Simply-realized crystal-oscillation-free circuit of USB (Universal Serial Bus) 1.1 device interface

Abstract

The invention relates to a simply-realized crystal-oscillation-free circuit of a USB (Universal Serial Bus) 1.1 device interface. The simply-realized crystal-oscillation-free circuit comprises a high-frequency oscillator, a sampling clock frequency divider, a USB1.1 data receiver, a USB1.1 data state machine, a USB1.1 built-in clock judgment device and a Delta-Sigma frequency divider, wherein the high-frequency oscillator is used for providing a high-frequency clock, the USB1.1 data receiver is used for receiving effective information sent by a host, the USB1.1 data state machine is used for analyzing characteristic information, then a USB1.1 built-in clock judgment device takes the time span or the time interval of the characteristic information as a reference clock, and dynamically adjusts the frequency demultiplication number of the Delta-Sigma frequency divider through calculation, and finally, a high-precision built-in system clock is produced. When obtaining high performance, the simply-realized crystal-oscillation-free circuit realizes the crystal-oscillation-free technology of the USB 1.1 device interface, and meets the requirement on the low cost of the design of the USB1.1 interface to the maximum extent.

Description

technical field [0001] The invention relates to the application of the USB interface, in particular to a crystal oscillator-free realization circuit applied to the USB1.1 device interface. [0002] Background technique [0003] With the advancement of technology and technology, the fourth generation of USB series interface - USB3.0 technology is also becoming mature, but in many application fields, because the data transmission rate is not high, the USB1.1 interface is also required. The low-threshold trend of USB1.1 interface circuit design will inevitably bring about increasingly fierce price competition and performance competition, and its cost reduction has become an important part of the cost reduction of USB1.1-related products. [0004] In most applications of the USB1.1 device interface, a high-quality crystal oscillator is required as the input clock source to generate a high-precision system clock. The cost of high-quality crystal oscillator occupies a large prop...

AI Technical Summary

Problems solved by technology

The common defect of these schemes is: after the frequency calibration, as the external environment changes, the system clock will produce a non-negligible frequency offset, which will lead

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