Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
2001-05-02
2002-11-05
Zweizig, Jeffrey (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
Reexamination Certificate
active
06476658
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a circuit configuration such as, for example, a memory device, in particular DRAM element, or the like. The circuit has at least one input region which is configured to receive a supplied electrical input signal and which, for this purpose, has at least one input line device. A protection device is provided in the input region and is configured at least for partial suppression of the formation and/or emission of a reflection signal caused by a received supplied input signal—in particular on the input line device.
In many electrical systems and circuit configurations, specific signals are transmitted from parts of the system, for example, what are referred to as drivers, and are provided and transmitted to other parts of the system referred to as receivers. A problem in electrical systems, circuit configurations, for example memory devices and in particular DRAM elements, is in this case that, in many cases—in particular if the input impedance is designed to be high and mainly capacitive—the characteristic impedance of the input region of such an electrical system or of a circuit configuration is at least partially and often even totally reflective for a signal edge or a voltage edge arriving in the input region of this system or circuit configuration. The reflected signal or reflection signal then passes out of the input region of the receiving circuit configuration, and back toward the transmitting unit. There, and/or furthermore, the reflection signal can lead to a malfunction and thus, overall, to an entire malfunction of the electrical system.
In prior art circuit configurations, particularly in the case of memory devices, in particular DRAM elements, as well, a wide range of measures have therefore been proposed in order to suppress the formation and/or the emission of reflection signals caused by input signals.
For example, protection devices have been proposed which are matched to the specific input/characteristic impedance of the input region of the circuit configuration and, with respect to the specific characteristic impedance of the input region, lead to at least partial suppression of a reflection signal.
Prior art protection devices of such a type in circuit configurations provide, for example, series resistors for attenuating the returning reflection signal. These attenuate firstly the forward wave and secondly, after reflection, also the reverse wave, and thus the amount of power transported back.
Another conventional measure for protection against reflection signals is the provision of a concentrated resistance connected in parallel in the input region of the circuit configuration, with the value of the resistance being chosen such that it matches the characteristic impedance, and which allows a high level of suppression of the formation and emission of a reflection signal to be achieved.
A disadvantage of these prior art circuit configurations and of the protection devices provided in them is that, for partial suppression of the formation and/or emission of reflection signals, this respective protection device is always matched to the specific value of the characteristic impedance in the input region of the circuit configuration. In this case, a particular disadvantage is that, if this characteristic impedance changes, the corresponding protection device can no longer be adjusted to the changed conditions, and protection can no longer be adequately ensured. Such changes to the characteristic impedance in the input region of known circuit configurations occur, for example, in conjunction with variations in the course of the production process for the circuit configuration, or else from interaction with electrical systems downstream from the circuit configuration.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a circuit configuration such as, for example, a memory device and in particular a DRAM element or the like, which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind, and in which the formation and/or emission of a reflection signal caused by received supplied input signals can be suppressed in a particularly simple but nonetheless reliable and flexible manner.
With the above and other objects in view there is provided, in accordance with the invention, a circuit configuration, for example a memory device such as, for example, a DRAM element, comprising:
an input line device;
an input region connected to the input line device for receiving via the input line device an electrical input signal;
a protection device in the input region for at least partially suppressing one of a formation and an emission of a reflection signal caused by the electrical input signal; and
the protection device having an active compensation device configured to generate and superimpose a compensation signal on a reflection signal being formed.
In the circuit configuration of this generic type, for example a memory device and in particular a DRAM element or the like, there is at least one input region which is designed at least to receive a supplied electrical input signal and which, for this purpose, has at least one input line device. Furthermore, a protection device is provided, which is formed at the input region and is designed at least for partial suppression of the formation and/or emission of a reflection signal caused by a received supplied input signal, in particular on the input line device.
In accordance with the invention, the protection device of the circuit configuration has an active compensation device, by means of which a compensation signal can be generated and/or can be superimposed on a reflection signal which is formed and/or emitted.
One basic idea of the present invention is that, instead of using passive reflection suppression, to at least partially compensate for any reflection signal that is produced, and/or for the emission of any reflection signal which has already been produced, by suitable superimposition, that is to say in particular by destructive interference, using a compensation signal. While passive protection measures which cannot be altered once selected, for example, fixed series resistors or constant concentrated parallel resistances, do not allow adaptation to changes in the boundary conditions since the selection of the components cannot be altered, the use, according to the invention, of an actively generated compensation signal offers the greatest possible flexibility for suppression of reflections, even when variations in the production conditions and/or other interacting circuit configurations downstream from the input region vary the apparent characteristic impedance, and hence the reflection behavior in the input region.
The basic idea of the present invention can also be achieved by carrying out active signal matching instead of passive reflection suppression, with the formation of a reflection signal resulting from use of the input signal being prevented or suppressed. This is achieved according to the invention by providing an active signal matching device, which actually provides for the use of the input signal and thus for the suppression or prevention of the formation of a reflection signal.
In the following text, the expression active compensation device, by means of which a compensation signal can be generated and can be superimposed on any reflection signal which is formed, should also always be understood as meaning an active signal matching device which prevents the formation of a reflection signal resulting from use of the input signal.
In this case, it is particularly advantageous for the compensation device to be designed such that it can be controlled, in particular, within a feedback control loop. This measure makes it possible, for example, for the actual formation and/or emission of a reflection signal to be monitored permanently or at given times via an appropriate sensor system in order for them to carry out appropriate matching of the compensation
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Stemer Werner H.
Zweizig Jeffrey
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