JP2001053591A - Initialization signal generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an initialization signal generation circuit capable of surely generating initialization signals, even to the various power sources of the different rising speeds of a power supply voltage. SOLUTION: This circuit is provided with plural initialization signal generation parts 11-1 to 11-n for generating the initialization signals of mutually different time widths, when power is supplied to an electronic device loaded with the initialization signal generation circuit and an initialization signal selection part 12 for selecting the initialization signals of one of the initialization signal generation parts 11-1 to 11-n corresponding to the rising speed of the power supply voltage and supplying the selected initialization signals to the circuit (circuit unit for constituting the electronic device) to be the object of initialization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an initialization signal generating circuit for generating an initialization signal for initializing a circuit unit when a power supply is turned on. The present invention relates to an initialization signal generation circuit capable of reliably generating an initialization signal.

[0002]

2. Description of the Related Art Various circuit units constituting an electronic device usually have a volatile signal holding unit such as a flip-flop. Such a signal holding unit is provided immediately after power is supplied. In many cases, the possible signal holding state is indefinite. This is because such a signal holding unit is characterized in that it determines the next possible holding state based on the signal value held last time, and therefore, usually includes a reset input terminal. Requires that an initialization signal be input to its reset input terminal at the start of use.

Therefore, usually, an electronic device is provided with an initialization signal generation circuit that automatically supplies an initialization signal to each circuit unit immediately after power is supplied to the electronic device itself. FIG. 6 is a diagram showing a circuit configuration of a conventional initialization signal generation circuit. The initialization signal generation circuit shown in FIG. 6 includes a capacitor 21 and a resistor 22 connected in series between a node N11 connected to a power supply voltage and a ground potential, and a connection point between the capacitor 21 and the resistor 22. , And an inverter G1 having an input terminal connected to the node N12.

In this initialization signal generating circuit, the signal output from the inverter G1 becomes an initialization signal, and the output timing and output width of a pulse indicating the initialization signal are as follows:
It is determined according to the state of the power supply voltage supplied from node N11. In particular, immediately after the power is turned on, a power supply voltage value in a steady state (hereinafter, referred to as a steady voltage value, which is assumed to be “5 V” here) is not immediately applied to the node N11, but a rising speed according to the characteristics of the power supply device. Therefore, it takes a certain time to reach the steady voltage value.

FIG. 7 shows a conventional initialization generating circuit.
It is a timing chart explaining the above-mentioned transient response. As shown in FIG. 7, in the node N11,
The voltage gradually increases from time T ₀ immediately after the power is turned on, and reaches the steady voltage value for the first time at time T ₂ . Next, the operation of the initialization signal generation circuit will be described using this timing chart.

First, when the power is turned on at time T ₀ , the capacitor 21 is charged with a time constant determined by the charge capacity of the capacitor 21 and the resistance value of the resistor 22. During this charge period, the potential of the node N12 also rises as the power supply voltage rises. And
When the increased voltage exceeds the threshold level of inverter G1, inverter G1 recognizes that a signal of logic level "H" has been input and outputs a signal of logic level "L" as node 13.

[0007] The signal of the logic level "L" corresponds to the initialization signal, and becomes a pulse output until the signal of the logic level "H" is output, as described later. This initialization signal is input to each circuit unit constituting the electronic device, and the initialization of the holding circuit and the like is achieved.

On the other hand, when the potential of node N12 is equal to or lower than the threshold level, inverter G1 recognizes that a signal of logic level "L" has been input and outputs a signal of logic level "H". In the state immediately after the power is turned on, the power supply voltage shows a sufficiently small value as compared with 5 V which is a steady voltage, so that the output signal of the logic level "H" also remains at a slight voltage value. In FIG. 7, the illustration of the slight voltage value is omitted.

