CN111404484B

CN111404484B - RC oscillator and electric device

Info

Publication number: CN111404484B
Application number: CN202010337600.2A
Authority: CN
Inventors: 周号
Original assignee: Zhuhai Maiju Microelectronics Co Ltd
Current assignee: Zhuhai Maiju Microelectronics Co Ltd
Priority date: 2020-04-26
Filing date: 2020-04-26
Publication date: 2020-12-08
Anticipated expiration: 2040-04-26
Also published as: CN111404484A

Abstract

The present disclosure provides an RC oscillator including an oscillation circuit, the oscillation circuit including a system resistance and a system capacitance, and the oscillation circuit generating and outputting an oscillation voltage according to at least the system resistance and the system capacitance; and a temperature control circuit for detecting a temperature of the RC oscillator and changing a resistance value of the system resistance and/or a capacitance value of the system capacitance according to the detected temperature so that an oscillation frequency of an oscillation voltage output by the RC oscillator is fixed. The present disclosure also provides an electrical device.

Description

RC oscillator and electric device

Technical Field

The present disclosure relates to an RC oscillator and an electrical device, and more particularly, to an RC oscillator with a fixed output frequency.

Background

In the oscillator circuit, since the oscillation frequency of the oscillator circuit varies with temperature, it is necessary to adjust the oscillation frequency so as not to be affected by temperature in a high-precision oscillator. The oscillation circuit is required to output an oscillation signal having a stable oscillation frequency regardless of temperature.

In a typical capacitive charge-discharge oscillator scheme as shown in FIG. 1, the up-down current I is used_S1And I_S2Charging and discharging capacitor C, comparing with VH and VL (VH and VL can be triangular wave high and low level), and oscillating period T ═ C (VH-VL)/I_S1+C*(VH-VL)/I_S2+2*T_DELAY(wherein T is_DELAYResponse time for comparator Comp), T_DELAYIt is possible to design a period much smaller than the target period, T ═ C (VH-VL)/I_S1+C*(VH-VL)/I_S2. But the temperature characteristic of the oscillator cycle is determined by the current I_S1And I_S2The difficulty and cost for designing a low-temperature coefficient current source are high, so that the scheme is only suitable for frequency and temperatureAnd (3) applications with low characteristic requirements.

Disclosure of Invention

In the present disclosure, in order to solve at least one of the above technical problems, an RC oscillator and an electric device are provided.

According to one aspect of the disclosure, an RC oscillator includes

An oscillation circuit that includes a system resistance and a system capacitance, and that generates and outputs an oscillation voltage in accordance with at least the system resistance and the system capacitance; and

a temperature control circuit for detecting a temperature of the RC oscillator and changing a resistance value of the system resistance and/or a capacitance value of the system capacitance according to the detected temperature so that an oscillation frequency of an oscillation voltage output by the RC oscillator is fixed.

According to at least one embodiment of the present disclosure, when the temperature control circuit detects the temperature of the RC oscillator, the temperature of the RC oscillator is detected by a base-emitter voltage of a transistor, or a PN junction voltage of a diode, or a PTAT voltage generated by a PTAT voltage generation circuit, or a thermistor.

According to at least one embodiment of the present disclosure, the power supply further includes a current source including one current source or two current sources, when the current source includes one current source, the one current source generates a first current provided to the system resistor and a second current provided to the system capacitor, when the current source includes two current sources, the two current sources respectively generate a first current provided to the system resistor and a second current provided to the system capacitor, and the system capacitor is connected in parallel with a discharge switch, by which charging and discharging of the system capacitor is controlled to generate a capacitor voltage, the oscillating voltage is generated based on a comparison of a resistor voltage generated by the system resistor and a capacitor voltage generated by the system capacitor.

According to at least one embodiment of the present disclosure, the temperature control circuit changes one or more of a resistance value of the system resistance, a capacitance value of the system capacitance, a current value of the first current, and a current value of the second current according to the detected temperature so that an oscillation frequency of an oscillation voltage output by the RC oscillator is fixed.

According to at least one embodiment of the present disclosure, the oscillator further includes a comparator into which the resistance voltage and the capacitance voltage are input, the comparator comparing the resistance voltage and the capacitance voltage and outputting a comparison voltage, and generating the oscillation voltage based on the comparison voltage.

According to at least one embodiment of the present disclosure, the comparator includes an offset voltage storage capacitor, the offset voltage storage capacitor is connected in series to an input end of a resistance voltage of the comparator, when the oscillation voltage is at a high level, the offset voltage storage capacitor is controlled to be charged by an output voltage of the comparator, and when the oscillation voltage is at a low level, the offset voltage storage capacitor is controlled to be discharged to offset an offset voltage of the comparator, so that an influence of the offset voltage on the oscillation frequency is eliminated.

According to at least one embodiment of the present disclosure, the comparator includes a first switch and a second switch, the offset voltage storage capacitor is charged by an output voltage of the comparator when the first switch is turned on and the second switch is turned off, and the resistance voltage and the capacitance voltage are input to the comparator when the first switch is turned off and the second switch is turned on.

According to at least one embodiment of the present disclosure, the apparatus further comprises a reset controller which controls on and off of the discharge switch by a discharge switch control signal, wherein when the oscillation voltage is at a high level, the discharge switch control signal is at a high level, the switch is controlled to be on to discharge the system capacitor, when the oscillation voltage is at a low level, the discharge switch control signal is at a low level, the switch is controlled to be off to charge the system capacitor,

the reset controller comprises an inverter circuit, and the high level duration time of the discharge switch control signal is only determined by the inverter circuit.

According to at least one embodiment of the present disclosure, the inverter circuit includes an inverter, an inverter resistor, and an inverter capacitor, the inverter resistor is connected in series to an output end or an input end of the inverter, one end of the inverter capacitor is connected to the inverter resistor, and the other end is grounded, the inverter resistor and the system resistor have the same temperature coefficient, when the resistance value of the system resistor is changed by the temperature control circuit, the resistance value of the inverter resistor is also changed accordingly, and/or the inverter capacitor and the system capacitor have the same temperature coefficient, when the capacitance value of the system capacitor is changed by the temperature control circuit, the capacitance value of the inverter capacitor is also changed accordingly.

According to another aspect of the present disclosure, an RC oscillator includes: a system resistor, a system capacitor, a current source, a comparator, a reset controller and a discharge switch,

the current source is one current source or two current sources of the same type and respectively supplies current to the system resistor and the system capacitor,

the discharge switch is connected in parallel to both sides of the system capacitor, and the reset controller controls on and off of the discharge switch to discharge and charge the system capacitor, thereby generating a capacitor voltage,

a resistance voltage generated by the system resistance and a capacitance voltage generated by the system capacitance are input into the comparator, the comparator generates a comparison voltage according to a comparison of the resistance voltage and the capacitance voltage, and the RC oscillator generates an oscillation voltage according to the comparison voltage,

wherein the system resistance is a low temperature coefficient resistance to implement a low temperature coefficient RC oscillator.

