I found the
problem in a few hours work (not actually my job, just helping the
team), but the lead engineer would not believe such a simple method was
valid so he took a month to find the problem with a lot of expensive
test equipment. At some point I may do a WebEx session on this method
which I have further developed over the years. If you might be
interested in this, contact me privately.
Magnetic field probes are not normally used for signal integrity
measurements. But in this case, such a probe was able to permit
measuring a critical noise voltage in the circuit that turned out to be
the problem.
Doug
On 11/1/11 3:49 PM, Lee Ritchey wrote:
> Cost!
>
> From: Jory McKinley
> Sent: Tuesday, November 01, 2011 12:55 PM
> To: Lee Ritchey ; Filion, Marc-Andre
> Cc: si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: 10 Layer Stack-up board/TWR PCB
>
>
>
>
> Same number of layers much much better noise/resonance isolation, where is
> the downside?
>
>
>
>
>
> --------------------------------------------------------------------------------
> From: Lee Ritchey<leeritchey@xxxxxxxxxxxxx>
> To: Jory McKinley<jory_mckinley@xxxxxxxxx>; "Filion,
> Marc-Andre"<marc-andre.filion@xxxxxxxxxxxxxx>
> Cc: si-list@xxxxxxxxxxxxx
> Sent: Tuesday, November 1, 2011 3:27 PM
> Subject: Re: [SI-LIST] Re: 10 Layer Stack-up board/TWR PCB
>
> Way too many ground planes.
>
> --------------------------------------------------
> From: "Jory McKinley"<jory_mckinley@xxxxxxxxx>
> Sent: Tuesday, November 01, 2011 9:02 AM
> To: "Filion, Marc-Andre"<marc-andre.filion@xxxxxxxxxxxxxx>
> Cc:<si-list@xxxxxxxxxxxxx>
> Subject: [SI-LIST] Re: 10 Layer Stack-up board/TWR PCB
>
>> My post are showing up either without content or partial? Hopefully this
>> one post correctly. This is the stack-up I would consider for Jayasuryan
>> board:
>>
>> TOP
>>
>> GND
>> DVDD1_2/D2VDD1_2/DVDD1_8
>>
>> GND
>>
>> SIG1/SIG2
>>
>> SIG3/SIG4
>>
>> GND
>>
>> DVDD5/DVDD3_3
>>
>> GND
>>
>> BOTTOM
>>
>>
>> Regards,
>> -Jory
>>
>>
>>
>>
--
-------------------------------------------------------
___ _ Doug Smith
\ / ) P.O. Box 1457
========= Los Gatos, CA 95031-1457
_ / \ / \ _ TEL/FAX: 408-356-4186/358-3799
/ /\ \ ] / /\ \ Mobile: 408-858-4528
| q-----( ) | o | Email: doug@xxxxxxxxxx
\ _ / ] \ _ / Website: http://www.dsmith.org
-------------------------------------------------------
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