[SI-LIST] Re: Terminating a branched clock line

It depends on the topology of your T-tree.

                                                +-------------Receiver A
Driver -------------------------------
                                                +-------------Receiver B

If the branch point is near the Driver, then two seperated termination 
resistors after the branch would be preferred for the reason Scott has pointed 
out; If the branch point is near the Receriver, then a single resistor near the 
Driver would be better. A 'source termination resistor' should be near the 
Driver under any circumstance. 

Put the branch either near the Driver, or the Receiver. Don't leave it far from 
both Driver and Receiver. In case of far from both, to double the trace 
impedance after the branch, or to put an isolate serial resistor at each 
branch, may help, but can't absorb all the reflection.

Regards,
Fred

> -----Original Message-----
> From: kevinlfitzgerald [mailto:kevinlfitzgerald@xxxxxxxx]
> Sent: Friday, April 12, 2002 11:12 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Terminating a branched clock line
> 
> 
> 
> Hi,
> 
> I have a clock signal with a 1ns rise time which is distributed to 2 
> parts.  The 50 Ohm lines are matched length within +/-50 thou after 
> the branch.  Our concern lies with the source termination. Should the 
> source termination be before the branch, or immediately after the 
> branch ?
> 
> Any thoughts,
> 
> Thanks,
> 
> Kevin
> 
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