Wide-range 16-phases DLL based on improved dead-zone phase detector and reduced gain charge pump

摘要

In this paper, a low jitter 16-phases DLL is proposed based on a simple and sensitive phase detector. Dead-Zone of the proposed PD is improved in compare to the conventional structures where the pulse generator postpones PD response and reduces the sensitivity. Also, the conventional structure of charge pumps is modified to inject small charge throughout the continuous outputs of PD. Smaller bias current is provided in charge pump via subtracting tail currents of intentionally mismatched differential pairs. Duty cycle of output differential phases is adjusted to around 50% using common mode setting strategy on delay elements. Simulation results confirm that DLL loop can provide 16-phases in frequency range of 80MHZ to 410MHz, consuming total power of 3.5mW and 5.6mW, respectively. The dead-zone of PD is also reduced from 80ps to 14ps when the pulse generator section is eliminated. Also, RMS jitter of about 45ps and 1.76ps are obtained at 80MHz and 410MHz, respectively, when the supply voltage is subject to around 50mvolts peak-to-peak noise disturbances. The proposed DLL can be implemented in less than 0.05mm active area in a 0.18μm CMOS technology.