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DDR2 termination

Hi,

After reading over the documentation for DDR2 and the SSTL signalling standard, I have a question about the role of termination in DDR2.

It appears to me that in addition to the usual termination function, the resistors provide some sort of biasing function around the Vref (1.8v/2) point. Is it the case that the IO on the DDR2 modules can "swing" around that midpoint without the presence of termination resistors, or are these necessary for correct operation (even using On- Die Termination). What I would like to know is whether, in addition to the unidirectional signals (Address, etc...) that do not have ODT, it is necessary to terminate the Bidirectional signals (even with ODT)?

Thanks for your assistance,

Stephen

Reply to
Steve
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Hi Stephen,

Have a look at Sheet 13 of this:-

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There are no terminations on the ODT signals to the DDR2 SODIMM, because the ODT takes care of it.

HTH., Syms.

Reply to
Symon

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