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A filter simulation error of TI-TINA

Yu-Hung
Expert 1130 points
Other Parts Discussed in Thread: ADS1281, THS4531, TINA-TI

Hi.

I want to simulate a filter with a differential input signal.

But it shows a error about format invalid.

Do I miss something? Please help.

Thanks.

Yu-hung

  • 0
    TI__Intellectual 2405 points

    Hi Yu-Hung,

    I am not completely sure why you are facing the issue, as I don't have details of source signal you have used. But after re-creating schematic, I would like to suggest a couple of things.

    1. This may be syntax error, in which case I would suspect input source signal. Please use test option if you are defining signal manually.

    2. Need ground connection at the VCVS output where you connect positive of one and negative of other terminal.

    3. If you are looking at -10V common mode and unit step as differential mode signal, it is not being transmitted that way. Both common mode and differential mode signals are added up and a step of -10V to -9V is going to inputs.

    4. Kindly use normal transient analysis with/without 'Use Initial Conditions' option to see the results in Diagram Window.

    diff_filt.TSC

    Hope this helps resolve the issue.

    Thanks!!

    Best Regards,

    Mahavir Jain.

  • 0 in reply to Mahavir Jain
    Expert 1130 points

    Thanks Mahavir,

    It is helpful for me.

    I have a differential signal(±20V) and want to give it a gain=0.125 to fit the ADS1281 input range.

    So there are two stage in the circuit.

    stage 1. Gain 0.125 with Fully Differential Amplifier(THS4531).

    Rg1=Rg2=8K and Rf1=Rf2=1K

    stage 2. Low-pass filter(the simulation of TI-TINA in this post)

    This is very interesting on the following images.

    If I separated the ground of source, the error reappeared!!!!

    I don't know why? they should be the same.

  • 0 in reply to Yu-Hung
    TI__Intellectual 2405 points

    Hi Yu-Hung,

    Based on schematic images from TINA-TI, I could make out that it is just wire connection to GND that is not happening properly when you connect them separately. It may be that, when you connected all wires at same GND point, there the connection is correct and a thick dot appears.  You can always cross-check these connections by generating netlist and looking at corresponding node numbers. File >> Export >> Netlist... >> for PSPICE (*.CIR)...

    We have THS4531 model available for both TINA-TI and PSPICE here. You can actually build-up complete application in TINA-TI around the THS4531 model and test it out. Kindly let us know if you face any difficulty.

    Thanks!!

    Best Regards,

    Mahavir Jain.

  • 0 in reply to Mahavir Jain
    Expert 1130 points

    Hi Mahavir,

    Here is my TINA file.

    4606.Pre-amplifier.TSC

    I think everything is fine, but otherwise the phase of filter is not good enough.

    Haha....:)