| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an oscillation frequency control circuit capable of reducing swiching noises to a level, that the effect of switching noise can be ignored, independently of the frequency used in a radio transmitting and receiving circuit without needing any special control circuit such as a microcomputer, to provide a DC-DC converter with the oscillation frequency control circuit, and to provide a semiconductor device. <P>SOLUTION: In accordance with output signals UP and DOWN from a first frequency comparator circuit 12 which compares a frequency of a first clock signal CLKA with that of a first frequency dividing clock signal CLKB1, and of a second frequency comparator circuit 13 which compares the frequency of the first clock signal CLKA and that of a second frequency dividing clock signal CLKB2, an UP/DOWN control circuit 11 performs frequency control of the second clock signal CLKB upon an oscillation circuit 2 such that the frequency of the second clock signal CLKB2 reciprocates while continuously varying between a predetermined lower limit value and a predetermined upper limit value. <P>COPYRIGHT: (C)2009,JPO&INPIT |
