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DRV8353RS-EVM: amplified signal is inverted

Cherry Zhou
Mastermind 22235 points
Part Number: DRV8353RS-EVM

Hi Team,

The customer samples the resistor current of the DRV8353RS-EVM using the Bidirectional current-sense Configuration with a gain design of 40 V/V.

But the amplified signal is found to be inverted. Is there a way to correct it? Like adding an inverter externally Or programically invert the captured current?

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Genius 12105 points

    Hi Cherry,

    Is the output of SOB also inverted? I believe for current-sense you would want to see the output of SOx and not SPB alone.

    Regards,

    Yara

  • 0 in reply to Yara Al Shami
    TI__Mastermind 22235 points

    Hi Yara,

    Thank you for the support.

    Yara Al Shami said:
    Is the output of SOB also inverted? I believe for current-sense you would want to see the output of SOx and not SPB alone.

    The SOB actually is ISENB which is just going through a low-pass filter:

    The signal that captures the SPB is essentially the source signal sampled by the resistance. The customer is wondering why the resistor source signal SPB passes through the current amplifier and outputs ISENB. Why is it inverting amplification?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Genius 12105 points

    Hi Cherry,

    There are a few benefits to using inverting amplifiers such as having less input and output impedance, non-inverting amplifiers often times have very high input and output impedance. This point leads to inverting amplifiers being able to provide more stability in a system than non-inverting. This is why inverting amplifiers are often the correct choice in integrated circuits.

    Regards,

    Yara

  • 0 in reply to Yara Al Shami
    Prodigy 10 points 
    Why don't I see the description of this inverting amplifier in the documentation? It is easy to mistake it for a forward amplifier
     unless you look at the picture.
  • 0 in reply to topgun
    TI__Genius 12105 points

    Hi Cherry and Gun,

    Apologies for the misunderstanding, the amplifier used that is integrated for current sense I believe is a differential amplifier meaning it will take the difference of SPx and SNx.

     

    using the image above I can also see that ISENA from your waveform is behaving as expected.

    Regards,

    Yara