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Queries about AD7606 Anti Aliasing Filter

Question asked by WayneQ on Nov 13, 2014
Latest reply on Nov 26, 2014 by jcolao

Hi,

 

On Page 23, Figure 37 of device datasheet, you state that anti aliasing filter is second order Butterworth however the graph shows attenuation significantly less than -6dB / octave which is expected from a second order Butterworth filter ?

 

This requires additional external filtering to attenuate signals with frequency content > 100KHz to below 305uV level, approx -90dB

 

My math tells me I should get  -60dB attenuation @ 100KHz with second order Butterworth but your second order Butterworth anti aliasing yields only -24dB attenuation, why ?

 

Thank You,

 

Wayne

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