Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Integrated structure
Patent
1996-02-02
1997-09-02
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Integrated structure
327313, H02H 320, H02H 904
Patent
active
056636784
ABSTRACT:
An FET with a lightly doped drain is connected between an input/output pad and ground and is protected from ESD at a pad by a structure that includes a resistor formed by the process step for the lightly doped drain. The resistor adjoins and interconnects a diffusion underlying the pad and the diffusion for the drain of the FET. A parasitic bipolar transistor is formed by the pad diffusion, the source diffusion for the FET, and the intervening substrate. When an ESD voltage appears at the pad, the FET conducts in circuit with the resistor and the voltage drop across the resistor helps to protect the FET and to turn on this parasitic bipolar transistor (in preference to a parasitic bipolar transistor otherwise formed by the FET) and thereby hold down the ESD voltage at the pad and at the drain of the FET. The FET and resistor can be formed as a number of parallel connected FETs and resistors located symmetrically on opposite sides of the pad diffusion. Protection for an input inverter circuit is also provided.
REFERENCES:
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patent: 4811155 (1989-03-01), Kuriyama et al.
patent: 4829350 (1989-05-01), Miller
patent: 4855620 (1989-08-01), Duvvury et al.
patent: 5051860 (1991-09-01), Lee et al.
patent: 5157573 (1992-10-01), Lee et al.
patent: 5208475 (1993-05-01), Mortensen
patent: 5565698 (1996-10-01), Obermeier
Callahan Timothy P.
Lam T. T.
Robertson William S.
Saile George O.
Vanguard International Semiconductor Corporation
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