| 摘要 |
PROBLEM TO BE SOLVED: To automatically perform trimming adjustment with higher accuracy in the case of needing the trimming adjustment of an oscillation frequency. SOLUTION: This circuit is provided with a variable CR oscillation circuit 11, a crystal oscillation circuit 12, a voltage comparator circuit 13 for power supply voltage change detection, a control logic circuit 14 that is actively controlled by the voltage comparator circuit and generates an enable signal with a pulse width related to a crystal oscillation output period and a latch signal, a counter 15 receiving and counting a CR oscillation output clock in an enable signal period, a data register 16 for comparison having reference data, a data latch circuit 171 latching a count output by a latch signal, and a data comparator circuit 172 which compares latch data with the reference data, outputs a binary m-bit trimming signal changing in response to the difference of both inputs to change the oscillation frequency of the variable CR oscillation circuit, and stops the control operation of the control logic circuit, when the difference between the both inputs is within a prescribed range. |
