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DDR3 length matching

ljo , 06-16-2016, 09:35 AM

I use circuitmaker for my project. I m doing the ddr3 length matching and i have question on the parameter "routed" in the software.
Is it the total length of the trace? i mean it counts all the segments of the different layers? Can i use it for the length matching?
ljo , 06-16-2016, 10:41 AM
By the way, i don't find the feature "length tuning" in circuit maker. Did i miss it? In the case it is not implemented, how can I do it? Do I have to draw the waves manually?
mairomaster , 06-16-2016, 10:55 AM
Routed Length is the sum of the lengths of all segments making the track of a net. I don't know about Circuit Maker, but in Altium you also have Signal Length which is the more accurate measurement. If you don't have Signal Length in CM you can do with Routed Length, just be careful when you are drawing/checking your tracks. It is useful to select the tracks and zoom to see if the segments seem right.

I don't know if Length Tuning is available in CM, you can check the documentation perhaps. It is more advanced future so it might not be. If not available you will need to do the tuning by hand.
ljo , 06-16-2016, 11:05 AM
ok thank you.
I have no choice i will do it by hand.
mairomaster , 06-16-2016, 02:12 PM
If you are doing it by hand it might be good to first create a few single waves of different sizes which you can copy and paste for the length matching. Drawing every wave by hand for each separate signal is quite time consuming and hard to make consistent.
ljo , 06-16-2016, 03:47 PM
You are right. Thank you a lot for this advice.
robertferanec , 06-16-2016, 10:49 PM
I do not use CM, but I agree with @mairomaster, I guess, length tuning and precise signal length calculation are advanced feature which may not be available in CM. You still should be able to measure the signal length by selecting segments and do the length matching manually - we designed quite advanced boards with this technique, no problem (e.g. I have designed AMD x86 PC104+ by this technique).

Very often I do the length matching manually, because Altium is not very smart in fitting the "waves" into small spaces. When you will be measuring the length by selecting tracks, be careful about "double segments" (if you by mistake draw two tracks on top of each other) - that would make your length measurement inaccurate. If you select the tracks, you will see the places with double segments.
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