On 04/16/2014 03:40 PM, Pierre Parent 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.
I once used the microwave tool to generate a delay line for a clock signal, this was to generate a fixed delay in a DDR RAM circuit on that one line only. (This was 5-6 years ago. We still make that board.) The output was a module, and I dropped that module onto the board after I got it to be the correct length. It did its job, but I think there was always a DRC error, because I did not put it into the schematic. Again, your tool will be useful. Matching the data and address lines in a DDR design is the big need these days. We're asking the electrons to do more in less time, but they seem lazy. Dick > > > > 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. >> >> >> _______________________________________________ >> Mailing list: https://launchpad.net/~kicad-developers >> Post to : [email protected] >> Unsubscribe : https://launchpad.net/~kicad-developers >> More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