According to at least one embodiment of the present disclosure, the reset controller controls the discharge switch to be turned on and off by a discharge switch control signal, wherein the discharge switch control signal is at a high level when the oscillation voltage is at a high level, the switch is controlled to be turned on to discharge the system capacitor, and the discharge switch control signal is at a low level when the oscillation voltage is at a low level, the switch is controlled to be turned off to charge the system capacitor,

According to yet another aspect of the disclosure, an electrical device comprises an RC oscillator as described above.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.

Fig. 1 shows a schematic diagram of a conventional capacitor charge-discharge oscillator.

Fig. 2 shows a schematic diagram of an oscillator with temperature calibration functionality according to one embodiment of the present disclosure.

Fig. 3 shows an example of an oscillation circuit according to an embodiment of the present disclosure.

Fig. 4 illustrates a waveform diagram of an oscillation circuit according to one embodiment of the present disclosure.

Fig. 5 shows a clock signal generation schematic according to an embodiment of the present disclosure.

Fig. 6 shows a temperature coefficient diagram of resistance of a semiconductor process.

Fig. 7 shows another form of RC oscillator circuit.

Fig. 8 shows another form of RC oscillation circuit.

Fig. 9 shows a schematic diagram of an oscillator with temperature calibration functionality according to one embodiment of the present disclosure.

Fig. 10 shows three examples of temperature detection units according to an embodiment of the present disclosure.

Fig. 11 illustrates two examples showing PTAT voltage generation circuits according to embodiments of the present disclosure.

Fig. 12 illustrates a manner of adjusting the resistance according to an embodiment of the present disclosure.

Fig. 13 illustrates a manner of adjusting capacitance according to an embodiment of the present disclosure.

Fig. 14 shows a first embodiment of a current source of a current varying manner according to an embodiment of the present disclosure.

Fig. 15 illustrates a second embodiment of a current source for a current varying manner according to an embodiment of the present disclosure.

Fig. 16 shows one example of a circuit diagram of an existing comparator used in an RC oscillator according to an embodiment of the present disclosure.

FIG. 17 illustrates a waveform diagram of a non-overlapping pulse calibration clock according to an embodiment of the disclosure.

FIG. 18 shows a schematic diagram of a zero offset comparator with offset calibration according to an embodiment of the present disclosure.

Fig. 19 shows a circuit diagram of a comparator according to an embodiment of the present disclosure.

FIG. 20 illustrates a non-overlapping clock generation circuit according to the present disclosure.

Fig. 21 shows a waveform diagram of a non-overlapping pulse calibration clock.

Fig. 22 shows a circuit waveform diagram for the embodiment of fig. 3 according to the present disclosure.

Fig. 23 shows a general representation of the delay time of the comparator.

Fig. 24 shows a schematic diagram of a two-stage comparator.

Fig. 25 shows a waveform diagram according to the present disclosure.

Fig. 26 shows a schematic circuit configuration of the inverter.

Fig. 27 shows a circuit configuration schematic of an inverter according to the present disclosure.

Detailed Description

The present disclosure will be described in further detail with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the present disclosure. It should be further noted that, for the convenience of description, only the portions relevant to the present disclosure are shown in the drawings.

It should be noted that the embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict. Technical solutions of the present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Unless otherwise indicated, the illustrated exemplary embodiments/examples are to be understood as providing exemplary features of various details of some ways in which the technical concepts of the present disclosure may be practiced. Accordingly, unless otherwise indicated, features of the various embodiments may be additionally combined, separated, interchanged, and/or rearranged without departing from the technical concept of the present disclosure.

The use of cross-hatching and/or shading in the drawings is generally used to clarify the boundaries between adjacent components. As such, unless otherwise noted, the presence or absence of cross-hatching or shading does not convey or indicate any preference or requirement for a particular material, material property, size, proportion, commonality between the illustrated components and/or any other characteristic, attribute, property, etc., of the components. Further, in the drawings, the size and relative sizes of components may be exaggerated for clarity and/or descriptive purposes. While example embodiments may be practiced differently, the specific process sequence may be performed in a different order than that described. For example, two processes described consecutively may be performed substantially simultaneously or in reverse order to that described. In addition, like reference numerals denote like parts.

When an element is referred to as being "on" or "on," "connected to" or "coupled to" another element, it can be directly on, connected or coupled to the other element or intervening elements may be present. However, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element, there are no intervening elements present. For purposes of this disclosure, the term "connected" may refer to physically, electrically, etc., and may or may not have intermediate components.

For descriptive purposes, the present disclosure may use spatially relative terms such as "below … …," below … …, "" below … …, "" below, "" above … …, "" above, "" … …, "" higher, "and" side (e.g., as in "side wall") to describe one component's relationship to another (other) component as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use, operation, and/or manufacture in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below … …" can encompass both an orientation of "above" and "below". Further, the devices may be otherwise positioned (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, when the terms "comprises" and/or "comprising" and variations thereof are used in this specification, the presence of stated features, integers, steps, operations, elements, components and/or groups thereof are stated but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof. It is also noted that, as used herein, the terms "substantially," "about," and other similar terms are used as approximate terms and not as degree terms, and as such, are used to interpret inherent deviations in measured values, calculated values, and/or provided values that would be recognized by one of ordinary skill in the art.

An RC oscillator comprising:

an oscillation circuit that includes a resistance and a capacitance, and that generates and outputs an oscillation signal in accordance with at least the resistance and the capacitance; and

a temperature control circuit for detecting a temperature of the RC oscillator and changing a resistance value of the resistor and/or a capacitance value of the capacitor according to the detected temperature so that an oscillation frequency of an oscillation signal output by the RC oscillator is fixed.

Fig. 2 shows a schematic diagram of an oscillator 1 with temperature calibration functionality according to an embodiment of the present disclosure.

As shown in fig. 2, the oscillator 1 may include an oscillation circuit 10 and a temperature control circuit 20.

The oscillating circuit 10 may be an RC oscillating circuit, which includes a resistor 11 and a capacitor 12, and the oscillating output frequency of the oscillating circuit 100 may be adjusted through the resistor 11 and the capacitor 12 included in the oscillating circuit 10.

In the oscillating circuit 10, the number of the resistors 11 is not limited to one, and may include more, and the number of the capacitors 12 is not limited to one, and may also be more.

It will be understood by those skilled in the art that although not shown in fig. 1, other elements may also be included in the oscillator circuit 10.

The temperature control circuit 20 is configured to detect the temperature of the oscillator system and adjust the oscillation output frequency of the oscillation circuit 1 according to the detected temperature, thereby enabling the oscillation circuit 10 to output an oscillation output frequency with a fixed frequency even in the case of a temperature change.

In the example shown in fig. 2, the resistance value of the resistor 11 and/or the capacitance value of the capacitor 12 may be adjusted in accordance with the temperature change detected by the temperature control circuit 20 so as to adjust the oscillation output frequency of the oscillation circuit 10 so as to be fixed.

Although in fig. 2, only the resistor 11 and the capacitor 12 are illustrated as being adjusted, when the oscillation circuit 10 includes other adjustable elements, the other elements may be adjusted so that the oscillation output frequency of the oscillation circuit 10 is fixed.

Hereinafter, embodiments of the present disclosure will be described in more detail by specific examples.

