A low-temperature drift ring oscillator

Abstract

This invention provides a low-temperature drift ring oscillator, comprising a ring oscillation circuit and a low-dropout linear regulator with a temperature coefficient. The ring oscillation circuit includes multiple inverters and resistive-capacitive elements. The ring oscillation circuit generates an oscillation signal. The low-dropout linear regulator with a temperature coefficient provides an adjustable temperature coefficient supply voltage to the ring oscillation circuit. The adjustable temperature coefficient supply voltage is generated by proportionally and numerically adjustable positive temperature coefficient current sources and negative temperature coefficient current sources flowing through resistors. This invention maintains frequency consistency and stability over a wide operating temperature range, featuring small frequency temperature deviation, simple circuit structure, and convenient adjustment. It is suitable for electronic systems with large temperature variations and has strong practicality.

Description

Technical Field

[0001] This disclosure relates to the field of analog integrated circuit technology, and more particularly to a low-temperature drift ring oscillator. Background Technology

[0002] Oscillators are commonly used to generate stable periodic signals to provide a fundamental clock for various digital or mixed-signal circuits, thus becoming a crucial component of modern electronic systems. Clock-dependent circuits typically require oscillators to generate clock frequencies that are stable and exhibit minimal temperature variation, facilitating timing design.

[0003] On-chip integrated oscillators mainly include LC oscillators and ring oscillators. LC oscillators generate signals of a specific frequency by forming a resonance through inductors and capacitors. They have advantages such as high quality factor, good frequency selectivity, and low phase noise. However, their disadvantages are that they use large inductor areas and small inductance values, so they are mainly used in high-frequency radio frequency circuits. Ring oscillators mainly form a ring structure through delay units. They have advantages such as simple circuit structure, large adjustable output frequency range, and easy on-chip integration. Therefore, they are widely used in various medium and low frequency clock generation applications. However, existing ring oscillators have technical problems with poor frequency consistency and stability over a wide operating temperature range. Summary of the Invention

[0004] In view of this, the present disclosure improves the ring oscillator and provides a ring oscillator with low temperature drift, which has better frequency stability and can maintain frequency consistency and stability over a wide operating temperature range. It has the characteristics of small frequency temperature deviation, simple circuit structure and convenient adjustment, and is suitable for electronic systems with large temperature variation range, and has strong practicality.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A low-temperature drift ring oscillator includes a ring oscillating circuit and a low-dropout linear regulator with a temperature coefficient.

[0007] The ring oscillation circuit includes multiple inverters and resistive-capacitive elements, and is used to generate an oscillation signal; the low-dropout linear regulator with a temperature coefficient provides an adjustable temperature coefficient supply voltage to the ring oscillation circuit.

[0008] The adjustable temperature coefficient supply voltage is generated by a positive temperature coefficient current source and a negative temperature coefficient current source with adjustable ratio and value flowing through a resistor. By adjusting the ratio and value of the positive temperature coefficient current source and the negative temperature coefficient current source, the temperature coefficient of the supply voltage is changed, thereby changing the delay temperature coefficient of the inverter in the ring oscillation circuit and compensating for the delay temperature coefficient of the resistor and capacitor elements in the ring oscillation circuit.

[0009] Furthermore, the plurality of inverters includes a first inverter, a second inverter, and a third inverter, and the resistive-capacitive elements include a first resistor, a first capacitor, a second capacitor, and a third capacitor;

[0010] The output of the first inverter is connected to the input of the second inverter. The output of the second inverter is connected to the input of the third inverter and one end of the third capacitor. The output of the third inverter is connected to one end of the first resistor. The other ends of the third capacitor and the first resistor are connected to one end of the first capacitor and the second capacitor, and the input of the first inverter, respectively. The other ends of the first capacitor and the second capacitor are connected to the circuit reference ground.

[0011] Furthermore, the second capacitor is an adjustable capacitor.

[0012] Furthermore, the first resistor is a non-metallized polycrystalline silicon resistor.

[0013] Furthermore, the first capacitor, the second capacitor, and the third capacitor are selected as metal-insulator-metal capacitors.

[0014] Furthermore, the threshold values ​​of the first inverter, the second inverter, and the third inverter are half of the supply voltage.

[0015] Furthermore, the plurality of inverters also includes a fourth inverter and a fifth inverter. The input of the fourth inverter is connected to the output of the first inverter, and the output of the fourth inverter is connected to the input of the fifth inverter. The output of the fifth inverter is the frequency output of the oscillation circuit.

[0016] Furthermore, the low-dropout linear regulator with temperature coefficient includes a power transistor, a second resistor, a third resistor, a fourth resistor, an error amplifier, a positive temperature coefficient current source, and a negative temperature coefficient current source.

