Could you explain us the use of the BAV116W diode please in the ADC circuitry example on this article ? I would like to add ESD protection to adc inputs, is this diode enough?
The diode between ground and the signal as shown in the adc page is used to clamp the voltage on the AD line in order to avoid it goes under 0V (-1V roughly). It is a good protection for reverse voltage made by mistake from the user and also a good protection against ESD especially after the resistor divider and the capacitor.
The resistor divider, is useful to limit a lot the spike current in case of a spark. This spike is also shorted to ground by the capacitor.
In order to fufther improve the protection of the ADC input you can add another diode between the ADC line (anode) and the power rail (cathode) as shown as optional in our Daisy 20 board.
And finally you can add on your input connector some spark-gap as shown in this photo:
You need to form a 0.2mm gap between uncovered by solder resist ADC input and ground pads with sharp copper tips. A spark arriving will choose hopefully this path instead of crossing the input resistor and produce more damage to the circuit.