Patent ID: 7605666

Claim:
A method to produce a digital on-demand digital oscillator of high frequency and to derive lower frequency clocks by digital division, and having the ability to start and stop oscillating, almost instantaneously, and remaining synchronized to an external clock, the method comprising the steps of: a) incorporating a base oscillator comprising a feedback loop, wherein the feedback loop comprises both a bulk delay and a fine delay, and wherein said base oscillator is designed to oscillate at a nominal frequency fn which is 2 n times that of the external clock fclk, with n being a integer; b) calculating the number nb of periods of the base oscillator which are equal or less than the period nclk of the external clock; c) setting the bulk delay delta B equal to nb*pn, where pn=1/fn; d) setting the fine delay delta F equal to pclk−delta B where pclk=1/fclk, so that after including the bulk and fine delays in the feedback loop the base oscillator will have a frequency of 2 n times the external clock, and the method further comprising the steps of: e) gating the on-demand oscillator to an “ON” state in synchronization with the external clock, in order to begin oscillating, wherein steps b) through e) are performed within one period of the external clock, and wherein phase locked loops are not used in the on-demand oscillator.