JPH048668Y2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Technical Field The present invention relates to an oscillator, and particularly to an RC oscillation circuit that can operate with low voltage and power requirements and does not require two reference voltage sources.

(b) Prior Art and its Problems In designing digital logic circuits, large scale integration techniques result in structures consisting of numerous components fabricated on a single silicon chip. Circuits such as those utilizing metal-oxide-semiconductor (MOS) technology utilize a number of clock signals to provide a time reference for constant access memory devices as well as other semiconductor circuitry. Such a clock signal is generated by an oscillator circuit. Oscillator circuits are used in telecommunication integrated circuits, such as memory dials, where low power and low voltage operation is essential.

A previously developed oscillator is shown in US Pat. Such previously developed oscillators do not exhibit operating characteristics at sufficiently low voltage and low power requirements. Moreover, such conventionally developed oscillators are temperature sensitive and are not completely independent of environmental temperature.

Thus, there is a need for RC oscillators for use in semiconductor circuits that operate with low voltage and low power requirements.
Additionally, an RC oscillator is required that is relatively insensitive to temperature and supply voltage parameters. A single, more reliable and cost-effective
There is a need for an RC oscillator that can be fabricated on a CMOS semiconductor chip.

Furthermore, the conventional RC oscillator described above requires two different reference voltage sources for the voltage comparison circuit. That is, if the voltage of the capacitor drops due to discharge through the transistor while the voltage comparator circuit is supplying a high level output voltage, the output voltage of the comparator circuit is switched to the low level after the discharge ends. In order to achieve this, another type of reference voltage source was required to be input to the comparator circuit. Providing such two types of reference voltage sources is undesirable because it increases the required circuit area and the required current and voltage.

(c) Solving the problems by the present invention The present invention provides an oscillation circuit having first and second voltage supply sources, (a) comprising first and second input terminals and an output terminal; (b) a differential amplifier coupled to a first input terminal of the differential amplifier and a second voltage source, the differential amplifier operating in an active mode and a second voltage source; a capacitor to be charged; (c) first switching means connected between the output terminal of the differential amplifier and the first voltage source; and (d) a second input terminal of the differential amplifier. and a second resistor connected between the second input terminal of the differential amplifier and the second voltage supply source, the differential amplifier being inactive. (e) first and second resistors adapted to apply a reference voltage to a second input terminal of the differential amplifier during a portion of the mode; and (e) connected to an output terminal of the differential amplifier to delay the output signal thereof. (f) discharging means coupled to the delay means and the capacitor and activated by an output signal that occurs when the differential amplifier is in its active mode, discharging the capacitor and discharging the differential amplifier into its non-active mode; (g) said first switch means being activated by an output signal produced by the differential amplifier during its inactive mode to control the generation of the reference voltage; (h) the delay means is arranged to include an inverter coupled to the output terminal of the differential amplifier, an input coupled to the inverter and an input coupled to the control signal output; The above-mentioned problem is solved by providing the oscillation circuit configured such that the discharge of the capacitor by the second switch means can be completely discharged by a NOR logic means having a terminal. It was very successful.

(d) Effect of the present invention According to the present invention, a voltage comparison circuit is provided which has first and second input terminals and an output terminal. This voltage comparator circuit produces an output signal at an output terminal.
The RC oscillator circuit further includes a capacitor coupled to the first input terminal of the voltage comparator circuit. A voltage generator is coupled to a second input terminal of the voltage comparison circuit and provides a reference voltage for application to the voltage comparison circuit.
The delay circuit is coupled to the output terminal of the voltage comparator circuit and delays the output signal so that the capacitor is fully discharged by the discharge device and the time constant of the RC oscillation circuit is constant. This discharge device is responsive to an output signal produced by a voltage comparator circuit. The RC oscillator circuit further includes a switch device coupled to the output terminal of the voltage comparator circuit and the voltage oscillator. The switch device is responsive to the output signal of the voltage comparator circuit and controls the operation of a voltage generator to remove the reference voltage from the second input terminal of the voltage comparator circuit when the switch device is activated.