[0017] The output of the low-dropout linear regulator is fed back to the non-inverting input of the error amplifier through a series voltage divider between the second and third resistors and the circuit reference ground. The inverting input of the error amplifier is connected to one end of the positive temperature coefficient current source, the negative temperature coefficient current source, and the fourth resistor. The other ends of the positive and negative temperature coefficient current sources are connected to the power supply. The other end of the fourth resistor is connected to the circuit reference ground. The output of the error amplifier is connected to the gate of the power transistor. The source of the power transistor is connected to the power supply, and the drain is connected to the output of the low-dropout linear regulator.

[0018] Furthermore, the low-dropout linear regulator with temperature coefficient also includes a fourth capacitor, one end of which is connected to the output of the low-dropout linear regulator, and the other end is connected to the circuit reference ground.

[0019] Furthermore, the low-dropout linear regulator with temperature coefficient also includes a fifth capacitor, one end of which is connected to the inverting input of the error amplifier, and the other end is connected to the circuit reference ground.

[0020] The ring oscillator circuit of the present invention has a simple structure, can compensate for the temperature drift caused by the internal circuit components of the ring oscillator, effectively reduce the sensitivity of the oscillator to the environment, ensure the consistency and stability of the generated frequency, and is suitable for electronic systems with a large temperature variation range, thus having strong practicality. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a block diagram of a ring oscillator circuit according to an embodiment of the present invention;

[0023] Figure 2 This is a circuit block diagram of the low-dropout linear regulator in an embodiment of the present invention;

[0024] Figure 3 The waveforms are key nodes of the ring oscillator in this embodiment of the invention. Detailed Implementation

[0025] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0026] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0027] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0028] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The drawings only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0029] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0030] This disclosure provides a low-temperature drift ring oscillator, including a ring oscillation circuit and a low-dropout linear regulator with a temperature coefficient. The ring oscillation circuit includes multiple inverters and resistive-capacitive elements, and is used to generate an oscillation signal. The low-dropout linear regulator with a temperature coefficient provides an adjustable temperature coefficient supply voltage to the ring oscillation circuit. The adjustable temperature coefficient supply voltage is generated by a positive temperature coefficient current source and a negative temperature coefficient current source with adjustable proportions and values ​​flowing through a resistor. By adjusting the proportions and values ​​of the positive and negative temperature coefficient current sources, the temperature coefficient of the supply voltage is changed, thereby changing the delay temperature coefficient of the inverters in the ring oscillation circuit and compensating for the delay temperature coefficient of the resistive-capacitive elements in the ring oscillation circuit.

[0031] The following is in conjunction with the appendix Figure 1-3 The embodiments disclosed herein will be further described.

[0032] Appendix Figure 1 The following is an embodiment of a cryogenic ring oscillator, including a ring oscillation circuit 101 and a low-dropout linear regulator 102 with a temperature coefficient.

[0033] The ring oscillation circuit 101 consists of a first inverter INV1, a second inverter INV2, a third inverter INV3, a fourth inverter INV4, a fifth inverter INV5, a first resistor R1, a first capacitor C1, a second capacitor C2, and a third capacitor C3. The output of the first inverter INV1 is connected to the inputs of the second inverter INV2 and the fourth inverter INV4. The output of the second inverter INV2 is connected to the input of the third inverter INV3 and one end of the third capacitor C3. The output of the third inverter INV3... The output is connected to one end of the first resistor R1, the other end of the third capacitor C3 and the first resistor R1, one end of the first capacitor C1 and the second capacitor C2, and the input of the first inverter INV1. The other ends of the first capacitor C1 and the second capacitor C2 are connected to the circuit reference ground gnd. The output of the fourth inverter INV4 is connected to the input of the fifth inverter INV5. The output of the fifth inverter INV5 is the frequency output osc_out of the oscillator. This ring oscillator circuit is powered by a low dropout linear regulator 102 with a temperature coefficient.

[0034] As attached Figure 2As shown, the low-dropout linear regulator 102 with temperature coefficient consists of a power transistor MP1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fourth capacitor C4, a fifth capacitor C5, an error amplifier A1, a positive temperature coefficient current source Iptat, and a negative temperature coefficient current source Ictat. The output of the regulator 102 is fed back to the non-inverting input of the error amplifier A1 via a series voltage divider between the second resistor R2 and the third resistor R3 and the circuit reference ground gnd. The inverting input of the error amplifier A1 is connected to the positive temperature coefficient current source Iptat and the negative temperature coefficient current source Ictat. The coefficient current source Ictat, the fourth resistor R4, and one end of the fifth capacitor C5 are connected. The other ends of the positive temperature coefficient current source Iptat and the negative temperature coefficient current source Ictat are connected to the power supply Vcc. The other ends of the fourth resistor R4 and the fifth capacitor C5 are connected to the circuit reference ground gnd. The output of the error amplifier A1 is connected to the gate of the power transistor MP1. The source of the power transistor MP1 is connected to the power supply Vcc, and its drain is connected to the output of the voltage regulator 102. One end of the fourth capacitor C4 is connected to the output of the voltage regulator 102, and the other end is connected to the circuit reference ground gnd.

