Questions about generating IBIS model

Hi, I facing a problem here on ibis model, there is couple of question about generating this ibis model.

1. How to extract the C_comp value through simulation? Although the cook book show that we can perform AC analysis using tanks circuit, and get the resonant frequency.. but I wonder how should I do the connectivity for the method.

2. How should I perform a power clamp and ground clamp simulation on a I/O open drain?

3. When I perform I/V simulation, I got a very high current at the I/O output, how should i reduce it to the normal value whereby, ibischkv4 will pass my ibis model?

your help will be appreciate.

Regards,
SkyNet

ibis model, .pkg file

Thanks for asking about IBIS!

1) On C_comp, you should connect your AC sweep source or transient ramp source to the output pad of the buffer; i.e., sweep the portion of the buffer that will connect to the package and eventually to the PCB. You would then measure the current through that source and derive the capacitance as mentioned in the cookbook. Power the buffer normally. You will want to keep the buffer in a fixed state (no switching frequency at the core-side input) whether using an AC or transient measurement. Note that your C_comp value may vary with the state of the buffer!

2) Simply put the buffer into its high-z or non-driving (input) state. In other words, if the buffer drives when the enable is high, keep the enable low. The buffer should show only leakage when the ESD and/or parasitic diodes are not active.

3) How realistic are your diodes and how high is "very high?" In designs without layout parasitics, you may see amperes of current due to the lack of realism in the diodes. The cookbook recommends a series resistor, perhaps 1-2 ohms, placed between the pad and any ESD diodes if this can be easily done in your circuit. Otherwise, try to use a realistic, parasitics-included diode model for any ESD protection devices on the die.

Good luck!

- Michael Mirmak
Intel Corp.
Chair, EIA IBIS Open Forum

ibis c_comp

Hi Michael,

Thanks for replying, it is more clearer now. I have some other question about ibis again.

1. How to extract [Package] RLC information from my ibis .pkg file that's generated from my vendor? is it possible for us to grab each pin RLC information for the .pkg file too?

Best Regards
Skynet