Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1999-05-03
2001-05-01
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S764010, C327S525000
Reexamination Certificate
active
06225818
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of integrated circuits in general and more particularly to the performance of multiple functions by integrated circuits.
BACKGROUND OF THE INVENTION
As the complexity of integrated circuits increases, so may the number of functions provided by the integrated circuits. The function provided by the integrated circuit may be selected and a label placed on the package of the integrated circuit to identify the function provided by the integrated circuit.
The function of the integrated circuit may later be identified by applying a voltage to the integrated circuit and observing the resulting current. U.S. Pat. No. 5,103,166 to Jeon et al. discusses identification circuitry including a voltage limiter which limits an input potential difference between a power supply terminal and an input terminal to a predetermined voltage. U.S. Pat. No. 4,480,199 to Varshney et al. discusses an identification circuit wherein, a single identification circuit may be electrically connected to a pad of the integrated circuit. As described above, a voltage may be applied to the pad, causing a current to flow which may be used to identify the function provided by the integrated circuit. As the number of functions provided by the integrated circuit increases, however, so may the number of required pads also increase, which may increase the cost and/or complexity of the integrated circuit. In view of the above, there continues to exist a need to further improve the identification of functions provided by integrated circuits.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to allow a reduction in the cost and/or complexity of integrated circuits including circuits with multiple functions.
It is another object of the present invention to allow a reduction in the number of pads that are used to identify the function of circuits.
These, and other objects, are provided by a function identification circuit that operates in a plurality of modes. The operating modes correspond to functions performed by a circuit in the integrated circuit. The function performed by the circuit can be identified by response to a series of voltage levels applied to the function identification circuit and observing the predetermined voltage at which current flows. The function which corresponds to the predetermined voltage at which current flows, is the function performed by the circuit. The function of the circuit may thereby be identified using fewer pads which may allow a reduction in the cost of the integrated circuit.
In particular, an integrated circuit according to the present invention includes first and seconds pads. A function identification circuit that operates in a plurality of modes is electrically connected to the first and second pads, wherein the plurality of operating modes correspond to the plurality of functions performed by the circuit.
In another aspect of the present invention, the function identification circuit includes a plurality of current circuits, that are electrically connected between the first and second pads. The current circuits conduct current when operating. A plurality of selection circuits are electrically connected to the plurality of current circuits, wherein the plurality of selection circuits select which of the plurality of current circuits operate. In one embodiment, the operating modes of function identification circuit are determined by fuses that are cut during a manufacturing process of the integrated circuit.
In another aspect of the present invention, the function identification circuit includes a first current circuit, including a first source node that is electrically connected to the first pad and a first gate/drain node. A second current circuit includes a second source node that is electrically connected to the first gate/drain node and a second gate/drain node. A third current circuit includes a third source node that is electrically connected to the second gate/drain node and a third gate/drain node. A fourth current circuit includes a fourth source node that is electrically connected to the third gate/drain node and a fourth gate/drain node that is electrically connected to the second pad.
A first selection circuit includes a first primary node that is electrically connected to the first gate/drain node and a first secondary node that is electrically connected to the second pad. A second selection circuit includes a second primary node that is electrically connected to the second gate/drain node and a second secondary node that is electrically connected to the second pad. A third selection circuit includes a third primary node that is electrically connected to the third gate/drain node and a third secondary node that is electrically connected to the second pad.
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Joo Jae-hoon
Kang Sang-seok
Park Cheol-hong
Hamdan Wasseem H
Metjahic Safet
Myers Bigel & Sibley & Sajovec
Samsung Electronics Co,. Ltd.
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