Anti-aliasing filter in arty-z7

[amolina]

Hi, I have a doubt about the reference manual in my board. In the reference manual I have read that the board has a anti-aliasing filter and Digilent provide the next image for the pins in ADC. I am using the pins A6, A7 as entry but in the figure is possible see the next message: 1 nf capacitor is only loaded in Vp,Vn. So, if I use others pins is not place the capacitor and there is not a filter? If there is a filter which is the cut off frequency?. Thanks in advance.

[xc6lx45]

Hi,

based on the information from the picture, the lowpass at V_P/V_N has a cutoff frequency of around 560 kHz, then -6 dB / octave. Unless the manual is wrong, I'd guess there is your anti-aliasing filter.

My first thought would be to tune it down with e.g. 2x1 kOhms resistors, depending of the highest frequency of interest. Otherwise it's not very effective at the first alias frequency (but good to suppress general high-frequency noise)