Patent ID: 8922289

Claim:
An oscillation circuit comprising: a reference voltage generation circuit that adds a proportional-to-absolute-temperature (PTAT) output, which increases in proportion to an absolute temperature, to a complementary-to-absolute-temperature (CTAT) output, which decreases in proportion to an absolute temperature, to generate and output a reference voltage; a first switching unit coupled to the reference voltage generation circuit, wherein the first switching unit switches an adding ratio of the PTAT output and the CTAT output to minimize a variation in an output from the reference voltage generation circuit that depends on temperature; a current source that generates current which has a current value based on the output from the reference voltage generation circuit; a regulator circuit that generates constant voltage based on the output from the reference voltage generation circuit; a first capacitor including one terminal coupled to the current source and charged and discharged by the current of the current source; a first voltage dividing resistor, a second voltage dividing resistor, and a third voltage dividing resistor that are coupled in series with one another to divide the constant voltage supplied from the regulator circuit; a comparator that compares a divided voltage between the second voltage dividing resistor and the third voltage dividing resistor with a voltage at the one terminal of the first capacitor; a switch that is driven in accordance with an output from the comparator, wherein the switch, when activated, short-circuits the first voltage dividing resistor; a second switching unit that switches a value of the current of the current source to adjust an oscillation frequency; and a third switching unit coupled to the first voltage dividing resistor, wherein the third switching unit switches resistance of the first voltage dividing resistor to adjust an oscillation amplitude at the one terminal of the first capacitor; wherein trimming of the first switching unit, the second switching unit, and the third switching unit is performed to generate an oscillation signal having a desired frequency.