looking for recommended trace impedance and termination values for C6678 DDR3 interface

jschipp

The evaluation board for the C6678 use 51 Ohm for termination resistors. It is hard to decide what to use without having to spend a lot of time and simulation. I would like to know what TI would recommend for termination values. I am sure some value between 51 and 39.9 ohm will work but it may degrade the interface just a little bit more if improperly selected. I also need to know what the recommended trace impedances should be for maximum performance.

Best Regards,
John

over 13 years ago

0 Bill Taboada over 13 years ago

TI__Mastermind 42545 points

Hi John,

Which termination are you referring to? I don't see any 51ohm resistors in the EVM design.

0 jschipp over 13 years ago in reply to Bill Taboada

Intellectual 350 points

I apologize. I was looking at a DM8148 dev board as well which uses 51 ohm termination values. The C6678 uses 39.9 ohm termination resistors.

John

0 Bill Taboada over 13 years ago in reply to jschipp

TI__Mastermind 42545 points

John,

Did you still have a question on termination? Just so you know we have done all our simulations with the 39.9 ohm resistors shown in the EVM schematic.

Bill

0 jschipp over 13 years ago in reply to Bill Taboada

Intellectual 350 points

Bill,

Thank you for the feedback. I'm assuming the traces were 50 ohm?

0 Bill Taboada over 13 years ago in reply to jschipp

TI__Mastermind 42545 points

John,

50 ohm is ideal but anywhere from 45 to 55 ohms is acceptable. Be sure to pick one value and remain consistent for all the traces. A good reference is the Jedec DIMM specification for DDR3 memory DIMMs.

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looking for recommended trace impedance and termination values for C6678 DDR3 interface