Silicon controlled rectifier electrostatic discharge protection device for power supply lines with powerdown mode of operation

1. An electrostatic discharge (ESD) protection circuit in a semiconductor integrated circuit (IC) having protected circuitry, the ESD protection circuit comprising:

a silicon controlled rectifier (SCR) having at least one first type high dopant region formed in a second type low dopant region coupled to a first reference potential of the protected circuitry and at least one second type high dopant region coupled to a second reference potential of said IC;

at least one trigger tap disposed outside of a surface area between the first type high dopant region and the second type high dopant region, said trigger tap formed in said second type low dopant region; and

a MOS transistor located outside of the surface area between the first type high dopant region and the second type high dopant region of the SCR, said transistor adapted for injecting a trigger current via said trigger tap into at least one gate of said SCR.

2. The ESD protection circuit of claim 1 , wherein said at least one trigger-tap; disposed proximate to at least one of the first type high dopant regions and the second type high dopant regions.

3. The ESD protection circuit of claim 2 , wherein said MOS transistor is coupled between said protected circuitry and said at least one trigger-tap.

4. The ESD protection circuit of claim 1 , further comprising a resistor that is not part of the SCR's internal series resistance, coupled between at least one of the first type high dopant region and the second type high dopant region, and the MOS transistor.

5. An electrostatic discharge (ESD) protection circuit in a semiconductor integrated circuit (IC) having protected circuitry, the ESD protection circuit comprising:

a SCR further comprising:

a substrate;

a first type conductive well and an adjacent second type conductive well formed in said substrate and defining a junction therebetween;

at least one first type doped region formed in said second type conductive well and coupled to first voltage reference of said protected circuitry;

at least one second type doped region formed in said first type conductive well and coupled to a second voltage reference of said protected circuitry;

at least one trigger tap dispose outside of a surface area between the first type doped region and the second type doped region, said trigger tap formed in said second type conductive well; and

a MOS transistor coupled to the SCR and protected circuitry, and adapted to inject a trigger current via said trigger tap into said second type conductive well, wherein said MOS transistor and SCR are separate and distinct devices incorporated on the IC such that the MOS transistor is located outside the surface area between the first type doped region and the second type doped region of the SCR.

6. The ESD protection circuit of claim 5 wherein said at least one trigger tap disposed proximate to at least one of said first type doped region in said second type conductive well and said second type doped region in said first type conductive well.

7. The ESD protection circuit of claim 6 , further comprising at least one shunt resistor coupled between said at least one trigger tap and at least one of said first type doped region and said second type doped region.

8. The ESD protection circuit of claim 5 , wherein distance between edge of said second type doped region and said junction is 4.0 microns or less and distance between edge of said first type doped region and said junction is 4.0 microns or less.

9. The ESD protection circuit of claim 8 wherein said distance is in the range between about 0.6 microns and about 0.8 microns.