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TPS7H4002-SP: Difficulties with TI supplied PSPICE file

Ian Lewis
Prodigy 30 points
Part Number: TPS7H4002-SP
Other Parts Discussed in Thread: PSPICE-FOR-TI

Hello, 

We are considering using the TPS7H4002 in a space grade design, and are currently evaluating it via Altium's PSPICE. However, there appears to be an issue with the supplied model (tps7h4002-sp_trans.lib).

I have assigned the model to an existing schematic symbol (as supplied by UltraLibrarian, via TI), and although simulation finished successfully, the output voltage is fixed at the input voltage, regardless of the values used for the VSENSE resistors. Altium also outputs an error message (along side "simulation stated" and "simulation succeeded" ) stating "unknown symbol "VSS"".

Can anyone shed some light on this?

Many Thanks

  • 0
    TI__Genius 14540 points

    Hi Ian,

    I'm going to defer this one to our modeling expert, Sarah, who might have some insight.

    Thanks

    Christian

  • 0
    TI__Expert 7085 points

    Hi Ian,

    Can you share your project files? This would make debugging easier. 

    Have you double-checked the pin assignments are correct between the symbol and the model? What voltage is the output stuck at? Do the simulation results look normal besides the errors and fixed output?

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    Prodigy 30 points

    Hi Sarah, thank you for getting back to me. 

    The output voltage always equals the input voltage. I have re-assigned pins to the schematic, and the circuit has been built in accordance with the datasheet and values derived using the TI supplied calculator spreadsheet. 

  • 0 in reply to Ian Lewis
    TI__Expert 7085 points

    Hi Ian,

    The source of the VSS error is one of the subcircuits in the model. There is a node that is set to an initial condition voltage equal to the VSS parameter of the subcircuit. It can be resolved by adding an equal sign to this line in the model lib file.

    However, I would not necessarily recommend using Altium to simulate this device due to the slightly more complex nature of the model. Because the model was developed in and intended for use in PSpice, there can be syntax differences that occur when it is used in other SPICE simulators that lead to incorrect simulation results (such as what you're observing). Sometimes it is possible to correct these errors, but without more information (files, schematics, simulation settings, or project files) it is hard to debug. 

    If you do not have access to PSpice, TI offers a powerful free version called PSpice for TI that includes a large library of TI devices (including the TPS7H4002-SP). After downloading, all you would need to do is search for the part, right-click on the transient model, and select the test circuit. This opens a default schematic that is already set up for simulation.

    Could this be an option for you?

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    Prodigy 30 points

    Thanks Sarah, I have installed PSpice for TI, but the model for the TPS7H4002-SP is missing. Is there a way to manually import this model, as downloaded from the datasheet? 

  • 0 in reply to Ian Lewis
    TI__Expert 7085 points

    Hi Ian,

    It looks like you probably need to update the built-in library. This is fairly simple to do. Just click "Reinstall TI Models and Libraries" in the Help tab. After the download is complete you will need to close down and restart PSpice-for-TI, then the parts should be displayed when you do a search.

    Let me know if you're able to get it working.

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    Prodigy 30 points

    Thanks, but this simply flashes an error on restart : "reinstallation could not be started, please try again later"

  • 0 in reply to Ian Lewis
    TI__Expert 7085 points

    I will need to check with our PSpice-for-TI team on that error as I have never encountered it before. It sounds like it may be an issue with contacting servers. 

    In the meantime, yes, you can download the PSpice models from the product page on ti.com here: https://www.ti.com/product/TPS7H4002-SP#design-tools-simulation 

    After you download an unzip the files, you will be able to open and run the project in PSpice-for-TI. The default schematics from the downloaded files will be identical to the default schematics that you would have seen through the built in PSpice-for-TI library. 

    Let me know if you run into any issues with this approach or if you're able to get it running.

    Thanks,

    Sarah

  • 0 in reply to Sarah Koch
    TI__Expert 5880 points

    Hi Ian,

    PSpice for TI will automatically pull updates each morning. Unfortunately, that means it won't pull the next update for you until tomorrow morning. Reinstalling the library will actually make the problem worse, so please do not reinstall the entire library. Please do not manually add the model lib either. Please allow PSpice for TI to automatically handle all library updates. 

    Please wait and try to launch PSpice for TI tomorrow morning. It should have a pop-up asking if you would like to update the library. Click Yes, and wait a minute for the updates to finish. This will take a minute because you will have quite a few model updates. When it finishes, you should be able to search the TPS7H4002 part without issue. 

    Thank you,

    Jackie