AD7176-2 has unknown noise in sample data.

Hi ADI,

I got EVAL-AD7176-2SDZ (Rev-A), and I use it to test audio signal.

I use AD7176-2 to sample a pure 12.5 kHz 0.1 Vrms sine wave, and sample rate is 125kHz.

But there is a stable low frequency noise as below picture, so it make the wave envelope is unstable.

I

My setting as below:

The attachment is my test data.

Do you have any idea about this problem?

Thanks.

Homeway

12.5kHz.csv.zip
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  • 0
    •  Analog Employees 
    on Nov 13, 2017 11:41 PM

    Hi,

    Regarding the number of samples. Same thing can be applied to the number of samples, the minimum number of samples needed to replicate the signal is at least twice the ratio of your ODR/input frequency since the part needs the filter settling time at the very first conversion. Regarding the decrease in voltage, we have a  Virtual Eval on ADI site that may help you evaluate and understand the performance of the AD7176 with any signal frequency or configurations and settings you want. If you take a look at the filter profile of the said tool you will see the attenuation at your operating frequency. At 250ksps ODR, you have -0.15dB, at 125ksp you have -0.26db with12.5KHz input frequency. I think this tool will help you answer to your question.

    Thanks,

    Jellenie

Reply
  • 0
    •  Analog Employees 
    on Nov 13, 2017 11:41 PM

    Hi,

    Regarding the number of samples. Same thing can be applied to the number of samples, the minimum number of samples needed to replicate the signal is at least twice the ratio of your ODR/input frequency since the part needs the filter settling time at the very first conversion. Regarding the decrease in voltage, we have a  Virtual Eval on ADI site that may help you evaluate and understand the performance of the AD7176 with any signal frequency or configurations and settings you want. If you take a look at the filter profile of the said tool you will see the attenuation at your operating frequency. At 250ksps ODR, you have -0.15dB, at 125ksp you have -0.26db with12.5KHz input frequency. I think this tool will help you answer to your question.

    Thanks,

    Jellenie

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