Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With particular connecting
Reexamination Certificate
2005-09-20
2005-09-20
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With particular connecting
C327S321000, C327S534000, C361S091100
Reexamination Certificate
active
06946904
ABSTRACT:
A transceiver circuit includes driver circuits, receiver circuits, and suspend-mode buffers that are arranged to withstand an over-voltage conditions that would otherwise damage those circuits. An over-voltage sense circuit is arranged to detect the over-voltage condition on a data line in the transceiver. Cascode devices are placed in critical points of the various circuits, while voltages are coupled to other critical points such that none of the transistor devices that are coupled to the data lines are damaged by the over-voltage condition. Selector circuits are arranged to couple the highest detected voltages to various transistor wells to prevent forward biasing parasitic diodes in the transistors. Series switching circuits are arranged to break critical conduction paths during the over-voltage condition. The over-voltage protection scheme is suitable for use in integrated USB transceivers.
REFERENCES:
patent: 5570043 (1996-10-01), Churchill
patent: 5654858 (1997-08-01), Martin et al.
patent: 5717557 (1998-02-01), Gonzalez et al.
patent: 2003/0227320 (2003-12-01), Davis
Nguyen Nghiem
Varma Seema
Vu Ha Chu
Callahan Timothy P.
Englund Terry L.
Hertzberg Brett A.
Merchant & Gould P,C,
National Semiconductor Corporation
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