[0035] The positive temperature coefficient current source Iptat is typically generated by a bandgap reference circuit.

[0036] The negative temperature coefficient current source Ictat is typically generated by the base-emitter voltage Vbe of a transistor across a resistor.

[0037] The inverter is preferably selected from those with a switching threshold of half the supply voltage.

[0038] The resistors are preferably unsalicided polycrystalline silicon resistors, whose resistance values ​​vary under different processes, typically several hundred ohms per square, and have a certain negative temperature coefficient, typically -200ppm / ℃.

[0039] The capacitors used are preferably metal-insulator-metal (MiM) capacitors, which have moderate capacitance per unit value, small temperature coefficient and voltage coefficient, and are suitable for circuits with high performance requirements.

[0040] Appendix Figure 3 The key node waveforms of the ring oscillator are shown. In the figure, when the second inverter INV2 flips each time, due to the presence of capacitor C3, the input voltage VY of the first inverter INV1 will always generate a step voltage Vstep. According to the law of conservation of charge, Vstep can be calculated by equation (1).

[0041] Vstep=C3*Vldo / (C1+C2+C3) (1)

[0042] In equation (1), Vldo is the output voltage of the low-dropout linear regulator 102.

[0043] When the voltage VY drops from the top or bottom of the step voltage Vstep to or rises to half of Vldo, the first inverter INV1 flips. After a delay of INV1 to INV3, it enters the next state, and this cycle repeats to form a loop oscillation. According to the first-order RC circuit model, the delay of the first resistor R1 and the first capacitor C1 to the third capacitor C3 can be calculated by equation (2).

[0044] t1=t2=R1*(C1+C2+C3)*ln(1+2Vstep / Vldo) (2)

[0045] Therefore, the clock signal period T generated by the ring oscillator can be calculated by equation (3).

[0046] T=t1+t2+2*tlogic=2*R1*(C1+C2+C3)*ln(1+2Vstep / Vldo)+2*tlogic (3)

[0047] In equation (3), tlogic is the delay of the link from the first inverter INV1 to the third inverter INV3.

[0048] As shown in equation (3), the clock signal period T generated by the ring oscillator mainly consists of two parts: the delay of the first resistor R1 and the delay of the first capacitor C1 to the third capacitor C3, and the delay of the first inverter INV1 to the third inverter INV3. The first resistor R1 is a non-metallic polysilicon resistor with a negative temperature coefficient, while the first capacitor C1 to the third capacitor C3 are MiM capacitors, whose temperature coefficients are much smaller than those of the resistors and can be ignored. Therefore, the delay of the first resistor R1 and the delay of the first capacitor C1 to the third capacitor C3 has a negative temperature coefficient. If the supply voltage of the ring oscillator remains unchanged, the delay of the first inverter INV1 to the third inverter INV3 has a positive temperature coefficient and varies greatly. If the temperature rises from -40℃ to 125℃, the inverter delay can almost double. In summary, in the clock period T of the ring oscillator, the temperature coefficients of the delay of the first resistor R1 and the first capacitors C1 to C3 are exactly opposite to those of the first inverters INV1 to INV3. Meanwhile, the resistance of the first resistor R1 and the capacitance of the first capacitors C1 to C3 are negligibly affected by voltage, while the delay of the first inverters INV1 to INV3 is significantly affected by voltage and decreases as the voltage increases. Therefore, this invention adjusts the temperature coefficient of the delay of the first inverters INV1 to INV3 to a suitable range by adjusting the temperature coefficient of the inverter's supply voltage Vldo, thereby compensating for the temperature coefficients of the delay of the first resistor R1 and the first capacitors C1 to C3, ultimately generating a clock signal whose frequency changes little with temperature. The second capacitor C2 is designed as an adjustable capacitor, allowing the oscillator frequency to be adjusted to the target value according to changes in the circuit process angle. The output of the first inverter INV1 is shaped by two inverters, the fourth inverter INV4 and the fifth inverter INV5, and finally produces the oscillator output osc_out.

[0049] The input reference voltage of the low-dropout linear regulator 102 with temperature coefficient is generated by the proportional and numerically adjustable positive temperature coefficient current source Iptat and negative temperature coefficient current source Ictat flowing through the fourth resistor R4. The fifth capacitor C5 serves as a filter capacitor to reduce coupling interference during circuit operation. The fourth capacitor C4 serves as the output voltage regulator capacitor to reduce fluctuations in the output voltage Vldo caused by load changes. The output voltage Vldo of the regulator 102 can be calculated by equation (4).

