kicad-developers team mailing list archive

[Jean-Paul Louis <louijp@xxxxxxxxx>]

Pierre,

Looking at the picture in your email, it is not just length matching, but also, timing adjustment.
As you can see in the picture on the left side, there are a bunch of lines that really look like
printed delay lines.

So it might be critical for ultra high speed memory designs, but might not be as critical in USB2 design.
USB3 might be more critical, similar to DDR3 or DDR4.

Regardless, that feature would be really nice in KiCad for me, as I plan to design a very high speed
RF generator with differential circuits where this feature might help me to make the circuit works 
great over the whole temperature range.

Just my $0.02

Jean-Paul
AC9GH



On Apr 16, 2014, at 4:40 PM, Pierre Parent <pierre.parent@xxxxxxxxxxxxx> wrote:

> Hi,
> 
> Well, someone reported to me that he could ran a board only in slower DDR 
> timing because he did not do any  length matching.
> 
> Also olimex has done length matching in their board olinuxino maxi (enclosed 
> image), and we can find plenty of design guidelines about DDR(2,3) routing 
> speaking of length matching. Eagle and Altium include length matching tool. So 
> I'm not an expert but it is probably not just a joke when it comes to Ram 
> (don't know about USB).
> 
> Pierre.
> 
> 
> 
> Le mercredi 16 avril 2014, 22:01:06 Lorenzo Marcantonio a écrit :
>> On Wed, Apr 16, 2014 at 08:33:45PM +0200, Pierre Parent wrote:
>>> I've sent to production my first length matched board, here is a picture!
>>> I
>>> hope it will work!
>> 
>> I did a board which contained an USB high speed hub (and an USB camera,
>> too). Didn't measure the impedance or looked at the eye pattern (no
>> equipment :P) but it worked. Luckily both TVS and common mode chokes
>> where designed to work with it, so no big meandering to do...
>> 
>> So it should work your too.
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