JP3732937B2 - Monostable multivibrator circuit with retrigger function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a monostable multivibrator circuit with a re-trigger function, and is particularly suitable for use in a CMOS-LSI.
A monostable multivibrator with a re-trigger function is characterized by low circuit operating current and low jitter.
[0002]
[Prior art]
A monostable multivibrator circuit with a re-trigger function can be configured using a D-FF, for example, as shown in FIG. That is, the potential of the output terminal Q of the D-FF is set to “H” level by the trigger input, and the output is returned to the reset input terminal R through the delay circuit by the resistor R and the capacitor C. The pulse ends after a set time determined by the threshold voltage at the end R.
[0003]
In the monostable multivibrator circuit configured as described above, the operation of the delay circuit by the resistor R and the capacitor C is initialized when there is a trigger input at the input terminal TIN as shown in the operation waveform diagram of FIG. Retrigger operation is performed.
[0004]
[Problems to be solved by the invention]
As is well known, in a CMOS logic circuit, if the input level to the logic gate is the power supply or the GND level, the current consumption can be extremely reduced. However, in the monostable multivibrator circuit with the retrigger function configured as shown in FIG. 4, since an intermediate level signal near the threshold level continues to be applied to the reset input terminal R, the CMOS logic circuit is penetrated during that time. There was a problem that current flowed and current consumption increased. In addition, when the pulse output is completed and returns to the stable state, it returns slowly, and there is a problem that current flows in the CMOS logic circuit during that time.
[0005]
Further, in the case of the conventional monostable multivibrator, there is a problem that the pulse width has a large time variation (jitter). This is because, after the output is set by the delay circuit, the voltage of the reset input rises slowly (in some cases, falls) and reaches the threshold voltage that accepts the input. This is because the timing at which the end of the pulse is determined varies.
[0006]
In view of the above problems, an object of the present invention is to provide a monostable multivibrator circuit with a re-trigger function that can reduce current consumption and jitter.
[0007]
[Means for Solving the Problems]
The monostable multivibrator circuit with a re-trigger function according to the present invention includes a charge storage means for storing charges and a side end of the charge storage means at an “L” level during a period when a trigger signal is applied to an input terminal. And holding the one side end of the charge accumulating means at “H” level during the one-shot pulse output after the trigger signal is released, and the charge during the period when the trigger signal is applied. A charging unit that charges the charge storage unit so that the other side end of the storage unit is at “H” level; and the other side end of the charge storage unit during the one-shot pulse output after the trigger signal is released A discharge means for discharging the charge stored in the charge storage means by connecting to a potential in a closed circuit, and starting output of a one-shot pulse by controlling the potential of the potential control means At this time, the potential at one end of the charge storage means is changed from “L” level to “H” level to increase the discharge start voltage of the charge storage means, and the voltage change at the other end of the charge storage means It is characterized by a large gradient.
[0008]
Another feature of the present invention is that it operates by receiving the voltage at the other end of the charge storage means, and the magnitude relationship between the voltage at the other end of the charge storage means and a predetermined threshold voltage. Further, waveform shaping means for changing the output logic level based on the above is further provided.
[0009]
Another feature of the present invention is that a first inverter that inverts and outputs a signal applied to an input terminal, and a signal output from the first inverter is supplied to one input terminal. In addition, a NOR circuit to which the potential of the output terminal is supplied to the other input terminal and a signal output from the first inverter are applied to the control electrode, and the output electrode is the second resistor, the first resistor A third transistor connected to the output terminal of the NOR circuit through a series circuit including a resistor and a capacitor, and a signal output from the first inverter are applied to the control electrode, and the output electrode is connected to the first electrode. A second transistor connected to a connection point between the first resistor and the second resistor, and an input terminal connected to the connection point between the first resistor and the second resistor; Applied to the input terminal It is characterized by comprising issue of a second inverter for deriving the output terminal by inverting the potential.
[0010]
Another feature of the present invention is that a first inverter that inverts and outputs a signal applied to an input terminal, and a signal output from the first inverter is supplied to one input terminal. In addition, a NOR circuit to which a voltage derived from the output terminal is applied to the other input terminal, a signal output from the first inverter is applied to the control electrode, and the output electrode is a second resistor. A third transistor connected to the NOR circuit through a series circuit composed of a first resistor and a capacitor, a signal output from the first inverter is applied to the control electrode, and an output electrode is connected to the first electrode. A second transistor connected to a connection point between the first resistor and the second resistor, a signal output from the first inverter is applied to the control electrode, and an output electrode is connected to the first resistor. Vessel The input terminal is connected to the connection point of the second transistor connected to the connection point of the capacitor and the first resistor and the second resistor, and the signal applied to the input terminal And a second inverter that inverts the potential and outputs the inverted signal to the output terminal.
