Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Reexamination Certificate
2000-05-24
2004-01-06
Jackson, Stephen W. (Department: 2185)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
C361S058000
Reexamination Certificate
active
06674623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microcomputer equipped with a built-in temperature sensor, which is capable of avoiding the occurrence of faulty operation and runaway of the microcomputer mounted on a semiconductor chip, even if the temperature of the semiconductor chip rises under the fluctuation of various conditions of circumstance during the operation of the microcomputer.
2. Description of the Related Art
In general, the entire electrical characteristic of a microcomputer is greatly changed under the fluctuation of the values of conductance and resistances of transistors incorporated in the microcomputer. This fluctuation is caused by the change of various conditions of circumstance, such as the operation temperature and the like, during the operation of the microcomputer.
When the temperature of the microcomputer rises during operation, the electrical characteristic thereof is shifted to a small operation margin. When the electrical characteristic is reached to and over the boundary of the operation margin, the runaway of the microcomputer occurs.
In order to avoid the occurrence of the runaway of the microcomputer, it must be necessary to compensate the operation of the microcomputer under the fluctuation of various conditions of circumstance during operation. In order to achieve this requirement, a simulation is performed in the design of the microcomputer under a temperature range. This temperature range is predicted under the various conditions of circumstance during operation.
However, it is difficult to get the optimum temperature range in the conditions of circumstance as actual operation under the state in which the microcomputer is incorporated in actual commercial products. Further, there is a drawback where different regions in the same semiconductor chip on which the microcomputer is mounted have difference temperatures.
Because the conventional microcomputer has the above configuration and the drawbacks, the simulation is executed under a wider and waste temperature range. However, in use of the microcomputer, there happens a case where the temperature of the microcomputer during operation becomes over the temperature range that has been predicted in the design. As a result, the runaway of the microcomputer occurs, so that the faulty operation of the microcomputer also happens.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is, with due consideration to the drawbacks of the conventional technique, to provide a microcomputer equipped with a built-in temperature sensor, which is mounted on a semiconductor chip, capable of avoiding the occurrence of faulty operation and runaway, even if the temperature of the semiconductor chip rises over a prescribed value by fluctuation of various conditions of circumstance during the operation of the microcomputer. The temperature sensor or both the temperature sensor and a voltage break circuit are incorporated in the microcomputer the voltage break circuit is operable under a predetermined temperature range. The temperature sensor is capable of detecting an inner temperature of the semiconductor chip in order to set the optimum operation conditions of the microcomputer.
In accordance with a preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has diodes incorporated in a pair of circuit blocks, the diodes being placed in opposite polarity connection to each other, a first terminal group connected commonly to the each diode, through which a constant current is supplied, and a second terminal group through which a voltage generated at each diode is read, and connected commonly to and placed at more adjacent nodes to the each diode when compared with the first terminal group. Thereby, optimum operation conditions of the microcomputer can be set according to the change of the temperature of the microcomputer.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a diode incorporated in each of a plurality of circuit blocks, a first terminal group connected commonly to the each of the plurality of diodes, through which a constant current is supplied, a second terminal group through which a voltage generated at each of the plurality of diodes is read, and connected commonly to and placed at more adjacent nodes to the each of the plurality of diodes when compared with the first terminal group, a selection switch for selecting one of the plurality of diodes, and a selection register in which a prescribed value to control operation of the selection switch is stored. Thereby, optimum operation conditions of the microcomputer can be set according to the change of the temperature of the microcomputer.
In the microcomputer equipped with a built-in temperature sensor described above, the plurality of circuit blocks are divided into plural pairs, each pair consists of two circuit blocks. The diodes incorporated in each pair are placed in opposite polarity connection to each other, and the selection switch selects one pair of the two circuit blocks in the plurality of circuit blocks according to the prescribed value stored in the selection register. Thereby, optimum operation conditions of the microcomputer can be set according to change of the temperature of the semiconductor chip.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a temperature sensor circuit having a diode and a first resistance connected in series between a first power source voltage and a second power voltage source, a MOS inverter circuit, and a terminal connected to a second node through which the second resistance and the first MOS transistor are connected. The MOS inverter circuit has a first MOS transistor whose gate is connected to a node through which the diode and the first resistance being connected, and a second resistance connected to the first MOS transistor in series. In the microcomputer, the second resistance is connected to the first power source voltage, and the first MOS transistor is connected to the second power source voltage, and the temperature sensor circuit and the MOS inverter circuit forms a voltage break circuit.
In the microcomputer equipped with a built-in temperature sensor described above, a plurality of the MOS inverter circuits are placed in parallel. Each MOS inverter circuit has the first MOS transistor and the second resistance. Threshold values of the first MOS transistors in the plurality of MOS inverter circuits are set stepwise. The gates of the first MOS transistors are commonly connected to the first node, and each of the second nodes of the plurality of MOS inverter circuits is connected to, instead of the terminal, a corresponding register in which a value corresponding to a voltage potential at each second node.
The microcomputer equipped with a built-in temperature sensor, as another preferred embodiment of the present invention, further has a selection switch for selecting one of the plurality of MOS inverter circuits in order to connect the selected MOS inverter to the temperature sensor circuit and the terminal through the first node and the second node, and a selection register for storing a prescribed value by which an operation of the selection switch is controlled.
In accordance with another preferred embodiment of the present invention, a microcomputer equipped with a built-in temperature sensor has a temperature monitor circuit for generating and outputting a control signal when a temperature of a semiconductor chip on which the microcomputer is mounted rises over a prescribed value, an interrupt circuit for inputting the control signal output from the interrupt circuit to initiate an interrupt operation, a CPU core for halting temporarily generation of a clock signal according to an instruction output from the interrupt circuit, and a timer circuit. The timer circuit initiates a counting operation according
Abe Toshihiro
Kitamura Masahiro
Mori Shintaro
Moriguchi Yasuo
Terayama Fumihiko
Burns Doane , Swecker, Mathis LLP
Jackson Stephen W.
Mitsubishi Denki & Kabushiki Kaisha
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