Compensated-clock generating circuit and usb device having same

A technology of clock generation circuit and generation circuit, which is applied in the direction of electric pulse generator circuit, generation/distribution signal, pulse generation by differential amplifier, etc., can solve the problem of unsatisfactory frequency accuracy of the oscillator, and achieve the effect of low cost
CN1940808AInactive Publication Date: 2007-04-04NEC ELECTRONICS CORP
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
NEC ELECTRONICS CORP
Publication Date
2007-04-04
Estimated Expiration
Not applicable · inactive patent

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Abstract

A compensated-clock generating circuit that complies with USB specifications includes an oscillating circuit that generates clock pulses; a counting circuit that counts the number of clock pulses from the oscillating circuit based upon a regular prescribed signal in accordance with a USB downstream signal; and a frequency compensation value generating circuit that compares the value counted by the counting circuit and a prescribed reference value and obtaining a compensation value. The oscillation frequency of the oscillating circuit is corrected to a prescribed value in response to receipt of the compensation value from the frequency compensation value generating circuit. Compensation is applied based upon a highly accurate signal that is based upon USB specifications, thereby making it possible to generate pulses of higher accuracy even if the accuracy of the oscillation frequency per se of the oscillator in the oscillation circuit is low.
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Description

technical field

[0001] The present invention relates to a corrected clock generating circuit, in particular to a corrected clock generating circuit realizing frequency accuracy complying with the USB specification and a USB device equipped with the same. Background technique

[0002] Recently, in personal computers (PCs) and the like, the USB specification has been popularized. Therefore, terminals such as keyboards, mice, and scanners also require the transfer rate of data to be within a given accuracy in compliance with the USB specification. Generally, these terminals that meet the USB specification are called USB devices. The USB specification has various cases such as low speed and full speed. As an example, the widely used full speed requires an accuracy of ±0.25% of the data transfer speed. In order to satisfy this value, it is of course necessary to make the clock more accurate than this value. For this reason, a method of using a high-precision external crystal r...

Claims

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