JPS60147822A - Power-on resetting circuit - Google Patents

Abstract

PURPOSE:To prevent sending out of wrong signals at the rising and falling times of power supply, by connecting a cerial circuit of a capacitor and diode in parallel with a resistor connected to the power supply side of a voltage detecting section and, at the same time, a diode between the connecting point of the capacitor and diode and an earth so that the earth side becomes an anode. CONSTITUTION:Since a comparator Z1 maintains a non-operating condition until time T1 after a supply voltage Vcc rises, an output Vo (waveform b) is raised. In a period rod from T1 to T2, the inversional input terminal 3 of the comparator Z1 is higher than the non-inversional input terminal 4 by the integrating effect of a capacitor C1 and resistors R2 and R3 and, therefore, the output Vo becomes low in level inclining toward earthing potential. Since the two input potential of the comparator Z1 are inverted, the output Vo becomes high in level inclining toward the supply voltage. When the supply voltage starts declining, a diode D2 becomes reverse bias and the delaying effect by the capacitor C1 disappears. As a result, the two input potential of the comparator Z1 are inverted at a preset point Vcc1 and the output Vo becomes low in level.

Description

Detailed Description of the Invention (Technical Field) -1-1 The present invention relates to a power-on reset circuit, and particularly to a power-on reset circuit suitable for a microprocessor.

□゛,“ (Prior art) A conventional power reset circuit consists of a reference voltage generation circuit section consisting of a Zener diode V and a resistor, a voltage detection section consisting of a series connection of two resistors, and a pre-reference electric circuit section. and voltage =
Connected to part i, 4゛, 7., 1, 1. ,,
,,,,.

Consisting of one comparator with a grounded amplifier amplification path, Reemo-8A1. , 1. stomach,.

, ・ ′ □ If the device has a crystal oscillator, such as a processor, and it is necessary to hold the reset signal until the oscillator becomes stable oscillation, the power reset circuit 41111 stage is also provided with a comparator, Resistance 1. It was constructed by connecting an integral delay circuit consisting of a capacitor and a protector.

・ ・ 1-1- □ Therefore, the conventional power-on reset circuit is complicated in a device applying a microprocessor. (Objective of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks of conventional power-on reset circuits, and to provide stable reset operation even when the power is turned off. It is an object of the present invention to provide a power reset circuit configured to do the following.

(Structure of the invention) According to the invention, a Zener diode and a resistor connected in series (
b) A power-on reset circuit consisting of a reference voltage generation section consisting of a circuit, a voltage detection section consisting of a series circuit of two resistors, and a comparator connected to the reference voltage generation section and the voltage detection section. To? A series circuit of a capacitor and a diode is connected in parallel with the resistor connected to the power supply side of the voltage detection section, and the ground side is an anode between the connection point of the capacitor and the diode and the ground line. A power-on reset circuit formed by connecting diodes is obtained.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the invention. In FIG. 1, there is shown a reference voltage generation section consisting of a series circuit of an unfired power reset Zener diode DI and a resistor 1, a voltage detection section consisting of a series circuit of two resistors R2, ) 13, and the reference voltage generation section. and a comparator Zl connected to the voltage detection section, the power-on reset circuit includes a capacitor C1 connected in parallel to a resistor R2 connected to the power supply side Vcc of the voltage detection section, and a diode D20 connected in series. circuit, the capacitor C1 and the diode D
2 and the ground 2170, the diode D3 is connected with the ground side serving as an anode.

