An infinite phase shift delay-locked loop with voltage-controlled sawtooth delay line

A wide-range delay-locked loop (DLL) with infinite phase shift and duty cycle control is presented. A voltage-controlled sawtooth delay line provides not only the delay control but also duty cycle control. The proposed DLL achieves infinite phase shift by using a single loop. Therefore, it has the benefits of good jitter and wide range compared with the conventional dual-loop DLL. The proposed DLL has been fabricated in a 0.18-mum CMOS process and the core area is 0.45 times 0.3 mm². The measurement results show the proposed DLL operates from 50 MHz to 500 MHz. The duty cycle of the output clock can be adjusted from 30% to 60% in the step of 5%. At 500 MHz, the measured peak-to-peak jitter is 11.1 ps and the power consumption is 6 mW.