A low current drain switch interface circuit includes an input terminal (105), coupled to a first terminal (201) of a diode (204). A voltage follower circuit (211) is coupled to a second terminal (203) of the diode (204). A current source (215) is coupled between an output terminal (213) of the voltage follower circuit (211) and a power supply terminal (111). A mechanical switch (101) is coupled to the input terminal (105). The voltage follower circuit (211) outputs a voltage (119) indicative of a physical state of the mechanical switch (101).