[ibis-quality] Correlation study for DDR style terminations with IBIS models
- From: "Mike LaBonte (milabont)" <milabont@xxxxxxxxx>
- To: <ibis-quality@xxxxxxxxxxxxx>
- Date: Mon, 26 Nov 2007 20:02:17 -0500
In the 30 Nov 2007 ibis-quality meeting we discussed:
5.4.5. {LEVEL 3} Output and IO buffers have should have 2 sets of V-T
tables
It was suggested that LVDS needs only 1 set of waveforms (1 rising + 1
falling). I had mentioned that a study by Arpad Muranyi shows that
signal accuracy is reasonable for simulation circuits that mimic the
waveform fixture well. The presentation I had in mind is here:
Correlation study for DDR style terminations with IBIS models
http://www.eda.org/pub/ibis/summits/sep01/muranyi1.pdf
It does show that, for example, an IBIS model with one set of 50 ohms to
VDD/2 waveforms correlates well when the load is 50 ohms to VDD/2. I'm
not sure however that a VDD/2 fixture is best for LVDS. It seems to me
the fixture voltage should be chosen to match the differential crossover
voltage, for best results.
Mike
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