[SI-LIST] Re: Series termination
- From: "Scott McMorrow" <scott@xxxxxxxxxxxxx>
- To: Edi_Fraiman@xxxxxxxxxx
- Date: Wed, 12 Mar 2003 02:30:12 -0800
Edi,
If the driver is not perfectly matched to the transmission line
impedance, and is lower than the line impedance, there will be
overshoot. Maximum overshoot occurs when the electrical length from
driver to receiver is greater than or equal to 1/2 of the risetime.
With modern devices risetime are on the order of 150 to 300 ps. 1/2
the rise time is 75 to 150 ps. Current BGA packages have an electrical
length (delay) of anywhere from 50 to 100 ps. If there are two BGA
packages in the signal path, then the delay of just the packages is
greater than the minimum length required for maximum overshoot.
Generally, unless the driver has an output impedance close to the line
impedance, you need to terminate.
regards,
scott
--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
Edi Fraiman wrote:
>Hi experts,
>
>
>
>I claim:
>
> If it possible to connect OSC. to chip with shortest trace as possible
>no series termination is required .
>
>Am I right?
>
>
>
>
>
>
>
>
>
>Best Regards,
>
> Edi Fraiman
>
>HW Engineer
>
>
>
>
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