DDR2 DIMM memory termination resistors?

Hi, everyone I am designing a FPGA PCB board with one DDR2 dimm memory slot. As current project will only need single dimm slot, is that mean I don't need any termination resistor on the board? Since the DDR2 will have ODT(On Die Termination) technology. Even without ODT, it should not cause signal reflection problem since this is only one dimm slot. There is no standby hi-Z on the end of transmission line. So there is no necessary to put termination resistors on the end? Normal ref design have two DDR2 Dimm Slots, I believe single slot is different. Can anyone tell this idea is correct or more things need to be concern?

Thanks, Chao

Reply to
Chao
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You shouldn't need termination on the board. Make sure the core you are using to talk to the DDR2 supports ODT! It's not just an on/off thing. (well, maybe it *could* be for a 1-module config, but even then your core has to set the mode registers right)

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Ben Jackson AD7GD

http://www.ben.com/
Reply to
Ben Jackson

Remember, ODT is for the bidirectional signals only (data, strobe, mask), not clock, address or command.

Micron has lots of application notes here:

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including the very interesting TN4720 which has recommendations on termination and trace length matching.

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Joe Samson
Pixel Velocity
Reply to
Joseph Samson

Yes, These signal need special care. Generally, ODT is new tech for decreasing the number of termination resistors from the board and increase integrity performance. Based on the information provided from

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I believe if there is no second DDR2/DDR RAM slot, the signal reflection won't happen at all. So, my thought is: if only one DDR2/DDR RAM slot, no matter ODT or not, termination resistors are not necessary, and they might even be harmful since extra path will increase more trouble. As far as I know, there is no where mention this situation. Since all the design I saw today come with two memory slots.

Good reference, thanks for all you guys information.

Chao

Reply to
Chao

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