An example of an oscillator circuit 10 according to an embodiment of the present disclosure is shown in fig. 3, which is to be noted as merely exemplary and not meant to limit the scope of the present disclosure.

As shown in fig. 3, the oscillation circuit 10 includes a resistor 110, a capacitor 120, a current source 130, a comparator 140, a reset controller 150, a switch 160, and a buffer 170.

The current source 130 converts the current I_s1Is supplied to the resistor 110 to form a reference voltage V₁. The current source 130 converts the current I_s2Is supplied to the capacitor 120, and the capacitor 120 is charged and discharged (the capacitor 120 is discharged when the switch 120 is turned on, and the capacitor 120 is charged when the switch 120 is turned off) by turning on and off the switch 160 connected in parallel with the capacitor 120, according to the current I_s2A waveform voltage V formed by the capacitance of the capacitor 120 and the charging and discharging of the capacitor 120₂E.g. the waveform voltage V₂May be a sawtooth waveform voltage, etc.

The comparator 140 outputs the voltage V to the input₁And V₂Comparing to obtain a comparison voltage V_COMPAnd comparing the voltage V_COMPThe buffer 170 is inputted, and the buffer 170 outputs an oscillating voltage V_CLK。

Further, the reset controller 150 may generate the oscillating voltage V according to the generated oscillating voltage V_CLKTo generate a control voltage V of the switch 160_SW. By the control voltage V_SWTo control the on/off of the switch 160, thereby realizing the charging and discharging of the capacitor 120.

In the present disclosure, the current I is based on the actual situation_s1、I_s2Can come from the same current source or from two different current sources.

In the oscillating circuit shown in fig. 3, the oscillation period T is R C I_s1/I_s2+T_DELAY. R is the resistance of the resistor 110, C is the capacitance of the capacitor 120, T_DELAYIs the delay time of comparator 140 and reset controller 150. Wherein T is_DELAYCan be designed to be much smaller than the target period of the oscillating circuit.

By mixing T_DELAYDesigned to be small enough, the oscillation period T of the oscillating circuit will be R, C, I_s1、I_s2And (4) determining.

This can be achieved by mixing I_s1、I_s2Are set equal, e.g.I can be provided by a current source_s1、I_s2I can also be provided by two current sources of the same type_s1、I_s2. Wherein the current source may be a ptat (proportional To Absolute temperature) current source or other reference current source.

Thus the oscillation period T will be determined by R, C. Since the temperature coefficient of the capacitor is typically an order of magnitude lower than the temperature coefficient of the resistor, the temperature characteristic of the oscillation period T will be determined only by the temperature coefficient of the resistor.

Since the oscillation period of the oscillation circuit is affected by the temperature characteristics of the elements included therein, the oscillation period of the output will vary with the temperature characteristics of the elements included therein, which will cause the oscillation period of the oscillation circuit to become unstable with the temperature of the oscillator system. Therefore, in order to make the oscillation period of the oscillation circuit fixed or substantially fixed, a specific design of the oscillation circuit is required.

For the example of fig. 3, the following is explained with reference to the waveform diagram shown in fig. 4.

Wherein the voltage across the resistor 110, V1 ═ I_s1R, the voltage V2 across the capacitor 120 is I_s2t/C. At time t during the charging phase of capacitor 120_r＝R*C*I_s1/I_s2And time t of the discharging phase of the capacitor 120_f＝T_DELAY. So that the period of oscillation T is T_r+t_f. Accordingly, during the capacitor charging phase, V_COMP、V_CLKAnd V_SWAt a high level, and during a capacitor discharge phase, V_COMP、V_CLKAnd V_SWAt a low level, such that the time t of the high level_H＝R*C*I_s1/I_s2Time t of low level_L＝T_DELAY. Due to T_DELAYMuch less than R C I_s1/I_s2Therefore, the oscillation period T can be considered equal to R C I_s1/I_s2。

Further, in the case where a clock signal of 50% duty ratio is obtained by the example shown in fig. 3, V may be converted by a D flip-flop or the like_CLKConverted to a 50% duty cycle clock signal,for example, as shown in FIG. 5, when the period of the clock signal is T_DCLK＝2*T_VCLK＝2*(I_S1*R*C/I_S2+T_DELAY)＝2*I_S1*R*C/I_S2Wherein T is_DELAYMuch less than R C I_s1/I_s2。

The relationship between the oscillation period and the temperature change will be described in more detail below.

Oscillation period T ═ R ═ C ═ I_s1/I_s2. Oscillation frequency f 1/T I_s2/(R*C*I_s1)。

Resistance value R (T) of resistor 110 at time T (T ═ R (T)₀)+*(T-T₀)＝R(T)＝R(T₀) +. DELTA.T, wherein R (T)₀) Is the resistance value of the resistor 110 at the temperature T0, R (T) is the resistance value of the resistor 110 at the temperature T, is the temperature coefficient of the resistor 110, and can be usually 0.2% -0.3%, T-T₀Is the amount of change in temperature.

Capacitance value C (T) of capacitor 120 at time T (T ═ C (T)₀)+β*(T-T₀)＝C(T₀) + β Δ T, wherein C (T)₀) Is the capacitance of the capacitor 120 at a temperature T0, C (T) is the capacitance of the capacitor 120 at a temperature T, β is the temperature coefficient of the capacitor 120, T-T₀Is the amount of change in temperature. The temperature coefficient of the capacitor is usually 0.001% or less, and therefore is much smaller than that of the resistor, and in practical applications, only the temperature coefficient of the resistor may be considered, or both the temperature coefficients of the resistor and the capacitor may be considered.

Suppose in the example shown in FIG. 3, I is generated by two current sources, respectively_s1、I_s2。

Current I at time T of temperature_s1Current value of_s1(T)＝I_s1(T₀)+η*(T-T₀)＝I_s1(T₀) + η Δ T, wherein I_s1(T₀) Is a current I_s1Current value at temperature T0, I_s1(T) is a current I_s1The current value at the temperature T, eta is the current I_s1Temperature coefficient of current source of (1), T-T₀Is the amount of change in temperature.

Current I at time T of temperature_s2Current value of_s2(T)＝I_s2(T₀)+γ*(T-T₀)＝I_s2(T₀) + γ Δ T, wherein, I_s2(T₀) Is a current I_s2Current value at temperature T0, I_s2(T) is a current I_s2The current value at temperature T, gamma is the current I_s2Temperature coefficient of current source of (1), T-T₀Is the amount of change in temperature.

Therefore, the oscillation frequency at the time T of the temperature of the oscillation circuit:

f(T)＝I_s2(T)/(R(T)*C(T)*I_s1(T))＝[I_s2(T₀)+γ*ΔT]/{[R(T₀)+*ΔT]^*[C(T₀)+β*ΔT]*[I_s1(T₀)+η*ΔT]} formula (1)

It can be known from the above equation (1) that the oscillation frequency is related to the temperature coefficients of the current, the capacitance and the resistance, so that the change of the current, the capacitance and the resistance with the temperature can be accurately predicted by measuring the real-time temperature of the system, and the change of the oscillation frequency can be eliminated by adjusting one, two or all parameters of the current, the capacitance and the resistance, so that the frequency does not change with the temperature. This allows for zero or low temperature coefficient oscillator systems.

