Sebastien Bourdeauducq wrote:
Hi,
I've had a look at the board schematics from Transversal Technology, and I
wonder why termination resistors that connect the DDRAM signal lines to a
1.25V (Vtt) supply are not present. From what can be read in various sources,
DDRAM uses SSTL-2 signaling which requires that resistor (see
http://download.micron.com/pdf/presentations/dram/plat7justin.pdf p.8 for
instance).
The presentation is about multiple DDR DIMM's, not single chips.
Is that because the PCB traces are short enough that you can get rid of that
resistor and still get good signal integrity ?
I think this is because point-to-point links. And the chips already
contain some termination circuitry. (but then what about the termination
of the shared address lines?)
D.
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