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ADC3443: Interfacing with pseudo-differential sensor output

Lionel Brixhe
Prodigy 40 points
Part Number: ADC3443
Other Parts Discussed in Thread: THS4541

Hi,

I have a pseudo-differential output from a sensor that has to be conditioned to match the input of the ADC with optimal noise performance.

The signal has the following shape :

What would be the best way to connect it to the ADC, without loosing half of the ADC range?

I considered using two op-amps to shift the common mode voltage of both signals to the one of the ADC and maybe using a differential amplifier to further refine the signal gain and common mode but I'm worried about the required accuracy for the common mode voltage shifting stage.

Do you have any recommendations for this application?

Thank you.

Best regards,

Lionel

  • 0
    TI__Genius 12780 points
    Hi Lionel,

    We are taking a look into your question, and will be back with you soon.

    Best Regards,

    Dan
  • 0 in reply to dBrock
    TI__Genius 15975 points

    Hi Lionel,

    Sorry for the delay in reply.

    I think using a fully differential amplifier such as the THS4541 would be the best and easiest way to interface the pseudo differential signal output with the ADC input, while level shifting the common mode voltage. You may want to take a look at this TI Design: http://www.ti.com/lit/ug/tidubs9a/tidubs9a.pdf which explains in detail the fully differential amplifier interface to the ADC.

    Please let me know if you have any questions.

    Best Regards,

    Rohit

  • 0 in reply to Rohit Bhat
    Prodigy 40 points

    Hi Rohit,

    We already plan to use a fully differential amplifier to adapt the common mode to the one of the ADC.

    The problem here is that the input signal is not fully differential. The P signal goes from 1,7V to 2,7V while the N signal goes from 1,7V to 0,7V. This signal can be seen like a fully differential signal whose resulting range never goes negative.

    If input this signal to the ADC, only passing through the differential amplifier for common mode shifting, half of the ADC range will be wasted.

    We try to find a way to adapt the signal so the full range of the ADC is used, without compromising too much the SNR.

    Best regards,

    Lionel