Can be combined with I_s1And I_s2It is arranged to mirror the two currents generated by the current sources, i.e. from the same current source, so that the temperature coefficients of the two currents cancel each other out.

Thus, the above formula (1) may be:

f(T)＝I_s2(T₀)/{[R(T₀)+*(T-T₀)]*[C(T₀)+β*(T-T₀)]*I_s1(T₀) } formula (2)

Wherein T-T is₀Denoted as Δ T. Then equation (2) is expressed as (frequency at temperature T):

f(T)＝(I_s2(T₀)/I_s1(T₀))/{[R(T₀)+*ΔT]*[C(T₀)+β*ΔT]}

＝(I_s2(T₀)/I_s1(T₀))/{[R(T₀)*C(T₀)+(β*R(T₀)+*C(T₀))*ΔT+β**(ΔT)2]

≈(I_s2(T₀)/I_s1(T₀))/{[R(T₀)*C(T₀)+(β*R(T₀)+*C(T₀))*ΔT]

≈(I_s2(T₀)/I_s1(T₀))/{[R(T₀)*C(T₀)*[(1+(β*R(T₀)+*C(T₀))*ΔT)/(R(T₀)*C(T₀))]]

at a temperature T₀Frequency of time f (T)₀)＝(I_s2(T₀)/I_s1(T₀))/(R(T₀)*C(T₀))。

Thus, f (T) and f (T) from above₀) It can be seen that when the temperature of the oscillator system changes, the frequency will change with the temperature due to the change of the resistance value of the resistor and the capacitance value of the capacitor.

Therefore, under the premise of knowing the temperature coefficients of the resistor and the capacitor, the real-time temperature of the oscillator system can be detected, the change of the real-time temperature is obtained, then the resistance value and/or the capacitance value are adjusted, and finally the product of the resistance value and the capacitance value is not changed along with the temperature, so that the product of the resistance value and the capacitance value is changed into a constant which is irrelevant to the temperature, and the frequency of oscillation output is not changed along with the temperature change.

In the preferred embodiment of the present disclosure, since the temperature coefficient of the capacitor is usually about 0.001%, and the temperature coefficient of the capacitor is usually 1 to 2 orders of magnitude smaller than the temperature coefficient of the resistor, in practical applications, the frequency of the oscillation output can be made to be unchanged or substantially unchanged with temperature by considering only the influence of the temperature coefficient of the resistor, that is, only the resistance value of the resistor.

For example, as shown in fig. 6, the resistor using the semiconductor process may have a stable positive temperature coefficient or a negative temperature coefficient. The temperature coefficient of the resistor is positive or negative depending on the doping type of the resistor, depending on its particular manufacturing process.

Likewise, the principles of the present disclosure are equally applicable to other forms of RC oscillator circuits.

By way of example only, fig. 7 and 8 provide other forms of RC oscillator circuits.

In fig. 7, R1 ═ R2 ═ R3 ═ R, C1 ═ C2 ═ C3 ═ C, and the oscillation frequency f of the oscillation circuit shown in fig. 7 is 1/(2 × R ═ C × (6)). Thus, the frequency of the oscillating output can be made invariant, or substantially invariant, to temperature variations by controlling the values of the resistors and/or capacitors.

In fig. 8, R1 ═ R2 ═ R, C1 ═ C2 ═ C, and the oscillation frequency f of the oscillation circuit shown in fig. 8 is 1/(2 × pi R × C). Thus, the frequency of the oscillating output can be made invariant, or substantially invariant, to temperature variations by controlling the values of the resistors and/or capacitors.

The principles of the present disclosure are equally applicable to RC oscillation circuits, not enumerated herein.

Specific examples of fixing the oscillation output frequency by a resistance method, a capacitance method, and a current method will be described below.

In the following description, these three ways are explained separately, but as emphasized in the present disclosure, two of the ways, or three of the ways, may also be employed to simultaneously make the oscillating output frequency fixed. When more than one mode is used, the principle is the same as the principle explained below by one mode.

Mode of resistance change

In the first embodiment of the resistance change manner, taking the oscillation circuit shown in fig. 3 as an example, the current I may be set to_s1、I_s2The temperature coefficients of the capacitors are set to be equal, and because the temperature coefficient of the capacitors is 1-2 orders of magnitude smaller than that of the resistors, the influence of the temperature coefficient of the resistors is far greater than that of the capacitors, so that the oscillation period T can be considered to be influenced by the temperature coefficient of the contained resistorsThe resistivity resistance may be a polysilicon resistance doped with various types of impurities.

When the resistor with low temperature coefficient is adopted, the influence of the temperature of the oscillator system on the output oscillation period can be effectively reduced, so that the oscillator system with low temperature coefficient can be realized.

It should be noted that although the above description is made with reference to the example shown in fig. 3, it will be understood by those skilled in the art that the above principle is also applicable to other forms of RC oscillation circuits. For example, if the temperature characteristics of other types of RC oscillation circuits are influenced by the temperature characteristics of other elements in addition to the resistance and capacitance, the influence of the temperature characteristics of other elements can be eliminated by canceling each other, and the like, so that the temperature characteristics are mainly determined by the resistance and capacitance. In this way, even in other types of RC oscillation circuits, a low temperature coefficient oscillator system can be realized using a low temperature coefficient resistor.

In the first embodiment of the resistance system, the oscillator system of low temperature coefficient is realized by using the resistance of low temperature coefficient. However, in view of the manufacturing cost limitations, it is desirable to avoid the use of special semiconductor manufacturing processes, and other preferred embodiments are provided in this disclosure. In the preferred embodiment, the real-time temperature of the oscillator system may be detected by the temperature sensing element, and then the resistance value of the resistor may be adjusted by performing feedback control according to the detected real-time temperature.

In a second embodiment of the resistance method, the resistance value of the resistance is changed according to the detected real-time temperature value. Continuing with the example of the oscillator circuit shown in fig. 3, it is noted that the oscillator circuit shown in fig. 3 is merely an example.

As shown in fig. 9, in this embodiment, the temperature of the oscillator system is detected by the temperature detection unit 210, and the control signal generation unit 220 generates a control signal by which the resistance value of the resistor 110 is adjusted according to the system temperature detected by the temperature detection unit 210.

Three examples of the temperature detection unit 210 are shown in fig. 10.

First embodiment of temperature detection (Vbe)

In fig. 10(a), the system temperature of the oscillator system is obtained by the base-emitter voltage Vbe of the NPN transistor 211, wherein the current source 212 may be a system current source. In the NPN transistor 211, the Vbe voltage changes linearly with a change in temperature, for example, decreases linearly with an increase in temperature. Thus, the amount of temperature change can be obtained from the amount of change in the Vbe voltage value.

The Vbe voltage value representing the temperature variation is input to the control signal generating unit 220, and the control signal generating unit 220 may generate a control signal according to the Vbe voltage value, thereby changing the resistance value of the resistor 110.

The control signal unit 220 may include an analog-to-digital converter ADC for converting the Vbe voltage value into a digital signal, and a digital control circuit for generating a corresponding digital control signal according to the digital signal, so as to change the resistance value of the resistor 110.

