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AD7176-2 filter frequency response

Question asked by iozana on Jul 24, 2017
Latest reply on Jul 24, 2017 by iozana

Hi,

I my application I need to measure ~30Hz analog signal. For that purpose, I thought to use the AD7176-2, 24-Bit, fully differential, Sigma-Delta ADC. In order to do so, I need you to clarify some issues about the digital filter. Figure 52 shows the frequency response for the Sinc5 + Sinc1 filter at 50 SPS ODR. The problem with that is with the ~30Hz that will get the ~6dbB attenuation of my signal. Here is my question: Is it true to say that when sampling at let's say 1000 SPS, the first notch (that in Figure 52 is at 50Hz) will now be at 1016Hz (Table 19)? If the answer is "Yes", in order to sample ~30Hz wave, I need that the pass-band of the filter (~-0.1dB) will be at let's say ~300Hz. How can I make sure that the center of the Sinc filter will be at the center of the wanted frequency?

The same for filter Sinc3…

http://www.analog.com/en/products/analog-to-digital-converters/ad7176-2.html#product-overview

Thanks,

Idan   

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