RC relaxation oscillator

Abstract

The embodiment of the invention provides an RC relaxation oscillator. The RC relaxation oscillator comprises a voltage generation circuit, a capacitor charging and discharging circuit, a voltage comparison circuit and a logic control circuit, the voltage generation circuit comprises a reference voltage generation circuit, a decision voltage generation circuit and a voltage establishment signal generation circuit. The capacitor charging and discharging circuit comprises a first charging and discharging branch circuit and a second charging and discharging branch circuit, the first charging and discharging branch circuit comprises a capacitor C1, the second charging and discharging branch circuit comprises a capacitor C2, and the capacitor C1 and the capacitor C2 alternately charge or discharge; the voltage comparison circuit comprises a comparator CMP; the comparator CMP is used for comparing each comparison object of the voltage comparison circuit with a reference voltage; and the logic control circuit comprises a frequency dividing circuit and a logic feedback circuit. According to the RC relaxation oscillator, the influence of time delay caused by a comparator CMP, signal transmission and the like on the oscillation frequency of a clock signal can be eliminated, and the stability of the oscillation frequency is improved.

Description

technical field [0001] The embodiments of the present application relate to the technical field of electronic circuits, and in particular to an RC relaxation oscillator. Background technique [0002] In integrated circuits, oscillators are generally used to generate clock signals to keep the circuit system running in an orderly manner; common oscillators include RC relaxation oscillators, quartz crystal oscillators, and phase-locked loop frequency synthesizers. Among them, the RC relaxation oscillator has the advantages of simple structure, easy integration, low power consumption and low cost, and thus has been widely used. [0003] Such as figure 1 As shown, it is a schematic diagram of the structure of the RC relaxation oscillator in the prior art, and its working principle is: the current source I1 generates the reference voltage Vref of the comparator CMP at both ends of the resistor R; the current source I2 charges the capacitor C, so that the capacitor The charging v...

AI Technical Summary

Problems solved by technology

However, the above-mentioned RC relaxation oscillator has the following defects: due to the delay in the comparator CMP and signal transmission, when the charging voltage Vc rises or falls to the reference voltage Vref, the comparator CMP needs to output the corresponding comparison after a delay. state, causing the oscillation frequency of the above-mentioned RC relaxation oscillator to be lower than the designed theoretical value; the delay of the comparator is related to the performance of the comparator CMP itself and the voltage difference between the positive and negative input signals

[0009] Combining formula 2 and formula 3, it is found that the period T of the clock signal CLK not only depends on the proportional coefficient K between the current sources, the size of the resistance R and the capacitance C, but also is affected by the comparison delay of the comparator CMP and the discharge capacity of the capacitance C The impact of the above RC relaxation oscillator causes the oscillation frequency of the above-mentioned RC relaxation oscillator to be lower than the designed theoretical value, and the voltage stability and temperature stability of the oscillation frequency are poor

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