In fig. 10(b), the system temperature of the oscillator system is obtained by the base-emitter voltage Vbe of the PNP transistor 211, wherein the current source 212 may be a system current source. In the PNP transistor 211, the Vbe voltage changes linearly with temperature, for example, decreases linearly with increasing temperature. Thus, the amount of temperature change can be obtained from the amount of change in the Vbe voltage value.

In fig. 10(c), the system temperature of the oscillator system is obtained by the PN junction voltage Vbe of the diode 211, wherein the current source 212 may be a system current source. In the diode 211, the Vbe voltage value linearly changes with temperature, for example, linearly decreases with increasing temperature. Thus, the amount of temperature change can be obtained from the amount of change in the Vbe voltage value.

Second embodiment of temperature detection (PTAT Voltage)

In this embodiment, the temperature may be measured using a PTAT (proportional To Absolute temperature) voltage that increases with increasing temperature.

Two examples of PTAT voltage generation circuits are shown in fig. 11. Wherein the PTAT voltage V_T＝k_BT/q, wherein V_TIs the Boltzmann constant, T is the temperature, q is the electronic quantity, V_TIs in first order proportional relationship with temperature.

In FIGS. 11(a) and 11(b), the resistor R₃The voltage across the terminals being a PTAT voltage of positive temperature coefficient, i.e. increasing with increasing temperature, where V_R3＝(k_BT/Q) InN, where N is the base emitter area ratio of transistors Q1 and Q2, and N is typically 8. Wherein V_R3The temperature coefficient of (A) is usually 0.176 mV/deg.C. In addition, a resistance R₁And R₂The voltage across is also a positive temperature coefficient PTAT voltage, where V_R1＝V_R2＝(k_B*T/q)*InN*(R₂/R₃) Wherein R is₁＝R₂＝11*R₃。V_R1And V_R2The temperature coefficient of (A) is usually 1.94 mV/DEG C.

The voltage value of the PTAT voltage varies linearly with temperature, for example, increases linearly with increasing temperature. Thus, the temperature change amount can be obtained by the change amount of the voltage value of the PTAT voltage.

The PTAT voltage value representing the temperature variation is input to the control signal generation unit 220, and the control signal generation unit 220 may generate a control signal according to the PTAT voltage value, thereby changing the resistance value of the resistor 110.

The control signal unit 220 may include an analog-to-digital converter ADC for converting the PTAT voltage value into a digital signal, and a digital control circuit for generating a corresponding digital control signal according to the digital signal, thereby changing the resistance value of the resistor 110.

Third embodiment of temperature detection (thermistor)

In this embodiment, a thermistor is used as the temperature detection element, and for example, a 103AT NTC thermistor can be used. Wherein the relationship between the NTC thermistor and temperature is: r (T) ═ R (T)₀)*e^B*(1/T-1/T0)Wherein R (T) is the resistance value of the NTC thermistor at the temperature T, R (T)₀) Temperature T₀B is a material constant of the NTC thermistor.

The voltage value of the thermistor changes with a change in temperature, for example, decreases with an increase in temperature. Thus, the temperature variation can be obtained from the voltage variation of the thermistor. The following table shows the resistance values corresponding to different temperatures of different models of NTC resistors.

The voltage value of the thermistor exhibiting the temperature variation is input to the control signal generating unit 220, and the control signal generating unit 220 may generate a control signal according to the voltage value of the thermistor, thereby changing the resistance value of the resistor 110.

The control signal unit 220 may include an analog-to-digital converter ADC for converting the voltage value of the thermistor into a digital signal, and a digital control circuit for generating a corresponding digital control signal according to the digital signal, so as to change the resistance value of the resistor 110.

The manner in which the resistor 110 is adjusted is given in fig. 12. When the resistor 110 is adjusted, the resistance value of the resistor 110 is adjusted according to the temperature variation detected by the temperature detection unit.

FIG. 12 shows an example of a resistive switching cell, resistor R₁、R₂、……、R_n-1、R_nIn series, and each resistor is connected in parallel with a switch S₁、S₂、……、S_n-1、S_n. The resistors are connected or shorted by the on or off of the switch, so that the resistance value of the series resistor is changed, and the purpose of changing the resistance value is achieved.

Control signal V for on or off of switch₁、V₂、……、V_n-1、V_nGenerated by the control signal generation unit 220.

Mode of capacitance change

Fig. 13 shows the manner in which the capacitance 120 is adjusted. When the capacitor 120 is adjusted, the capacitance value of the capacitor 120 is adjusted according to the temperature variation detected by the temperature detecting unit.

FIG. 12 shows an example of a capacitive switching cell, capacitor C₁、C₂、……、C_n-1、C_nIn parallel, and each capacitor is connected in series with a switch S₁、S₂、……、S_n-1、S_n. Each capacitor is switched on or off by switching on or off the switch, so that the capacitance value of the parallel capacitor is changed, and the purpose of changing the capacitance value is achieved.

When the capacitance value of the capacitor 120 is adjusted according to the temperature variation detected by the temperature detection unit, the temperature detection unit may adopt the form of the temperature detection first embodiment, the temperature detection second embodiment, or the temperature detection third embodiment described above, which is not described herein again.

Mode of current change

Fig. 14 and 15 show a first embodiment and a second embodiment of a current source of a current varying manner, respectively.

In the first embodiment of the current source shown in fig. 14, the output current Is of the current source Is realized by adjusting the resistance value of the resistor R. Wherein the change of the resistance R may be changed according to the amount of temperature change detected by the temperature detecting unit. Thus, the resistance value of the resistor R Is adjusted to enable the value Is to be I_ref＝V_ref/R。

In the second embodiment of the current source shown in FIG. 15, the different currents are provided by N FETs mirrored with the FET providing the reference current I, where N ≧ 1.

As shown in fig. 15, different current values are supplied to the resistor 110 or the capacitor 120 by controlling a plurality of MOS transistors MN1 … … MN (n) having different channel aspect ratios.

Including MOS transistor MNB, and MOS transistors MN0 … … MN (n), MN0 … … MN (n) each having a gate connected to the gate of MNB via a switch SW0 … … SW (n), respectively. Thus, when the respective switch SW0 … … SW (n) of MN0 … … MN (n) transistor is turned on, MNB provides a bias voltage to the respective transistor to turn on the respective transistor, so that each transistor will flow a different current due to the difference in the aspect ratio of the channel of the transistor. In one example, the width to length ratios of MN0 … … MN (n) transistors are 2 for MNB, respectivelyⁿAnd (4) doubling. For example, when the n-th MOS transistor is turned on, the current is 2ⁿI, where I is the bias current flowing through the MNB.

Control signal V of switch SW0 … … SW (n)₁、V₂、……、V_n-1、V_nThe feedback value may be preset or may be feedback value of the detection resistor 400 and/or the thermistor 500.

Further, the MOS transistor MP1And the channel aspect ratio of the MOS transistor MP2 may be set to 1: 1, when the switch SW0 … … SW (n) is controlled to be turned on, the current generated by the transistor MP2 is 2ⁿ I。

It should be noted that, in the current changing mode, one current source may be used to generate two currents, and two current sources may also be used to generate two currents, respectively, and one or both of the two currents may be changed to implement an oscillator system with a zero temperature coefficient.