Therefore, the present invention has the advantage that the voltage and power required for operation are low and it is less sensitive to parameter changes in temperature and power supply voltage.
An RC oscillator made on a CMOS semiconductor substrate can be obtained.

Furthermore, the RC oscillator of the present invention has two types of operating states. One is an active mode in which the comparator circuit gives a signal corresponding to the sign of the voltage difference between its two inputs; It is an inactive mode that provides a sign independent signal, such as a low voltage signal. Active mode is e.g. when at least one of the two inputs is at a higher voltage than some minimum voltage (e.g. the threshold voltage of a MOS transistor in the circuit), and inactive mode is e.g. when both of the two inputs are This corresponds when the voltage is lower than the minimum voltage.

In the present invention, the comparison circuit output is switched to a low level output voltage by this change from active mode to inactive mode. Therefore, two types of reference voltage sources are not required.

(E) Embodiment FIG. 1 illustrates a resistor-capacitor (RC) oscillation circuit 10 according to the present invention. The RC oscillation circuit 10 includes a voltage comparison circuit 12 having a non-polarity inverting input terminal 14 and a polarity inverting input terminal 16. Voltage comparator circuit 12 comprises, for example, a differential amplifier circuit, which will be further described below with reference to FIG.
Voltage comparator circuit 12 operates in active mode and inactive mode. In active mode, the output voltage of voltage comparison circuit 12 depends on the input voltage applied to each input terminal 14,16. In non-active mode, voltage comparator circuit 1
The output voltage of No. 2 is in a known state independent of the input voltage applied to each input terminal 14, 16. RC of this example
In the oscillation circuit 10, this known state is defined as low logic.

The period of vibration of the RC oscillation circuit 10 is controlled by component values selected for the capacitor 20 and resistor 22. Capacitor 20 and resistor 22 are interconnected to form connection point 24 . Connection point 24
is the signal line 2 connected to the input terminal 14 of the voltage comparator circuit 12.
It is connected via 6. Capacitor 20 is connected to a negative voltage supply. Resistor 22 is connected to a positive voltage supply. A capacitor 20 and a resistor 22 are an RC oscillation circuit 10 made on a single MOS board.
It is built outside the. The resistor-capacitor oscillation circuit 10 uses only one resistor to set the period of oscillation, unlike previously developed RC oscillation circuits that require two resistors.

The reference voltage applied to voltage comparator circuit 12 is provided by resistor voltage divider network 30 comprising resistor 32 and resistor 34 . Each resistor 32, 34 is interconnected to form a connection point 36. The reference voltage is applied from connection point 36 to input terminal 16 of voltage comparison circuit 12 via signal line 38 . Voltage comparison circuit 1
The application of the reference voltage to the input terminal 16 of No. 2 is controlled by, for example, a transistor constituting a P-channel MOS device. Transistor 40 is connected to the positive voltage supply and to resistor 32 of resistor divider network 30. The gate terminal of the transistor 40 is connected to the output terminal of the voltage comparison circuit 12 at a connection point 42 via a signal line 44. transistor 40
is rendered conductive by the output of voltage comparator circuit 12 operating in an inactive mode, and is reset to a reference voltage before beginning to charge capacitor 20 at the beginning of each cycle, as described below.
The voltage is applied to the input terminal 16 of No. 2.

The output of voltage comparison circuit 12 is applied to inverter 50. The output of inverter 50 is applied to NOR logic circuit 52. NOR logic circuit 52 receives an oscillator control input signal. The output terminal of NOR logic circuit 52 produces the oscillator output signal of RC oscillator circuit 10. The output of NOR logic circuit 52 is also applied to transistor 54 via signal line 56. Transistor 54 comprises, for example, an N-channel MOS device. Transistor 54 is connected to the negative voltage supply and to node 24 via signal line 58. Inverter 50 and NOR logic circuit 5
2 functions as a delay circuit and delays application of the output of the voltage comparison circuit 12 to the transistor 54. Transistor 54 is rendered conductive by the output of NOR logic circuit 52 and acts to discharge node 24.

