Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Reexamination Certificate
1999-12-01
2002-08-20
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
C361S018000, C361S058000
Reexamination Certificate
active
06437959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to integrated electrical and/or electronic circuits.
2. Description of Related Art
Systems for protecting functional systems against overvoltages are known. Here, one may cite U.S. Pat. No. 3,737,725 which describes a circuit overvoltage protector having a fuse and a zener diode arranged in the electrical supply circuit of the functional module.
Also, designers of integrated electrical and/or electronic circuits often provide electrical terminals to one or more functional modules of an electrical and/or electronic system, in addition to electrical power supplies. Such external electrical terminals prove necessary, for example, for programming or configuring the functional module, to input a specific code into the system (and/or to a user), or to test, measure, and/or calibrate the functional module.
When the testing, calibration, or programming phase is complete, it may be desirable effectively to isolate the functional module from elements outside of the functional module or the electrical system. In other words, it is necessary to eliminate the external electrical terminal to prevent changes in the programming, configuration, or coding and/or to ensure better protection for the functional module, particularly against powerful electromagnetic fields and/or ultraviolet radiation which may be encountered in an industrial setting for example. Such isolation is also required in very harsh environments such as those that may be encountered in the space and nuclear arenas.
Various techniques have already been proposed to achieve this result. Thus, numerous devices that program by isolation are known. They generally call on physical circuit-breaking techniques, for example, using mechanical methods for applying laser beams, electrical segmentation using semiconductor switches, or by inhibiting logical accesses from the nonvolatile memory programming. The first method has the advantage of physically breaking off access to the terminal. However, it has the disadvantage of being implemented only when the electrical and/or electronic system is being manufactured, and before the system housing and/or protective device is sealed with resins or varnishes. Hence, this technique cannot be used by the end user, who is thus, unable to carry out the programming, configuration, or testing operations listed above.
The second set of techniques, based on the programming of memories or semiconductor switches, also has several drawbacks. To begin with, these techniques call on sophisticated, fragile, relatively expensive, and sometimes bulky components. They also do not enable their own programming to be protected by radically eliminating access paths.
Moreover, the technology based on floating-grid cells that is generally used has the drawback of substantial sensitivity to harsh environments, powerful electromagnetic fields, and ultraviolet radiation.
SUMMARY OF THE INVENTION
The main aspect of the invention is to overcome these drawbacks of the prior art. More specifically, one of the aspects of the invention is to provide a technique that effectively eliminates the external electrical terminal connected to a functional module that needs to be isolated (for example, after a testing, measurement, calibration, programming, configuration, or coding, etc. phase).
An additional aspect of the invention is to provide such a technique permitting utilization in harsh environments and/or in the presence of electromagnetic field(s) and/or high environmental radiation.
Another aspect of the invention is to provide such a technique whose cost, development, and/or implementation are reduced by comparison to known techniques.
Another aspect of the invention is to provide a device for electrical isolation of a functional module enabling the functional module to be programmed (particularly the decision as to the moment in time of isolation) by the end user.
These various aspects, as well as others that will emerge in the following text, are achieved according to the invention with the aid of an integrated electrical and/or electronic system that has at least one functional module connected to a supply voltage and connected via a pin external to the functional module by an electrical terminal. An isolation device electrically isolates the electrical terminal from the functional module, The isolation device may include a fuse whose first pole is connected to the pin of the functional module and the second pole corresponds to the external electrical terminal, a first semiconductor dipole that can be energized by a priming voltage, a first pole of which is connected to the first pole of the fuse and the second pole is externally accessible to the system, and a second dipole whose first pole is connected to the pin of the functional module and the second pole is connected to a preset voltage.
Therefore, application of a sufficient isolating voltage relative to the priming voltage between the second pole of the fuse and the second pole of the energizable semiconductor dipole causes the fuse to break physically, and thereafter, a preset voltage on the pin is exclusively maintained via the second dipole. Thus, after the fuse has broken, this voltage enables the operation of the functional module to be controlled.
The general principle of the invention is thus based on the combination of three single components (a fuse, an energizable semiconductor dipole, and a second dipole). By internally or externally controlling the breakage of the fuse, such a combination enables the functional module to be electrically isolated permanently at the desired point in time.
It is thus possible to program the moment in time at which the fuse breaks either by external, for example, human, intervention by manually operating an adequate isolating voltage or by internal control, for example, with the development of one or more particular conditions linked to the environment causing an isolating voltage to be generated.
It is important to note that exceeding a threshold voltage (imposed by the presence of the energizable semiconductor dipole) is necessary for programming the prohibition of electrical terminal to the functional module. As long as the fuse has not been broken, neither the fuse nor the dipoles disrupts operation of the system, and access to the functional module is direct.
Since the isolating voltage can be applied to the electrical terminal from the outside the system or the functional module, this system has the advantage of being accessible by the end user before this electrical terminal is eliminated, and prohibits all electrical terminals to the functional module. Electrical terminal to the functional module can be so prohibited, for example, following programming or testing of the functional module.
It will be noted that the technique of the invention can easily be duplicated within a single system (access to several modules and/or several accesses to one module). It can also easily be adapted to isolation between two functional modules.
The second dipole enables the preset voltage to be maintained for the terminal to the functional module after the fuse is broken. Thus, when the fuse has broken, the input to the functional module is permanently configured at a given value (which can in particular indicate to the module that it is henceforth isolated).
According to a first embodiment of the invention, the preset voltage is created internal to the system and/or corresponds to a predetermined logic level. For example, when the logic level is “1,” a pin is connected to a polarizing voltage of the functional module by way of an element having a resistance with a sufficiently high equivalent impedance value to not disrupt operation of the electrical terminal before the fuse breaks.
According to a second embodiment of the invention, when the logic level is “0,” the pin is connected to a polarizing voltage of the functional module by way of an element having a resistance with a sufficiently high equivalent impedance value so as to not disrupt operation of the
Andrieu Claude
Besset Jean-Claude
Hourdequin Marc
Delegation Generale pour l'Armement
Jackson Stephen W.
Oliff & Berridg,e PLC
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