[SI-LIST] Re: OUTPUT IMPEDANCE CALCULATION [IBIS]

by the way, in the equation I wrote below the "3D" is a formatting
artifact and shouldn't be in the equation...
(I'll try again to write here); Vout <equals> Vin * (Zo/(Zo+Zs)) ...and
solving for Zs
 
-Jim
________________________________

From: Benny Yan [mailto:bennyzhi@xxxxxxxxx] 
Sent: Tuesday, September 19, 2006 8:10 PM
To: Peterson, James F (EHCOE)
Cc: torocar@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: OUTPUT IMPEDANCE CALCULATION [IBIS]


Eric Bogatin mentioned a method in his book<Signal
Integrity:Simplified>.
 
Benny Yan

 
On 9/19/06, Peterson, James F (EHCOE) <james.f.peterson@xxxxxxxxxxxxx>
wrote: 

        Another method to establish the source impedance (Zs) of a
driver from
        an IBIS model is in a simulation (still using Ohms law): 
        
        Create a circuit with the ibis model driving a very long
transmission
        line (12 inches) with a known trace impedance (Zo). Drive the
line both
        high and low and observe the porch in the waveform. The porch is
caused 
        by the ratio of Zs and Zo. Zs can be solved by rearranging this
very
        familiar equation :
        
        Vout =3D Vin * (Zo/(Zo+Zs)) ...solve for Zs, Vout is Vporch and
Vin is =
        the
        total voltage swing
        
        The porch will last as long as 2x the propagation time of the
T-line. 
        
        -----Original Message-----
        From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
        On Behalf Of Scott McMorrow 
        Sent: Monday, September 18, 2006 4:48 PM
        To: torocar@xxxxxxxxx
        Cc: si-list@xxxxxxxxxxxxx
        Subject: [SI-LIST] Re: OUTPUT IMPEDANCE CALCULATION [IBIS] 
        
        Carlos
        
        Ohms law (Z=3D V/I).  You have a V/I curve at min/typ/max device
=
        corners.
        
        
        regards,
        
        Scott
        
        Scott McMorrow
        Teraspeed Consulting Group LLC
        121 North River Drive
        Narragansett, RI 02882 
        (401) 284-1827 Business
        (401) 284-1840 Fax
        
        http://www.teraspeed.com
        
        Teraspeed(r) is the registered service mark of Teraspeed
Consulting
        Group LLC
        
        
        
        Carlos Toro wrote:
        > Hello members of the SI list.
        > Does anyone has experience with calculating the output
impedance of a=20
        > microcontroller pin given its IBIS model?.
        >
        > I don't have access to the silicon yet, just the IBIS for now.
I=20 
        > intend to match impedances of critical PCB traces of our
design.
        >
        > Thanks in advance.
        >
        >
        >  =20
        
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