Protective circuit

A protective circuit for limiting a voltage at a pad of an integrated circuit, the protective circuit being connected between the pad and a reference-earth potential of the integrated circuit, the protective circuit comprising:

• a threshold detector device connected to the pad and deriving a threshold voltage from the voltage at the pad, the threshold detector device having:
• a first transistor, whose load path is connected to the pad at a first terminal and to whose control terminal the threshold voltage is fed,
• a resistor connected between the second terminal of the load path of the first transistor and the reference-earth potential,
• a second transistor, whose control terminal is connected to a second terminal of the load path of the first transistor and whose load path is connected between the pad and the reference-earth potential,
• a high-resistance voltage divider connected between the pad and the reference-earth potential, the voltage divider having a node for enabling tapping of the threshold voltage, and
• a diode connected between the pad and the load paths of the first transistor and of the second transistor such that the diode is reverse-biased when the voltage at the pad falls below a predetermined value, thereby switching off the protective circuit.