Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Reexamination Certificate
2001-07-02
2003-09-30
Callahan, Timothy P. (Department: 3816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
C327S162000, C327S237000, C375S364000
Reexamination Certificate
active
06628156
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an integrated circuit having a timing circuit which has a connection for emitting an output signal whose time can be adjusted, and which has a switching time which is delayed with respect to a reference time, and to a method for adjustment of the output signal from the timing circuit.
Integrated circuits in which a number of digital signals are received and processed at comparatively high switching speeds require, since the specification is often very tight with regard to time, signal switching times whose timings are matched very precisely, for example between different functional groups in the integrated circuit. This can be controlled, for example, by using timing circuits or delay circuits (which are referred to as timing delay circuits), which have an output signal as a control signal which has a switching time delayed with respect to a reference time. Such timing circuits are used, for example, for what is referred to as auto-refresh for dynamic random access memory (DRAM) circuits, or for the constant precharging of differential amplifiers. In this case, it is particularly desirable for the operation of the timing circuits and their output signals to be as independent as possible of process fluctuations during the production of the integrated circuit. A largely standard method of operation and functionality of a number of timing circuits in the integrated circuit or in different integrated circuits can thus be achieved.
In order to match a timing circuit in an integrated circuit to the given requirements as well as possible and in order to make it possible to compensate for process fluctuations that occur during production, a circuit part of a timing circuit, for example a power source, is, for example, adjustable within a specific range. During the adjustment of such circuit parts, influences of the operating voltage of the integrated circuit, process fluctuations and temperature fluctuations must, in particular, be taken into account. During the course of production of the integrated circuit, the respective circuit part of a timing circuit can be set, and hence matched, on its own. This is done, for example, by varying a reference value in a suitable manner so as to compensate, for example, for the influence of process fluctuations in a specific manner.
Such an indirect adjustment process for the switching time of the output signal from a timing circuit, which is also referred to as trimming, and is normally carried out by an external test set, is generally difficult and is subject to inaccuracies. Normally, this involves a relatively high level of instrumentation complexity. Furthermore, such an adjustment process can normally not be carried out via external connections for all the envisaged timing circuits in the integrated circuit.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an integrated circuit having a timing circuit, and a method for adjustment of an output signal from the timing circuit which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which the method of operation and the functionality of the timing circuit can be adjusted as independently as possible of process fluctuations and other production-dependent influences.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated circuit. The integrated circuit contains a timing circuit having a connection for emitting an output signal whose time can be adjusted and the output signal has a switching time which is delayed with respect to a reference time. A drive circuit is connected to the timing circuit for assessing and adjusting the output signal from the timing circuit with regard to the switching time. The drive circuit has a connection connected to the timing circuit for outputting a control signal for adjusting the output signal with regard to the switching time. The timing circuit has an adjustable power source connected to the connection for the control signal. The timing circuit has a capacitance connected to and able to be charged and discharged through the adjustable power source. The output signal from the timing circuit is adjustable on a basis of a potential applied to the capacitance. The connection for the output signal of the timing circuit is connected to the drive circuit for assessing the output signal with regard to the switching time and with respect to the reference time.
Thus, according to the invention, the output signal from the timing circuit can be adjusted by the drive circuit such that the switching time of the output signal has a desired time delay with respect to a reference time. This allows the switching time to be influenced directly. The method of operation and functionality of the timing circuit can thus be adjusted largely independently of process fluctuations and other production-dependent influences.
This furthermore makes relatively simple handling and measurement possible, since the measurement, assessment and adjustment of the switching time of the output signal from the timing circuit can be carried out by the drive circuit. In consequence, no external test equipment is required. Since, when carrying out such a measurement, the corresponding switching flanks need not be measured or analyzed directly by an external test system, this results in higher measurement accuracy. Since the measurement is carried out directly on the chip of the integrated circuit, the measurement accuracy is not constrained by a tolerance of the external test system or of the entire test configuration.
In principle, the method can be used with a number of types of timing circuits that have an output signal whose time can be adjusted. The timing circuit has an adjustable power source which is connected to the connection for the control signal for the drive circuit, and a capacitance which can be charged or discharged through the power source. The switching time of the output signal is thus adjusted by suitable adjustment of the power source. In this case, the power source is adjusted in such a manner that the output signal has the desired switching time.
Adjustment can be carried out on the basis of a potential that is applied to the capacitance. The potential on the capacitance is in this case variable and depends on the current from the power source. For example, the capacitance is discharged from a charged state through the power source, so that the potential on the capacitance falls. It is likewise possible for the capacitance to be charged from the power source, so that the potential that is applied to the capacitance rises. The switching time of the output signal from the timing circuit can be derived from the potential profile on the capacitance.
In one development of the invention, the timing circuit has a comparison circuit for comparison of a reference potential with the potential that is applied to the capacitance. One output of the comparison circuit is in this case connected to the connection for the output signal from the timing circuit. If, for example, the capacitance is discharged through the power source, then the potential that is applied to the capacitance falls from an initial charge potential. If the value falls below the value of the reference potential in this process, then a corresponding signal is produced at the output of the comparison circuit. The signal has, for example, a switching flank from a low potential level to a high potential level. The switching flank in this case occurs at a time in which the potential that is applied to the capacitance is below the reference potential. The signal produced by the comparison circuit may be used as the output signal from the timing circuit.
During normal operation, for example, the timing circuit is used as what is referred to as a timing delay circuit. The timing circuit can be used, for example, to control the timing of what is referred to as autorefresh for a DRAM memory. However, it is also
Kaiser Robert
Schaffroth Thilo
Callahan Timothy P.
Greenberg Laurence A.
Infineon - Technologies AG
Mayback Gregory L.
Nguyen Minh
LandOfFree
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