Ring oscillator circuit with low temperature drift and low voltage drift

Abstract

The invention discloses a ring oscillator circuit with low temperature drift and low voltage drift. The circuit comprises a reference current generation module, a current mirror module, an inverter chain module, a waveform shaping module, a voltage stabilizing module and a starting module. The reference current generation module outputs current with a monotonic temperature coefficient, and the current mirror image module copies the current in proportion and provides tail current for the inverter chain module. The voltage stabilizing module ensures that the power supply voltage of the phase inverter chain module is kept stable when the power supply voltage changes, the phase inverter chain module generates a periodic oscillation signal, and the waveform shaping module shapes the oscillation signal into a clock signal with a voltage amplitude. The starting module is used for providing starting current for the reference current generation module. Through a temperature coefficient and resistance feedback network compensation method, the interference of temperature and power supply voltage on clock signal frequency can be reduced, so that the stability of the system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oscillators, and in particular to a ring oscillator circuit with low temperature drift and low voltage drift. Background Art

[0002] An oscillator is an electronic circuit that can continuously generate periodic waveforms (such as sine waves, square waves, triangle waves, etc.). It generates output signals stably through a feedback mechanism without external signal input. An oscillator usually consists of an amplifier and a feedback network. The feedback signal is amplified and returned to the input end to form a self-excitation process, thereby maintaining a continuous waveform output. As a clock generator and frequency source, oscillators have become core components in most electronic circuit systems and are widely used in communications, electronic equipment, aerospace, navigation, medical, bioengineering and other fields.

[0003] Oscillators can be divided into two categories according to the different integration methods: on-chip integrated oscillators and off-chip non-integrated oscillators. On-chip integrated oscillators are usually further subdivided into hysteresis oscillators, ring oscillators and capacitor-inductor oscillators according to their topological structure. Ring oscillators are widely used in system-on-chip (SoC) because of their simple structure, easy implementation, adjustable frequency range and high integration. On the other hand, off-chip non-integrated oscillators mainly refer to quartz crystal oscillators, which are usually used in occasions with high requirements for frequency stability and noise, such as high-precision clock signal generation and wireless communication systems.

[0004] The ring oscillator is mainly composed of several inverters, which achieve oscillation through the feedback principle. Specifically, the output signal of the inverter is connected to the input through feedback to form a closed-loop system. If the gain of the closed loop is greater than or equal to 1, and the sum of the phase delays of the feedback signal is 360 degrees or an integer multiple thereof, the system can continuously and stably generate a periodic oscillation signal. The frequency of the ring oscillator is usually determined by the number of inverters, the delay time of each inverter, and the characteristics of other circuit elements (such as capacitors, inductors, etc.).

[0005] Due to its simple structure, high frequency, wide frequency adjustment range, and high integration, ring oscillators are widely used in phase-locked loops, frequency synthesizers, clock recovery circuits, and other fields. Despite this, the performance of ring oscillators is still subject to external factors such as process changes, temperature fluctuations, and power supply noise, resulting in unstable frequency and output waveform distortion. For example, when the temperature changes by 50°C, the oscillation frequency of the ring oscillator may shift by more than 50%; power supply noise may also cause output waveform distortion and clock jitter, seriously affecting circuit performance. These instabilities are mainly due to the fact that the mobility and threshold voltage of the MOS tube are easily affected by changes in temperature, power supply voltage, and process parameters. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a ring oscillator circuit with low temperature drift and low voltage drift, which can input a square wave signal with a relatively stable frequency while maintaining the changes in temperature and power supply voltage, and provide a clock signal for the remaining peripheral circuits. The present invention aims to further improve the stability of the ring oscillator through temperature and voltage compensation control. Specifically, the present invention will explore a multi-factor comprehensive compensation solution to optimize the impact of temperature and power supply voltage changes on oscillator performance, thereby achieving a more stable frequency output. In addition, the present invention will also be committed to reducing the dependence on external signal processing modules, reducing circuit area and power consumption, improving the overall performance of the oscillator, and enhancing its application value in modern electronic systems.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A ring oscillator circuit with low temperature drift and low voltage drift comprises: a reference current generating module, a current mirror module, an inverter chain module, a waveform shaping module, a voltage stabilizing module and a starting module.

[0008] The reference current generating module provides a positive temperature coefficient current and adopts NMOS and PMOS Cascode structures to reduce the power supply rejection ratio; it includes two bipolar transistors with emitter areas having a certain ratio, and the ratio is related to the layout, power consumption, and process library MOS tube characteristics. The voltage difference between the emitter and the collector generates a current with a monotonic temperature characteristic through a resistor with a temperature characteristic, and the current is the input of the current mirror module; The current mirror module copies the current output by the reference current generating module as the tail current input of the inverter chain module; The inverter chain module is composed of an odd number of inverters, providing an oscillating clock signal for the peripheral circuit, the frequency of which is linearly related to the number of stages of the inverter chain module, and the signal is used as the input of the waveform shaping module; The waveform shaping module includes several stages of inverters, which convert the oscillating clock signal generated by the inverter chain module into a square wave oscillation signal with full power supply swing; The voltage stabilizing module includes an error amplifier and a feedback network to ensure that the power supply voltage of the inverter chain module remains stable when the power supply voltage changes, and its output is used as the power supply voltage of the inverter chain module; The startup module ensures that the reference current generating module is separated from the zero degeneracy point and operates normally during the power-on process.

