Miscellaneous active electrical nonlinear devices – circuits – and – External effect – Temperature
Reexamination Certificate
1999-09-01
2001-08-28
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
External effect
Temperature
C327S077000, C327S143000, C327S170000, C326S032000
Reexamination Certificate
active
06281738
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bus driver and a driver each of which has a temperature detecting system. The present invention also relates to an output adjusting method for controlling operations of a circuit in accordance with a temperature of the circuit.
2. Description of the Related Art
A plurality of units (Central Processing Unit, Memory Unit or the like) included in a single system are connected with each other via a bus comprising a plurality of transmission paths. Signals (data and the like) are transmitted between the plurality of units via the bus.
Each of the units connected to the bus includes an output buffer for driving the bus (i.e. for outputting signals to the bus) and an input buffer for receiving signals transmitted on the bus.
Since the signal is transmitted via the output buffer, a voltage level of an output signal becomes stable, and the output signal can be stabilizingly output to the bus.
To maximize driving performance of the bus, as shown in
FIG. 6
, an output buffer may be used, wherein an “n” (“n” is an integer equal to or greater than “2”) number of buffer circuits
501
are connected in parallel. This type of output buffer can accurately drive the bus at high speed compared to the case where a single buffer circuit is used, because the driving performance (performance for current-supply) of the bus can be enhanced by “n” times.
However, as a temperature of the output buffer including the plurality of parallelly-connected buffer circuits
501
rises, signals are output from the buffer circuits
501
respectively at different phases. Therefore, a ringing event occurs in a signal which is generated as a combination of the signals from the buffer circuits
501
.
If the ringing event occurs in the signal generated as the combination of the output signals from the output buffer, a problem may arise that the unit receiving the generated signal is operated inappropriately.
A similar problem commonly appears not only in the output buffer circuit, but in an electric circuit comprising a plurality of parallelly-operating circuits.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a bus driver and a driver both of which can stabilizingly outputs a signal without being influenced by a temperature of the drivers.
Another object of the present invention is to provide an output adjusting method for controlling ringing, which occurs in a signal, without being influenced by a temperature of a circuit.
According to the first aspect of the present invention, there is provided a bus driver comprising:
a plurality of output buffer circuits which are connected to a common input terminal and a common output terminal and each of which outputs a signal, for driving a bus, having a signal level corresponding to a signal level of a signal supplied to the input terminal, to the output terminal;
a temperature detecting circuit which detects a temperature of at least one of the output buffer circuits; and
a controlling circuit which determines whether the detected temperature of at least one of the plurality of output buffer circuits is equal to or above a first reference temperature, and which inactivates at least one of the plurality of output buffer circuits when determined that the detected temperature is equal to or above the first reference temperature.
According to the present invention, when the temperature of the output buffer circuits is equal to or above the first reference temperature, at least one of the output buffer circuits is inactivated. Thus, the bus drivers can be controlled to be appropriately operated, by setting the first reference temperature at a temperature at which the circuits are not operated appropriately.
The plurality of output buffer circuits may include three or more circuits.
The controlling circuit may compare the temperature detected by the temperature detecting circuit with the first reference temperature and also with a second reference temperature which is above the first reference temperature, inactivates a first predetermined number of output buffer circuits when the temperature detected by the temperature detecting circuit is equal to or above the first reference temperature but below the second reference temperature, and inactivates a second predetermined number of output buffer circuits in addition to the first predetermined number of output buffer circuits when the detected temperature is equal to or above the second reference temperature.
The temperature detecting circuit may include a diode and a resistor which are connected in series between a power source and a ground.
The controlling circuit may compare a voltage of a connecting point, where the diode circuit and the resistor are connected, with a first reference voltage substantially equal to a voltage of the connecting point when said plurality of output buffer circuits are at the first reference temperature, and also with a second reference voltage substantially equal to the voltage of the connecting point when the plurality of output buffer circuits are at the second reference temperature, and output a signal for activating or inactivating the plurality of output buffer circuits in accordance with a compared result to the plurality of output buffer circuits.
At least one of the plurality of output buffer circuits which is inactivated by the controlling circuit comprises a three state buffer circuit.
The controlling circuit prevents ringing from occurring in a signal output from the plurality of output buffer circuits, by inactivating at least one of the plurality of output buffer circuits.
According to the second aspect of the present invention, there is provided an output adjusting method comprising:
detecting a temperature of at least one of plurality of output buffer circuit connected to a common input terminal and an output terminal;
comparing the detected temperature of said plurality of output buffer circuits and a first reference temperature;
inactivating at least one of the plurality of output buffer circuits when determined the temperature of the at least one of the plurality of output buffer circuits is equal to or above the first reference temperature;
controlling the entire output buffer circuits to output signals substantially at an identical phase parallelly to the output terminal when the detected temperature is below the first reference temperature; and
controlling at least one of the plurality of activated output buffer circuits to output a signal in which any ringing event does not substantially occur, to the output terminal, when the detected temperature is equal to or above the first reference temperature.
According to this invention, the number of buffer circuits outputting a signal can be controlled, because the buffer circuits are activated and inactivated in accordance with their temperature. Hence, a signal substantially having no ringing can be output from the output terminal.
The signals from the buffer circuits are controlled to be appropriately output, by setting the reference temperature at a temperature at which the ringing occurs in the signals output from the buffer circuits.
The output buffer circuits may include three or more circuits.
The inactivating may include
inactivating a first number of output buffer circuits when determined that the detected temperature is equal to or above the first reference temperature, and
inactivating a second number of output buffer circuits when determined that the detected temperature is equal to or above a second reference temperature above the first reference temperature.
The second number may be larger than the first number.
According to the third aspect of the present invention, there is provided a driver comprising:
an “n” number of driver circuits which are connected to a common input terminal and a common output terminal, respectively output signals at an identical phase, and drive a target device to be driven in cooperation with each other;
a temperature detecting circuit which detects a temperature o
Cunningham Terry D.
Foley & Lardner
NEC Corporation
Nguyen Long
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