Oscillator

Abstract

An oscillator, generating multiple phases of clock signals having a uniform phase difference with a high precision by a simple configuration, includes a plurality of NAND circuits ND1 to ND8 having the same number of input terminals connected in a ring. Eight NAND circuits are connected, and an output node of each NAND circuit is connected to an input node of each NAND circuit up to the NAND circuit connected exactly two places, that is, the number of input terminals' worth of places, ahead.

Description

[0001] The present application is a continuation application of U.S. patent application Ser. No. 10 / 785,957, filed on Feb. 26, 2004, the entire contents being incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention The present invention relates to an oscillator. [0003] 2. Description of the Related Art [0004] One of the methods employed in digital phase-locked loop (PLL) circuits is to select the optimum pulse from generated multiple phases of clock signals and use it as an output signal of the PLL circuit. In this case, if a difference arises in the phase differences between clock signals forming the multiple phases of clock signals, jitter of the output signal ends up increasing in accordance with the magnitude of the difference. Therefore, it is demanded that the phase difference be made constant with a high precision. [0005] Further, processing for the selection is realized by a digital circuit, but when the number of phases of the multi-pha...

AI Technical Summary

Benefits of technology

[0009] An object of the present invention is to provide an oscillator for generating an even number of phases of clock signals having a uniform phase difference with a high precision by a simple configuration.

Problems solved by technology

Further, processing for the selection is realized by a digital circuit, but when the number of phases of the multi-phase clock signals is an odd number, the arithmetic operations to be executed in the digital circuit become complex, so a processing circuit having a large circuit size is considered needed.

However, these oscillators do not have symmetry in circuit configuration.

From this, there is the problem that power supply noise is generated by fluctuation of the consumed current for every period in the oscillator, so a difference occurs in the phase difference between clock signals forming the multiple phases of clock signals.

However, a ring oscillator using inverters as components is large in circuit size.

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