[0011]
[Action]
Since the present invention has the technical means, when the output of the one-shot pulse is started, the potential control means changes the potential at one side end of the charge storage means from the “L” level to the “H” level. Since the discharge start voltage of the charge storage means is increased, the voltage change gradient of the charge storage means is increased, and the pulse end timing can be easily determined.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a monostable multivibrator circuit with a re-trigger function according to the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram showing a functional configuration of a monostable multivibrator circuit with a re-trigger function according to the present embodiment. As shown in FIG. 1, the monostable multivibrator circuit with a retrigger function according to the present embodiment includes a charge storage unit 1, a charging unit 2, a discharging unit 3, a potential control unit 4, and a waveform shaping unit 5. The potential of the output terminal OUT is inverted according to a trigger signal applied to the input terminal TIN.
[0014]
That is, when the trigger signal is not applied to the input terminal TIN, the potential control unit 4 holds the one end 1a of the charge storage unit 1 at the “L” level potential. At this time, the charge accumulating means 1 is charged from the other end 1b by the charging means 2, and the potential at the other end 1b is increased by a predetermined potential from the one end 1a by a predetermined potential.
[0015]
When a trigger signal is applied to the input terminal TIN, the potential of the one end 1a of the charge storage unit 1 is inverted to “H” level by the control of the potential control unit 4 and the operation of the charging unit 2 is stopped. To do. At the same time, the operation of the discharge means 3 is started, and the electric charge accumulated at the one end 1a is discharged to the reference potential, in this case, the ground GND.
[0016]
As a result, the discharge start voltage of the charge accumulated in the charge accumulating means 1 is increased, and the gradient of the potential change of the charge accumulating means 1 due to the discharge is increased. For this reason, the terminal voltage of the charge accumulating unit 1 rapidly approaches and departs from the threshold voltage for the waveform shaping unit 5 to start the waveform shaping operation. Therefore, the timing at which the waveform shaping unit 5 operates and inverts the output. The variation becomes as small as possible, and a good operation with little jitter can be performed. When the waveform shaping means 5 inverts the output, the potential control means 4 inverts one side end 1a of the charge storage means 1 to "L" level.
[0017]
Further, since the period of the potential close to the threshold voltage of the waveform shaping means 5 is short, when the waveform shaping means 5 is constituted by a CMOS inverter, both the PMOS transistor and the NMOS transistor are turned on and a through current flows. Since the period can be reduced, current consumption can be reduced.
[0018]
FIG. 2 is a circuit diagram showing a specific configuration of a monostable multivibrator circuit with a retrigger function according to the present invention.
In FIG. 2, TIN is a trigger input terminal, and is configured to be triggered / retriggered at “L” level of a signal applied to the input terminal TIN. OUT is an output terminal.
[0019]
Further, INV1 is an input inverter circuit, and NOR is a NOR circuit, and holds one end C ₁ of the capacitor C at the “L” level during a period when the trigger signal is applied to the input terminal TIN. Further, during the period when the trigger signal is applied to the input terminal TIN and the one-shot pulse is output, the potential control means is configured to hold the one end C ₁ of the capacitor C at the “H” level.
[0020]
The first transistor Q1, Q2 is the second transistor, the other end C ₂ "H" level of the capacitor C during the trigger signal is applied (power supply voltage Vdd- threshold voltage V _TH ) To operate as a charging means.
[0021]
R1 is the first resistor, a second resistor R2, Q3 is the third transistor, these series circuits is connected between the other end C ₂ and the ground GND of the capacitor C, charging the capacitor C Discharging means for discharging the generated charges is configured.
[0022]
INV2 is an output inverter, and is composed of, for example, a CMOS transistor. The output inverter INV2 well as to an output terminal OUT is inverted by receiving a voltage of the other end C ₂ of capacitor C, it is intended to derive the other side terminal of a NOR circuit NOR. In the present embodiment by reducing the value of the first resistor R1, so that can be output without significantly lowering the voltage of the other end C ₂ of the capacitor C.
[0023]
The NOR circuit NOR is provided as a potential control means for holding the potential of the one end C ₁ of the capacitor C at the “L” level when the potential at the output end of the output inverter INV2 becomes the “H” level.
[0024]
The first resistor R1 and the second transistor Q2 constitute means for maintaining the input of the output inverter INV2 at the “H” level when a trigger voltage is applied to the input terminal TIN.
[0025]
FIG. 3 shows operation waveforms of each part of the monostable multivibrator circuit with a re-trigger function of the present embodiment configured as described above.
As shown in FIG. 3, when a trigger signal is input to the first transistor Q1, the other end C _{2 of the} capacitor C is raised to the “H” level.
[0026]
In addition, when a re-trigger is applied while outputting a pulse signal, the output of the NOR circuit NOR may become “L” level, so that the drive capability of the first transistor Q1 and the NOR circuit NOR is improved. I will collide.
[0027]
This collision is not a big problem because it is canceled when the charging of the capacitor C proceeds rapidly, but the input of the output inverter INV2 must be kept at the “H” level even during that time. For this reason, it is not necessary if the first transistor Q1 is sufficiently strong, but the total area can be reduced by providing the second transistor Q2 and the second resistor R2 as in the present embodiment. .
