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Issue with modeling in TINA TI-7

David9391
Prodigy 80 points
Other Parts Discussed in Thread: THS4521, TINA-TI

I am trying to model a Butterworth High-Pass Filter 4 Order based on a MFB Fully Differential Circuit Type using TINA-TI 7 (calculated with FilterPro V.2.0). On the model the filter is based on two THS4521 fully differential amplifiers.  ERS gives 0 errors and 0 warnings.

Any DC or AC analysis gives an error: “TLD pin: VIN+ does not match any pin of the macro component. {THS4521)”. I wonder if somebody knows what that error means and how I can correct the schema.

Thanks in advance.

David.

  • 0
    TI__Mastermind 40295 points

    Hi David.

    Thanks for taking the time to point this out.

    I am on the Analog eLab team and will take a look at this right away & hope to have a solution later today.

    Regards,

    John Miller

     

  • 0
    TI__Expert 5515 points

    David,

    Can you post your TINA schematic (the .TSC file) please? I'd like to have a look at the exact circuit you're using.

    Rick

  • 0 in reply to John Miller - Sensing
    TI__Mastermind 40295 points

    David,

    I tried some quick sims using circuits similar to those shown in figures 60 and 61 in the device data sheet and could not reproduce the error.

    If you could post your schematic as Rick suggested it would be a big help. It might also be helpful to post the TINA file itself, if that's possible.

    John

  • 0 in reply to John Miller - Sensing
    Prodigy 80 points

    Thanks for your responds. I'm attaching the schematics in TINA.

    M1.TSC
  • 0 in reply to David9391
    Prodigy 80 points

    Just in case, here are the results of Filter-Pro.

  • 0 in reply to David9391
    TI__Mastermind 40295 points

    David,

    Many thanks for uploading the schematic and FilterPro results.

    It appears the amplifer symbols in the uploaded schematic are mssing the power-down pins. This is giving the symbol only seven pins while the underlying subcircuit in the netlist has eight "pins".

    Not sure of the root cause of this, but we are investigating.

    As a work-around I replaced the amp symbols with the ones available from the Spice Macro menu in my current version of TINA-TI (Version 7.0.80.96 SF-TI with a build date: 2009 April 6, 11:48:24 AM). This seemed to fix the error message, but gave an "Irregular Circuit" error when I tried to run a transient or AC response. This can be common in AC-coupled differential circuits. To fix this, I split the differential resistors into two grounded resistors.
    The AC response seemed to agree with the CircuitPro results you uploaded.

    The modified schematic is uploaded. Please give it a look and let me know if you have any questions.

     

     

    M1_rev.TSC
  • 0 in reply to John Miller - Sensing
    Prodigy 80 points

    Thank you John for the proposed solution.
    Unfortunately, we have already implemented the original circuit, so we are locked on that design.
    It did not work as expected, so I wanted to use TINA to help me with the debugging.
    Bad luck, I guess.

  • 0 in reply to David9391
    TI__Mastermind 40295 points

    David,

    Your circuit should work fine. My circuit was only a work-around to avoid convergence issues in the simulator (e.g. numerical artifacts that won't show up in a real circuit).

    The 1meg resistors across the signal source (R9,R10) are just a simulation trick and won't be needed in your implementation. They are included to provide a ground reference for the diff paths so the simulator will converge a little easier.

    The resistor pairs R3/R11 and R6/R12 are also single-ended versions of your original diff resistors, and they are also tricks used to help sim convergence. The values in my schematic were chosen to give the same differential resistance shown in your schematic. Your single diff resistors will give the same results in your implementation.

    Please let me know if I can be of any help troubleshooting the implementation. In my previous life I was a systems & apps engineer in the group responsible for the THS4521. If I can't help, we can get someone who can. Active filters with high speed amps can be kind of tricky. Its very common to see differences between theoretical performance and an implementation.

    I'd be glad to give you a call to talk about what you are seeing. If you would like to give it a try, please send your contact information to my email (jemiller@ti.com), or give me a call at my office (214-567-0217).

    Regards,

    John