JP3040464U - Abnormal voltage detector for microcomputer - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To reliably detect an instantaneous abnormal voltage (abnormality of power supply voltage) generated in a microcomputer. SOLUTION: A detection circuit 1 for detecting the occurrence of an abnormal voltage, and a latch circuit 2 for latching a signal output from the detection circuit 1 and outputting a signal (PFF signal) for informing the occurrence of the abnormal voltage. The detection circuit 1 includes a NOT gate 10, and the current connection terminal P1 of the NOT gate 10 is included.
Is connected to the reset voltage terminal Vres in the microcomputer, the input terminal P2 of the NOT gate 10 is connected to the power supply terminal VDD of the microcomputer, and the output terminal PFDO of the NOT gate 10 is connected to the latch circuit. 2 is connected to the input terminal P3 of the latch circuit 2, and when the detection circuit 1 detects a momentary voltage fluctuation outside the predetermined voltage range within the microcomputer, a signal (indicated by the output terminal PFDO of the latch circuit 2 that an abnormal voltage is generated) PFF signal) is output to suspend or reset the operation of the microcomputer.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to an abnormal voltage detection device for a microcomputer capable of reliably detecting an instantaneous abnormal voltage (abnormal power supply voltage) generated in a microcomputer.

[0002]

[Prior art]

 Normal microcomputers operate normally within a certain power supply voltage range, and normal operation cannot be guaranteed at voltages outside this range. In other words, it causes inaccuracies such as calculation errors. Therefore, a device that detects that the power supply voltage is within a certain range (normal range) is installed, and this voltage is monitored. If it is detected that the voltage is outside the certain range, the microcomputer A reset signal is output to stop the operation of the microcomputer. When the power supply voltage reaches within a certain range, the microcomputer can be restarted.

An apparatus for detecting such an abnormal power supply voltage is shown in FIG. What is shown in FIG. 1A is a voltage abnormality detection device including an analog circuit. This device constantly monitors the power supply voltage VDD and outputs a reset signal when an abnormal voltage occurs. However, since it is composed of analog circuits, a relatively large amount of power is required to operate the circuits. This is contrary to the recent design concept of reducing power consumption.

In response to this request, there is an abnormal voltage detecting device having a configuration as shown in FIGS. In other words, an RC series circuit that generates a comparison voltage based on the power supply voltage is provided, and if the comparison voltage generated by this circuit is within a certain voltage range (between V1H and V1L), the reset signal is not output. If the voltage is out of this range, the reset signal is output. When the circuit for generating the comparison voltage is configured by the series circuit of RC in this way, the charging current of the capacitor does not always flow in this circuit, so that the power consumption is extremely reduced. You can do that.

[0005]

[Problems to be solved by the device]

 However, such a conventional abnormal voltage detector is satisfactory in terms of suppressing the power consumption, but the RC series circuit constitutes a kind of low-pass filter. Therefore, as disclosed in the application number PCT / WO / 96/21 158 (published on July 11, 1996), when the power supply voltage V CC rises and falls relatively slowly, the fluctuation of the comparison voltage Can respond, but cannot respond to momentary fluctuations. That is, the reset signal is not output in the case of the abnormal voltage which is generated instantaneously.

This means that even if a momentary abnormal voltage (a sudden voltage drop from a stable voltage and a rapid voltage rise) that causes a calculation error in the microcomputer occurs, This means that the voltage detection circuit cannot detect this.

The present invention has been made to solve such conventional problems, and provides an abnormal voltage detection device for a microcomputer capable of reliably detecting an abnormal voltage that occurs momentarily. With the goal.

[0008]

[Means for Solving the Problems]

 The invention according to claim 1 includes a detection circuit for detecting that an abnormality has occurred in the voltage, and a latch circuit for latching a signal output from the detection circuit and outputting a signal for notifying the occurrence of the abnormal voltage. The detection circuit is composed of a NOT gate, the current connection terminal of the NOT gate is connected to the reset voltage terminal in the microcomputer, while the input terminal of the NOT gate is connected to the power supply terminal of the microcomputer, Further, the output terminal of the NOT gate is connected to the input terminal of the latch circuit, and when the detection circuit detects a momentary voltage fluctuation outside a predetermined voltage range in the microcomputer, an abnormal voltage is output from the output terminal of the latch circuit. Is output, and the operation of the microcomputer is interrupted or reset. A microcomputer abnormal voltage detecting apparatus.

