US Patent 7091633 Current-limiting logic interface circuit

A circuit of interface between a logic sensor and a logic input isolation barrier of a processing circuit, including an element of protection against input overvoltages, a current-limiting circuit connected in series between an input terminal and an output terminal of the interface circuit, and a control stage connected in parallel with the galvanic isolation element to be controlled to control the logic states thereof, the control stage inhibiting the operation of the galvanic isolation element if the input current is smaller than a predetermined threshold.