Next, regarding Figures 1 and 2, according to the present invention
The operation of the RC oscillation circuit 10 will be described. FIG. 2 shows the voltage waveforms present at node 24 (FIG. 2a), node 42 (FIG. 2b) and node 36 (FIG. 2c). Assuming that the RC oscillation circuit 10 is in its initial state and the capacitor 20 is not charged, the connection point 24 is at zero volts, the connection point 42 is at a low voltage, and the connection point 36 has a voltage equal to the reference voltage. .
Due to the action of resistor 22, capacitor 20 begins to supply node 24 towards the value of the reference voltage. When node 24 is powered to a value slightly above the reference voltage value, the input to voltage comparator circuit 12 is such that voltage comparator circuit 12 operating in the active mode produces an output 60 at node 42. Output 60 turns transistor 40 into a non-conducting state, removing the reference voltage from input terminal 16 of voltage comparison circuit 12, and voltage 62 (FIG. 2c) at node 36 becomes zero.

The output of voltage comparator circuit 12 in the active mode causes NOR logic circuit 52 to produce its output causing transistor 54 to conduct and discharge node 24. Node 24 operates voltage comparator circuit 12 in an inactive mode by discharging to an N-channel threshold 63, which in this case is about 1 above V-. In this case, the output of the voltage comparison circuit 12 is a low value 64 (second b
Figure). This low output is applied to the previously non-conducting transistor 40 by the output of the voltage comparator circuit 12 in active mode, thereby causing the transistor 40 to become conductive and applying the reference voltage 68 (FIG. 2c) to the voltage comparator circuit 12. Apply again to start a new cycle.

The delay between the time at which node 42 goes to a low logic value and the time at which the output of NOR logic circuit 52 goes to a low value causes transistor 54 to completely discharge node 24 to a zero value 66 (FIG. 2a). create a sufficient time limit for By completely discharging the capacitor 20, the time constant of the RC oscillation circuit 10 remains constant, making the RC oscillation circuit 10 less sensitive to changes in the power supply voltage.

Prior to complete discharge of node 24, transistor 40 becomes conductive due to the low output of voltage comparator circuit 12 operating in an inactive mode, causing node 3 to become conductive.
6 is again at the voltage reference level 68 (FIG. 2c). Since the output of voltage comparator circuit 12 is low in this case, the output of NOR logic circuit 52 is low and transistor 54 is non-conducting so that node 24 can be powered. The cycle repeats in this manner, with node 24 powered to a value slightly higher than the value of the reference voltage, allowing voltage comparator circuit 12 to send an output to node 42.

In one embodiment of the RC oscillator circuit 10 according to the present invention, which produces an 8kHz clock signal at the oscillator output terminal, the values of capacitor 20 and resistor 22 are set at connection point 2.
4 is selected so that the time period for supplying power to the reference voltage level is approximately 125 μsec. The pulse width of the output of the voltage comparison circuit 12 is, for example, about 1 to 5 μsec, making the RC oscillator circuit 10 of the present invention insensitive to temperature, power supply voltage fluctuations, and process parameters.

Therefore, it is clear that the RC oscillation circuit of the present invention operates with low voltage and power requirements. The accuracy of the period of vibration is primarily controlled by the values of capacitor 20 and resistor 22. With this selection, RC
The degree to which the oscillation circuit 10 depends on temperature is determined.

FIG. 3 shows a circuit corresponding to voltage comparison circuit 12 (FIG. 1). Input terminal 14 of voltage comparison circuit 12
consists of the gate electrode of transistor 80. Input terminal 16 of voltage comparison circuit 12 comprises the gate terminal of transistor 82. The source terminal of each transistor 80, 82 is connected to a current source 84. The drain terminal of each transistor 80, 82 is connected to a transistor 86 which functions as a gain device. The gate terminal of transistor 86 is connected to the gate terminal of transistor 88, which functions as a second gain device.

The source terminal of transistor 88 is connected to a current source 90 that acts as a load to transistor 88.
It is connected to. The output terminal or node 42 of voltage comparison circuit 12 is formed between transistor 88 and current source 90. Each transistor 86, 88
is supplied with positive voltage. Current sources 84 and 90 are supplied with negative voltage. Each transistor 80, 82
consists of, for example, an N-channel MOS device. Each transistor 86, 88 comprises, for example, a P-channel MOS device. Therefore, it is clear that the voltage comparison circuit 12 constitutes the differential comparator illustrated in FIG.