When the charge of the above-mentioned charge capacity is completed in the capacitor 21 (time T ₁ ), the charge is subsequently pulled in by the resistor 22 (discharge). Thereby, the potential of the node N12 becomes equal to the ground potential, and the inverter G1 recognizes that the signal of the logic level "L" has been input, and outputs a signal of the logic level "H". However, as shown in FIG. 7, the output signal of the logical level “H” increases as the power supply voltage rises because the power supply voltage has not reached the steady voltage of 5V.

As described above, the initialization signal generation circuit operates in a transient state until the power supply voltage reaches the steady voltage, and has a time constant (time T) determined by the capacitor 21 and the resistor 22.
_{0 to} T ₁ ), an initialization signal is output. However, in the initialization signal generating circuit, the power supply voltage instantaneously reaches the steady voltage, and then the power supply voltage instantaneously increases, rather than the power supply voltage increasing process and the capacitor 21 charging process operating in parallel as described above. Often, a pulse which is an initialization signal having a predetermined width is generated.

In any case, in the initialization signal generation circuit, the initialization signal is output with a pulse width having a time constant determined by the capacitor 21 and the resistor 22.

[0012]

However, in the initialization signal generation circuit having the above-described configuration, an initialization signal is generated for an electronic device equipped with a power supply device whose power supply voltage rises extremely slowly. In some cases, a situation in which initialization cannot be performed without performing the above operation may occur.

More specifically, in the conventional initialization signal generation circuit, the generation period of the initialization signal is set to the above-described value of the capacitor 21.
When the rising speed of the power supply voltage is extremely slow, that is, when it takes a long time from when the power is turned on to reach the steady voltage, the capacitor 21 is used. Before the completion of the charging of the charge, the state in which the charge is discharged by the resistor 22 may occur.

As a result, after the power is turned on, the potential of the node 12 immediately becomes equal to the ground potential, so that the inverter G1 does not recognize the input signal of the logic level "H" and shifts to the steady state of the electronic device. Had been done. That is, the logic level “L” is used as the initialization signal.
Is not output, and in each of the circuit units constituting the electronic device, the initial state of the holding circuit and the like becomes unstable, and there is a problem that the electronic device does not operate normally.

The above-described initialization signal generation circuit is supplied as a general-purpose IC in a chip or package state together with a circuit that enables a forced reset operation to be performed while the electronic device is activated. ing. At present, many electronic devices on the market are trying to reduce costs by mounting these general-purpose ICs as initialization signal generation circuits.

For this reason, in an electronic device equipped with a power supply device having a low rising speed as described above and a general-purpose IC as an initialization signal generating circuit, a situation occurs in which the initialization signal is not generated. There was a problem that the possibility was high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an initialization signal generation method capable of reliably generating an initialization signal even for various power supplies having different rising speeds of a power supply voltage. It is intended to provide a circuit.

[0018]

According to a first aspect of the present invention, there is provided an initialization signal generating circuit for initializing a circuit unit constituting an electronic device when the electronic device is powered on. Signal generation circuit,
When the power is turned on, a plurality of initialization signals having different time widths are generated, and any one of the plurality of generated initialization signals is selected according to a rising speed of a power supply voltage, and the selected initialization is performed. Since the signal is supplied to the circuit unit, the initialization can be reliably performed even between electronic devices having different power supply voltage rising speeds.

According to a second aspect of the present invention, in the initialization signal generating circuit according to the first aspect,
Since at least one of the plurality of initialization signal generation units generates an initialization signal having a time width determined based on a time constant determined by a capacitor and a resistor, even between electronic devices having different power supply voltage rising speeds. With a simple circuit configuration, an initialization signal having a fixed time width can be obtained.

According to a third aspect of the present invention, in the initialization signal generation circuit according to the first or second aspect, at least one of the plurality of initialization signal generation units is configured such that the power supply voltage is Since the initialization signal of the time width from when the power is turned on to when the power supply voltage reaches a predetermined voltage value is generated, the initialization can be reliably performed even between electronic devices having different power supply voltage rising speeds with a simple circuit configuration. it can.

