THE CORRECTION CIRCUIT OF DUTY CYCLE BASED ON DLL

摘要

A correction circuit of a duty cycle based on DLL(delay lock loop) is provided to correct output duty cycle with an input duty cycle signal having low variation by performing XOR operation of the input duty cycle, the input duty cycle having phase different of 90 degree, 2T duty cycle. A T-flip-flop(110) receives a duty cycle signal and generates a duty cycle having double period. A phase/frequency detection module(120) receives the 2T duty cycle signal from the T-flip-flop and receives a duty cycle of 90 degree from the voltage controlled module. The phase/frequency detection module produces 2T duty cycle signal from the applied signal. A charge pump receives 2T duty cycle signal, a phase / frequency information, and the duty cycle signal of 90 degree from the phase/frequency detection module and generates DLL locked voltage. The voltage controlled delay module(140) adds up DLL lock voltage and generates the duty cycle signal of 360 degree and duty cycle of 90 degree. An XOR gate(150) performs XOR operation of 2T duty cycle signal and duty cycle of 90 degree and outputs the duty cycle of 50%.