RE: [SI-LIST] : HSTL Termination

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From: ruston, matt (ruston_matt@emc.com)
Date: Tue Jun 05 2001 - 07:23:22 PDT


Dori:

 Hi. Yes, that termination is acceptable. The 1.5V supply is always sourcing
current (no need for a source/sink). This would be fine if you only had a
relatively small number of lines to terminate. If you had a lot of lines,
the drawbacks could be tough to swallow.

 The drawbacks include a higher power consumed in the thevenin termination
(always drawing "idle" currents between 1.5V and ground) and it takes twice
as many resistors. The advantages are if you have a small number of lines,
you don't need to design any fancy (source/sink) power supply circuit.

 If you want a 0.75V source/sink supply, look at what Synergy/Micrel have
done for SSTL2 termination supplies
(http://www.micrel.com/product-info/SSTL-Term.shtml). Maybe it can be
adapted for HSTL.

Later,

Matt

-----Original Message-----
From: Dori Itzhaki [mailto:dorii@mysticom.com]
Sent: Tuesday, June 05, 2001 9:14 AM
To: SI List
Subject: RE: [SI-LIST] : HSTL Termination

Just making the subject clear :
Is the following termination solves the problem of source and sink current ?
Is that OK to use it with ordinary power supply ?
What are the drawbacks?

                  ___ 1.5V
                     |
                     /
                      \ 100 ohms.
                     /
     |\ \ |\
     | \_____________|_| \
     | / | | /
     |/ / |/
                         \
                         / 100 ohms
                         \
                          |
                         ---
                        ///

Thanks,

Dori Itzhaki
MystiCom Ltd.

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