Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
1998-09-28
2002-08-20
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C340S693400, C361S018000, C361S100000, C713S340000
Reexamination Certificate
active
06438462
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a semiconductor circuit for an electronic unit.
Control technologies which rely on a two-wire bus as a communications medium are becoming increasingly important both in the industrial sector and in mobile applications, such as vehicles. Bus networks according to the CAN standard (CAN=Controller Area Network) are an example of this. In this case, a multiplicity of electronic units communicate with one another via only two conductor cores.
Without exception, such units perform their control task by means of a microcontroller. Particular bus protocol chips or protocol functionalities are provided for communication via the bus, and may be monolithically co-integrated in microcontrollers which are specialized for such applications, and function as a communicative transmitting/receiving link between bus and controller. They reduce the burden of tasks defined by the communications protocol on the microcontroller of the relevant unit and, in this way, considerably increase its availability and throughput for the actual control application.
Both the microcontroller and the bus protocol function require an operating voltage which must be kept within narrow limits, and as a rule is derived from a superordinate potential by means of a voltage regulator included in the control unit. If corresponding control units are used, for example, in means of transport, such voltage regulators must be particularly operationally reliable within wide temperature ranges and, above all, resistant to overvoltages and to interfering radio-frequency irradiation. Not all realization technologies for semiconductor circuits are equally suited to resistance to be optimized accordingly in practical operation. Particular so-called high-voltage technologies have been developed which take account precisely of the extreme loading situations in the case of voltage regulators, and which concern overload protection of the semiconductor chip against static and dynamic current, voltage and thermal stress. Correspondingly produced products have a high MTBF and an accordingly low failure rate.
It is also known to assign so-called watchdog circuits to microcontrollers or, for reasons of reducing costs and saving structural space, to co-integrate corresponding circuit functions as a subfunction of a microcontroller, using the production technology of the respective microcontroller. As a rule, these circuits are provided with means for generating and broadcasting a temporally defined reset signal to the microcontroller after the build-up of its operating voltage. However, problems arise when current-supplied areas are present on the chip of the microcontroller at different voltage levels and one of these areas may be subjected to high interference signal loading from the supply end. Corresponding solutions therefore demand very effective external protective measures for a corresponding semiconductor chip.
Moreover, discrete auxiliary modules for microprocessors are known which have means for monitoring at least one operating voltage, in order to generate a reset for the microcontroller for the purpose of a reliable program stop when the operating voltage leaves a predetermined tolerance window. They are predominantly produced using low-voltage technology in the range of 0.8 to 1.5 &mgr;v.
German patent document DE 196 11 945.6, which was filed at the same time as the priority application DE 196 11 942.1, discloses a device for the bus-networked operation of an electronic unit with a microcontroller that takes account, inter alia, of the requirement of minimizing the total current consumption of a CAN during times of relative operational inactivity thereof.
The device comprises a specific semiconductor circuit having the bus function, of a communications transceiver and also a voltage regulator which can be electrically switched on and off. Both parts interact with one another such that the semiconductor circuit, in a specific operating state, outputs to the voltage regulator a signal which causes it to switch off, thereby also switching off the supply current generated at the output side to the electronics. In this state, only the semiconductor circuit and the regulator then draw very small quiescent currents from a superordinate supply potential; the microcontroller is deenergized. The semiconductor circuit which performs the transceiver function also includes additional functions therein for detecting bus faults and wake-up requests for reinitialization the microcontroller, as well as analog and digital functional components mixed.
Within the scope of that invention, it is proposed, inter alia, to integrate these functional components, together with the microcontroller and the bus protocol function monolithically on a single chip, thereby providing an electronic control unit that would essentially comprise, for example, three semiconductor modules. The latter include the (1) voltage regulator, the (2) single-body composite of microcontroller and bus protocol function, extended by the functional scope of the semiconductor circuit—to be understood conceptually as “Bus Application (BA) Controller”—, and also (3) an input/output interface which is connected downstream of the microcontroller in the direction of the application and serves to receive application-specific sensor signals and to drive requisite actuators, etc. The implementation and integration of such a semiconductor circuit is possible, but proves to be cost-intensive in relation to the range of applications that can be covered by such a special module.
An alternative to this would consist in integrating elements (1) to (3) to form a single “hyperchip”. However, such a fully integrated “hyperchip” based on a microcontroller is no less restricted in its applicability.
Thus, different hyperchip variants are necessary for different unit requirements. However, type spreading means that economies of scale for the desired cost reduction factor are limited. Furthermore, such a hyperchip is a customized module with consequent ties to a particular manufacturer. This may be a disadvantage, under certain circumstances, if there are second and trisource imperatives. Moreover, corresponding customized solutions render any standardization difficult, thereby diminishing the cost advantage. EMC problems are to be expected both in the case of the hyperchip and of the BA controller since interference from the bus can easily reach as far as the micro-controller. Necessary EMC protection measures may vary considerably from hyperchip to hyperchip or BA controller to BA controller, for different applications. Thus, apart from their costs, they must be implemented differently in different applications, so that the design rules repeatedly have to be observed anew. This inevitably opens up possibilities of faults as well. Furthermore, not every microcontroller technology that is of interest now or in the future is equally suited to incorporate circuit components which, in practice, either have to withstand residual interference voltage loading (which may be of the order of magnitude of the operating voltage of the microcontroller), or stress the chip material with spot power densities which, in the event of an fault, may reach a point near to thermal breakdown. These ambient conditions which result in such stresses are a familiar occurrence e.g. in industrial control technology and in means of transport.
The abovementioned problems increase exponentially as the system shrink dimension grows with advancing &mgr;C technology. The spot power losses of, for example, drivers that may prevail on-chip are also becoming increasingly smaller. It may be assumed that the system shrink dimension of monolithic LS technologies will soon have reached 0.25 &mgr;m. However, interface functions using 0.25 &mgr;m technology are too sensitive to be connected directly with an industrial or vehicle environment, which is exposed to the risk, for example, of jump start, load dump and static overvoltage and to be operated with sufficient avail
Hanf Peter
Minuth Juergen
Reeb Max
Setzer Juergen
Crowell & Moring LLP
Daimler-Chrysler AG
Frank Elliot
Picard Leo
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