[IBIS-Users] ECL Termination Voltage Question


Subject: [IBIS-Users] ECL Termination Voltage Question
From: Fisher, Thomas (tomfisher@ti.com)
Date: Fri Jan 09 2004 - 11:16:25 PST


All,

I have a PECL driver that I am modeling that has a non-standard load (pi
network to ground) which results in a larger Vod. (1.2-V vs. 800mV) What
happens during simulation is the single-ended waveform depicts a slowness of
the rising edge which results in a plateau effect on the rise/fall of the
differential waveform. (It looks great when simulating in TISpice) Most
(P)ECL termination is going to be 50 ohms to Vtt for both non-inverting and
inverting outputs whereas Vtt = Vcc - 2-V. Under the load I am simulating
we are using 200 ohms to ground. (customers' request)

 

Having said that, looking in the 3.2 spec on page 78 under ramp rates
model_type for output_ECL it mentions 50 ohm resistor to the termination
voltage (Vterm = Vcc - 2-V). Is this Vterm embedded into the
specification? Is there a way to specify that the load is 200 ohms to
ground? I believe this might be causing the abnormality. Any help/insight
would be appreciated. Thanks in advance.

 

Regards,

Tom Fisher

 

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