Patent ID: 7551707

Claim:
A programmable integer and fractional frequency divider, dividing a frequency of an input signal by a first divisor to generate an output signal, wherein the first divisor is an integer or a fraction, and the programmable integer and fractional frequency divider comprises: a programmable integer frequency divider, dividing the frequency of the input signal by a second divisor to generate the output signal, wherein the second divisor is set to be first or second integers according to a divisor switching signal; and a fractional number switch, calculating a pulse count of the output signal, and generating the divisor switching signal to switch from the first integer to the second integer when the pulse count of the output signal equals to a predetermined pulse count, wherein the predetermined pulse count is determined by a fractional part of the first divisor, and the fractional number switch receives at least a fractional divisor control signal to change the predetermined pulse count, thereby changing the fractional part of the first divisor.