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THS3491: Request for spice model

Part Number: THS3491
Other Parts Discussed in Thread: THS3095, THS3091

Dear Technical Support Team,

Do you provide spice model ? I couldn't find it on web site.

http://www.ti.com/product/THS3491/toolssoftware

Its status is preview, so if you have a plan for spice model, could you share it?

Best Regards,

ttd

  • Hi,

    The THS3491 model is still in works and should be available to play with sometime next week. Please let us know in the meanwhile if you have any questions or concerns about the part.

    Best Regards,
    Rohit
  • Hi Rohit,

    Thank you for your quick reply.
    I'm looking forward to being updated on website.

    www.ti.com/.../toolssoftware

    Best Regard,
    ttd

  • Hi Rohit,

    When will spice model of THS3491 upload on website?
    I guess that this week is thanks giving , so I'm happy to get spice model by next week.

    Best Regards,
    ttd
  • Hi,

    We are making some final edits to the spice model and should be released to the web any moment.

    Thanks for your patience.

    Best Regards,
    Rohit
  • Hi,

    The THS3491DDA model should now be available in the THS3491 product folder under Tools/Software folder: 

    Best Regards,

    Rohit

  • Hi Rohit,

    Would you be able to confirm if there are any more changes to be made to this model? The noise performance at low frequencies is quite a lot worse than I expected from these simulations (see image). Is this just the model?

    Also, does the model currently replicate harmonic distortion? It doesn't seem so from my simulations (THD ~0% compared to ~0.03% for a comparable THS3095).

    Thanks!

  • Hi JS,

    I don't think there are any more changes to be made to the model. The increase in noise at low frequencies is probably due to 1/f noise contribution from each of the input voltage noise, non-inverting and inverting input current noises which is what's typically seen in almost any amplifier. Would it be possible for you to clarify as to what noise numbers you were expecting?

    No, the model does not currently handle harmonic distortion numbers. It is very difficult to predict HD numbers at high frequencies because of the dependence on board input and output layout routing, which is why it is not captured in the model. 

    Best Regards,

    Rohit

  • Hi Rohit,

    Thanks for the quick reply. I was expecting the 1/f increase at lower frequencies, but not up to uV/rtHz levels even at low frequencies. I've simulated the THS3095 (which as far as I can tell should be about the same as the THS3491 for noise) in the same circuit configuration and get <100 nV/rtHz (see image) at 1 Hz. It's possible I'm missing something here, but I wouldn't have expected an order of magnitude difference between the THS3095 and THS3491.

    Thanks again

     

  • Hi JS,

    The 1/f noise corner for the THS3491 is shifted to the right by ~9x compared to the THS391 as shown below, which is primarily the reason as to why you are seeing higher low frequency noise in the THS3491 compared to the THS3091. Would it be possible for you to explain in further detail the use case for the THS3491 at such low frequencies?

    Best Regards,

    Rohit

  • Thanks for the response Rohit, that clarifies it a lot for me. The shift in the corner frequency makes it clearer looking at those plots again.