DIFFERENTIAL QUADRATURE DIVIDE-BY-THREE CIRCUIT WITH DUAL FEEDBACK PATH

摘要

A divide-by-three circuit includes a chain of three dynamic flip-flops and a feedback circuit of combinatorial logic. The divide-by-three circuit receives a clock signal that synchronously clocks each dynamic flip-flop. The feedback circuit supplies a feedback signal onto the first dynamic-flop of the chain. In a first mode, a signal from a slave stage of the first flip-flop and a signal from a slave stage of the second flip-flop are used by the feedback circuit to generate the feedback signal. In a second mode, a signal from a master stage of the first flip-flop and a signal from a master stage of the second flip-flop are used by the feedback circuit to generate the feedback signal. By proper selection of the mode, the frequency range of the overall divider is extended. Combinatorial logic converts thirty-three percent duty cycle signals from the flip-flop chain into fifty percent duty cycle quadrature signals.