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ADS1672: how to drive ADS1672 with a ground-referenced single-ended signal

Alberto Aloisio
Intellectual 910 points
Part Number: ADS1672
Other Parts Discussed in Thread: OPA320, OPA192

Dear Support,


 I need driving the ADS1672 with a single-ended signal, 4Vpp from a low-noise
voltage amplifier, while keeping the ADC specs.

The voltage amplifier has low output impedance (about 300 Ohm) and it can not drive

a load lower than 10k.Ohm. Required BW is 250Khz. Power consumption is not an issue,

The ADS1672 will be used to analyze 1/f noise in material science tests, so
the 1/f noise of any preamp/driver should be as low as possible. Its current noise, is not an issue,

due to the low output impedance of the amplifier. However, Voltage noise could be a problem.
Could you please suggest me the best front-end (driver/circuit). In the ADS1672 datasheet I only found a scheme

(Fig.41) with a single-ended signal referenced to CM and not to GND.

Thank you for your help.
Kind Regards,

Alberto

  • 0
    TI__Mastermind 46140 points

    Hello Alberto,

    Please take a look at this Analog Engineer's Circuit:

    http://www.ti.com/lit/an/sbaa246a/sbaa246a.pdf

    For your specific requirements, the above circuit will need the following modifications:

    1.  The gain needs adjusted for +/-4V input to +/-3V differential output.  Change Rg1,Rg2 from 1kohm to 2.67kohm.

    2.  Change Vocm to 2.5V to meet common mode input requirements for ADS1672.

    3.  Change OPA320 to OPA192 to support higher input voltage ranges.

    4.  Change OPA192 supplies to 5V<V+<15V and -5V>V->-15V range to support +/-4V input.

    5.  Rfilt1, Rfilt2 will need to change values, datasheet values of 10ohm will be a good starting value.

    6.  Cfilt should change to at least 750pF, but this can typically be increased to a much higher value in the range of 1nF to 10nF.

    There may be other amplifier combinations that give better performance, but these devices are a good starting point.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Intellectual 910 points

    Dear Keith,

    thank you so much for your help.

    I will start from your suggestions.

    Kind Regards,

    Alberto