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THS4551: Differential Outputs are not differential

Miguel Holguin
Prodigy 40 points

Part Number: THS4551

Tool/software:

I am using the developing board THS4551DGKEVM and have modified to have a single ended input and differential output. I followed the instructions provided with the development board. However, my output signals are not differential. They are the same, with the positive signal having lower voltage. Not sure what I am missing, but I need to get diff signals. 

The input signal is 5V and has a frequency of 15.75Khz.

  • 0
    TI__Mastermind 24524 points

    Hello Miguel,

    I am glad to help resolve this for you.

    Could you share your modifications on either the EVM schematic in the user guide or describe them to me in this thread?  If you are still using the populated transformer, you would need to populate R14 with a zero-Ohm resistor and remove R12.

    You may also remove the transformer entirely and bypass it with larger zero-Ohm resistors or wires, if you do not need the transformer.  The transformer is there to facilitate diff-to-single-ended conversion of the differential outputs of the amplifier.

    Could you also provide image or data of your measurement?  

    I can take an RGT EVM and replicate your setup if you share your resistor (gain) configuration, input source signal amplitude/offset, and any other modifications you have made.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 40 points

    I didn't remove the JMP5. Seems to be working now. I still wonder how I was able to get signals on both outputs though. Thank you!

  • 0 in reply to Miguel Holguin
    TI__Mastermind 24524 points

    Hell Miguel,

    No worries on the debug, that is why we are here!  As for why it operates even with some jumpers in place, I imagine there could be coupling/reflections which allowed for a signal.  

    Glad to hear it is working as expect now; please follow-up if you have any other questions.

    Best,

    Alec