When the current value of the current source is adjusted according to the temperature variation detected by the temperature detection unit, the temperature detection unit may adopt the form of the above-described first embodiment, second embodiment or third embodiment of temperature detection, and details are not repeated here.

Comparator with a comparator circuit

Fig. 16 shows an example of a circuit diagram of a conventional comparator used in an RC oscillator, in which Vin serves as two input terminals. In the conventional comparator, due to the mismatch between the channel width-length ratio and the threshold voltage of the differential input pair transistors M1 and M2, the transistor pair M3 and M8, and the transistor pair M4 and M6, an equivalent offset voltage V is generated at the input terminal of the comparator_OSThe voltage value is usually 1-10 mV.

Wherein in the above formula, I_D1And I_D2For the bias currents of the transistor pairs M1 and M2, which are temperature dependent, the offset voltage caused by the mismatch of the transistor pairs M3 and M8 and the transistor pairs M4 and M6 is also reflected to the input terminal, and the offset voltage can also be expressed by the above equation.

According to the principle of RC oscillator, the equivalent offset voltage V_OSWill be superimposed on the comparatorInput reference voltage V₁＝I_s1In R. The oscillation period T ═ I of the oscillator system is thus obtained_s1*R+V_OS)*C/I_s2。

If the equivalent offset voltage V is neglected_OSThe oscillation period will inevitably be affected.

In order to eliminate the equivalent offset voltage V in the present disclosure_OSBased on the output voltage of the comparator itself, a pair of stable non-overlapping pulse calibration clocks Φ 1 and Φ 2 is implemented. Thereby the equivalent offset voltage V_OSThe calibration is zero, so that the equivalent offset voltage V can be eliminated_OSThe influence of (c).

Wherein the waveforms of the non-overlapping pulse alignment clocks Φ 1 and Φ 2 are shown in fig. 17. Wherein the low level time of the pulse alignment clock phi 1 and the high level time of phi 2 are (I)_s1*R)*C/I_s2Low level time of pulse alignment clock Φ 1 and high level time T of Φ 2_DELAY。

A zero offset comparator with offset calibration according to one embodiment of the present disclosure is shown in fig. 18 (a). Wherein at a reference voltage V₁The input end of the voltage regulator is connected in series with an offset voltage storage voltage C_AZ. Wherein the reference voltage V is exemplified as shown in FIG. 3₁A reference voltage generated by a resistor, and a switch SW connected in series with the input end₂。

At V₂The input end of (the voltage end of the capacitor in FIG. 3) is connected in series with a switch SW₂. In addition, at V₁And V₂Is connected with a switch SW₁At the output of the comparator with V₂Is connected with SW₁And at V₁Is connected with SW between the input end of the switch and the ground₁。

Pulse alignment clock Φ 1 for controlling switch SW₁On and off, the pulse alignment clock Φ 2 being used to control the switch SW₂On and off. For example, when the pulse alignment clock Φ 1 is high, the switch SW₁Conducting; when the pulse alignment clock Φ 1 is at low level, the switch SW₁Disconnecting; when the pulse alignment clock Φ 2 is high, the switch SW₂Conducting; in pulse calibrationWhen the clock phi 2 is at low level, the switch SW₂And (5) disconnecting.

When the pulse alignment clock Φ 1 is at a high level and the pulse alignment clock Φ 2 is at a low level, the switch SW₁Conducting and switching SW₂And (5) disconnecting. FIG. 18(a) will then be equivalent to FIG. 18(b), where C is_AZWill store offset voltage V_OS。

When the pulse alignment clock Φ 1 is at a low level and the pulse alignment clock Φ 2 is at a high level, the switch SW₁Open and switch SW₂Conducting, as shown in FIG. 18(C), C_AZIs connected in series at V₁To the input terminal of (1). Because of C_AZIs equal to the storage offset voltage V_OSAnd direction and V_OSInstead, V will therefore be cancelled out_OS. So that V_OSIs no longer superposed on V₁Thereby eliminating V_OSInfluence on the oscillation period.

FIG. 19 shows a circuit diagram of a comparator according to the present disclosure, in which the equivalent offset voltage V is cancelled, compared to the comparator in the prior art as shown in FIG. 16_OSIn addition, a compensation capacitor C is connected between the drain and the gate of the MOS transistor M6_C1And switch SW₁And a compensation capacitor C is connected between the drain and the gate of the MOS transistor M7_C1And switch SW₁The series circuit of (1). Wherein SW₁Controlled by a pulse alignment clock Φ 1.

Reset controller

According to an embodiment of the present disclosure, the charging and discharging of the capacitor 120 is also controlled by the reset control, which is the switch control signal V shown in fig. 3_SWA pair of stable non-overlapping pulse alignment clocks Φ 1 and Φ 2 are generated by the non-overlapping clock generation circuit.

A non-overlapping clock generation circuit according to the present disclosure is shown in fig. 20. According to a switch control signal V_SWTo generate the pulse alignment clocks Φ 1 and Φ 2.

Fig. 21 shows a waveform diagram of non-overlapping pulse alignment clocks Φ 1 and Φ 2. In which the pulse aligns the low level time of clock phi 1 and the high level time of phi 2Is (I)_s1*R)*C/I_s2Low level time of pulse alignment clock Φ 1 and high level time T of Φ 2_DELAY. The waveform diagram is the same as the waveform diagram shown in fig. 17.

In the present disclosure, after the novel reset control logic is added, the area of the comparator can be reduced, the power consumption of the comparator can be reduced, and the area size of the discharge switch 160 can be reduced at the same time.

A waveform diagram for the circuit of the embodiment of fig. 3 according to the present disclosure is shown in fig. 22. It can be seen from the figure that the discharge time of the delay capacitor cannot be longer than the delay time t of the comparator at the longest_pRequires t_p>＝t₂+t₃That is to say (t)₂+t₃) Must be less than the comparator output V_COMPThe rise time (output delay time of the comparator) from the low level to the high level. Thus, the voltage of the capacitor can be changed from V_pFrom the change to 0, the next cycle of charging is started.

As can be seen from FIG. 22, the period T of the oscillating output_CLK＝T_Vcomp＝t₀+t₁+t₂+t₃Wherein t is₀＝(I_S1/I_S2) R C, the design target value of the oscillator. In I_S1And I_S2T is from the same current source or the same type of current source under the condition that the temperature coefficients are mutually counteracted₀The variation with temperature is only related to the temperature coefficients of the resistor and the capacitor, and the temperature coefficient of the capacitor is one order of magnitude smaller than that of the resistor, so t₀Only with respect to the temperature coefficient of resistance.

t₁Is the output voltage V of the comparator_COMPDelay time from high level to low level.

t₂Is the voltage V across the capacitor_pBecomes V₁The discharge time of (C) is determined by the size of the capacitor C and the on-resistance of the discharge switch SW.

t₃Is the output voltage V of the comparator_COMPRise time from low to high.

t₂+t₃Is the output voltage V of the comparator_COMPThe low level duration of (c) is actually the comparator output delay time.

t₁、t₂、t₃Depending on the process parameters and the magnitude of the comparator bias current, the oscillation period will deviate from the design value. At the same time, t₁、t₂、t₃And also temperature dependent, resulting in a variation of the oscillation period with temperature variation. Therefore, in the design process, it is necessary to minimize t₁、t₂、t₃. Thereby enabling the output T of the oscillator system_CLK＝T_Vcomp＝t₀＝(I_S1/I_S2)*R*C。

It can also be seen from fig. 22 that the discharge time of the capacitor is obviously no longer than the comparator delay time t_p，t_p>＝t₂+t₃I.e. (t)₂+t₃) Is less than the rising time of the comparator output from low level to high level, during which the capacitor voltage changes from V_pBecomes 0 and then the charge phase of the next cycle begins. It is also desirable that the delay time of the comparator is not too short, otherwise the capacitor voltage cannot be driven from V in a short time_pBleeding to 0.

