| 摘要 |
PROBLEM TO BE SOLVED: To provide an integrated circuit 11 having a frequency detecting circuit which supplies one or more digital signals to a current source according to the detected operation frequency of a generated reference clock. SOLUTION: With a signal 50, the current source 26 can change the operation state among two on more discrete current output levels by a digital control system. The signal 50 is used to select and supply a high-current output level to an external oscillator circuit 16 by the current source in startup mode, thereby guaranteeing that the integrated circuit 11 can start up in an optimum shortened time period. After the startup operation is completed, the current source 26 can be switched to a low-current operation mode by making use of the signal 50 and then the influence of electromagnetic interference(EMI) is reduced in normal operation mode after the startup operation. |
