Granted Patent B2

US 8,680,621 · App. 13/695,670 · Granted Mar 25, 2014

Abstract

Claims (29)

1. An integrated circuit comprising electro-static discharge, ESD, protection circuitry arranged to provide ESD protection to an external terminal of the integrated circuit, the ESD protection circuitry comprising:

a thyristor circuit comprising a first bipolar switching device operably coupled to the external terminal and a second bipolar switching device operably coupled to another external terminal, a collector of the first bipolar switching device being coupled to a base of the second bipolar switching device and a base of the first bipolar switching device being coupled to a collector of the second bipolar switching device; and

a third bipolar switching device having a base terminal operably coupled to the thyristor circuit and having a threshold voltage for triggering the thyristor circuit to provide a current path from the external terminal to the another external terminal, the threshold voltage being independently configurable of the thyristor circuit; wherein

the first and second switching devices, when in use, exhibiting a bidirectional snapback characteristic and a snapback voltage associated therewith.

2. A circuit as claimed in claim 1 , wherein the thyristor circuit is a Silicon-Controlled Rectifier.

3. A circuit as claimed in claim 1 , wherein the first bipolar switching device is a PNP bipolar transistor.

4. A circuit as claimed in claim 1 , wherein the second bipolar switching device is a first NPN bipolar transistor.

5. A circuit as claimed in claim 1 , wherein the third bipolar switching device is a second NPN bipolar transistor.

6. A circuit as claimed in claim 1 , wherein a base of the third switching device is also coupled to the collector of the first switching device.

7. A circuit as claimed in claim 1 , wherein an emitter of the second bipolar switching device is coupled to an emitter of the third bipolar switching device.

8. A circuit as claimed in claim 1 , wherein an emitter terminal of the first switching device is coupled to the external terminal via an external resistance.

9. A circuit as claimed in claim 1 , wherein the first bipolar switching device provides, when in use, a first current path from the collector to the emitter of the first bipolar switching device when a voltage across the external terminal and the another external terminal exceeds a trigger voltage, and the second bipolar switching device provides a second substantially lateral current path and a third substantially vertical current path.

10. A circuit as claimed in claim 9 , wherein the first bipolar switching device is arranged to provide, when a current associated with an electrostatic discharge event exceeds a predetermined trigger current value, a fourth substantially vertical current path that crosses the first current path, thereby providing thyristor functionality in response thereto.

11. A circuit as claimed in claim 1 , further comprising a semiconductor substrate and a layer of n-type material disposed adjacent the semiconductor substrate.

12. A circuit as claimed in claim 11 , further comprising:

a first p-region disposed in the n-type material and a second p-region disposed in the n-type material, the first and second p-regions being laterally spaced with respect to each other;

a first p+ region disposed between a first n+ region and a second n+ region in the first p-region, the first n+ region, the second n+ region and the first p+ region being laterally spaced with respect to each other; and

a third n+ region and a second p+ region disposed in the second p-region and laterally spaced with respect to each other.

13. A circuit as claimed in claim 12 , wherein the external terminal is operably coupled to the third n+ region and the second p+ region, the external terminal constituting a second common contact.

14. A circuit as claimed in claim 12 , wherein the another external terminal is operably coupled to the first n+ region, the first p+ region and the second n+ region, the another external terminal constituting a first common contact.

15. A circuit as claimed in claim 12 , wherein a lateral distance between the first p-region and the second p-region defines a snapback voltage of the thyristor circuit.

16. A circuit as claimed in claim 12 , further comprising:

a lateral isolation layer disposed opposite the first p-region, a lateral distance between the first p-region and the lateral isolation layer defining the trigger voltage for the thyristor circuit.

17. A circuit as claimed in claim 11 , wherein the layer of n-type material is operably coupled to a biasing element.

18. An electronic device comprising the integrated circuit of claim 1 .

19. A method of providing electro-static discharge, ESD, protection to an external terminal of an integrated circuit, the method comprising:

providing a thyristor circuit coupled across the external terminal and another external terminal in order to provide a current path from the external terminal to the another external in response to an ESD event associated with the external terminal; and

a third bipolar switching device operably coupled to the thyristor circuit, the third bipolar transistor triggering the thyristor circuit in response to a voltage of the ESD event exceeding a threshold voltage associated with the third bipolar switching device, thereby providing the current path from the external terminal to the another external terminal in order to provide a conductive path for the ESD event; wherein

the threshold voltage is independently configurable of the thyristor circuit; and the thyristor circuit, when in use, exhibits a bidirectional snapback characteristic and a snapback voltage associated therewith.

Assignments (31)