Author Topic: DDR3 Fly-By Routing length matching at terminator  (Read 479 times)

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Offline RoadRunnerTopic starter

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DDR3 Fly-By Routing length matching at terminator
« on: September 29, 2023, 06:10:59 pm »
I am trying to do Fly-By Routing with few DDR3 Chips and a SOC.
I have length/Delay matched everything. Now I am wondering how closely do I need to length match trace from last Memory chip the termination resistors?  Do they even need to matched?
I have attached an image to  help you understand what I am talking about. Trace Marked Red in the attached image are trace that goes to termination resistor from last Chip.

Regards
 

Offline Terry Bites

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Re: DDR3 Fly-By Routing length matching at terminator
« Reply #1 on: October 02, 2023, 09:19:14 pm »
I imagine that at those speeds termination is mandatory.
Why not do it?
 

Offline Someone

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Re: DDR3 Fly-By Routing length matching at terminator
« Reply #2 on: October 02, 2023, 09:38:47 pm »
Why is length matching used?

Theoretically that stub to the terminator will have no reflection and the terminators don't care if they are time aligned. What happens when some reflections from non ideal termination occur?
 


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