[SI-LIST] Re: VIH(AC)& VIH(DC) DDR3
- From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
- To: kbmanick@xxxxxxxxx
- Date: Sat, 11 Aug 2012 17:09:50 +0200
Hello,
your signals need first to cross the AC level to give the Receiver some
overdrive for fast switching and short input setup times.
Once your receiver is switched the level is allowed to go below the AC
level (min) worst case back to DC (min).
Reason for this definition is the difficult signaling with Point to
Multipoint connections that cause a lot of reflections.
You can close your timing budget either with the VIH AC175 or the VIH
AC150. I would need to check in detail, but there should be different
setup/hold times given if you assume one or the other level (maybe also
just the derating is different...)
So if you can not provide the DRAM enough swing to reach Vref + 175mV
you can also work with Vref + 150mV, but you have to accept worse
setup/Hold times ..
Hermann
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schrieb Balamanikandan K:
> Hi,
> 1. I would like to know the difference and importance of AC & DC Logic
> input levels (VIH(AC)& VIH(DC) ) for single-ended signals in DDR3.
>
>
> 2. For logic High (input) , should the signal level be higher than VIH
> (AC)min or VIH(DC)min?
>
> 3. What is the importance and meaning of VIH(AC 175) and VIH(AC 150)
>
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