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EOS/ESD Protection circuit for an integrated circuit with operating/test voltages exceeding power supply rail voltages

  • US 5,751,525 A
  • Filed: 01/05/1996
  • Issued: 05/12/1998
  • Est. Priority Date: 01/05/1996
  • Status: Expired due to Term
First Claim
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1. An electrical overstress protection circuit for protecting an active circuit from electrical overstress, the electrical overstress protection circuit having first and second inputs for respectively receiving first and second reference voltages, first and second outputs for respectively providing the first and second reference voltages to the active circuit, first and second signal pads for respectively connecting to an external circuit and the active circuit, the electrical overstress protection circuit comprising:

  • first and second clamping circuits series connected between the first input and the first signal pad of the electrical overstress protection circuit, the first clamping circuit including a breakdown device that is constructed and arranged to conduct current in a first direction when a voltage across the breakdown device exceeds a forward conduction threshold, the second clamping circuit including a breakdown device constructed and arranged such that in a first direction of current through the breakdown device, the breakdown device has an active mode of operation and a breakdown mode of operation, the breakdown mode of operation occurring when a voltage across the breakdown device exceeds a reverse breakdown threshold, the breakdown device switching from breakdown mode to active mode when a magnitude of current through the breakdown device in the first direction exceeds a current threshold level; and

    third and fourth clamping circuits series connected between the first output and the second signal pad of the electrical overstress protection circuit.

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