[0028]
Since the monostable multivibrator circuit with a retrigger function of this embodiment operates as described above, the potential during pulse output is held at a potential sufficiently higher than the threshold of the output inverter INV2. As a result, it is possible to prevent both the PMOS transistor and the NMOS transistor of the CMOS inverter constituting the output inverter INV2 from being turned on at the same time, thereby preventing a through current from flowing, thereby reducing current consumption.
[0029]
Furthermore, after the end of the pulse, the output inverter INV2, the NOR circuit NOR, and the positive feedback loop effected by the capacitor C immediately change the potential to a range where no through current flows through the output inverter INV2. Also, current consumption can be reduced.
[0030]
Further, according to the present embodiment, since the change per unit time of the voltage approaching the threshold voltage of the output inverter can be increased, the deviation (jitter) of the pulse end time due to noise can be reduced.
[0031]
As a specific circuit example, FIG. 2 shows an example using a MOS transistor, but a bipolar transistor may be used as the transistor. In addition, the circuit shown in FIG. 2 can be replaced with an equivalent circuit such as using a negative logical product (AND) circuit instead of the logical negative circuit NOR.
[0032]
【The invention's effect】
As described above, according to the present invention, when the output of the one-shot pulse is started, the potential at one side end of the charge storage means is changed from the “L” level to the “H” level by the potential control means. Since the discharge start voltage of the charge storage means is increased, the voltage change gradient of the discharge character of the charge storage means can be increased and the pulse end timing can be determined with high accuracy. .
[0033]
As a result, the time variation of the pulse width, that is, the jitter can be greatly reduced. In addition, since the change gradient of the discharge voltage can be increased, when a CMOS inverter is used as an output circuit, both the PMOS transistor and NMOS transistor constituting the CMOS inverter are simultaneously turned on to prevent a through current from flowing. Thus, current consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration for each function of a monostable multivibrator circuit with a retrigger function according to the present invention.
FIG. 2 is a circuit diagram illustrating an example of a monostable multivibrator circuit with a re-trigger function according to an embodiment of the present invention.
3 is a waveform diagram for explaining the operation of each part of the circuit of FIG. 2;
FIG. 4 is a circuit diagram showing a conventional technique.
5 is a waveform diagram for explaining the operation of each part of the circuit of FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Charge storage means 1a One end 1b The other end 2 Charging means 3 Discharge means 4 Potential control means 5 Waveform shaping means

Claims (4)

Charge storage means for storing charge;
While the trigger signal is applied to the input terminal, one side end of the charge storage unit is held at the “L” level, and one side of the charge storage unit is output during the one-shot pulse output after the trigger signal is released. A potential control means for holding the end at the “H” level;
Charging means for charging the charge storage means so that the other end of the charge storage means is at the “H” level during the period in which the trigger signal is applied;
Discharge means for discharging the charge stored in the charge storage means by connecting the other end of the charge storage means and a reference potential to a closed circuit while the trigger signal is released and the one-shot pulse is being output. And
Due to the potential control of the potential control means, when one-shot pulse output is started, the potential at one side of the charge storage means is changed from "L" level to "H" level to start discharging of the charge storage means A monostable multivibrator circuit with a re-trigger function, wherein the voltage is increased to increase the gradient of voltage change at the other end of the charge storage means. Waveform shaping means that operates in response to the voltage at the other end of the charge storage means and changes the output logic level based on the magnitude relationship between the voltage at the other end of the charge storage means and a predetermined threshold voltage. The monostable multivibrator circuit with a retrigger function according to claim 1, further comprising: A first inverter that inverts and outputs a signal applied to the input terminal;
A NOR circuit in which a signal output from the first inverter is supplied to one input terminal, and a potential of an output terminal is supplied to the other input terminal;
A signal output from the first inverter is applied to the control electrode, and the output electrode is connected to the output terminal of the NOR circuit through a series circuit including a second resistor, a first resistor, and a capacitor. A third transistor,
A second transistor in which a signal output from the first inverter is applied to a control electrode, and an output electrode is connected to a connection point between the first resistor and the second resistor;
A second inverter having an input terminal connected to a connection point between the first resistor and the second resistor, and inverting the potential of a signal applied to the input terminal to derive the output terminal; A monostable multivibrator circuit with a re-trigger function. A first inverter that inverts and outputs a signal applied to the input terminal;
A NOR circuit in which a signal output from the first inverter is supplied to one input terminal, and a voltage derived from an output terminal is applied to the other input terminal;
A signal output from the first inverter is applied to the control electrode, and the output electrode is connected to the NOR circuit through a series circuit including a second resistor, a first resistor, and a capacitor. Transistors
A second transistor in which a signal output from the first inverter is applied to a control electrode, and an output electrode is connected to a connection point between the first resistor and the second resistor;
A second transistor in which a signal output from the first inverter is applied to a control electrode, and the output electrode is connected to a connection point between the first resistor and the capacitor;
An input terminal is connected to a connection point between the first resistor and the second resistor, and a second inverter for inverting the potential of a signal applied to the input terminal and leading to the output terminal A monostable multivibrator circuit with a re-trigger function.

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