Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1998-04-20
2001-02-27
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S082000, C327S543000
Reexamination Certificate
active
06194953
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a circuit configuration for generating an internal supply voltage, with which integrated circuits can be operated.
As the scale of integration in integrated circuits increases, the dimensions of the integrated components become smaller and smaller. It is highly important that the space requirement per memory cell be slight, especially in semiconductor memories, in which the storage capacity and thus the number of memory cells are being increased more and more.
However, the increased scale of integration has meant that the electrical field intensity at the individual components of the integrated circuit, for instance at the gate oxides of transistors, is greater in comparison with memories having a lesser scale of integration. Thus the stress exerted on the components also rises, leading to a growth in failure rates. In order to avoid that, the cell fields of semiconductor memories are operated with an internal supply voltage. As a rule, it is below the external supply voltage with which the external circuit located outside the cell fields is operated. For instance, in the case of the cell field, the voltage of 5 V of the outer circuit is reduced to the internal supply voltage of 3.3 V. Various circuits for reducing the voltage are known.
The dependency of the service life of the cell field on the internal supply voltage being applied and on the resultant electrical field can be exploited in a so-called burn-in test. In it, the cell field is operated at a higher voltage than the internal supply voltage used for proper operation. The resultant failures of the memories make quality control possible.
Only the external supply voltage can be applied to the semiconductor memory from outside. The internal supply voltage, which should be as constant as possible and as independent as possible of external interfering factors, is generated by a voltage generator provided specifically for that purpose. Since the internal supply voltage is regulated to a certain value by the voltage generator, increasing the external supply voltage does not at the same time lead to an increase in the internal supply voltage. It is therefore not possible to perform the burn-in test with conventional voltage generators.
A voltage generator which furnishes a regulated, constant internal supply voltage as long as the external supply voltage is below a certain value, is known from German Published, Non-Prosecuted Patent Application DE 42 26 048 A1. If the external supply voltage exceeds that certain value, then the internal supply voltage rises with the external supply voltage. That is attained due to the fact that either a constant comparison voltage or the external supply voltage, depending on whether the external supply voltage is below or above that certain value, is supplied to a closed control loop that generates the internal supply voltage.
The disadvantage of that voltage generator is that a relatively complicated and expensive device is needed for the burn-in test in which semiconductor memories with that voltage generator are to be tested. That is because in order to expose the semiconductor memory to a defined stress, the external supply voltage must be kept at a very specific value, which to that end should be as constant as possible.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a circuit configuration for generating an internal supply voltage, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and with which a defined, disproportionately increased internal supply voltage is furnished in a simple way.
With the objects of the invention in view, there is also provided a circuit configuration, comprising a device for generating an internal supply voltage derived from an external supply voltage for operating an integrated circuit; and a reference voltage generator for detecting a voltage proportional to the external supply voltage and for generating a reference voltage as a function of a magnitude of the voltage proportional to the external supply voltage, to control the device for generating the internal supply voltage, the reference voltage generator generating at least two constant voltage values of the reference voltage.
The invention has the advantage of ensuring that the disproportionately increased internal supply voltage is not sensitive to fluctuations in the external supply voltage. Testing the semiconductor memories into which the circuit configuration of the invention is integrated makes only slight demands of a testing device, for instance for performing the burn-in test.
In accordance with another feature of the invention, the reference voltage generator has at least two voltage sources.
In accordance with a further feature of the invention, the reference voltage generator has a switching transistor connected through a circuit node in series with a diode chain.
In accordance with an added feature of the invention, at least one of the voltage sources has a double current mirror circuit.
In accordance with an additional feature of the invention, there is provided a circuit device controllable as a function of a potential at the circuit node for causing one of the voltage sources to assume the reference voltage.
In accordance with yet another feature of the invention, the diode chain has ends, and the switching transistor has a channel side connected to the external supply voltage and to one of the ends of the diode chain.
In accordance with a concomitant feature of the invention, the internal supply voltage is proportional to a voltage value of the reference voltage.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit configuration for generating an internal supply voltage, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 5077518 (1991-12-01), Han
patent: 5272393 (1993-12-01), Horiguchi et al.
patent: 5446397 (1995-08-01), Yotsuyanagi
patent: 5530640 (1996-06-01), Hara et al.
patent: 5554953 (1996-09-01), Shibayama et al.
patent: 5566185 (1996-10-01), Hori et al.
patent: 42 26 048 A1 (1993-02-01), None
patent: 43 32 452 A1 (1994-05-01), None
patent: 0 063 483 A2 (1982-10-01), None
Mueller Gerhard
Weller Joerg
Callahan Timothy P.
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Nguyen Minh
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