To eliminate a range, wherein a PLL circuit does not have its phase locked as to a frequency synthesizer device which varies a resolution ratio with time.
Data setting the output signal of the frequency synthesizer device are set by a frequency division ratio control circuit 7 to an N counter 9 and an A counter 10. When this timing Fck overlaps with the variation timing of the set data because of the delay time τ of the frequency division ratio control circuit 7, the N counter 9 and A counter 10 input abnormal data, so that the phase of the PLL circuit is not locked. For shifting the timing in such a case, a means 12 which inverts the clock signal of the frequency division ratio control circuit 7 and a means 13 which selects whether the clock signal is inverted or not are provided. The data output timing of the frequency ratio control circuit 7 is shifted at a region close where τ=1/Fck. Since a variable frequency divider 2 can input the frequency division ratio setting data in a correctly determined state, malfunctions will not occur. Thus, a range wherein the phase is not locked in the output signal frequency range of the frequency synthesizer can be eliminated, without increasing the current consumption for reducing the circuit delay.
HIRANO SHUNSUKE