Circuit for generating usb peripheral clock and method therefor

Abstract

A circuit for generating USB peripheral clock comprises: an internal oscillator, a controllable frequency divider, a frequency multiplier, a receiving counter and a frequency division controller, wherein the internal oscillator generates a clock having a fixed frequency; the controllable frequency divider processes frequency division on the clock generated by the internal oscillator; the frequency multiplier processes frequency multiplication on the clock after frequency division and transmits the clock after frequency multiplication to the USB main structure; the receiving counter receives an SOF packet which is transmitted by a host according to the clock outputted by the frequency multiplier, and counts intervals of receiving the SOF packet; and the frequency division controller compares the difference between the counting result of the receiving counter and a standard interval, controls and regulates frequency division parameters of the controllable frequency divider according to a comparing result thereof.