Latch-up protection circuit for integrated circuits biased with multiple power supplies and its method

A latch-up protection circuit for an integrated circuit powered through a first power rail and a second power rail, said integrated circuit having at least one semiconductor bulk of a conductivity type;

• said latch-up protection circuit comprising:
• a control circuit comprising a differential amplifier configured with a first input coupled to said second power rail, a second input coupled to said first power rail for detecting a relative voltage therebetween and an differential amplifier output, the control circuit generating a first control signal and a second control signal, the control circuit Her comprising a first inverter powered trough said second power rail and provided with a first input terminal coupled to the differential amplifier output and a first output terminal providing said first control signal, and a second inverter powered through said first power rail and provided with a second inverter input teal coupled to the first output terminal of the first inverter and a second output terminal for providing said second control signal;
• a first switch circuit connected to said first power rail and said control circuit wherein said first switch circuit in response to said first control signal electrially connects said first power rail with said at least one semiconductor bulk when said relative voltage is greater than a fist predetermined value, and said first switch circuit in response to said first control signal electrically disconnects said first power rail from said at least one semiconductor bulk when said relative voltage is smaller than said first predetermined value;
• and a second switch circuit connected to said second power rail and said control circuit, wherein said second switch circuit in response to said second control signal electrically disconnects said second power rail from said at least one semiconductor bulk when said relative voltage is greater than a second predetermined value, and said second switch circuit in response to said second control signal electrically connects said second power rail with said at least one semiconductor bulk when said relative voltage is smaller than said second predetermined value.

A latch-up protection circuit for an integrated circuit powered through a first power rail and a second power rail, said integrated circuit having at least one semiconductor bulk of a conductivity type, said latch-up protection circuit comprising:

• a control circuit connected to said first power rail and said second power rail for detecting a relative voltage therebetween and generating a first control signal and a second control signal, the control circuit comprising a first differential amplifier powered through said second power rail and configured with a first negative input coupled to said second power rail and a first positive input coupled to said first power rail, a second differential amplifier powered through said first power rail and configured with a second negative input coupled to said first power rail and a second positive input coupled to said second power rail;
• a first switch circuit connected to said first power rail and said control circuit;
• wherein said first switch circuit in response to said fist control signal electrically connects said first power rail with said at least one semiconductor bulk when said relative voltage is greater than a first predetermined value, and said first switch circuit in response to said first control signal electrically disconnects said first power rail from said at least one semiconductor bulk when said relative voltage is smaller than said first predetermined value;
• and a second switch circuit connected to said second power rail and said control circuit, wherein said second switch circuit in response to said second control signal electrically disconnects said second power rail from said at least one semiconductor bulk when said relative voltage is greater than a second predetermined value, and said second switch circuit in response to said second control signal electrically connects said second power rail with said at least one semiconductor bulk when said relative voltage is smaller than said second predetermined value.