According to a fourth aspect of the present invention, there is provided an initialization signal generating circuit for initializing a circuit unit constituting an electronic device when the power of the electronic device is turned on. A first initialization signal generating unit for generating a first initialization signal having a time width determined based on a constant, and a second initialization signal generating unit having a time width from when the power supply is turned on to when the power supply voltage reaches a predetermined voltage value
A second initialization signal generating unit for generating the first initialization signal and the first initialization signal and the second initialization signal, and an initialization signal having a longer time width among the initialization signals. An initialization signal selection unit that supplies an initialization signal to the circuit unit. Therefore, the first initialization signal generation unit outputs the first And the second initialization signal output from the second initialization signal generator can be adopted for a power supply device having a slow rising speed of the power supply voltage.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an initialization signal generating circuit according to the present invention. The present invention is not limited by these embodiments.

FIG. 1 is an explanatory diagram for explaining the principle configuration of the initialization signal generating circuit of the present invention. In FIG.
The initialization signal generation circuit according to the embodiment of the present invention includes n (n ≧ 2) initialization signal generation units 11-1 to 11-n,
And an initialization signal selection unit 12.

The initialization signal generators 11-1 to 11-n are:
This is a circuit for generating initialization signals having different time widths when an electronic device equipped with the initialization signal generation circuit is powered on, and inputs the generated initialization signals to the initialization signal selection unit 12. Things. Initialization signal selector 1
2 selects any one of the above-described initialization signal generators 11-1 to 11-n according to the rising speed of the power supply voltage, and sets the selected initialization signal as an initialization target. Circuits (circuit units that make up electronic devices)
Circuit.

In the following description, in order to facilitate the understanding of the present invention, two initialization signal generators are provided, and the generation principle of the initialization signal of these initialization signal generators is different. An initialization signal generation circuit will be described as an example. In this embodiment, the effect of the present invention is most remarkably exhibited.

FIG. 2 is a circuit block diagram of the initialization signal generation circuit according to the embodiment of the present invention. The initialization signal generation circuit shown in FIG. 2 includes two initialization signal generation units 20 and 30 and an initialization signal selection unit 40. In particular, the initialization signal generation section 20 has a circuit configuration similar to that of a conventional initialization signal generation circuit, and corresponds to the circuit shown in FIG. Therefore, portions common to those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted.

On the other hand, the initialization signal generator 30 is a voltage detection circuit used for general purposes. In FIG. 2, an initialization signal generating unit 30 includes a resistor 31, a constant current circuit 32,
3, an enhancement type N-channel MOS transistor M1, and an inverter G2.
The operation (transient response) of the initialization signal generator 30 after the power is turned on will be described below.

FIG. 3 shows generation of an initialization signal according to the embodiment.
In the circuit, the error of the initialization
It is a timing chart explaining a handover response. First, figure
The power supply voltage supplied to the second node N1 is as shown in FIG.
Time t immediately after power-on ₀Gradually rising from the time
t_TwoRise for the first time to reach the steady-state voltage value
Speed.

When the power is turned on at time t ₀ , a constant current determined by the constant current circuit 32 continues to flow through the resistor 31. Therefore, the resistance 31 and the constant current circuit 3
The potential of the connection point with the node 2 increases as the power supply voltage increases. The gate of the MOS transistor M1 is connected to this connection point.
The off state is indicated until the potential of the gate reaches the threshold level due to the rise of the power supply voltage.

On the other hand, the drain of the MOS transistor
It is connected to the constant current circuit 33 and supplies a constant current. In the initial stage after power-on, as described above,
Since the S transistor is in the off state, the inverter G2 connected to the node N2, which is the connection point between the constant current circuit 33 and the drain of the MOS transistor, is proportional to the rise of the power supply voltage as shown in FIG. It recognizes that the signal of the logic level “H” has been input by the input of the voltage, and outputs a signal of the logic level “L” to the node 3.

The signal at the logic level "L" corresponds to the initialization signal output from the initialization signal generator 30, and as will be described later, the pulse output until the signal at the logic level "H" is output. Becomes Note that this initialization signal is not directly input to the initialization target circuit as in the conventional initialization signal generation circuit, but is input to the initialization signal selection unit 40.

