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CN-122026861-A - Relaxation oscillator, relaxation oscillator method and relaxation oscillator system capable of calibrating temperature and frequency simultaneously

CN122026861ACN 122026861 ACN122026861 ACN 122026861ACN-122026861-A

Abstract

The invention discloses a relaxation oscillator, a method and a system for calibrating temperature and frequency simultaneously, wherein the relaxation oscillator comprises a voltage average feedback VAF circuit, the voltage average feedback VAF circuit comprises an oscillation capacitor, a comparator, a latch and a voltage dividing network for generating a reference voltage Vref, the voltage dividing network comprises a main voltage dividing branch, a main voltage dividing branch and a first type resistor and a second type resistor, the main voltage dividing branch is connected between a power supply voltage and the ground and used for generating the main reference voltage, the first type resistor is provided with a first temperature coefficient, the second type resistor is provided with a second temperature coefficient, a first programmable regulating unit is used for responding to a first digital control signal to regulate the effective resistance value of the first type resistor, and a second programmable regulating unit is used for responding to a second digital control signal to regulate the effective capacitance value of the oscillation capacitor, and the circuit and the method can independently, accurately and efficiently calibrate the output frequency and the temperature coefficient of the oscillator simultaneously, and greatly improve the product performance and the production yield.

Inventors

  • XU JIANCHAO
  • SUN TIANPING
  • Lv Qipu

Assignees

  • 深圳市爱协生科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260116

Claims (10)

  1. 1. A relaxation oscillator comprises a voltage average feedback VAF circuit, wherein the voltage average feedback VAF circuit comprises an oscillation capacitor, a comparator, a latch and a voltage division network for generating a reference voltage Vref, and is characterized in that the voltage division network comprises a main voltage division branch connected between a power supply voltage and ground and used for generating a main reference voltage, the voltage average feedback VAF circuit comprises at least one first type resistor and one second type resistor, the first type resistor has a first temperature coefficient, the second type resistor has a second temperature coefficient with a sign opposite to that of the first temperature coefficient, an auxiliary voltage division branch connected between the power supply voltage and ground and used for generating an auxiliary reference voltage, the auxiliary voltage division branch comprises at least the second type resistor, a switching unit and used for selectively outputting the main reference voltage or the auxiliary reference voltage as the reference voltage Vref to the voltage average feedback VAF circuit, a first programmable regulating unit is coupled with the first type resistor in the main voltage division branch and used for responding to a first digital control signal so as to regulate the effective resistance value of the first type resistor, an auxiliary voltage division branch is connected between the power supply voltage and ground, and an auxiliary voltage division branch is used for generating an auxiliary reference voltage which at least comprises the second type resistor.
  2. 2. The relaxation oscillator of claim 1, wherein said first temperature coefficient is a negative temperature coefficient and said second temperature coefficient is a positive temperature coefficient.
  3. 3. The relaxation oscillator of claim 2, wherein said first type of resistor is an N-type polysilicon resistor and said second type of resistor is a P-type polysilicon resistor or a diffusion resistor or a well resistor.
  4. 4. The relaxation oscillator of claim 1, wherein the second type of resistor in the auxiliary voltage dividing branch is made of the same material and has the same resistance as the second type of resistor in the main voltage dividing branch.
  5. 5. The relaxation oscillator of claim 1, wherein the first programmable tuning element and the second programmable tuning element are in a switch array configuration.
  6. 6. A method for calibrating a relaxation oscillator according to any of claims 1 to 5, comprising a first measuring step of controlling said switching unit to output said auxiliary reference voltage and measuring a first output frequency f2 of said relaxation oscillator; the method comprises a first measuring step of controlling a switching unit to output a main reference voltage and measuring a first output frequency f1 of a relaxation oscillator, a second measuring step of controlling the switching unit to output the main reference voltage and measuring a second output frequency f1 of the relaxation oscillator, a parameter resolving step of resolving an actual proportion value beta of a first type resistor and a second type resistor in a main voltage dividing branch based on the first output frequency f2 and the second output frequency f1, a temperature coefficient calibrating step of enabling the actual proportion value beta to approach a preset target proportion value by adjusting a first digital control signal to change an effective resistance value of the first type resistor, and a frequency calibrating step of enabling the output frequency of the relaxation oscillator to approach the target frequency by adjusting a second digital control signal to change an effective capacity value of an oscillation capacitor after the temperature coefficient calibrating step or simultaneously adjusting R1, R2, R3 and R4, and keeping the proportion values of R1/R2, R4/R3/R4 unchanged.
  7. 7. The method according to claim 6, wherein the parameter resolving step resolves the actual scale value β based on the following relation: Wherein β0 is a known design ratio value of the corresponding resistor in the auxiliary voltage divider branch, and K1 and K2 are constants related to the voltage divider network and the voltage average feedback VAF circuit topology.
  8. 8. The method of claim 6, wherein the temperature coefficient calibration step is performed sequentially with the frequency calibration step, and the frequency calibration step does not change the actual scale value β for which calibration has been completed.
  9. 9. The method of claim 6, wherein the parameter calculation step includes calculating a first voltage division ratio parameter α2 using a first linear relationship of 1/α2=a- (f2×r+c) +b, where a and B are fitting constants, R is a typical value of the second type of resistor, and C is a typical value of the oscillating capacitance, based on the first output frequency f2 and the known parameters of the auxiliary voltage division branch, calculating a second voltage division ratio parameter α1:1/α1=a- (f1×r+c) +b based on the second output frequency f1 and the first linear relationship, and calculating the actual ratio value β based on the first voltage division ratio parameter α2 and the relationship of the second voltage division ratio parameter α1 to the resistor ratio.
  10. 10. A calibration system for calibrating a relaxation oscillator, characterized in that the system comprises a measuring unit for measuring the output frequency of the relaxation oscillator, a control unit for generating a control signal in the method according to any of claims 6 to 9 for manipulating a switching unit, a first programmable regulating unit and a second programmable regulating unit within the relaxation oscillator, and a calculating unit for performing the calculation in the parameter resolving step.

