US Patent 7248665 Prescaler

Disclosed is a Dual-Modulus Prescaler (DMP) dividing an input signal into an output signal, comprising: a synchronous counter, including a D-Flip-Flop (DFF), a first NOR-Flip-Flop and a second NOR-Flip-Flop, receiving the input signal, the division ratio thereof being based on an intermediate signal; a control logic, controlling the division ratio of the synchronous counter and selecting the output frequency based on first and second control signals, and outputting the intermediate signal to the synchronous counter; and an asynchronous counter, coupled to the control logic and the synchronous counter, having a chain of five DFFs.