Low noise electrostatic discharge protection circuit for mixed signal CMOS integrated circuits
First Claim
1. An apparatus including an integrated circuit with an electrostatic discharge (ESD) protection circuit for protecting said integrated circuit during an ESD event, comprising:
- a first plurality of functional circuit cells;
a first plurality of signal terminals connected to said first plurality of functional circuit cells;
a second plurality of functional circuit cells;
a second plurality of signal terminals connected to said second plurality of functional circuit cells;
a first ESD pad ring which includes first positive and negative power supply nodes connected to said first plurality of functional circuit cells;
a first plurality of unidirectional conductive circuits connected between said first plurality of signal terminals and said first positive and negative power supply nodes;
a first plurality of intra-ring clamp circuits connected between said first positive and negative power supply nodes;
a second ESD pad ring which includes second positive and negative power supply nodes connected to said second plurality of functional circuit cells;
a second plurality of unidirectional conductive circuits connected between said second plurality of signal terminals and said second positive and negative power supply nodes;
a second plurality of intra-ring clamp circuits connected between said second positive and negative power supply nodes; and
first and second pluralities of inter-ring clamp circuits connected between said first positive and negative power supply nodes and said second positive and negative power supply nodes.
1 Assignment
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Accused Products
Abstract
An electrostatic discharge (ESD) protection circuit includes circuitry for providing protection against ESD events which occur either within an ESD pad ring (intra-ring) or between different ESD pad rings (inter-ring). Self-triggering voltage clamp circuits or back-to-back diode circuits can be used to properly interconnect the positive polarity rails and the negative polarity rails of the ESD pad rings. Self-triggering voltage clamp circuits are advantageous in that they provide improved ac signal isolation (i.e. reduced noise coupling between the ESD pad rings, and thus reduced noise coupling from the digital I/O pads to the analog I/O pads).
24 Citations
25 Claims
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1. An apparatus including an integrated circuit with an electrostatic discharge (ESD) protection circuit for protecting said integrated circuit during an ESD event, comprising:
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a first plurality of functional circuit cells; a first plurality of signal terminals connected to said first plurality of functional circuit cells; a second plurality of functional circuit cells; a second plurality of signal terminals connected to said second plurality of functional circuit cells; a first ESD pad ring which includes first positive and negative power supply nodes connected to said first plurality of functional circuit cells; a first plurality of unidirectional conductive circuits connected between said first plurality of signal terminals and said first positive and negative power supply nodes; a first plurality of intra-ring clamp circuits connected between said first positive and negative power supply nodes; a second ESD pad ring which includes second positive and negative power supply nodes connected to said second plurality of functional circuit cells; a second plurality of unidirectional conductive circuits connected between said second plurality of signal terminals and said second positive and negative power supply nodes; a second plurality of intra-ring clamp circuits connected between said second positive and negative power supply nodes; and first and second pluralities of inter-ring clamp circuits connected between said first positive and negative power supply nodes and said second positive and negative power supply nodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus including an electrostatic discharge (ESD) protection circuit for protecting a functional circuit during an ESD event, comprising:
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a first positive power supply node; a first negative power supply node; a first signal node; a first clamp circuit connected between said first positive power supply node and said first negative power supply node; a first unidirectional conductive circuit connected between said first signal node and said first positive power supply node; a second unidirectional conductive circuit connected between said first signal node and said first negative power supply node; a second positive power supply node; a second negative power supply node; a second signal node; a second clamp circuit connected between said second positive power supply node and said second negative power supply node; a third unidirectional conductive circuit connected between said second signal node and said second positive power supply node; a fourth unidirectional conductive circuit connected between said second signal node and said second negative power supply node; a third clamp circuit connected between said first positive power supply node and said second negative power supply node; and a fourth clamp circuit connected between said second positive power supply node and said first negative power supply node. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A method of protecting a functional circuit during an electrostatic discharge (ESD) event, comprising the steps of:
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when a first ESD voltage appears between first and second signal nodes connected between a first positive power supply node and a first negative power supply node, conducting a first ESD current from said first signal node to said first positive power supply node, sensing and clamping a first inter-node voltage between said first positive power supply node and said first negative power supply node while conducting said first ESD current from said first positive power supply node to said first negative power supply node, and conducting said first ESD current from said first negative power supply node to said second signal node; and when a second ESD voltage appears between said first signal node and a third signal node connected between a second positive power supply node and a second negative power supply node, conducting a second ESD current from said first signal node to said first positive power supply node, sensing and clamping a second inter-node voltage between said first positive power supply node and said second negative power supply node while conducting said second ESD current from said first positive power supply node to said second negative power supply node, and conducting said second ESD current from said second negative power supply node to said third signal node. - View Dependent Claims (19, 20, 21)
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22. A method of protecting a functional circuit with multiple ESD pad rings during an electrostatic discharge (ESD) event, comprising the steps of:
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when a first ESD voltage appears between first and second signal nodes connected within a first ESD pad ring, conducting a first ESD current from said first signal node to a positive power supply node within said first ESD pad ring, sensing and clamping a first inter-node voltage between said first ESD pad ring positive power supply node and a first negative power supply node within said first ESD pad ring while conducting said first ESD current from said first ESD pad ring positive power supply node to said first ESD pad ring negative power supply node, and conducting said first ESD current from said first ESD pad ring negative power supply node to said second signal node; and when a second ESD voltage appears between said first signal node and a third signal node connected within a second ESD pad ring, conducting a second ESD current from said first signal node to said first ESD pad ring positive power supply node, sensing and clamping a second inter-node voltage between said first ESD pad ring positive power supply node and a second negative power supply node within said second ESD pad ring while conducting said second ESD current from said first ESD pad ring positive power supply node to said second ESD pad ring negative power supply node, and conducting said second ESD current from said second ESD pad ring negative power supply node to said third signal node. - View Dependent Claims (23, 24, 25)
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Specification