National Chiao-Tung University

Department of Electronics Engineering & Institute of Electronics





An All-Digital Fast-Lock Self-Calibrated Multiphase DLL






Student : Li-Pu Chuang

Advisor : Dr. Wei Hwang



Abstract

An all-digital fast-lock self-calibrated DLL is proposed in this thesis. Base on the proposed rapid self-calibration (RSC) algorithm, the timing error caused by process mismatch and various output loading can be effectively self-calibrated. Besides, an unbalance binary search algorithm is proposed to extend the locking range and avoid harmonic lock at the same time. An unbalance binary search algorithm based (UBS) controlled is implemented in UMC 90nm CMOS technology. The simulation results show that, the operating frequency is 100MHz to 500MHz (up to 5X) and the lock-in time is down to 22 reference clock cycles in the worst case.

A 300MHz-1.08GHz all-digital multiphase delay-locked loop with precise multi-phase output has been designed with UMC 90nm CMOS technology. The linear approximate delay element property of linearity and insensitive to PVT variation is good for digitally controlled delay line. In addition, a digital calibration unit is designed based on RSC algorithm, which makes the phase error among the multiple outputs can be self-calibrated. The entire calibration unit could be turned off after calibration procedure is complete to reduce power consumption. The simulation results show the DLL exhibits a lock range from 300MHz to 1.08GHz. The maximum phase is reduced from 20.9ps to 4.5ps when the DLL is operating at 500MHz. The total power dissipation of the all-digital self-calibrated multiphase delay-locked loop is 2.16mW at 1GHz with 1V power supply. The presented DLL can be robustly used in embedded memory applications.