A low-temperature drift oscillator and method for obtaining low-temperature drift clock frequency

Abstract

The invention relates to a low-temperature drift oscillator, which belongs to the technical field of oscillators. A low-temperature drift oscillator and a method for obtaining a low-temperature drift clock frequency, characterized in that it includes a positive temperature coefficient current generation circuit, a negative temperature coefficient current generation circuit, a current mixing conversion circuit and a capacitance shaping circuit, and the positive temperature coefficient current generation circuit passes through The current mirror generates a positive temperature coefficient main branch and a positive temperature current calibration branch, and the negative temperature coefficient current generation circuit generates a negative temperature coefficient main branch and a negative temperature current calibration branch through the current mirror; through the current mixing conversion circuit After mixing, the zero temperature coefficient current is obtained, and the zero temperature coefficient current is adjusted according to the needs, and then the constant capacitance in the capacitance shaping circuit is charged and discharged to obtain different low-temperature drift clock frequencies. The invention utilizes the positive temperature curve and the negative temperature curve of the current to correct the temperature drift of the oscillator, which has higher accuracy and is easier to adjust than using other forms of circuits to control the temperature drift.

Description

technical field [0001] The invention relates to an oscillator, in particular to a low-temperature drift oscillator and a method for obtaining a low-temperature drift clock frequency. Background technique [0002] In the prior art, the oscillator usually adopts a ring or RC charge-discharge oscillation structure. The frequency of the ring oscillator is closely related to the device temperature characteristics and process of the power supply and inverter. Due to the large difference between chips and the temperature drift cannot be calibrated , resulting in poor product consistency. Because the RC oscillator uses the bandgap voltage to generate the charging current, the final frequency is only related to the temperature characteristics of the resistor R and the capacitor C. In fact, both the resistor R and the capacitor C have a temperature drift of about 10%, even if they are used in combination The resistance of positive and negative temperature drift can be reduced. Genera...

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Problems solved by technology

[0002] In the prior art, the oscillator usually adopts a ring or RC charge-discharge oscillation structure. The frequency of the ring oscillator is closely related to the device temperature characteristics and process of the power supply and inverter. Due to the large difference between chips and the temperature drift cannot be calibrated , leading to poor product consistency

Because the RC oscillator uses the bandgap voltage to generate the charging current, the final frequency is only related to the temperature characteristics of the resistor R and the capacitor C. In fact, both the resistor R and the capacitor C have a temperature drift of about 10%, even if they are used in combination The resistance of positive and negative temperature drift can be reduced. Generally, the difference between chips will be higher than 2%, and when calibrating the temperature drift, it will also affect the absolute value of the oscillator frequency; and when calibrating the absolute value of the oscillator frequency, it will be Temperature drift that affects the oscillator frequency

Because the existing oscillator structure cannot calibrate the temperature drift and the absolute value of the frequency independently, the final temperature drift between chips must be guaranteed by the process, which requires high process consistency.

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