Therefore, in order to make the oscillator system output a clock signal with a fixed frequency, it is necessary to reduce the delay time of the comparator in the case of meeting the demand.

A general representation of the delay time of the comparator is shown in fig. 23. Wherein V_ILFor inputting low level, V_IHTo output high level, (V)_OH+V_OL) /2 is 1/2 level between high level and low level, which represents the dividing point of the comparator output from low level to high level, t_pFor comparator input v_inFrom low level to (V)_IH+V_IL) Start of/2, output v_outFrom low level to (V)_OH+V_OL) Delay time of/2.

The output delay time for a two-stage comparator as shown in fig. 24 can be generally expressed as:

wherein, 1/g_dsIs the output resistance of the MOS transistor, and λ is the channel modulation effect parameter of the MOS transistor, I_DFor the static bias current of MOS transistor, the larger the current is, the larger g_dsThe larger the comparator delay time, the smaller λ, I_DAre temperature dependent and are generally approximately proportional to temperature.

C_IIs the first stage output v of the comparator_o1The parasitic capacitance of the node is proportional to the sizes of M2, M4 and M6, and the smaller the sizes of M2, M4 and M6 are, the smaller the size of C_IThe smaller the comparator delay time. But C is_IIIs the output v of the comparator_outParasitic capacitance of node, measured by size of M6 and M7 and load capacitance C_LDetermined M6 and M7 sizes and load capacitance C_LThe smaller the comparator delay time.

From the above analysis, it can be seen that it is desirable that the comparator delay time is short on the one hand, and not too short on the other hand, because the capacitor C needs enough time to discharge, and therefore, how to resolve the contradiction between the two needs to be considered.

If the delay time of the comparator is unlimitedly reduced, the discharge time of the capacitor needs to be unlimitedly accelerated, but in this way, the on-resistance of the discharge switch can be reduced only by continuously increasing the width-to-length ratio W/L of the discharge switch, and the discharge time is accelerated, so that the area of a chip is increased.

(t₂+t₃) Is the voltage V across the capacitor_PThe discharge time to 0 is determined by the size of the capacitor and the on-resistance of the discharge switch. The discharge time constant of the capacitor C is R_on*C，R_onIs the on-resistance of the discharge switch. The discharge switch is usually designed by a MOSFET, and its on-resistance is:

due to the mobility μ_nThreshold voltage V_THFixed, the discharge time cannot be accelerated by reducing the capacitance value of the capacitor because the oscillation period of the oscillator system is made of (I)_S1/I_S2) R C is dependent on the capacitance C and therefore the discharge time cannot be adjusted by C. At this time, the on-resistance of the switch can only be reduced by increasing the width-to-length ratio W/L of the MOSFET switch, thereby reducing t₂。

In the present disclosure, in order to solve this problem, a discharge pulse reset circuit is provided in which the high level of the output of the discharge pulse reset circuit is determined not by the comparator delay time but by the delay time of the inverter inv1 shown in fig. 25. Thus, t₂Delay time T by inverter inv1_dlyTherefore, the delay time of the comparator can be reduced as much as possible, and the delay time of the comparator can be designed independently without influencing the discharge time of the capacitor C. Finally, the delay time T of the inverter can be designed appropriately_dlyTo design a reasonably acceptable discharge switch size.

Fig. 26 is a schematic diagram showing a circuit configuration of the inverter. Delay time T of inverter_dlyComprises the following steps:

wherein, W_n/L_nIs the width-to-length ratio of NMOS, W_p/L_pIs the width-to-length ratio of PMOS, C_LLoading the output terminal of the inverter with a capacitor, mu_nFor electron mobility, μ_pFor hole mobility, V_DDIs a supply voltage, C_oxIs the capacitance per unit area of gate oxide.

Can see T_dlyDepending on both temperature and process, it is desirable to minimize T in the ideal case_dlySo as to reduce the influence of temperature on the oscillation period. However, T_dlyAnd can not be reduced without limit because of the discharge time of the capacitor CMust be less than T_dly. Usually T_dlyNeed to be designed as 8R_SW*C<0.001-0.01*T_CLK＝(I_S1/I_S2)*R*C。

Thus, T is reduced_dlyThere is a need to increase the discharge switch R without limitation_SWThe aspect ratio of (2) will increase the chip area. And too large a size of the discharge switch may also result in a parasitic capacitance (C) of a drain of the discharge switch_d) Is increased and C_dEquivalently, the oscillation period becomes T_CLK＝t₀＝(I_S1/I_S2)*R*(C+C_d) Deviation from the target design value T_CLK＝t₀＝(I_S1/I_S2)*R*C。

To solve the problem that T can be reduced without increasing the width-length ratio of a discharge switch_dlyIn the present disclosure, the inverter inv1 in the pulse reset circuit shown in the lower left side of fig. 25 is replaced with any one of the circuit configurations shown in fig. 27.

In the circuit configuration of fig. 27, a resistor R is connected in parallel to the inverter_dlyAnd at the resistance R_dlyA capacitor C is connected with the ground_dly. Thus, the input-to-output delay time of the circuit shown in fig. 27 can be expressed as: t is_dly(total)≈T_dly(inv)+R_dly*C_dlyWherein T is_dly(inv) is the inverter delay time, R_dlyIs a resistance R_dlyResistance value of C_dlyIs a capacitor C_dlyThe capacitance value of (2).

In practice, the minimum T can be achieved by using the inverter inv1 with the smallest size in the given process conditions_dly(inv), typically in ns order, compared to R_dly*C_dlyCan be ignored.

Wherein R is_dly*C_dly＝8*R_SWC, in practical design, C may be_dlyC, then R_dly＝8*R_SW。

Will resistance R_dlyUsing the same type of resistor as resistor 110, that is to say having the same temperature coefficient, by the above temperature calibration method it is possible to useTo change R equally while adjusting the resistor 110_dlySize of (1), keep T_dlyIndependent of temperature, thereby enabling the oscillation period T_CLK＝(I_S1/I_S2)*R*C+T_dlyIndependent of temperature.

In addition, the capacitor C_dlyWith the same temperature coefficient as that of the capacitor 120, by the above temperature calibration method, C can be changed identically while adjusting the capacitor 120_dlySize of (1), keep T_dlyIndependent of temperature, thereby enabling the oscillation period T_CLK＝(I_S1/I_S2)*R*C+T_dlyIndependent of temperature.

