Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Integrated structure
Reexamination Certificate
1999-09-28
2001-02-13
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Integrated structure
C326S038000
Reexamination Certificate
active
06188273
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to an integrated circuit having a contact-making point for selecting an operating mode of the integrated circuit.
An integrated circuit of this type is described in Published, European Patent Application EP 0 570 158 A2, for example. The contact-making point can optionally be connected to one of two different supply potentials of the integrated circuit. The integrated circuit has a control device that is connected to the contact-making point, identifies the supply potentials to which the contact-making point is connected, and generates a corresponding operating mode signal.
Furthermore, it is known to provide, for test purposes, contact-making points on integrated circuits which are connected to test circuits via which signals supplied from the test circuits can be monitored in the context of a test. The fact of whether specific voltages generated on the integrated circuit are actually present in the desired manner is often of interest here.
Since each contact-making point occupies a specific area on the integrated circuit and, in general, the area of an integrated circuit is intended to be kept as small as possible for reasons of cost, it is desirable to keep the number of contact-making points of the integrated circuit as small as possible.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an integrated circuit having a contact-making point for selecting an operating mode of the integrated circuit which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which makes it possible, by use of just one contact-making point, to set an operating mode of the integrated circuit and also to monitor a voltage generated on the circuit.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated circuit, including:
a switching element having a control input;
a contact-making point for making external contact;
a voltage generator which has an output connected via the switching element to the contact-making point and the voltage generator generates a potential exceeding a first limit value in a first direction;
a first digital control device which has an input connected to the contact-making point and an output for outputting a digital control signal received by the control input of the switching element;
a second digital control device which has an input connected to the contact-making point and an output for outputting a digital operating mode signal;
the first digital control device only switching on the switching element via the digital control signal and the second digital control device outputting the digital operating mode signal with a first potential level, if a given potential of the contact-making point exceeds the first limit value in the first direction; and
the first digital control device turning off the switching element via the digital control signal and the second control device outputting the digital operating mode signal with a second potential level, if the potential of the contact-making point exceeds a second limit value in a second direction.
The integrated circuit according to the invention has a first voltage generator having an output which is connected via a first switching element to a contact-making point for externally making contact with the circuit. At its output, the first voltage generator generates a first potential which exceeds a first limit value in a first direction. Furthermore, it has a first digital control device which has an input that is connected to the contact-making point, and has a first output for outputting a first digital control signal which is connected to a control input of the first switching element. A second digital control device has an input that is connected to the contact-making point, and an output for outputting a digital operating mode signal. The first control device only switches on the first switching element via the first digital control signal, and the second control device outputs the operating mode signal with a first potential level, when the potential of the contact-making point exceeds the first limit value in the first direction. The first control device turns off the first switching element via the first digital control signal, and the second control device outputs the operating mode signal with a second potential level, when the potential of the contact-making point exceeds a second limit value in a second direction. The first and second limit values are therefore chosen in such a way that they each exceed logical switching thresholds of the two control devices. In other words, one of the limit values is smaller than the smallest lower switching threshold of the two control devices and the other limit value is larger than the largest upper switching threshold of the two control devices. When the first limit value is exceeded in the first direction, the first switching element is turned on and the operating mode signal signals, with the first potential level, the presence of a first operating mode of the integrated circuit. When the second limit value is exceeded in the second direction, the first switching element turns off and the operating mode signal has a second potential level, which causes the integrated circuit to change over to a second operating mode.
The first control device ensures that the first switching element remains in the on state, as soon as it has been turned on, by feeding the first potential generated by the first voltage generator. The first potential then being present at the contact-making point, is fed back to the control input of the first switching element. As long as the first potential generated by the first voltage generator and present at the contact-making point via the first switching element does not exceed or fall below the first limit value, the first switching element remains switched on.
If, on the other hand, the intention is not for the first potential generated by the first voltage generator to be monitored by the contact-making point but rather for the operating mode of the integrated circuit to be altered, the contact-making point can have a fixed potential applied to it externally, the fixed potential exceeding the second limit value in the second direction. As a consequence of this, the digital output signals of the two control devices change their levels. The first switching element is turned off as a result of this, so that the first voltage generator is disconnected from the contact-making point and no current can then flow between the two. At the same time, the integrated circuit changes over its operating mode, since the operating mode signal at the output of the second control device also changes its level.
The contact-making point can, of course, also be connected to an external terminal of the integrated circuit—for example via a bonding wire. The operating mode of the circuit can then be set or the first potential monitored via the terminal.
The integrated circuit according to the invention affords the advantage that its contact-making point can be utilized both for monitoring the voltage generated by the first voltage generator and for setting the operating mode signal generated by the second control device. In order to monitor the voltage generated by the first voltage generator, the contact-making point can be connected to a corresponding measuring circuit.
According to a development, the integrated circuit has a resistance element, via which the contact-making point is connected to a terminal for a supply potential of the integrated circuit which exceeds the first limit value in the first direction or the second limit value in the second direction.
This has the advantage that the integrated circuit is put into a defined state during start-up, since the supply potential is also present at the contact-making point via the resistance element. By choosing a suitable supply potential, it is possible for example to achieve the situation where, during start-up of the i
Bartenschlager Rainer
Manyoki Zoltan
Sichert Christian
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Wells Kenneth B.
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