Patent ID: 7696832

Claim:
A digital loop filter, installed in an all-digital phase-locked loop (PLL), for controlling an output signal of a digitally controlled oscillator (DCO) in said all-digital PLL, and said digital loop filter comprising: a controller, for receiving a DCO control code and another DCO control code transmitted from a PLL controller in said all-digital PLL; a plurality of registers, for storing said DCO control code and said another DCO control code updated and transmitted by said controller; an adder, for receiving and calculating a total of said DCO control codes in said registers; and a divider, for receiving and calculating an average value of said totals of said DCO control codes calculated by said adder, and then transmitting said average value to said PLL controller, and driving said PLL controller to generate said another DCO control code, so as to control and adjust an output signal of said DCO in a neighborhood of said average value, and keep compensating a phase difference and a frequency difference with an input signal in said all-digital PLL.