Oscillation frequency regulating circuit and method

1. An oscillation frequency regulating circuit comprising:

a measuring section that performs measurement based on an oscillation frequency of an oscillation circuit;

a comparator section that compares a measurement value measured by the measuring section against a set comparison value over a set comparison duration;

a setting section that sets a comparison value selected from a plurality of comparison values of different magnitudes responsive to higher order bits of a multi-bit input trimming regulation signal, and that sets in the comparator section the comparison duration according to the magnitude of the selected comparison value; and

a regulation section that, based on the comparison result of the comparator section, regulates the oscillation frequency of the oscillation circuit such that the oscillation frequency that is measured by the measuring section becomes a target oscillation frequency.

2. The oscillation frequency regulating circuit of claim 1 , wherein the setting section:

sets a first comparison value of a small value and a first comparison duration of a short length until a number of times of regulation of the oscillation frequency by the regulation section equals a specific number of times; and

sets a second comparison value greater than the first comparison value and a second comparison duration longer than the first comparison duration when the number of times of regulation has exceeded the specific number of times.

3. The oscillation frequency regulating circuit of claim 1 , wherein the regulation section:

causes the oscillation circuit to oscillate at an intermediate regulation frequency between a maximum regulation frequency and a minimum regulation frequency;

regulates so as to oscillate at regulation frequency between the maximum regulation frequency and the intermediate regulation frequency and to oscillate to gradually approach the target oscillation frequency each time regulation is performed when the comparison result indicates that the measured oscillation frequency is less than the set comparison value; and

regulates so as to oscillate at regulation frequency between the minimum regulation frequency and the intermediate regulation frequency and to oscillate to gradually approach the target oscillation frequency each time regulation is performed when the comparison result indicates that the measured oscillation frequency is the set comparison value or greater.

4. The oscillation frequency regulating circuit of claim 3 , wherein the regulation section employs the trimming regulation signal configured from a bit string of m-bits to regulate the oscillation frequency of the oscillation circuit, and performs regulation repeatedly m times employing 2 m individual values of the trimming regulation signal, m being an integer that is equal to or greater than 2.

5. The oscillation frequency regulating circuit of claim 4 , wherein the setting section sets the comparison value and the comparison duration for setting in the comparator section based on a value of the higher order bits in the trimming regulation signal input from an external device that is shifted in sequence one bit at a time from a higher order bit to a lower order bit each regulation duration.

6. A semiconductor device comprising:

the oscillation frequency regulating circuit and the oscillation circuit of claim 1 ; and

a processor that performs operation control of the oscillation frequency regulating circuit and the oscillation circuit.

7. An electronic device comprising:

the semiconductor device of claim 6 ; and

a sensor.

8. A method of regulating an oscillation frequency comprising:

measuring an oscillation frequency of an oscillation circuit;

selecting a single comparison value from a plurality of comparison values of different magnitudes responsive to higher order bits of a multi-bit input trimming regulation signal, and setting a comparison duration according to the magnitude of the selected comparison value;

comparing the oscillation frequency measured by the measuring with the comparison value set by the setting over the comparison duration set by the setting; and

regulating the oscillation frequency of the oscillation circuit such that the oscillation frequency measured by the measuring becomes a target oscillation frequency.