This application claims priority to Korean Patent Application No. 2001-36585 filed on Jun. 26, 2001.
1. Technical Field
The present invention relates to a semiconductor memory device, and more particularly, to a control signal generating circuit suitable for a programmable mode selector using a fuse.
2. Description of Related Art
Semiconductor memory devices comprise programmable mode selectors that are used to select various operational modes including tests and repairs.
FIG. 1 is a circuit diagram of a conventional control signal generating circuit used for a programmable mode selector. Referring to FIG. 1, a conventional control signal generating circuit 100 comprises a resistance R11 connected to a power supply voltage VCC, a break-link type fuse BL, an NMOS transistor MN11, an inverter I11 linked to a node between the break-link type fuse BL and the NMOS transistor MN11, an NMOS transistor MN12, and a ground voltage VSS.
The break-link type fuse BL is an electrical fuse which can break a connection by over-current or a laser fuse cut by a laser beam. A control signal (MODESEL) is generated to select various operational modes when the break-link type fuse BL is cut and the NMOS transistor MN11 is turned on by an input signal (IN). The break-link type fuse BL is usually not break a connection when a small amount of current flows through the break-link type fuse BL, because the fuse is lined with a conductor.
Different from a break-link type fuse, a make-link type fuse makes a connection (that is, the make-link type fuse is linked) by application of energy such as a laser beam or a surge of current. The make-link type fuse has a configuration which is simpler than the configuration of the break-link type fuse, thereby increasing the integration density of a semiconductor memory device.
A problem with a make-link type fuse is when a make-link type fuse is installed in a control signal generating circuit instead of a break-link type fuse, the make-link type fuse can unintentively make a connection by electro-migration, even from a small amount of current flowing through the make-link type fuse. Accordingly, the control signal generating circuit having a make-link type fuse is less reliable.
A need therefore exists for a control signal generating circuit having a make-link type fuse which is stable and reliable in current flowing through the make-link type fuse.
It is an object of the present invention to provide a control signal generating circuit that inhibits current flowing through a make-link type fuse, thereby improving the stability and reliability of operation.
According to one aspect of the present invention, there is provided a circuit for generating a control signal. The circuit comprises a first transistor for receiving an input signal at a gate thereof, the first transistor being connected to a first voltage, a second transistor for receiving the input signal at a gate thereof, the second transistor being connected to a second voltage, a make-link type fuse serially linked between the first and second transistors by application of energy, and a sensing circuit, connected to the make-link type fuse, for sensing whether the make-link type fuse is linked or not and for outputting a control signal based on the sensed result and the input signal. The first and second transistors are complementarily connected to turn on one of the first and second transistors in response to the input signal, thereby preventing current from flowing between the first and second transistors when the make-link type fuse is linked between the first and second transistors.
In an embodiment of the present invention, the sensing circuit preferably comprises a first inverter connected to a node connecting to the make-link type fuse, a third transistor having a gate and first and second ends, and a second inverter, connected to the first inverter, for outputting the control signal. In the third transistor, the gate receives an output signal of the first inverter, the first end is connected to the node and the second end is connected to the first voltage.
According to another aspect of the present invention, there is provided a circuit for generating a control signal. The circuit comprises a first transistor for receiving an input signal at a gate thereof, the first transistor being connected to a first voltage, a current limiter connected to a second voltage, a make-link type fuse serially linked between the first transistor and the current limiter, and a sensing circuit, connected to the make-link type fuse, for sensing whether the make-link type fuse is linked or not and for outputting a control signal based on the sensed result and the input signal.
According to further aspect of the present invention, there is provided a semiconductor device comprising a control signal generating circuit. The control signal generating circuit of the semiconductor device comprises a first transistor for receiving an input signal at a gate thereof, the first transistor being connected to a first voltage, a second transistor for receiving the input signal at a gate thereof, the second transistor being connected to a second voltage, a make-link type fuse serially linked between the first and second transistors, and a sensing circuit, connected to the make-link type fuse, for sensing whether the make-link type fuse is linked or not and for outputting a control signal based on the sensed result and the input signal. In an embodiment of the present invention, the control signal selects an operation mode of the semiconductor device. The first and second transistors are complementarily connected to turn on one of the first and second transistors in response to the input signal, thereby preventing current from flowing between the first and second transistors when the make-link type fuse is linked between the first and second transistors.
Advantageously, a control signal generating circuit according to an embodiment of the present invention inhibits current from flowing through a make-link type fuse to prevent unintentively making a connection. Thus, a semiconductor device comprising the control signal generating circuit can perform a stable and reliable operation. Further, since the control signal generating circuit can be configured in various ways and to realize a narrow fuse pitch, it is possible to increase the integration density of a semiconductor device.