Patent attributes
A delay locked loop includes a control loop receiving reference and feedback clock signals, and generating biasing voltages therefrom. A delay chain receives the reference clock signal and generates N successively delayed versions thereof, each at a successive tap thereof. The Nth delayed version is the feedback clock signal. The control loop has a phase detector asserting an up signal when a phase of the feedback clock signal lags that of the reference clock signal, asserting a down signal when the phase of the feedback clock signal leads that of the reference clock signal. A digital filtering block compares a number of assertions of the up signal during the period of the reference clock signal to those of the down signal, and asserts an up or down command signal based thereupon. A biasing voltage generation circuit receives the up and down command signals and generates the biasing voltages therefrom.
