TimmyBB
Newbie level 1
Hello,
I am trying to do simulation of a single net in an lvds pair with CST design studio. The outputbuffer-ibis model used is the following: lvds25_ro_p0_v0 which can be found in the attached ibis model of the altera stratix IV device. (Stratix4.zip)
My setup in CST can be found in the attached LVDS.jpg
![](https://obrazki.elektroda.pl/46_1257338987_thumb.jpg)
To simulate the single ended net in CST, I terminated the output with a 50Ohm resistor to Vfixture, which is 1.2V.
The excitation signal on the ctrl pin of the ibis block is defined as 50MHz with a voltage level of 2.5V. But I am not quite sure if this is correct... I would expect that the voltage levels, and rise/fall times would come out of the ibis outputbuffer block... I connected also the Supply and En pin of the IBIS block to 2.5V. I also don't know if this is correct.
Then at the bottom of the image, you can find the simulated waveform at the output... This is really not what I expected... I expected a voltage waveform of 50Mhz (this is correct) with Vol = 1V and Voh = 1.4V. And also the waveform is not uniform, I have an overshoot every other pulse.
Any suggestions?
Thx,
Tim
I am trying to do simulation of a single net in an lvds pair with CST design studio. The outputbuffer-ibis model used is the following: lvds25_ro_p0_v0 which can be found in the attached ibis model of the altera stratix IV device. (Stratix4.zip)
My setup in CST can be found in the attached LVDS.jpg
![](https://obrazki.elektroda.pl/46_1257338987_thumb.jpg)
To simulate the single ended net in CST, I terminated the output with a 50Ohm resistor to Vfixture, which is 1.2V.
The excitation signal on the ctrl pin of the ibis block is defined as 50MHz with a voltage level of 2.5V. But I am not quite sure if this is correct... I would expect that the voltage levels, and rise/fall times would come out of the ibis outputbuffer block... I connected also the Supply and En pin of the IBIS block to 2.5V. I also don't know if this is correct.
Then at the bottom of the image, you can find the simulated waveform at the output... This is really not what I expected... I expected a voltage waveform of 50Mhz (this is correct) with Vol = 1V and Voh = 1.4V. And also the waveform is not uniform, I have an overshoot every other pulse.
Any suggestions?
Thx,
Tim