[SI-LIST] Re: Series termination greater than the characteristic impedance?
- From: <Cortex.Chen@xxxxxxxxxxxx>
- To: <aminotg@xxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 18 Jan 2006 12:23:06 +0800
Gilles,
Output impedance of buffer PLUS (source) series termination should =
roughly equal the characteristic impedance of transmission line of PCB.
In addition, don't forget to take care the topology effect.=20
In detail, refer to the chapter 7 of High-Speed Digital System Design - =
A Handbook of Interconnect Theory and Design Practices.
Regards,
Cortex=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of aminotg@xxxxxxx
Sent: Tuesday, January 17, 2006 11:13 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Series termination greater than the characteristic =
impedance?
Hi All,
I was wondering if there is ever a case where a series termination =
should be higher than the characteristic impedance of a trace?=20
We had an SI analisys performed on our DDR2 interface and the conclusion =
was to change the series terminations of our data bus to 60ohms. The =
characteristic impedance of the traces on our board is 50ohms.=20
I always thought that a series termination was added to match the driver =
to the characteristic impedance of the trace, now I am confused, because =
the analysis on our board doesn't agree with this thinking.
Kindest Regards,
Gilles
=20
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=20
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