[SOLVED] Placement of Termination Resistor location dependancy

[hioyo]

Dear Team,

For series termination, we need to place the termination resistor close to the driver
and for parallel termination, we need to place the resistor close to the receiver.

what will happen if did not place it close to the driver/receiver and why?

Regards
Hai

 

[KlausST]

Hi,

It depends how "far away" and on the dV/dt of the signal (frequency bandwidth).

The transmitted signal travels along the signal lines. On every impedance jump there will be an "echo" generated. The bigger the impedance step the higher the amplitude of the echo. The "longer" the (trace of the) impedance mismatch the lower the echoed frequencies (from very high frequency down to this lower limit).

I guess there are some online simulators for impedance mismatch. Do an internet search. Maybe videos.

Klaus

 

[hioyo]

Hi Klaus,

Thank you very much

so if the termination resistor is placed near to the receiver(parallel termination) or near to driver(series termination)
we can avoid reflections.
If they are far away from the receiver/driver reflections will be more.
Please correct me if I am wrong.

Regards
Hai

 

[KlausST]

Hi

we can avoid reflections.

Most probably not avid, but reduce. In best case to a negligible value.

Klaus

Added:
if there is a signal line with controlled impedance. ... then there is is receiver....and then then again is a long signal line, then a termination:
Then the "reciever" will cause a little jump in impedance. ... with low echoes.

You may have a bus with multiple receivers, maybe each several meters apart....still with low echoing.

The bus should be "linear" with only very short branches .. and a termination at the end.

I guess you didn´t yet follow my recommendation to do internet search on your own....
There are really very many good cdcouments and videos...

Klaus