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SN74AVC32T245: IBIS Model Inquiry

David Schmidt
Prodigy 10 points
Part Number: SN74AVC32T245

I’m currently working on some signal integrity analysis for a spin of a PCBA, and we are using the TI SN74AVC32T245NMJR level-translator on our board (three of them actually).

During some post-route sims I noticed some unexpected waveforms related to the corresponding IBIS model (attached). I also dug up some forum posts and compared to measurements in the lab that lead me to believe there is something wrong with the model, specifically when using the “typical” IC model case.

 

TI Support case I found related to this: https://e2e.ti.com/support/logic-group/logic/f/logic-forum/829351/sn74avc8t245-ibs-model-avc8t245_io_33-show-non-monotonic-falling-edges

 

My observations:

  • My net topology

  • My Hyperlynx simulated waveform with 100MHz oscillator model measured at pin of U113 with “typical” IC modeling.
    • Non-monotonic falling edge is predicted – this is only for typical case

  • Lab observation (using active probe with <1pF capacitance)

As you can see, the falling edge is different when comparing simulation to reality. The non-monotonicity of the model almost lead us to select a different part, and really erodes my confidence in using TI parts/IBIS models in the future.

 

Is there an updated model that can be used? I see this model is from 2004 and hasn’t been updated recently.

SN74AVC32T245.IBS

  • 0
    TI__Guru* 96591 points

    Hello,

    I'm afraid we don't have any newer models for this device available.

    We always work to continue to improve our modelling processes, however generally speaking, models are only created when the device is released and aren't updated due to all that goes into creating the split lots of material required to take these measurements.

    I was able to get a similar result in ADS, but my non-monotonicity ended up on the rising edge.

    It looks to me like there's a slight slope change in the measured rising/falling edges in the IBIS file:

    Unfortunately, that's just how the waveform was recorded -- I'm glad that the device works better than what we predicted with the IBIS model.