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Termination resistors

Hi,

Can anyone explain what is the need of termination resistors and also how they can be placed such that its need is met.

Thanks in advance

Originally posted in cdnusers.org by kingshar

archive over 17 years ago

The most common termination resistor is a source termination. It is used to match the output impedance of a driver to the transmission line impedance to reduce overshoots and undershoots. It should be placed as close as possible to the driver. Practially speaking, a distance of 750 mils is usually acceptable unless you have a very fast driver such as a high frequency clock fan out buffer.

Originally posted in cdnusers.org by Kalevi2
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archive over 17 years ago

Thank you very much ,Kai Keskinen

Regards,
Sarath Kumar

Originally posted in cdnusers.org by kingshar
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archive over 17 years ago

PCB traces should be terminated when the trace length exceeds the following condition:

Length > t_r / (2 x t_{pd )}
Where t_r = Signal rise time, t_pd = Signal propagation delay.
Most used termination types:

Series [Source] Termination :
should only be used with one load on the line, but only requires one resistor [R], placed near the source.
Parallel Termination :
Used with any number of loads.Requires one resistor,placed near the receiver.
Thevenin Termination [or Split Termination]:Placed near the receiver.

Regards,
Satya Shankar.G
at&s Ecad.

Originally posted in cdnusers.org by satya1234
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archive over 17 years ago

Thank you satya

Originally posted in cdnusers.org by kingshar
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archive over 17 years ago

Hi satya,
You discussed about series and parallel termination and that was really nice. can u make me clear about other terminations ex Differential , AC, Thevenin.
And what are the conditions for each of them to be used?

It would be so nice of you!!!

Thanks and regards
Niraj

Originally posted in cdnusers.org by nforniraj
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