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Modeling >> Behavioral Models >> some questions when making IBIS model of LVDS driver ?
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Message started by DP_Design on Mar 29^th, 2011, 11:12pm

Title: some questions when making IBIS model of LVDS driver ?
Post by DP_Design on Mar 29^th, 2011, 11:12pm

I don't know whether this is the subject treated in this part (Analog_Design) but, I just will start. sorry about that.

I want to make IBIS model for LVDS driver.
As you know, LVDS Driver hss a pair of differential outputs and the outputs are connected to each other by termination resistor about 100ohm at RX side.
And LVDS driver has always a feedback circuit to control common level of differential outputs.

Q1.When I prepare netlist used in pull-up/down I-V for IBIS, how can I control the feedback circuit? When I sweep one pad of outputs, another output and output common level move together and the feedback circuit would be off or wrong. Then, pull-up I-V must not be correct.

Q2.Because we can't sweep both output pad, we just sweep one pad for example, positive output and fix negative pad at output common level. Is it right to do as written above?

Q3.When we do the simulation V-I for pull-up/down, How can we choose the range of sweep voltage? Usually LVDS driver is designed to have constant output swing (Vdod) and fixed output common level (Vcm). The range should cover twice of voltage swing, so in the case of LVDS driver, I think the range should be -Vdod+Vcm to Vdod+Vcm. Am I right?

Q4.Finally, When we do the simulation for V-t curve, How can we choose the parameters like Vfixture, Rfixture, Cfixture?

Thank you for reading my long question :)
Have a nice day.