Re: output impedance of a driver

Jason,

If the ibis model has been extracted correctly, then the Ramp data
will tell you what the saturated output impedance is.

The IBIS V/I curves give you the impedance of an output buffer
at any voltage. I usually use 1 volts as a good place to measure
impedance, since it is in the linear portion of the buffer curve.
For the pullup and pulldown curve, go to the 1V row and read
off the current. Since R=V/I, the output channel resistance can
be calculated.

For example, if at 1 Volt the current is 35mA, then the
output impedance is 28.57 ohms.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com
Jason Leung wrote:
> Hi all:
> Morning!
> I am trying to obtain the output impedance of a driver, so that I can
> match the driver with a transmission line and proper termination.
> The way that I have tried is I used the IBIS model and then translate
> the model into QUAD model, so that I can used the XNS to observe their
> rising and falling waveform. Moreover I am trying to find its output
> impedance in XNS.
> My question is : Does anyone ever try finding the output impedance of a
> driver? AND how did you achieve that?
>
> Thanks very much for your comment!
> Jason leung