(f) Effects of the present invention As is clear from the above explanation, the RC oscillation circuit of the present invention can reduce power consumption and operate at low voltage.
Furthermore, the RC oscillation circuit of the present invention operates substantially independently of temperature conditions. The accuracy of the period of oscillation is substantially controlled by the accuracy of the values of capacitors and resistors external to the oscillator circuit, making the processing of the circuit of the invention less sensitive to temperature conditions. Furthermore, the RC oscillation circuit of the present invention does not require two types of reference voltage sources.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the RC oscillation circuit of the present invention. FIG. 2 is a signal waveform diagram showing the operation of the circuit of FIG. 1. FIG. 3 is a circuit diagram illustrating details of the voltage comparison circuit in FIG. 1. 10...Oscillation circuit, 12...Differential amplifier, 20
... capacitor, 40 ... first switching means,
54...second switch means, 32...first resistor, 34...second resistor, 50...inverter, 52...NOR logic means.

Claims (1)

[Claims for Utility Model Registration] (1) An oscillator circuit having first and second voltage supply sources, (a) comprising first and second input terminals and an output terminal, and outputting an output to the output terminal; a differential amplifier that generates a signal and operates in an active mode and a non-active mode; (b) coupled to a first input terminal of the differential amplifier and a second voltage source, the differential amplifier being charged during the non-active mode; (c) first switching means connected between the output terminal of the differential amplifier and the first voltage supply source; and (d) between the first switching means and the second input terminal of the differential amplifier. a first resistor connected to the differential amplifier; and a second resistor connected between the second input terminal of the differential amplifier and the second voltage supply source;
(e) first and second resistors connected to the output terminal of the differential amplifier for applying a reference voltage to a second input terminal of the differential amplifier during a portion of the inactive mode of the differential amplifier; delay means for delaying the output signal; (f) discharging means coupled to the delay means and the capacitor and activated by the output signal produced by the differential amplifier during its active mode for discharging the capacitor; (g) activating said first switch means by an output signal produced by the differential amplifier during its non-active mode to operate the differential amplifier in its non-active mode; and (h) connecting said delay means to an inverter coupled to an output terminal of the differential amplifier, an input terminal coupled to said inverter, and a control circuit for controlling the generation of said reference voltage so that said reference voltage occurs after completion of discharging of said capacitor; NOR logic means having an input terminal coupled to a signal output, the oscillator circuit being configured such that the discharge of the capacitor by the second switch means can be a complete discharge. (2) a differential amplifier having first, second, third and fourth terminals each having a first and second terminal and a control terminal;
a transistor and first and second current sources, a first terminal of the first transistor is connected to a first terminal of the second transistor and a first terminal of the third transistor, and a second current source of the first transistor is connected to a first terminal of the second transistor and a first terminal of the third transistor. The terminal is connected to the second terminal of the fourth transistor and the first current source, the control terminal of the first transistor is configured by the second input terminal of the differential amplifier, and the second terminal of the second transistor is connected to the second terminal of the fourth transistor. the first terminal is connected to the control terminal of the second transistor and the control terminal of the third transistor, the second terminal of the third transistor is constituted by the output terminal of the differential amplifier and connected to the second current source; The oscillation circuit according to item (1) above, wherein the control terminal of the transistor is configured by the first input terminal of a differential amplifier. (3) the second switching means is constituted by a transistor having first and second terminals and a control terminal;
The oscillation circuit according to the preceding item (1), wherein the control terminal is connected to the delay means, the first terminal is connected to the capacitor, and the second terminal is connected to the second voltage supply source. (4) the first switch means is constituted by a transistor having first and second terminals and a control terminal;
The control terminal is connected to the output terminal of the differential amplifier, the first terminal is connected to the first voltage supply source, and the second terminal is connected to the first resistor.
The oscillation circuit described in . (5) The oscillation circuit according to the preceding paragraph (1), comprising a capacitor and a third resistor connected to the first voltage supply source.