A Gigahertz Cyclic Injection DLL Clock Generator with an Infinite Acquisition Range

This paper presents the implementation of a cyclic injection DLL based clock generator with an infinite acquisition range and low timing jitter, low phase noise performance. A novel switching scheme with a resettable divider is designed to synchronize the operation of the other blocks in the circuit and to eliminate the need of a start-up or locking detection circuitry. The phase noise performance is improved by injecting the reference edge periodically. Programmable multiplication ratios from 13 to 20 are achieved with an output frequency range of 900 MHz to 2.9 GHz. The circuit is implemented in TSMC 0.18 mum CMOS technology. The measured cycle-to-cycle timing jitter at 2.5 GHz is 2.49 ps (rms) and 20 ps (pk-pk), and the phase noise is -119 dBc/Hz at 1 MHz offset for a carrier frequency of 2.756 GHz.