High-linearity relaxation oscillator

Abstract

The invention provides a relaxation oscillator of which the linearity is significantly improved. The relaxation oscillator comprises an oscillating circuit, a reference level self-regulating circuit and a transmission gate selective signal generating circuit. Capacitor voltage overshoot caused by delay of a control circuit is worked out by detecting the voltage peak of charge and discharge capacitors in the oscillating circuit, and accordingly the reference level of comparators in the oscillating circuit is reduced by a corresponding quantity to serve as a new reference level so that the oscillation amplitude of the charge and discharge capacitors can be just a theoretical value. According to the high-linearity relaxation oscillator, when the new reference level is larger than zero, influence, brought by the capacitor voltage overshoot caused by delay of the control circuit, of the charge and discharge capacitors on output frequency is eliminated, and the linearity of a frequency-control circuit of the relaxation oscillator is significantly improved. The transmission gate selective signal generating circuit provides the initial reference level for the comparators by controlling transmission gates and transmits the new reference level to the reverse phase ends of the comparators when the new reference level is generated, and therefore the initial reference level can be isolated from the reverse phase ends of the comparators.

Description

technical field [0001] The invention relates to the field of CMOS integrated circuits, in particular to a relaxation oscillator with high linearity, which remarkably improves the frequency-control current linearity through self-regulation of a comparator reference level. Background technique [0002] In large-scale integrated circuits, clock signals are generally generated by oscillators. The relaxation oscillator has a simple structure, low cost, easy integration, and relatively low power consumption. It is the most widely used clock generation circuit in the oscillator. [0003] In the application of signal modulation and demodulation, data recovery of storage system, etc., it is required that the frequency-control current of the relaxation oscillator used has a high linearity, so as to reduce distortion and increase the relaxation oscillation frequency range of the device. In relaxation oscillators, the frequency-control current linearity is related to the delay of the ...

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Problems solved by technology

[0028] Although, a current-controlled relaxation oscillator with dual timing capacitors will delay by 4t in one cycle d reduced to 2t d , but the output frequency of the oscillator is still subject to the control circuit of the oscillation amplitude of the timing capacitor and the delay 2t of the PMOS transistor M1, NMOS transistor M2, PMOS transistor M3, and NMOS transistor M4 as control switches d effect, especially at high frequencies, the 2t d The delay is even greater than the period of the oscillator output waveform, which not only reduces the linearity of the frequency-controlled current, but also limits the maximum frequency range of the oscillator. Therefore, it is necessary to further improve the current-controlled relaxation oscillator with dual timing capacitors. , to reduce the effect of delay

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