[0050] Vldo=(Iptat+Ictat)*R4*(1+R2 / R3) (4)

[0051] As can be seen from equation (4), adjusting the ratio and value of the positive temperature coefficient current source Iptat and the negative temperature coefficient current source Ictat can change the temperature coefficient of Vldo, thereby changing the temperature coefficient of the delay of the first inverter INV1 to the third inverter INV3 in the ring oscillator, and finally compensating for the temperature coefficient of the delay of the first resistor R1 and the first capacitor C1 to the third capacitor C3, generating a clock signal with very small frequency temperature drift.

[0052] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A low temperature drift ring oscillator characterized by, The application relates to a ring oscillator circuit and a low-dropout linear voltage regulator with a temperature coefficient. The ring oscillator circuit comprises a plurality of inverters and resistance-capacitance elements, and is used for generating an oscillation signal; and the low-dropout linear voltage regulator with a temperature coefficient provides a power supply voltage with an adjustable temperature coefficient for the ring oscillator circuit. The power supply voltage with the adjustable temperature coefficient is generated by a resistance through which a proportional and numerical adjustable positive temperature coefficient current source and a negative temperature coefficient current source flow; by adjusting the proportion and numerical value of the positive temperature coefficient current source and the negative temperature coefficient current source, the temperature coefficient of the power supply voltage is changed, the temperature coefficient of the delay time of the inverters in the ring oscillator circuit is changed, the temperature coefficient of the delay time of the resistance-capacitance elements in the ring oscillator circuit is compensated, and a clock signal with a small change in the output frequency of the ring oscillator with temperature is obtained. The temperature coefficient of the delay time of the inverters in the ring oscillator circuit is a positive temperature coefficient when the power supply voltage is constant; and the temperature coefficient of the delay time of the resistance-capacitance elements in the ring oscillator circuit is a negative temperature coefficient.

2. The low temperature drift ring oscillator of claim 1, wherein, The plurality of inverters comprises a first inverter, a second inverter and a third inverter; and the resistance-capacitance elements comprise a first resistance, a first capacitance, a second capacitance and a third capacitance. The output of the first inverter is connected to the input of the second inverter, the output of the second inverter is connected to the input of the third inverter and one end of the third capacitance, the output of the third inverter is connected to one end of the first resistance, the other end of the third capacitance and the first resistance is connected to one end of the first capacitance and the second capacitance and the input of the first inverter, and the other end of the first capacitance and the second capacitance is connected to a circuit reference ground.

3. The low temperature drift ring oscillator of claim 2, wherein, The second capacitance is an adjustable capacitance.

4. The low temperature drift ring oscillator of claim 2, wherein, The first resistance is a non-metallized polysilicon resistance.

5. The low temperature drift ring oscillator of claim 2, wherein, The first capacitance, the second capacitance and the third capacitance are metal-insulator-metal capacitors.

6. The low temperature drift ring oscillator of claim 2, wherein, The threshold value of the first inverter, the second inverter and the third inverter is half of the power supply voltage.

7. The low temperature drift ring oscillator of claim 2, wherein, The plurality of inverters further comprises a fourth inverter and a fifth inverter, the input of the fourth inverter is connected to the output of the first inverter, the output of the fourth inverter is connected to the input of the fifth inverter, and the output of the fifth inverter is the frequency output of the oscillation circuit.

8. The low temperature drift ring oscillator according to any one of claims 2 to 7, characterized in that The low-dropout linear voltage regulator with a temperature coefficient comprises a power tube, a second resistance, a third resistance, a fourth resistance, an error amplifier, a positive temperature coefficient current source and a negative temperature coefficient current source. The output of the low-dropout linear voltage regulator is fed back to the non-inverting input terminal of the error amplifier through the series voltage division of the second resistance and the third resistance on the circuit reference ground, the inverting input terminal of the error amplifier is connected to the positive temperature coefficient current source, the negative temperature coefficient current source and one end of the fourth resistance, the other end of the positive temperature coefficient current source and the negative temperature coefficient current source is connected to a power supply, the other end of the fourth resistance is connected to the circuit reference ground, the output of the error amplifier is connected to the gate of the power tube, the source level of the power tube is connected to the power supply, and the drain is connected to the output of the low-dropout linear voltage regulator.

9. The low temperature drift ring oscillator of claim 8, wherein, The low-dropout linear voltage regulator with temperature coefficient further comprises a fourth capacitor, one end of the fourth capacitor being connected with an output of the low-dropout linear voltage regulator, and the other end being connected with a circuit reference ground.

10. The low temperature drift ring oscillator of claim 9, wherein, The low-dropout linear voltage regulator with temperature coefficient further comprises a fifth capacitor, one end of the fifth capacitor being connected with an inverting input end of the error amplifier, and the other end being connected with the circuit reference ground.

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