[SI-LIST] Re: A question about the tIS,tIH derating value of DDR2
- From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 15 Jul 2010 11:48:42 +0200
Hello sujingguo,
I have to admit, that I do not exactly understand the two options that
you are referring too, nevertheless I hope the following explanation helps:
There should be a value for setup (tIS) and hold (tiH) in the datasheet.
This value is valid for a slewrate of 1V/ns on the CCA signals and 2V/ns
on the differential clock signal.
In addition to this there is a derating table whih defines drating
values ( delta(tIS) ) dependent on the real slewrate of your system. So
you should simulate/measure the real slewrate and select the correct
delta(tIS) which needs to be added to the nominal setup time (tIS). Than
you do have the final value which is required for your System (be
careful not to mix Vref based vs. AC/DC based values which are also
mentioned in several datasheets)
sorry if I did not answer your question .. in this case just respond to
my e-mail ...
Regards
Hermann
EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer@xxxxxxxxxxxxx
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
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schrieb sujingguo 00138059:
> Hi all，
>
> We have a question about the tIS,tIH derating value of ddr2.
>
>
> According to the datasheet of Hynx:
>
> 1) For all input signals the total tIS(setup time) and tIH(hold time)
> required is calculated by adding the
> datasheet value to the derating value listed in above Table. (PS:"the
> derating value" is marked as delta(tIS) & delta(tIH) here,and the table is
> not listed for some reason.)
>
> Should the delta(tIS) and delta(tIH) above be added to the total tIS/tIH
> or the minimum value of tIS/tIH which is required by the receiver to ensure
> the right sampling?
>
> If the latter is the choice,does this mean that the the minimum value of
> tIS/tIH will change with the alterance of the skew rate of clk & AC / DQS &
> DQ？
>
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