Electrostatic discharge event protection for an integrated circuit

An integrated circuit comprising:

• power supply rail means for distributing a power supply signal;
• ground rail means for distributing a ground signal;
• at least one signal processing transistor means for performing signal processing under control of a processing control signal;
• clamp transistor means coupled between said power supply rail means and said ground rail means and controlled by a clamp control signal for providing a current path between said power supply rail means and said ground rail means;
• and
• detector means coupled to said power supply rail means and said ground rail means for generating said clamp control signal, said detector means being responsive to a change in voltage difference between said power supply rail means and said ground rail means indicative of an electrostatic discharge event to generate said clamp control signal with a value that switches said clamp transistor means to a conductive state in which current flow through said clamp transistor means suppresses said change in voltage difference;
• wherein
• said detector means generates an electrostatic discharge event signal when said electrostatic discharge event is detected;
• and
• said electrostatic discharge event signal controls protection means for forcing said processing control signal to a protection state in which said signal processing transistor means has an increased resistance to damage from said electrostatic discharge event.

A method of protecting an integrated circuit from electrostatic discharge events, said integrated circuit having a power supply rail, a ground rail and at least one signal processing transistor controlled by a processing control signal to perform signal processing, said method comprising the steps of:

• using a clamp transistor coupled between said power supply rail and said ground rail and controlled by a clamp control signal to provide a current path between said power supply rail and said ground rail;
• and
• in responsive to a change in voltage difference between said power supply rail and said ground rail indicative of an electrostatic discharge event, generating a clamp control signal with a value that switches said clamp transistor to a conductive state in which current flow through said clamp transistor suppresses said change in voltage difference;
• generating an electrostatic discharge event signal when said electrostatic discharge event is detected;
• and
• controlling a protection circuit element with said electrostatic discharge event signal to force said processing control signal to a protection state in which said signal processing transistor has an increased resistance to damage from said electrostatic discharge event.