Determine on resistance of buffer via IBIS model

[stelik]

I am fairly new to IBIS models and I need some help simulating an IBIS file in HSpice. I am going to make a test circuit for a new I/O signaling scheme, and I will be using a buffer from On Semiconductor (like this: NB100LVEP17). However, before I do that, I need to determine the "on resistance" of the buffer, the resistance across the buffer when it is high. I need to determine this value in order to calculate the values of other components in the circuit. So what is the best way to simulate this?

I know IBIS models give you I/V curves for the buffer. Can I just use the slope of the pull-up curve and use that as the on resistance, or is there a more accurate way?

Also, how can I simulate the entire driver using IBIS model? For example, if I want to connect a PRBS signal to the input pin of the driver and view the signal on the driver's output pin, would I need to cascade the buffer's input model followed by the buffer's output model? I have been using ADS and MWO to do this, since they have built-in IBIS components, but maybe HSpice would be a better tool for this problem. Any thoughts? Thanks in advance.

 

[FvM]

IBIS models are only covering I/V curves and transient output waveforms of I/O pins. If you are interested in driver impedances, they have all available information.

I know IBIS models give you I/V curves for the buffer. Can I just use the slope of the pull-up curve and use that as the on resistance, or is there a more accurate way?

Depends on. Because I/V curves show FET output characteristics rather than constant resistances, the effective driver impedance depends on the output load. Determining the slope for the curve points achieved with the intended load is rather accurate and can't be improved much. The most serious accuracy limitation is caused by the fact, that fast and slow corner IBUS curves differ by a factor of about two according to PVT (process, voltage, temperature) variations.

 

[stelik]

What do you mean "they have all available information"? You mean in the datasheet? Unfortunately, I was not able to find this info in there.

 

[FvM]

No, I was referrring to the Ibis files.