According to a second aspect of the present invention, in the abnormal voltage detection device for a microcomputer according to the first aspect, the detection circuit is formed of a NOT gate of CMOS, and the abnormal voltage detection for a microcomputer is performed. It is a device.

According to a third aspect of the present invention, in the abnormal voltage detection device for a microcomputer according to the first or second aspect, the latch circuit is one flip-flop or the same operation as this flip-flop. An abnormal voltage detection device for a microcomputer, characterized in that it is configured by a latch circuit that operates.

According to a fourth aspect of the present invention, in the abnormal voltage detection device for a microcomputer according to the third aspect, the latch circuit is composed of one flip-flop or a latch circuit having the same operation as the flip-flop. At this time, the input terminal of the flip-flop or the latch circuit is connected to the output terminal of the NOT gate, the D terminal and the power supply terminal of the latch circuit are both connected to the reset voltage terminal in the micro computer, and the latch circuit is connected. An abnormal voltage detection device for a microcomputer, which outputs a signal notifying the occurrence of an abnormal voltage to the Q terminal and the R terminal of the circuit.

According to a fifth aspect of the present invention, in the abnormal voltage detection device for a microcomputer according to the first or second aspect, the voltage within a predetermined range for detecting an abnormal voltage in the detection circuit is: This is an abnormal voltage detector for a microcomputer, which is fixedly set (mask option) at the time of manufacture.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. The circuit shown in FIG. 2 is a specific circuit diagram of the abnormal voltage detection device for a microcomputer according to the present invention. The abnormal voltage detection device of the present invention comprises a detection circuit 1 for detecting an abnormality in the power supply voltage VDD and a latch circuit 2 (flip-flop 11) for latching the signal output from the detection circuit 1. It

The NOT gate 10 constituting the detection circuit 1 is preferably composed of CMOS, and the voltage Vres of the reset voltage terminal in the microcomputer is directly applied to the current connection terminal P1 of the gate 10, and The power supply voltage VDD of the power supply terminal of the microcomputer is applied to the input terminal P2 of the gate 10. When the direct power supply voltage is input to the NOT gate in this way, the NOT gate can detect an abnormal power supply voltage that has occurred momentarily with high sensitivity. The signal from the output terminal PFDO of the gate 10 is input to the input terminal P3 (CB terminal) of the latch circuit 2. Although the D-type flip-flop is used as the latch circuit 2, other various flip-flops such as a JK flip-flop and a master-slave flip-flop can be used. Further, a latch circuit that operates in the same manner as these flip-flops may be used.

When a D-type flip-flop is used as in the present invention, as described above, its CB terminal is connected so that the signal from the PFDO output terminal of the NOT gate 10 is input, and D Both the terminal and the power supply terminal P4 are connected to the reset voltage terminal Vres in the microcomputer. When the power supply voltage VDD is abnormal due to such a connection, it is detected with high sensitivity, and at the same time, the PFF signal from the Q terminal of the latch circuit 2 and the RESET signal from the R terminal are detected at the same time. It is output respectively.

Since this PFF signal (phase signal) is a signal output when the power supply voltage VDD has an abnormal voltage, it is input to the reset circuit of the microcomputer to interrupt the operation of the microcomputer. Alternatively, the PFF signal may simply be used as a trigger for displaying the occurrence of abnormal voltage.

If the circuit is configured as described above, when an abnormal voltage occurs in the microcomputer, it can be reliably detected even if the abnormal voltage is instantaneous. The detection of the abnormal voltage causes the latch circuit 2 to continuously output the PFF signal for notifying the occurrence of the abnormal voltage. Therefore, by using this PFF signal as the reset signal of the microcomputer, the operation of the microcomputer can be performed. Will be able to stop.

Since the detection voltage of the detection circuit 1 (reference voltage for determining an abnormal voltage) varies depending on the specifications of the microcomputer, the optimum voltage depends on the power supply voltage of the target microcomputer. Set to (by mask option etc.).

