| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an adjustment process in an IC user, to save pins and to save components by controlling a D/A conversion circuit by the serial control of a conversion circuit and supplying a prescribed current to a VCO. SOLUTION: Optimum serial data when the oscillation frequency of the VCO 8 in an output terminal 9 becomes closer to a target frequency are found and the data are inputted through an S/P conversion circuit 12 to a PROM 13. At this time, write pulses are impressed to a terminal 18 and the data are fixed to the PROM 13. The adjustment data of the PROM 13 are sent to a D/A converter 14 and the output becomes a fixed current at all times. As a result, by controlling the D/A converter 14 by the serial control of the conversion circuit 12 and supplying a prescribed current to the VCO 8, the oscillation frequency of the VCO 8 is limited to a desired frequency. |
