Patent ID: 8299828

Claim:
A method of an ABS (Auto Band Select) operation of an ADPLL (All Digital Phase Lock Loop) including an ABS circuit, a digital phase detector and a digital controlled oscillator, comprising: (a) inputted an ON signal to the ABS circuit, (b) outputting a first shift amount of a phase error in beginning of start of the ABS operation between a frequency division signal (DIV) dividing an output of the digital controlled oscillator and a reference signal (REF) from the digital phase detector to the ABS circuit, (c) storing the first shift amount of the phase error in beginning of start of the ABS operation in a flip-flop of the ABS circuit, (d) detecting a second shift amount of a phase error between a frequency division signal dividing an output of the digital controlled oscillator and the reference signal (REF) in the digital phase detector after a reference time elapses, (e) outputting the second shift amount from the digital phase detector to the ABS circuit, and (f) comparing the first shift amount in the flip-flop with the second shift amount, and detecting a shift direction of a phase error between the first shift amount and the second shift amount in a digital frequency comparator of the ABS circuit.