The apparatus of the present invention thus constructed generates a waveform as shown in FIG. 3 when an abnormal voltage occurs. That is, the curve L1 in the figure is the voltage-time curve of the power supply voltage VDD, the curve L2 is the voltage-time curve of the reset voltage Vres, the curve L3 is the voltage-time curve of RESET, and the curve L4 is the NOT gate 10. The voltage-time curve of the PFDO (power failure detector output) and the curve L5 show the voltage-time curve of the PFF, respectively, and the voltage drop occurs momentarily or for a relatively long time. I understand.

Particularly, the difference from the conventional abnormal voltage detecting device is that even if a momentary (T1 in FIG. 3) voltage drop occurs in the power supply voltage VDD, the abnormal voltage can be reliably detected ( PFF voltage change (see curve L5)) By the way, inputting this pulse-shaped PFF signal to the reset circuit of the microcomputer to interrupt the operation of the microcomputer, or simply using this PFF signal to cause abnormal voltage Can be displayed.

[0021]

[Effect of the invention]

 As described above, the present invention makes it possible to instantaneously and reliably detect the occurrence of an abnormal voltage in the microcomputer by the configurations of claims 1 to 5, and by using a signal obtained by this detection. It becomes possible to suspend or reset the processing of the microcomputer. Therefore, unlike the conventional case, the abnormal voltage generated instantaneously cannot be detected.

[Brief description of the drawings]

FIG. 1A is a conventional abnormal voltage detection device composed of an analog circuit, FIG. 1B is a conventional abnormal voltage detection device for detecting an abnormal voltage in a microcomputer, and FIG. , Another abnormal voltage detection device for detecting an abnormal voltage in a conventional microcomputer.

FIG. 2 is an abnormal voltage detector according to the present invention.

FIG. 3 is a voltage-time curve at the time of detecting an abnormal voltage of each part in the device of FIG.

[Explanation of symbols]

1 ... Detection circuit, 2 ... Latch circuit, 10 ... NO
T gate, 11 ... Flip-flop, VDD ... Power supply voltage, Vres ... Reset voltage terminal, PFF ... Phage signal, P1 ... Current connection terminal, P2 ... Input terminal,
P3 ... Input terminal.

Claims (5)

[Utility model registration claims] 1. A detection circuit (1) for detecting the occurrence of an abnormal voltage, and a signal (PFF signal) for latching the signal output from the detection circuit (1) and notifying the occurrence of the abnormal voltage. And a latch circuit (2) for resetting, the detection circuit (1) is composed of a NOT gate (10).
The current connection terminal (P1) of the T gate (10) is connected to the reset voltage terminal (Vres) in the micro computer, while the input terminal (P) of the NOT gate (10) is connected.
2) is a power supply terminal (VDD) of the microcomputer
Further, the output terminal (PFDO) of the NOT gate (10) is connected to the input terminal (P3) of the latch circuit (2), and the detection circuit (1) is out of a predetermined voltage range in the microcomputer. When a momentary voltage fluctuation is detected, the output terminal of the latch circuit (2) outputs a signal (PFF signal) notifying the occurrence of an abnormal voltage to interrupt or reset the operation of the microcomputer. Abnormal voltage detector for microcomputer. 2. The detection circuit (1) is a CMOS NOT.
The abnormal voltage detection device for a microcomputer according to claim 1, wherein the abnormal voltage detection device is formed of a gate (10). 3. The microcomputer according to claim 1, wherein the latch circuit (2) is composed of one flip-flop or a latch circuit having the same operation as this flip-flop. Abnormal voltage detection device. 4. When the latch circuit (2) is composed of one flip-flop or a latch circuit having the same operation as this flip-flop, the input terminal (CB) of the flip-flop or the latch circuit is the NOT circuit.
It is connected to the output terminal (PFDO) of the gate (10), and the D terminal and the power supply terminal (P4) of the latch circuit (2) are both reset voltage terminals (Vre) in the micro computer.
signal (PFF signal, R which is connected to the latch circuit (2) and notifies the Q terminal and R terminal of the latch circuit (2) that an abnormal voltage is generated
The abnormal voltage detection device for a microcomputer according to claim 3, wherein the abnormal voltage detection device outputs an ESET signal). 5. The voltage in a predetermined range for detecting the occurrence of an abnormality in the voltage in the detection circuit (1) is fixedly set (mask option) at the time of manufacturing. The abnormal voltage detection device for a microcomputer according to claim 2.