Patent ID: 8063710

Claim:
A self-calibrating oscillator, comprising: an oscillation circuit that outputs a frequency corresponding to a calibration value; a pulse counter that counts an output signal from the oscillation circuit a predetermined number of times and outputs a control output signal when the counting is completed; a charging circuit that supplies and charges a capacitor in response to the control output signal; and a calibration circuit that compares a voltage at a connection node of the capacitor and a reference voltage and generates the calibration value from the comparison result, wherein the calibration circuit includes: a first comparator that compares a charging voltage at the connection node when the charging ends with a high potential reference voltage that defines an upper limit value of the charging voltage; a second comparator that compares the charging voltage with a low potential reference voltage that defines a lower limit value of the charging voltage; and a calibration up-down counter that has an initial predetermined count value, which outputs the calibration value in correspondence with a stored count value, wherein the calibration up-down counter updates the count value by adding to or subtracting from the count value to decrease the frequency when the charging voltage is lower than the low potential reference voltage, and the calibration up-down counter updates the count value by subtracting from or adding to the count value to increase the frequency when the charging voltage is higher than the high potential reference voltage.