A 6 MHz-130 MHz DLL with a fixed latency of one clock cycle delay

Abstract

In this paper, a wide range delay-locked loop (DLL) with a fixed latency of one clock cycle is proposed. Using the phase selection circuit and the start-controlled circuit enlarges the operating frequency range of this DLL and eliminates the harmonic locking problems. The operating frequency range of the DLL can be from 1/T/sub Dmin/ to 1/(N/spl times/T/sub Dmax/), where T/sub Dmin/ and T/sub Dmax/ are the minimum and maximum delay of a delay cell, respectively, and N is the number of delay cells used in the delay line theoretically. Fabricated in a 0.35 /spl mu/m 1P3M standard CMOS process, the DLL occupies an active area of 880 /spl mu/m/spl times/515 /spl mu/m and consumes a maximum power of 132 mW at 130 MHz. The measurement results show that the operating frequency range is from 6 MHz to 130 MHz and the latency is just one clock cycle. From the entire operating frequency range, the maximum r.m.s. jitter would not exceed 25 ps.