iMX6D DDR3 Fly-by Termination

[sithara]

In my application, i have two DDR3( 2x 1Gbx16) interfaced to iMX6D. Fly by topology is used for better SI. Any freescale recommendation for parallel termination resistor value ? Does series termination required for DDR3 interface of iMX6D? If so, what is the optimum value?

[Yuri]

   According to the i.MX6 Design Checklist, it is suggested to use "T" topology

when the number of DDR3 chips are not more than four. Otherwise "Fly-by"

Topology is recommended, since it allows to decrease timing / trace length

requirements because of additional calibration procedures.

[sithara]

Is there any issue when i use Fly by topology for 2 DDR3 ? I have checked hardware user guide and design checklist of iMX6D. Nowhere it is mentioned fly-by is not recommended for less than 2 chips.

Also, i have seen that DDR3 is built for Fly-by routing...

[Yuri · Accepted solution]

You may try the fly-by for 2 parts, using general recommendations of 

Chapter 3 (i.MX 6 Series Layout Recommendations) in "Hardware Development Guide

for i.MX 6 ...". Next, simulation should be provided to define termination resistors.  

Also, let me remind, DDR calibration must be provided for such topology.

"i.MX 6 Series DDR Calibration"

< http://cache.freescale.com/files/32bit/doc/app_note/AN4467.pdf >

[sithara]

Is there any recommendations for the resistor values when i opt fly-by?

[Yuri]

Please look at the enclosed.