Patent ID: 7310022

Claim:
An oscillation frequency control circuit comprising: a plurality of D/A converters that convert a respective plurality of digital values to produce a respective plurality of analog control voltages; a plurality of voltage/current converters that convert the plurality of analog control voltages into respective currents, wherein a variation in output current corresponding to a variation in input voltage being different for each of the plurality of voltage/current converters; a current combining circuit that combines the plurality of currents outputted from the current/voltage converters to provide a combined current; a current controlled oscillation circuit that produces an oscillating signal having a frequency corresponding to a value of the combined current; a frequency counter that counts to measure the frequency of the oscillating signal outputted from the oscillation circuit; an operation circuit that compares the frequency measured by the frequency counter with a reference frequency and produces control signals; and a digital value generator that generates the plurality of digital values according to the control signals.