When the potential of the gate of the MOS transistor M1 exceeds the threshold level due to a further increase in the power supply voltage, the MOS transistor M1 is turned on (time t ₁ ). As a result, the node N2 becomes at the same potential as the ground potential, and the inverter G2 recognizes that the signal of the logic level “L” has been inputted as shown in FIG. Is output.

As described above, the initialization signal generator 30 including the voltage detection circuit outputs the initialization signal only for a period of time (time t _{0 to} t ₁ ) until the power supply voltage reaches the predetermined voltage. Therefore, even if the rising speed of the power supply voltage is extremely slow, the presence of the point in time when the power supply voltage reaches the predetermined voltage value ensures that the logic level “L” is used as the initialization signal.
Can be output.

However, the initialization signal generator 30
With respect to the power supply voltage having a fast rising speed, the MOS transistor M1 is turned off immediately after the power is turned on, so that an initialization signal having a sufficient time width cannot be obtained. On the other hand, as described above, the initialization signal generator 20 always outputs an initialization signal having a time width determined by a time constant determined by the capacitor 21 and the resistor 22 for a power supply voltage having a fast rising speed. You.

Therefore, the initialization signal selector 40 is set to the NAN
D gate 41, and this NAND gate 2
The above-described initialization signal of the initialization signal generator 20 and the initialization signal of the initialization signal generator 30 including a voltage detection circuit are input to each of the two input terminals. That is, the initialization signal selection unit 40 outputs the logic level “H” only when one of the two initialization signals indicates the logic level “L”.

Therefore, in this configuration, the logic level "H"
Is an initialization signal supplied to the initialization target circuit (another circuit unit). Note that the above NAND gate 41
By further connecting an inverter to the output, the logic level "L" may be used as the initialization signal as in the conventional initialization signal generation circuit.

The initialization signal generator 30 comprising the above-described voltage detection circuit is not particularly limited as long as it is a circuit configured to detect a predetermined voltage. 4 and 5 are circuit configuration diagrams showing examples of other voltage detection circuits. Portions common to the initialization signal generation unit 30 are denoted by the same reference numerals. FIG. 4A is a circuit in which the constant current circuit 32 of the initialization signal generator 30 is replaced with a band gap circuit B1.
(B) shows that the constant current circuit 33 of the initialization signal generator 30 is
Enhancement type P-channel MOS transistor M
2, a current mirror circuit composed of M3 and a depletion type N-channel MOS transistor M4.

FIG. 5A shows an initialization signal generator 3.
Enhancement type P in which a resistor 31 of 0 is saturated and connected.
FIG. 5B is a circuit in which the constant current circuit 32 of the initialization signal generator 30 is replaced with a depletion type N-channel MOS transistor M6. Further, the above-described replacement portions may be combined so as not to overlap with each other.
In particular, the examples of the other voltage detection circuits shown in FIGS. 4 and 5 are suitable for an integrated circuit.
The initialization signal generation circuit according to the present invention is also preferably provided as one of integrated circuits arranged on a circuit board of an integrated electronic device.

As described above, according to the initialization signal generating circuit according to the embodiment, the initialization signal for generating the initialization signal having the time width determined based on the time constant determined by the capacitor 21 and the resistor 22. An initializing signal generating unit 30 comprising a generating unit 20 and a voltage detecting circuit for generating an initializing signal having a time width from when the power supply is turned on to when the power supply voltage reaches a predetermined voltage value; Since one of the initialization signals having a longer time width is supplied to the circuit unit constituting the electronic device, the output from the initialization signal generation unit 20 is provided for a power supply device having a fast rising speed of the power supply voltage. For a power supply device that adopts an initialization signal to be supplied and whose power supply voltage rises slowly, the initialization signal output from the initialization signal Regardless of the rate of rise, certainly initialization signal can be supplied to other circuit units to be initialized target.

