A frequency divider includes a first shifter and a second shifter. The first shifter includes first to M-th clock control components connected together to form a first ring. The control components in the first shifter are controlled by an input clock signal such that signals are shifted along the first ring. An output of selected clock control components in the first shifter is provided as a carry signal of the first shifter. The second shifter includes first to N-th clock control components connected together to form a second ring. The control components in the second shifter are controlled by the carry signal of the first shifter such that the signals are shifted along the second ring. An output of selected clock control components in the second shifter is provided as a carry signal of the second shifter. M and N are integers greater than one.

An electronic latch circuit, a 4-phase signal generator, a multi-stage frequency divider and a poly-phase signal generator are disclosed. The electronic latch circuit comprises an output circuit comprising a first output and a second output. The electronic latch circuit further comprises an input circuit comprising a first input, a second input and a clock signal input. The electronic latch circuit is configured to change state based on the input signals' level at the inputs of the input circuit and a present state of the output circuit. The 4-phase signal generator is built with two electronic latch circuits. The multi-stage frequency dividers and poly-phase signal generators comprise a plurality of the electronic latch circuits and 4-phase signal generators.

A fractional dividing module includes an output clock generating circuit, for receiving an input clock signal and generating an output clock signal according to a first control signal, comprising a first delay unit, for delaying the input clock signal to generate a delayed input clock signal; and a selecting unit, for selecting one of the input clock signal and the delayed input clock signal to generate the output clock signal according to the first control signal; and a control circuit, for dividing the output clock signal to generate the first control signal according to a dividing control signal, wherein the dividing control is adjusted to control a frequency ratio between the output clock signal and the input clock signal.

A fractional dividing module includes an output clock generating circuit, for receiving an input clock signal and generating an output clock signal according to a first control signal, comprising a first delay unit, for delaying the input clock signal to generate a delayed input clock signal; and a selecting unit, for selecting one of the input clock signal and the delayed input clock signal to generate the output clock signal according to the first control signal; and a control circuit, for dividing the output clock signal to generate the first control signal according to a dividing control signal, wherein the dividing control is adjusted to control a frequency ratio between the output clock signal and the input clock signal.

A digital control oscillator circuit includes: a ring oscillator having delay elements delaying a pulse signal; a counter circuit counting the circulation number of the pulse signal; a rough period generation unit acquiring a period setting value as a magnification ratio for a reference clock, and counting the reference clock using an integer part of the ratio to generate a rough period timing; a fraction conversion unit converting a decimal point part of the ratio into the number of the elements passed by the pulse signal to generate a fraction; and an output processing unit selecting a timing when outputs of the ring oscillator and the counter circuit become values corresponding to the fraction as an output timing when a time corresponding to the fraction has passed after the rough period timing, and generating an output signal oscillating at a period represented by the period setting value according to the output timing.

A feedback module for preventing voltage controlled oscillator (VCO) runaway in a phase locked loop (PLL) circuit can include a first, a second, and a third input to receive a first output signal from a PLL circuit, a reference signal, and a first control signal. The feedback module may also include a feedback circuit to generate a second control signal, the second control signal being coupled to an input of the PLL circuit, wherein the feedback circuit generates the second control signal by comparing a number of cycles of the first output signal to a first threshold, and a number of cycles of the reference signal to a second threshold.

An IC that performs integer and fractional divisions is disclosed. The IC comprises a plurality of shift registers that forms a shift register ring. Consecutive shift registers are coupled to each other through a multiplexer. The IC also includes a multiplexer controller that determines the shift registers to be activated within the shift register ring. The multiplexer controller determines the activation based upon a divisional factor. The IC also includes a pattern controller that generates the control signal to program the shift register.