A 50% duty-cycle correction circuit for PLL output

A 50% duty-cycle correction circuit was proposed to tighten duty-cycle into an allowable range to increase the yield of PLLs designed with deep submicron design rules. The circuit composed of duty-detection and duty-correction sub-circuits reduces the duty-cycle fluctuation of PLLs originating from the mismatches of devices and transient responses in signal paths. The 50% duty-cycle correction circuit fabricated with a 0.6mum design rule demonstrated that all the input signals in the range of duty-cycle from 20 to 80% turn out to be duty-cycle fluctuation of 0.21% at the output, achieving one-three hundreds of reduction of duty-cycle fluctuation.