The initialization signal generating circuit is a general-purpose IC.
As a result, even between electronic devices having different power supply voltage rising speeds, it is not necessary to prepare an initialization signal generation circuit having a design specification suitable for each electronic device, and a reliable initialization process can be performed.
Cost reduction can be achieved.

In addition to the above-described embodiments, a plurality of initialization signal generators 20 having different time constants are input to the initialization signal selector 40 as a plurality of initialization signal generators. The initialization signal generator 30 may be added as one of them. In this case, for example, the initialization signal selection unit is configured to have an initialization signal generation unit having a time constant next to the time constant of the initialization signal generation unit that cannot generate the initialization signal due to the rising speed of the power supply voltage. It can be configured to employ an initialization signal.

[0042]

As described above, according to the present invention,
In an initialization signal generation circuit for initializing a circuit unit constituting an electronic device when the electronic device is powered on, a plurality of initialization signals having different time widths are generated and generated when the power is turned on. Any one of the plurality of initialization signals is selected according to the rising speed of the power supply voltage, and the selected initialization signal is supplied to the other circuit units to be initialized. Initialization can be reliably performed between devices.

In particular, by providing a circuit for generating an initialization signal having a time width from when the power supply is turned on to when the power supply voltage reaches a predetermined voltage value as the initialization signal generation unit, a power supply having a slow rising speed of the power supply voltage is provided. The initialization process can be reliably performed on the device.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining the principle configuration of an initialization signal generation circuit according to the present invention.

FIG. 2 is a circuit block diagram of an initialization signal generation circuit according to the embodiment of the present invention.

FIG. 3 is a timing chart illustrating a transient response of an initialization generation unit including a voltage detection circuit in the initialization signal generation circuit according to the embodiment;

FIG. 4 is a circuit configuration diagram showing another example of a voltage detection circuit in the initialization signal generation circuit according to the embodiment;

FIG. 5 is a circuit configuration diagram showing an example of another voltage detection circuit in the initialization signal generation circuit according to the embodiment;

FIG. 6 is a diagram showing a circuit configuration of a conventional initialization signal generation circuit.

FIG. 7 is a timing chart illustrating a transient response when power is turned on in a conventional initialization generation circuit.

[Description of Signs] 11-1 to 11-n Initialization signal generation unit 12 Initialization signal selection unit 20, 30 Initialization signal generation unit 21 Capacitor 22, 31 Resistance 31 Resistance 32, 33 Constant current circuit 40 Initialization signal selection Part 41 NAND gate B1 Band gap circuit G1, G2 Inverter M1 to M6 MOS transistor

Claims (4)

[Claims] 1. An initialization signal generating circuit for initializing a circuit unit constituting an electronic device when power of the electronic device is turned on, wherein when the power is turned on, a plurality of initialization signals having different time widths are provided. Generating an initialization signal, selecting one of the generated initialization signals according to a rising speed of a power supply voltage, and supplying the selected initialization signal to the circuit unit. . 2. The apparatus according to claim 1, wherein at least one of the plurality of initialization signal generators generates an initialization signal having a time width determined based on a time constant determined by a capacitor and a resistor. An initialization signal generating circuit as described in the above. 3. The apparatus according to claim 1, wherein at least one of the plurality of initialization signal generators generates an initialization signal having a time width from when the power supply is turned on to when the power supply voltage reaches a predetermined voltage value. The initialization signal generation circuit according to claim 1. 4. An initialization signal generating circuit for initializing a circuit unit constituting an electronic device when the power of the electronic device is turned on, wherein a first signal having a time width determined based on a time constant determined by a capacitor and a resistor. A first initialization signal generating unit for generating a second initialization signal for generating a second initialization signal having a time width from when the power supply is turned on to when the power supply voltage reaches a predetermined voltage value A signal generation unit, an initialization signal that receives the first initialization signal and the second initialization signal, and supplies an initialization signal having a longer time width among the initialization signals to the circuit unit An initialization signal generation circuit, comprising: a selection unit.