Abstract: Embodiments of present disclosure relate to a protection unit, an ADC module, and a system. The protection unit includes a first terminal; a second terminal; a first switch unit disposed between the first terminal and an output terminal of the protection unit; a second switch unit disposed between the second terminal and a ground of the protection unit; and a positive over voltage protection unit coupled to the first terminal, the first switch unit, and the second switch unit. The protection unit is configured to switch off the first switch unit and the second switch unit when a positive voltage at the first terminal exceeds a positive threshold.