Relaxation oscillator with average voltage feedback

Abstract

The invention provides a relaxation oscillator with average voltage feedback, comprising a two-capacitance relaxation oscillator unit and an average voltage generating circuit unit, wherein the two-capacitance relaxation oscillator unit comprises two current sources which are symmetrical with each other, two comparators, two charging and discharging capacitors, two transmission gates, two phase inverters and an S-R latch. The relaxation oscillator with average voltage feedback of the invention can be used for generating an adjustable threshold voltage for controlling overturn of a comparator by introducing a circuit of the average voltage feedback. When delay time of the comparator is added, the average value of a sawtooth voltage on the charging and discharging capacitor is added too. An average voltage generating circuit is used for adjusting the threshold voltage for overturning the comparator to reduce so that the comparator can be overturned in advance to hold the period of the oscillator not to be changed basically. Through this manner, the relaxation oscillator with average voltage feedback of the invention reduces the requirement of output frequency accuracy in a traditional relaxation oscillator to a response speed of the comparator and realizes closed-loop regulation to the output frequency of the oscillator with a comparator circuit with simple structure and the average voltage generating circuit.

Description

technical field [0001] The invention relates to analog integrated circuit technology, in particular to a relaxation oscillator with an average voltage feedback topological structure. Background technique [0002] Relaxation oscillators are often used as operating clocks in switching electronic devices. Compared with active or passive crystal oscillators, it has the advantages of small size, simple design, and easy integration. However, its voltage characteristics, temperature characteristics and other properties are relatively poor. The circuit structure of a common dual-capacitor relaxation oscillator is as follows: figure 1 As shown, two currents I are generated by two current sources 1 and I 2 , the two currents alternately flow to the two capacitors C 1 and C 2 charging, the voltage across the capacitor is the same as the I ref The reference voltage generated across the resistor R is compared when the capacitor C 1 After the voltage reaches the threshold, the com...

AI Technical Summary

Problems solved by technology

In order to reduce this effect, the traditional method is realized by speeding up the response speed of the comparator, but this increases the design difficulty and design cost

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