The comparator Zl is a single comparator having a common collector amplifier circuit in the first stage, operates with the voltage VCC between the ground terminal l and the power supply terminal 2, and has 1 inverting input terminal, 3 valley non-inverting input terminals 4, and an output terminal 5. . This comparator Zl
A series circuit consisting of a Zener diode DI and a resistor R1 connected between the distribution power supply terminal 2 and the ground terminal 1 to generate a reference voltage (Vz) for the power supply terminal 2. is connected via a resistor R6 connected between the connection point between the Zener diode DI and the resistor R1\ and the non-inverting input terminal 4, and is further connected between the power supply terminal 2 and the ground terminal l. View E, one end of the resistor R2 is connected to the resistor F#R2, which generates the detection voltage on the side of the power source 2! ! One line of the resistor 3 is connected to the inverting input terminal 3 through the connection point between the resistor R2 and the pXi resistor R3. The resistor R
A diode D20 cathode is connected to the connection point between the diode D2 and the resistor R3, and a capacitor CI connected between the diode D2 and the anode 0 of the diode D2 and the power supply electronics 2 is connected to the resistor. Connected in parallel to R2. The ground terminal l is connected between the anode of the diode D2 and the ground terminal 1.
Diode D3 connected in such a direction that the side thereof becomes the anode.
2), a resistor 5 is provided between the non-inverting input terminal 4 and the output terminal 5, and a resistor 5 is provided between the power supply terminal 2 and the output terminal 5 of the comparator Zl. A resistor R4 is provided.

The operation of this embodiment will be explained with reference to FIG. 2. Waveform a in FIG. 2 has a smooth rise 9. Falling also comparator z
The comparator Zl is in an inactive state after the rise of the power supply voltage VCC up to T1, that is, until the power supply voltage V CCO, so the waveform rises in the same way as waveform a. let

Between T1 and T2, h capacitor rC1 and resistor R
2, and R3, the inverting input terminal 3 of the comparator Zl becomes higher than the non-inverting input terminal 4 and becomes 29.
The potential of the output terminal 5 becomes the 9 level, which is close to the ground potential.

Since the potentials of the two inputs of the comparator Zl change at point T2O, the potential of the output terminal 5 is close to the power supply voltage d...
level and continues until T3. Next, as shown in waveform a in Figure 2, when the power supply voltage Vcc begins to drop, the diode rD2 becomes reverse biased.9. capacitor ci
The delay effect due to the voltage drop is eliminated, and the comparator Z
The potentials of the two inputs of I are inverted, and the output terminal 5 becomes low level. This state continues until T4.

At the voltage VCCOO point (ie, point T4) at which the comparator Zl becomes inoperable, the potential at the output terminal 5 of the comparator Zl rises almost to Vcco, and thereafter drops to approximately the same potential as the waveform U. -The electric charge of the capacitor CI is discharged to the power supply side through the diode D3.

This power-on reset circuit a is a period from when the output terminal 5 of the comparator Zl is connected to the reset terminal of the microcomputer until the power supply voltage rises and the crystal oscillation circuit becomes stable.

In addition to stopping the operation, by similarly giving the output terminal 5 to the peripheral output circuit of the micro combiator as a channel lock signal, it is possible to prevent other devices from erroneously outputting the p7' (signal It is definitely possible to prevent this from happening.

P, resistors R5 and R6 are IJ of comparator zl
,=A is a positive feedback circuit for passing through the operating region in a short time and preventing chattering of the output voltage, and is unnecessary if chattering is not an issue.

(Effects of the Invention) As explained above, the present invention is capable of reliably operating a single comparator with a minimum number of parts to prevent the sending of error signals when the power supply rises and falls, and that , low cost and high reliability.

[Brief explanation of the drawing]

Diagram R1 is a circuit diagram showing an embodiment of the present invention, and diagram R2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a waveform diagram showing the operation of the circuit shown in the figure. 1... Ground terminal, 2... Power terminal, 3
...Inverting input terminal, 4...Non-inverting input terminal, 5...Output terminal, Dl...Zener diode, D2. D3-...Diode, Zl...Comparator, R1-R6...
-・Resistor, CI... Capacitor.

Claims (1)

[Claims] A reference voltage generating section consisting of a Zener diode and a resistor connected in series, a voltage detecting section consisting of a straight circuit of two resistors, and a cable connected to the base voltage generating section and the voltage detecting section. ``V'' is connected to the telephone side of the voltage detecting section and connected in parallel with the t resistor. series! ! 9. Connect the capacitor and diode? A pi-on reset circuit characterized in that a diode is connected between a connecting point and a ground line so that the ground side serves as an anode.