FRACTIONAL-N FREQUENCY DIVIDER

摘要

A fractional-n frequency divider that overcomes the presence of so-called dead zones in known frequency divider circuits. n divider cells are connected so as to form a ripple counter (n being an integer greater than or equal to two) and an output multiplexer is provided with a clock signal and an inverted clock signal by the nth divider cell. A polarity circuit generates a polarity signal which clocks the output multiplexer so as to controllably combine the clock signal and the inverted clock signal to produce an output signal. A toggle signal toggles between a first and a second integer division configuration so as to provide for fractional divisional outputs therebetween. With n 2/3 divider cells the division ratio therefore can take any fractional value that satisfies the following inequality 2n-1 n+1 - 1.