Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Reexamination Certificate
2001-06-14
2002-08-13
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
C327S530000
Reexamination Certificate
active
06433615
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor device and particularly concerns an integrated circuit (hereinafter, referred to as an IC) having a function of temperature compensation to be used in combination with a variety of sensors, and a sensor IC combining a sensor with the IC having the temperature compensation function.
BACKGROUND ART
Conventionally, a sensor IC, which combines a sensor and an IC for processing a signal, has been used in a variety of fields. As a sensor IC with the function of turning on/off in response to an output signal of a sensor, a sensor IC for detecting magnetic fields has been particularly known. For example, a magnetic sensor IC is used for detecting rotation of a cooling fan for a CPU of a personal computer and so on.
Incidentally, in case of an IC which operates amplification on an output signal (electric signal) from the sensor and turns on/off the output at predetermined sensitivity, the output from the sensor normally changes with temperature. Thus, a temperature-compensating circuit is necessary for turning on/off the output of the IC at predetermined sensitivity all the time regardless of temperature. As temperature compensation, a conventional method has been known which changes an amplification degree of an output signal or voltage and current applied to the sensor according to a temperature characteristic of the output signal from the sensor.
For example, according to the invention disclosed in Japanese Patent Laid-Open No. 57-197883, temperature compensation is performed by applying to a sensor voltage increasing monotonously with temperature and driving the sensor by the voltage. However, some sensors require an extremely high voltage for driving, thereby increasing power consumption or heat generation. Consequently, the operation becomes unstable with temperature.
Further, the invention disclosed in Japanese Patent Publication No. 3-51118 has been known. The invention is provided with a Hall element (sensor) for generating Hall voltage, a reference voltage generating means for generating reference voltage relative to current passing through the Hall element, a comparing means for generating an output signal depending upon a relative magnitude of the Hall voltage and the reference voltage, and so on. Temperature compensation can be performed on a variety of sensors having sensitivity as a function of applied current.
As described above, the invention described in Japanese Patent Publication No. 3-51118 is applicable to a sensor where sensitivity is a function of applied current. However, the invention is not applicable to a sensor where sensitivity has no correlation to applied current. Moreover, the temperature-compensating circuit is not for general purpose use and cannot be combined with other sensors, resulting in narrow applicability.
Additionally, even in the case where a sensor is formed in the same manner, the same current is not always applied at the same sensitivity. Conversely, the same sensitivity is not always obtained at the same current. Therefore, in case of a large irregularity in characteristic of the sensor, monitoring current may be an adverse effect.
Incidentally, in the temperature-compensating circuit formed on widely used bulk silicon, leakage current rapidly increases on a PN-junction at a high temperature of 125° C. or above, causing a problem in temperature compensation. Temperature compensation is not possible particularly at a high temperature of 150° C. or above.
Meanwhile, as a technique for a high-temperature IC, a method has been known, which forms circuits on a semiconductor layer on an insulating base such as an SOI (silicon on insulator) substrate. It has been known that this method makes it possible to reduce an area of a PN-junction, reduce leakage current in a high temperature range, prevent a latch-up phenomenon, and permits an operation at a higher temperature. Hence, if the temperature-compensating circuit according to the conventional method is formed on the semiconductor layer on the SOI substrate, it is expected to somewhat improve the operation at a high temperature.
However, in the case where the temperature-compensating circuit of the conventional method is formed on the semiconductor layer on the SOI substrate, it is difficult to achieve accurate temperature compensation with reliability at a high temperature, and durability is deteriorated at a high temperature due to heat generated by power consumption.
In order to solve the above problem, it is necessary to accurately amplify a fine signal from the sensor and to perform accurate temperature compensation with a low driving voltage and small power consumption at a high temperature. However, it is not easy to realize a sensor IC meeting these conditions.
Hence, a sensor IC combining a sensor and an IC with temperature compensation, that accurately operates in a stable manner at a high temperature of 200° C. or above, has not been achieved yet. Also, the IC for temperature compensation for the sensor IC has not been achieved. Such a sensor IC has been demanded.
Further, as a detector for rotation of a gear wheel, a silicon-monolithic sensor IC using a CMOS circuit has been known. However, the highest temperature of the sensor IC is limited to 150° C. in practical use. It has been desirable to set the highest temperature at 200° C. or above.
The present invention is therefore devised against the above backdrop. The first object thereof is to provide a semiconductor device as an IC with temperature compensation (hereinafter, referred to as an IC for a sensor IC) that combination can be made with various sensors and can perform accurate temperature compensation on an output signal from the sensor with reliability at a high temperature.
The second object of the present invention is to provide a semiconductor device as a sensor IC (hereinafter, referred to as a sensor IC) that can accurately operate with reliability in a stable manner at a high temperature.
DISCLOSURE OF THE INVENTION
The present invention provides a semiconductor device (IC for a sensor IC) including amplifying means for inputting a sensor output signal from the sensor, amplifying the sensor output signal at a required temperature-independent amplification factor, and canceling an offset, reference signal producing means for producing a reference signal varying at a temperature coefficient equal to that of the sensor output signal from the sensor, comparing means which compares the magnitude of an amplification output signal from the amplifying means with that of the reference signal from the reference signal producing means and outputs a required signal according to a comparison result, and constant voltage generating means for generating temperature-independent constant voltage to be supplied to the sensor, characterized in that the amplifying means, the reference signal producing means, the comparing means, and the constant voltage generating means are formed using a semiconductor layer provided on an insulating substrate.
Here, the above “equal temperature coefficient” includes not only an equal temperature coefficient but also a substantially equal temperature coefficient. A permissible error value depends upon the accuracy of the semiconductor device (sensor IC).
As an embodiment of the IC for the sensor IC of the present invention, an IC for a sensor IC is applicable, in which the semiconductor layer is composed of a silicon thin film.
Further, as an embodiment of the IC for the sensor IC of the present invention, an IC for a sensor IC is applicable, in which the silicon thin film is 30 nm to 1000 nm in thickness.
As described above, according to the IC for the sensor IC, the amplifying means receives a sensor output signal, amplifies the sensor output signal at a required temperature-independent amplification factor, and operates to cancel an offset, thereby accurately amplifying the sensor output signal.
Furthermore, the reference signal producing means produces a reference signal varying at a temperature coefficient equal to that of the senso
Fiedler Horst-Lothar
Nagano Shuichi
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Cunningham Terry D.
LandOfFree
Semiconductor device having a sensor with the temperature... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device having a sensor with the temperature..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device having a sensor with the temperature... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2929784