[SI-LIST] Re: DDR2 inteface consultant needed

Yes, I meant whatever termination with Thevenin equivalent circuit, can 
be composed out of one or two resistors. May is soon so I am looking 
forward for your results.

You say that you use HSTL drivers not SSTL drives on a Virtex 4 device. 
May I ask you what is a reason? The problem with Spartan 3 is that it 
does not support differential SSTL18 IO standard but it does support 
differential HSTL. The clock output which is a differential output is 
configured as two separate single ended outputs with 180 degree phase 
shift between them.

Robert

Chris Johnson wrote:
> Robert,
>
> I usually use termination to Vtt generated by a National LP2995.   I 
> have not used Thevenin termination, but as long as the equivalent 
> resistance and voltage are the same, the results should be very 
> similar.  I have successfully used the HSTL_I_18 with DDR2 SRAMs on a 
> Virtex 4.  An upcoming design uses a Spartan 3 with Vtt termination, 
> but that won't be built until May, so I won't be able to comment about 
> what Spartan I/O looks like until then.
>
> Chris
>
> Robert Szumowicz wrote:
>> I do not use DCI, I tried DCI driver as well with the same effect. 
>> The only difference was that amplitude of output signal was slightly 
>> reduced.
>>
>> I have also tried LVCMOS 1.8V-16mA-Fast and I terminated it to 0.9V 
>> at the end of a line. The result was similar to SSTL18-I/SSTL18-II 
>> driver: there was a shelf on the rising edge. I tested 
>> LVCMOS25-24-Fast driver (another FPGA bank) terminated to 1.25V and I 
>> didn't have this issue. There was an idea to change Vdd of the bank 
>> which suffers the problem from 1.8V to 2.5V and to see what happens 
>> but it is not straight forward (other devices use the same 1.8V) so 
>> it wasn't done.
>>
>> Have you used Spartan3 with 1.8V IOs terminated by Thevenin termination.
>>
>> thank you for suggestions,
>> Robert
>>
>>  
>

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: