[SI-LIST] Re: How to generate unloaded driver waveform

John,

The R_fixture in the waveforms should be nearly equal to the impedance of the 
transmission lines in the intended environment of the driver.  Actually, a 50 
ohm transmission line looks like a 50 ohm resistor during the transition of the 
driver (assuming the line is long enough that there are no reflections reaching 
the driver during the transition).  It is not unloaded.

Most simulators can create an unloaded driver waveform because they use the 
rising and falling waveforms along with the I-V curves to generate internal 
time-dependent switching factors.  In this way the specific R_fixture and other 
elements are calculated out to make a simulator model that is independent of 
these factors.

Regards,
Weston


-----Original Message-----
From: John@xxxxxxxxxxxx [mailto:John@xxxxxxxxxxxx]
Sent: Tuesday, June 24, 2003 3:48 AM
To: silists
Subject: [SI-LIST] How to generate unloaded driver waveform 


Dear all SI gurus,
 
How to compose a unloaded driver waveform at die from a given IBIS driver 
model?   I think inside the IBIS model, the VT tables provides the information 
of  driver waveforms with specific test loads, for example, 50 ohms pull up 
/pull down.   
 
However, when the driver drive a transmission line , ie, system load., the 
unloaded driver waveform  shall be used  instead of the test loaded driver 
waveform.
 
Thank you for your helps in advance.
 
 
John Lin

Quanta Computer Inc.,Taiwan, R.O.C.
Email: John@xxxxxxxxxxxx
Tel: 886+3+3272345 ext. 5183



 

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