[0009] The temperature slope of the current generated by the reference current generating module is related to the emitter area ratio of the bipolar transistor and the resistance value between the emitter and the current mirror.

[0010] The current generated by the current mirror module is related to the area of ​​the PMOS Cascode structure.

[0011] The inverter chain module is formed by cascading an odd number of inverters, and the oscillation frequency of the inverter chain module is related to the number of stages and the size of the inverters.

[0012] The voltage stabilizing module controls the power supply voltage of the inverter chain module through the non-inverting input terminal of the error amplifier and the feedback resistor network, and the voltage is closely related to the value of the feedback resistor.

[0013] The waveform shaping module converts the output signal of the inverter chain module into a square wave oscillation signal with full power supply swing through strong pull-up and pull-down buffer stages.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The circuit structure is simple, the power consumption is low, and it is easy to integrate on a chip. The ring oscillator of the present invention adopts a simple circuit structure, has low power consumption, and can be easily integrated on a chip, and is suitable for application in integrated circuits.

[0015] The oscillation frequency has good stability and is less affected by voltage and temperature changes. Under the conditions of the designed process, the ring oscillator can maintain a relatively stable oscillation frequency, and the influence of voltage and temperature changes on the oscillation frequency is minimal. Under the conditions of civilian-grade voltage and temperature changes, the change of the oscillation frequency is controlled within ±2%, with high stability.

[0016] Good transplantability and adaptability to various process platforms. The ring oscillator principle of the present invention does not rely on special processes, has good transplantability, can be applied to different process platforms, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a system block diagram of the ring oscillator in the present invention.

[0018] Figure 2 It is a specific implementation circuit diagram of the ring oscillator in the present invention.

[0019] Figure 3 It is a schematic diagram of the output waveform of the ring oscillator in the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific implementations, but the examples are not intended to limit the present invention.

[0021] As attached Figure 1 As shown, a ring oscillator circuit with low temperature drift and low voltage drift includes: A reference current generating module for providing a positive temperature coefficient current adopts an NMOS and PMOS cascode structure to reduce the power supply rejection ratio; it includes two bipolar transistors with emitter areas having a certain ratio, and the voltage difference between the emitter and the collector generates a current with a monotonic temperature characteristic through a resistor with a temperature characteristic; A current mirror module, which copies the current output by the reference current generation module as a tail current input of the inverter chain module; An inverter chain module, composed of an odd number of inverter stages, provides an oscillating clock signal, the frequency of which is linearly related to the number of stages of the inverter chain module; A waveform shaping module, including several stages of inverters, converts the oscillating clock signal generated by the inverter chain module into a square wave oscillation signal with full power supply swing; A voltage regulator module, including an error amplifier and a feedback resistor network, ensures that the supply voltage of the inverter chain module remains stable when the power supply voltage changes; The startup module ensures that the reference current generation module is out of the zero degeneracy point and operates normally during the power-on process.

[0022] The oscillation frequency of the ring oscillator circuit is controlled by the number of inverter stages, the tail current of the inverter chain module, and the area of ​​the inverter MOS tube.

[0023] The voltage stabilizing module utilizes the virtual short characteristic of the error amplifier input terminal to directly generate the control voltage of the inverter chain module through the feedback resistor network, and the voltage value is related to the in-phase input terminal of the error amplifier and the feedback resistor value.

[0024] The reference current generating module changes the temperature characteristics of the reference current by changing the emitter area ratio of the bipolar transistor, the resistance value between the emitter and the current mirror, and the replication ratio of the current mirror module.

[0025] As attached Figure 2 As shown, it is a schematic diagram of the circuit structure used to generate a reference current source: The source of M1 is connected to the drain of M2, the upper plate of C1, and the gate of M3. The source of M1 is connected to the power supply voltage VDD, and the gate of M1 is connected to the ground line GND. The source of M2 is connected to the ground line GND, and the gate of M2 is connected to the drain of M9, the gate of M10, the gate of M11, and the lower end of R3. The drain of M3 is connected to the lower end of R2 and the drain of M8, and the source of M3 is connected to the ground line GND. The source of M4 is connected to the power supply voltage VDD, the gate of M4 is connected to the gate of M5 and the gate of M12, and the drain of M4 is connected to the upper end of R2 and the drain of M6. The source of M5 is connected to the power supply voltage VDD, and the drain of M5 is connected to the source of M7. The gate of M6 is connected to the gate of M7 and the gate of M13. The drain of M7 is connected to the upper end of R3, the gate of M8, and the gate of M9. The source of M8 is connected to the drain of M10. The source of M10 is connected to the upper end of R1. The source of M11 is connected to the emitter of Q2. The emitter of Q1 is connected to the lower end of R1, and the base electrode of Q1 is connected to the collector of Q1, the base electrode of Q2, the collector of Q2, and the ground line GND. The source of M12 is connected to the power supply voltage VDD, and the drain of M12 is connected to the source of M13. The drain of M13 is connected to the upper end of RF1, the output end of the error amplifier EA, and the sources of all PMOS tubes in the inverter chain module. The lower end of RF1 is connected to the upper end of RF2 and the non-inverting input end of the error amplifier. The lower end of RF2 is connected to the ground line GND. The inverting input end of the error amplifier EA is connected to the external reference voltage. The sources of all NMOS tubes in the inverter chain module are connected to the ground line GND, the output of each inverter is connected to the input of the next inverter, and the output of the last inverter is connected to the input of the first inverter and the input of the rectifier module. The PMOS of each inverter in the rectifier module is connected to the power supply voltage VDD, the NMOS tubes are connected to the ground line GND, the output of the previous inverter is connected to the input of the next inverter, and the output of the last inverter is the required square wave clock signal CLK.

