Q3. What is the recommended anti-aliasing filter required for the AD4111/AD4112/AD4114/AD4115?
For the AD4111/ AD4112/AD4114/AD4115 the recommend anti-aliasing is 4.7nF/180Ω as this combination will give you the optimum performance and were used in the EMC evaluation.
For AD4111, when using open-wire detection on voltage inputs, a 1kΩ resistor and 680pF capacitor should be placed between voltage pins and compensation pins. The value of the anti-aliasing filter can be changed but the 680pF compensation capacitor must be taken into consideration. See Figure 1.
Note that one should always consider the effect of a resistor connected in series with the internal input resistance of the AD411x. This will affect the divider ratio resulting in a gain error. The nominal internal resistor value for AD4111/AD4112 is 1.17MΩ and may vary from part to part. If for example the 180 resistor is used then this would introduce a worst-case error of 180/1170000 * 100 = 0.015%, however, this additional error can be removed by a system calibration or by adjusting the Gain register appropriately. For more details about calibration, please see the Calibration section of the AD4111/AD4112/AD4114/AD4115 datasheet.
Figure 1. Antialiasing RC filter with Open wire detection
