FreeLists / si-list / [SI-LIST] Re: effect of termination on slew rate

[Bill.Cohen@xxxxxxxxxxxxxxxx]

Nidhir,

The GDDR3 driver is actually a POD (pseudo open drain) driver. There is a
device to pull down (40 ohms) and a device to pull-up (60 ohms). It is
weaker than the 40 ohm pull down device but it is there to help the 60 ohm
resistor at the far end pull up the signal line.

--------------------------------------------------------------
| Bill Cohen
| Toshiba America Electronic Components
| Mixed Signal Design Group
--------------------------------------------------------------


                                                                           
             "Nidhir Kumar"                                                
             <nidhir.kumar@gma                                             
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             03/13/2006 03:12          slew rate                           
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Dear Gurus

I am designing graphical DDR3 driver which has 40 ohm
push-pull driver and 60 ohm termination (ODT) to the
VDDQ at the far end. Since the termination is to the
supply, I would assume that rise slew at the far end
should be higher. But rise and fall slews looks very
symmetrical in the HSPICE simulations.

Can someone please explain me the theory behind this
phenomenon. I read somewhere that DC terminations
don't affect AC behavior. But I find it difficult to
digest. Any thoughts?

Thanks,
Nidhir
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