Description

Relaxation oscillator, relaxation oscillator method and relaxation oscillator system capable of calibrating temperature and frequency simultaneously Technical Field The present invention relates to the field of integrated circuits, and in particular, to a relaxation oscillator, a relaxation oscillator method and a relaxation oscillator system for calibrating temperature and frequency simultaneously. Background The relaxation oscillator is widely applied to the field of clock generation due to the simple structure and easy integration. The conventional relaxation oscillator adopts a dual comparator and current source charge-discharge structure, as shown in the background art fig. 1. The working principle is that the current source I1/I2 charges and discharges the capacitor C under the control of a switch to generate a sawtooth voltage Vosc, and the latch is triggered to turn over by comparing with a high/low threshold voltage (Vhigh/Vlow), so that oscillation is formed. However, this conventional structure has an inherent disadvantage (as shown in the waveform of fig. 2) in that the comparator delay (td) directly affects the frequency accuracy, resulting in an oscillation period containing a delay error term. The current source is affected by the groove length modulation effect, the charge and discharge current is not constant, and nonlinearity is introduced. Flicker noise of the current source may deteriorate phase noise. To overcome the above drawbacks, the prior art proposes a Voltage-Average-Feedback (VAF) relaxation oscillator as shown in fig. 3. The structure uses a resistor to replace a current source to charge a capacitor, and a negative feedback loop (the average value of a forced oscillation waveform is equal to a stable reference voltage Vref.) the method effectively suppresses the influence of comparator delay and current nonlinearity, as shown in the waveform of the background art figure 4. VAF oscillators still face significant challenges in practical applications: The temperature stability is poor, the core oscillation frequency is determined by the RC time constant, and the resistance in the integrated circuit has a significant temperature coefficient (P-type polysilicon temperature coefficient of resistance is usually positive, N-type polysilicon temperature coefficient of resistance is usually negative), resulting in frequency drift with temperature. Calibration coupling difficulties-to compensate for temperature drift, it is often necessary to introduce elements with opposite temperature coefficients (e.g., positive temperature coefficient resistors) and adjust the ratio thereof. However, while adjusting this ratio to change the temperature coefficient, the split ratio is inevitably changed, thereby directly affecting the frequency, α being strongly correlated with T/RC as shown in fig. 5. This strong coupling between temperature compensation and frequency adjustment makes it impossible to calibrate the frequency and temperature coefficients to target values simultaneously independently in mass production. Process angle sensitivity, namely, under different process angles, the absolute value changes of different types of resistors are inconsistent, so that the preset temperature compensation proportion is invalid, and the yield is reduced. Therefore, there is a need in the art for a VAF oscillator solution that decouples temperature calibration from frequency calibration to achieve high precision, high stability output over a full temperature range and at various process angles. Disclosure of Invention The invention aims to solve the technical problem of providing a relaxation oscillator, a relaxation oscillator method and a relaxation oscillator system for simultaneously calibrating temperature and frequency, wherein the relaxation oscillator circuit and the relaxation oscillator method can independently, accurately and efficiently calibrate the output frequency and the temperature coefficient of the oscillator simultaneously, and greatly improve the product performance and the production yield. To solve the above-mentioned problems, the present invention provides a relaxation oscillator, comprising a voltage-averaging feedback VAF circuit, the voltage-averaging feedback VAF circuit comprising an oscillating capacitor, a comparator, a latch and a voltage dividing network for generating a reference voltage Vref, the voltage dividing network comprising a main voltage dividing branch connected between a supply voltage and ground for generating a main reference voltage, the main voltage dividing branch comprising at least a first type resistor and a second type resistor, the first type resistor having a first temperature coefficient and the second type resistor having a second temperature coefficient opposite in sign to the first temperature coefficient, an auxiliary voltage dividing branch connected between the supply voltage and ground for generating an auxiliary reference voltage, the auxil