[0026] The following is an introduction to the implementation of the entire ring oscillator: As attached Figure 2As shown, when the power supply starts to power on, the startup module starts working first. M1 is turned on, and the drain of M1 is pulled high, so that M3 is turned on and current is injected into the drain of M8. Afterwards, M3 is cut off due to the reduction of the gate voltage, and only the branch where M1 and M2 are located in the startup module works. At the same time, the reference current generation module flows a current with a positive temperature coefficient through R1, and is proportionally copied to the inverter chain module through the current mirror module where M4, M6, M12, and M13 are located, providing the tail current IOR. The voltage regulator module generates a stable voltage VOR to power the inverter chain module. Afterwards, the inverter chain module generates an oscillation signal, and outputs it as a regular square wave signal through the rectifier module.

[0027] The oscillation frequency of the oscillator circuit is controlled by the number of inverter chain modules, the power supply current of the inverter chain modules, and the area of ​​the inverter MOS tube. The final input frequency is ; in I OR is the supply current of the ring oscillator, V OR is the supply voltage of the ring oscillator, C L is the load capacitance of each inverter stage.

[0028] in, V OR Determined by the voltage regulator module structure.

[0029] As attached Figure 3 As shown, it is a schematic diagram of the clock signal waveform generated by the ring oscillator.

[0030] The embodiments described above can be further combined or replaced, and the embodiments are only descriptions of preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various changes and improvements made by ordinary technicians in this field to the technical solution of the present invention belong to the protection scope of the present invention. The protection scope of the present invention is given by the attached claims and any equivalents thereof.

Claims

1. A ring oscillator circuit with low temperature drift and low voltage drift, characterized in that: include: Reference current generation module, current mirror module, inverter chain module, waveform shaping module, voltage stabilization module, startup module; The reference current generating module provides a positive temperature coefficient current and adopts NMOS and PMOS Cascode structures to reduce the power supply rejection ratio; it includes two bipolar transistors with emitter areas having a certain ratio, and the ratio is related to the layout, power consumption, and process library MOS tube characteristics. The voltage difference between the emitter and the collector generates a current with a monotonic temperature characteristic through a resistor with a temperature characteristic, and the current is the input of the current mirror module; The current mirror module copies the current output by the reference current generating module as the tail current input of the inverter chain module; The inverter chain module is composed of an odd number of inverters, providing an oscillating clock signal for the peripheral circuit, the frequency of which is linearly related to the number of stages of the inverter chain module, and the signal is used as the input of the waveform shaping module; The waveform shaping module includes several stages of inverters, which convert the oscillating clock signal generated by the inverter chain module into a square wave oscillation signal with full power supply swing; The voltage stabilizing module includes an error amplifier and a feedback network to ensure that the power supply voltage of the inverter chain module remains stable when the power supply voltage changes, and its output is used as the power supply voltage of the inverter chain module; The startup module ensures that the reference current generating module is separated from the zero degeneracy point and operates normally during the power-on process.

2. The ring oscillator circuit according to claim 1, characterized in that: The temperature slope of the current generated by the reference current generating module is related to the emitter area ratio of the bipolar transistor and the resistance value between the emitter and the current mirror.

3. The ring oscillator circuit according to claim 1, characterized in that: The current generated by the current mirror module is related to the area of ​​the PMOS Cascode structure.

4. The ring oscillator circuit according to claim 1, characterized in that: The inverter chain module is formed by cascading an odd number of inverters, and the oscillation frequency of the inverter chain module is related to the number of stages and the size of the inverters.

5. The ring oscillator circuit according to claim 1, characterized in that: The voltage stabilizing module controls the power supply voltage of the inverter chain module through the non-inverting input terminal of the error amplifier and the feedback resistor network, and the voltage is closely related to the value of the feedback resistor.

6. The ring oscillator circuit according to claim 1, characterized in that: The waveform shaping module converts the output signal of the inverter chain module into a square wave oscillation signal with full power supply swing through strong pull-up and pull-down buffer stages.

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