Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1999-04-16
2001-02-20
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S538000
Reexamination Certificate
active
06191645
ABSTRACT:
BACKGROUND INFORMATION
The present invention relates to an electronic circuit. Electronic circuits with power devices, for example VDMOS (Vertical Double Diffuse Metal Oxide Semiconductor) transistors composed of multiple parallel-connected cells, are already known. Aside from parasitic effects caused by plating, these cells are controlled by the same electrical potential. This produces a power loss more or less homogeneously across the surface of the power device, producing a hot spot, i.e., a point having the maximum temperature, on the surface of the power device.
SUMMARY OF THE INVENTION
The circuit according to the present invention has the advantage over the related art that it spreads the region of maximum temperature across a wider area on the surface of power devices, for example, thus also reducing the temperature at the point of maximum temperature. A further advantage is the fact that homogenization of the temperature distribution increases device reliability and service life and reduces the necessary chip area due to the ability to use smaller power loss producers, i.e., smaller power devices; this, in turn, reduces the unit cost of the IC.
It is especially advantageous to provide a separate temperature sensor for each partial actuator or for each cell of the power device. This makes it possible to regulate the temperature, over time, to give a uniform operating temperature in places that can be freely selected by the placement of the temperature sensors, provided that the overall device power loss available for regulation is physically sufficient and the sensor can be clearly situated in a location that is directly next to the partition or cell to be regulated. It is possible to generate certain isothermal fronts for placing temperature-sensitive circuit groups directly next to the power device. In addition, the distribution of the overall power loss predetermined by the circuit to the individual partitions can be controlled so that corresponding operating temperatures are produced at predetermined points in the layout of the circuit containing the actuator or the power device. The spatial variation of the isotherms can be independent of time providing a greater selection of possible layouts. Previously, locating temperature-sensitive circuit groups in the vicinity of power devices required placing these circuit groups equidistant from the power loss producers and as far apart from them as possible. The isothermal fronts can be preferably provided parallel to the chip edges, additionally simplifying the layout.
Symmetrical circuit groups, e.g., current mirrors, are used to neutralize production tolerances in electronic circuits. If circuit groups of this type are positioned in the vicinity of large power loss producers, such as power transistors, it is important to make sure that the components of these circuit groups are operated at the same operating temperature, since the electrical characteristics of semiconductor devices are known to be greatly dependent on temperature (with 1 to 2 millivolts per Kelvin, the forward voltage of a diode is dependent on temperature). Especially in the case of symmetrical circuit groups, such as current mirrors, the provision of multiple temperature sensors in the electronic circuit according to the present invention is therefore advantageous. These symmetrical devices should, if possible, be placed on an isotherm, i.e., a line of equal temperature. In addition to the current flowing through the partial actuators of the actuator, the isotherms are dependent on the geometry (i.e., the layout, of the power loss producers integrated on the chip, for example the power transistor functioning as an actuator) as well as on the operating state of the circuit (i.e., the variation, over time, of the power loss produced.) The circuit containing the temperature sensors allows for transient correspondence between the sensor temperatures, i.e., correspondence between the sensor temperatures at any time during circuit operation.
REFERENCES:
patent: 4675594 (1987-06-01), Reinke
patent: 4683382 (1987-07-01), Sakurai et al.
patent: 5254883 (1993-10-01), Horowitz et al.
patent: 5493234 (1996-02-01), Oh
patent: 5506541 (1996-04-01), Herndon
patent: 5999041 (1999-12-01), Nagata et al.
Cunningham Terry D.
Kenyon & Kenyon
Robert & Bosch GmbH
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