Apparatus and methods for setting up a tuning frequency of a PLL demodulator

摘要

The present invention concerns apparatus and method for setting up the tuning frequency of a PLL demodulator (100) that includes a VCO. Frequency synthesizing circuitry (150) controls the VCO via a first switched control path. Comparison circuitry (360) provides a first signal that corresponds to the difference between the output frequency of the VCO and a reference frequency (fREF). Control circuitry (180) is provided that is responsive to a plurality of signals including the first signal for imperatively controlling the apparatus. The apparatus further includes: a ceramic resonator oscillator (170) for providing the reference frequency (fREF); a non-volatile memory (MEM) for storing the value of the first signal; and comparison circuitry (360) for comparing a stored value of the first signal with a current value of the first signal so as to produce a second signal for adjusting the tuning frequency of the frequency synthesizing circuitry (150) in response to the second signal. <IMAGE>