Through the various embodiments of the present disclosure, the oscillation output frequency of the RC oscillator can be fixed by changing the current, the resistance and/or the capacitance, and the influence of the elements used in the oscillator on the oscillation output frequency can be eliminated, so that a stable fixed output frequency can be obtained.

In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to be the same embodiment/mode or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

It will be understood by those skilled in the art that the foregoing embodiments are merely for clarity of illustration of the disclosure and are not intended to limit the scope of the disclosure. Other variations or modifications may occur to those skilled in the art, based on the foregoing disclosure, and are still within the scope of the present disclosure.

Claims

1. An RC oscillator, comprising:

an oscillation circuit that includes a system resistance and a system capacitance, and that generates and outputs an oscillation voltage from a resistance voltage generated by the system resistance and a capacitance voltage generated by the system capacitance;

a temperature control circuit for detecting a temperature of the RC oscillator and changing a resistance value of the system resistance and/or a capacitance value of the system capacitance according to the detected temperature to thereby change the resistance voltage and/or the capacitance voltage so as to make an oscillation frequency of an oscillation voltage output by the RC oscillator fixed according to the changed resistance voltage and/or capacitance voltage; and

a current source providing a current to the system resistance so that the system resistance generates the resistance voltage, and providing a current to the system capacitance so that the system capacitance generates the capacitance voltage,

the system capacitor is connected with a discharge switch in parallel, the discharge switch is used for controlling the charging and discharging of the system capacitor so as to generate the capacitor voltage, the discharge switch is controlled by a reset controller, the reset controller generates a discharge switch control signal to control the on and off of the discharge switch so as to discharge and charge the system capacitor, the reset controller comprises an inverter circuit, and the duration time of the discharge switch control signal for controlling the discharge switch to discharge is determined only by the delay time of the inverter circuit.

2. The RC oscillator of claim 1, wherein the temperature control circuit detects the temperature of the RC oscillator by a base-emitter voltage of a transistor, or a PN junction voltage of a diode, or a PTAT voltage generated by a PTAT voltage generation circuit, or a thermistor.

3. The RC oscillator of claim 1 or 2, wherein the current source comprises one current source or two current sources, the one current source generating a first current provided to the system resistance and a second current provided to the system capacitance when the current source comprises one current source, the two current sources generating a first current provided to the system resistance and a second current provided to the system capacitance when the current source comprises two current sources, respectively, and generating the oscillating voltage based on a comparison of a resistance voltage produced by the system resistance and a capacitance voltage produced by the system capacitance.

4. The RC oscillator of claim 3, wherein the temperature control circuit changes one or more of a resistance value of the system resistance, a capacitance value of the system capacitance, a current value of the first current, and a current value of the second current according to the detected temperature so that an oscillation frequency of an oscillation voltage output by the RC oscillator is fixed.

5. The RC oscillator of claim 4, further comprising a comparator into which the resistance voltage and the capacitance voltage are input, the comparator comparing the resistance voltage and the capacitance voltage and outputting a comparison voltage, and generating the oscillating voltage based on the comparison voltage.

6. The RC oscillator as claimed in claim 5, wherein the comparator includes an offset voltage storage capacitor connected in series to an input terminal of a resistance voltage of the comparator, the offset voltage storage capacitor is controlled to be charged by an output voltage of the comparator when the oscillating voltage is at a high level, and the offset voltage storage capacitor is controlled to be discharged to cancel an offset voltage of the comparator when the oscillating voltage is at a low level, thereby eliminating an influence of the offset voltage on the oscillating frequency.

7. The RC oscillator of claim 6, wherein the comparator comprises a first switch and a second switch, the offset voltage storage capacitor is charged by the output voltage of the comparator when the first switch is turned on and the second switch is turned off, and the resistance voltage and the capacitance voltage are input to the comparator when the first switch is turned off and the second switch is turned on.

8. The RC oscillator of claim 3, wherein when the oscillating voltage is high, the discharge switch control signal is high, controlling the discharge switch to conduct to discharge the system capacitor, and when the oscillating voltage is low, the discharge switch control signal is low, controlling the discharge switch to open to charge the system capacitor.

9. The RC oscillator of claim 8, wherein the inverter circuit includes an inverter, an inverter resistance, and an inverter capacitance, the inverter resistance being connected in series to an output terminal or an input terminal of the inverter, the inverter capacitance having one end connected to the inverter resistance and the other end grounded,

the inverter resistor has the same temperature coefficient as the system resistor, and when the resistance value of the system resistor is changed by the temperature control circuit, the resistance value of the inverter resistor is also changed accordingly, and/or

The inverter capacitor and the system capacitor have the same temperature coefficient, and when the capacitance value of the system capacitor is changed through the temperature control circuit, the capacitance value of the inverter capacitor is also changed correspondingly.

10. An electrical device comprising an RC oscillator as claimed in any one of claims 1 to 9.

11. An RC oscillator, comprising: a system resistor, a system capacitor, a current source, a comparator, a reset controller, a discharge switch and a temperature control circuit,

the temperature control circuit is used for detecting the temperature of the RC oscillator and changing the resistance value of the system resistor and/or the capacitance value of the system capacitor according to the detected temperature so as to change the resistance voltage and/or the capacitance voltage, so that the oscillation frequency of the oscillation voltage output by the RC oscillator is fixed,

the system resistor is a low temperature coefficient resistor so as to realize a low temperature coefficient RC oscillator, wherein the reset controller comprises an inverter circuit, and the duration of the discharge switch control signal for controlling the discharge switch to discharge is determined only by the delay time of the inverter circuit.

12. The RC oscillator of claim 11, wherein the comparator includes an offset voltage storage capacitor connected in series to an input terminal of a resistor voltage of the comparator, and the offset voltage storage capacitor is controlled to be charged by an output voltage of the comparator when the oscillating voltage is at a high level, and is controlled to be discharged to cancel the offset voltage of the comparator when the oscillating voltage is at a low level, so as to eliminate an influence of the offset voltage on the oscillating frequency.

13. The RC oscillator of claim 12, wherein the comparator comprises a first switch and a second switch, the offset voltage storage capacitor being charged by the output voltage of the comparator when the first switch is on and the second switch is off, the resistance voltage and the capacitance voltage being input to the comparator when the first switch is off and the second switch is on.

14. The RC oscillator of any of claims 11 to 13, wherein the reset controller controls the discharge switch to be turned on and off by a discharge switch control signal, wherein when the oscillating voltage is high, the discharge switch control signal is high, controlling the discharge switch to be turned on to discharge the system capacitance, and when the oscillating voltage is low, the discharge switch control signal is low, controlling the discharge switch to be turned off to charge the system capacitance.

15. The RC oscillator of claim 14, wherein the inverter circuit includes an inverter, an inverter resistance, and an inverter capacitance, the inverter resistance being connected in series to an output terminal or an input terminal of the inverter, the inverter capacitance having one end connected to the inverter resistance and the other end connected to ground,

16. An electrical device comprising an RC oscillator as claimed in any one of claims 11 to 15.