An Adaptive Pulse-Width Control Loop

In high-speed CMOS clock buffer design, the duty cycle of a clock is liable to be changed when the clock passes through a multistage buffer (Fenghao and Svensson, 2000). In this paper, we propose a pulsewidth control loop referred as APWCL (adaptive pulsewidth control loop) that adopts the same architecture as the conventional PWCL, but with two modifications. The first one relates to implementation of the pseudo inverter control stage (PICS), while the second to involvement of adaptive control loop. The first modification provides generation of output pulses during all APWCL´s modes of operation and the second faster locking time. For 1.2 mum CMOS process with V_dd = 5V and operating frequency of 100 MHz, results of SPICE simulation show that the duty cycle can be well controlled in the range from 20% up to 80% if the loop parameters are properly chosen