Patent ID: 7349516

Claim:
A trimming method for a PLL circuit which operates on the principle of two-point modulation, comprising the following steps, which are carried out in the stated sequence: (a) injecting a digital modulation signal into the PLL circuit, with the PLL circuit regulating at a first frequency; (b) deactivating the digital modulation signal, with the PLL circuit regulating at a second frequency, which is not the same as the first frequency; (c) outputting a difference signal, which corresponds to the change in a control signal, which is produced by the deactivation of the digital modulation signal, for a frequency-generating unit in the PLL circuit; (d) comparing the difference signal with a comparison signal, which is characteristic of a modulation shift of an analog modulation signal; and (e) changing the modulation shift such that any discrepancy between the difference signal and the comparison signal which is determined during the comparison is corrected.