[SI-LIST] Re: termination resistor
- From: "Lambert Simonovich" <bertsimonovich@xxxxxxxxxx>
- To: <emcesd@xxxxxxx>
- Date: Sun, 23 Dec 2012 21:37:19 -0500
IV curves of output transistors. Slope of the curves represent output
impedance. Over the linear portion, the output behaves like a resistor.
Here is a good presentation from Todd Westerhoff:
http://www.eda.org/ibis/summits/jun05/westerhoff.pdf
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Tesla
Sent: December-23-12 8:16 PM
To: bertsimonovich@xxxxxxxxxx
Cc: tanxiaoliang1987@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: termination resistor
Hi,
How could it be that--Driver impedance varies somewhat with load? it should
be a contant value if the circuit is decided.
Thanks.
Tesla
At 2012-12-24 08:06:53,"Lambert Simonovich" <bertsimonovich@xxxxxxxxxx>
wrote:
>Because the driver is a semi-conductor, it's output impedance could
>vary based on rising/falling edge transitions, manufacturing process
>(slow, typical, fast), and the load it is driving. One way to estimate
>the driver's impedance is by using an IBIS model of the device. Since
>IBIS models are ASCII based, you can simply use your favourite text
>editor to view and quickly estimate the output impedance when driving
>50 Ohms by using two of the four V-T waveform tables.
>
>Here is the link to one of my blog postings, I did a while back titled,
>"Determining Output Impedance from IBIS".
>
>http://blog.lamsimenterprises.com/2010/12/22/drivers-output-impedance-f
>rom-i
>bis/
>
>Bert Simonovich
>LAMSIM Enterprises Inc.
>Web Site: http://lamsimenterprises.com
>Blog: http://blog.lamsimenterprises.com/
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of XiaoLiang Tan
>Sent: December-22-12 10:02 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] termination resistor
>
>Dear Expert,
> Hello, I am designing a high speed system.Since I don't know
>my driver's output resistance, thus the termination resistor value is
>not known. Thus may I use the variable resistor? If I use the variable
>resistor, the size is big thus I am unable to put all the resistor near
>the driver.( I have more than 10 outputs needs to be terminated). Which
>means the termination resistor could not be put close to the drivers.
> However, if I use a fixed and small size resistor, I need to
>trim the resistor manually when I doing the testing.
> So may I know that which one is more suitable? Thanks.
>--
>Best Regards
>
>==================================
>*Xiaoliang, Tan*
>*
>*
>
>
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