Analog Devices,inc.

Keith A Moloney

David J Clarke

Denis Ellis

Michael G Tuthill

Brian Anthony Moane

Michael P Daly

Kieran K Heffernan

Denis J Doyle

Liam Joseph White

An input protection device is provided for protecting a circuit structure which is coupled to a first node, the device comprising a first lightly-doped region of P-type material with a lightly doped well of N-type material formed in it. Two regions of heavily doped N-type and P-type material, which are electrically connected to the first node, are formed in the well of N-type material. A third heavily doped region of N type material is formed in the first lightly-doped region of P-type material and is electrically connected to a reference node. In a first aspect of this invention, the third heavily doped region of N type material is formed in a second well of N-type material, which in turn is formed in the first lightly-doped region of P-type material. In this first aspect of the invention a further region of heavily doped P-type material is formed in the second well of N-type material, this further region of heavily doped P-type material being electrically connected to the reference node. In a second aspect to the invention, a further region of heavily doped P-type material is formed in the first lightly-doped region of P-type material. In a third aspect to the invention, the third heavily doped region of N type material is formed in a second well of N-type material, which in turn is formed in the first lightly-doped region of P-type material. In this third aspect of the invention a further region of heavily doped P-type material is formed in the second well of N-type material, this further region of heavily doped P-type material being electrically connected to the reference node, with a further region of heavily doped P-type material formed in the first lightly-doped region of P-type material. Accordingly, an input protection device for protecting pins of an integrated circuit is described having both bipolar and unipolar characteristics. The input protection device may be constructed as a discrete device or as part of an integrated circuit and provides for breakdown voltages in excess of a supply voltage to an integrated circuit. The characteristics, in particular the breakdown voltage, of the input protection device are alterable by adjusting its layout, in contrast to a known method of altering such characteristics by altering doping levels.

SCR cell for electrical overstress protection of electronic circuits

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Crecora, Ireland

Keith A Moloney