High-accuracy resistance-capacitance (RC) oscillator

Abstract

The invention relates to a complementary metal-oxide-semiconductor (CMOS) integrated circuit, in particular to a high-accuracy resistance-capacitance (RC) oscillator. The RC oscillator provided by the invention adopts a two-stage regulation way, wherein first-stage regulation is the regulation of a comparison reference voltage, and aims to regulate the output frequency of the oscillator into the range of second-stage regulation; and the second-stage regulation is the regulation of charging current, and aims to make the accuracy of the output frequency of the oscillator meet designing requirements. The generation of the comparison reference voltage and the constant current source designing of the charging current are both based on a band gap reference source so as to achieve the advantage that the reference voltage and the charging current both have low temperature coefficients to endow the RC oscillator with the advantage of low temperature drift. The RC oscillator adopting the two-stage regulation design overcomes the shortcoming of the conventional structure that variations of integrated circuit process parameters may cause function failures, and simultaneously, the two-stage regulation is operable and convenient to actually operate.

Description

technical field The invention relates to a CMOS integrated circuit, in particular to a high-precision RC oscillator. Background technique The RC oscillator is a resistor-capacitor oscillator (R stands for resistance and C stands for capacitance). In modern CMOS integrated circuits, the commonly used RC oscillator design principle is the way that a constant current source charges a capacitor. In order to achieve a precise oscillation frequency, it is necessary to design an internal adjustable constant current source circuit, and adjust the charging current through registers to achieve the purpose of changing the oscillation frequency. Accompanying drawing 1 is a kind of common RC oscillator circuit diagram, wherein charging capacitance C1=C2, charging current Icharge1=Icharge2, the design of up and down symmetrical structure, guarantee the output clock duty cycle of the oscillator is 50%, according to the design oscillation frequency Requires selection of capacitor value an...

AI Technical Summary

Problems solved by technology

Although the above RC oscillator circuit has the advantages of high precision and 50% duty cycle, in order to meet the requirements of trimming accuracy, constant current source matching and implementation cost, the number of trimming bits generally cannot exceed 7 bits, that is, 128 levels. Under the premise of ensuring the frequency accuracy, the frequency adjustable range is generally relatively small

Therefore, the above-mentioned RC oscillator has high requirements on the process parameters of the integrated circuit. Once the process parameters deviate greatly, the output frequency is more likely to exceed the adjustable range, resulting in circuit failure.

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