A Semi-Digital Delay-Locked Loop Using an Analog-Based Finite State Machine

Abstract

This brief describes a low-power full-rate semi-digital delay-locked loop,(DLL) architecture using an analog-based finite state machine,(AFSM) and a polyphase filter. The AFSM architecture uses low-power analog blocks to map high-frequency loop feedback information to low frequency, thus reducing the total power required for digital signal processing and for the macro as a whole. The polyphase filter generates full-rate multiphase outputs for a phase rotator, hence a reference clock of the semi-digital DLL can be generated by any reference source including a phase-locked loop with an LC voltage-controlled oscillator. The prototype semidigital DLL in 0.12-μm CMOS exhibits less than 10-12 bit error rate at 3.2 Gb/s consuming 60 mW. © 2004, The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.