| 摘要 |
An oscillator (1) is trimmed by a digital-to-analog converter (5) that receives a digital trimming signal in response to difference between a desired frequency and a reference frequency. The oscillator (1) generates a frequency that is M times higher than the desired frequency. A divider (2) divides the oscillator frequency by M to provide the desired frequency. A splitter (4) splits the digital trimming signal into a digital coarse trimming signal, and a digital fine trimming signal. The converter (5) converts the digital coarse trimming signal into an analog coarse trimming signal. A comparator (6) receives the digital fine trimming signal, compares it with a counter signal received from a counter (7) repeatedly counting M periods of the oscillator output signal, and generates an output signal until the value of the digital fine trimming signal and the counter signal are equal. The converter (5) receives said comparator output signal and converts it into an analog fine trimming signal that is added to said analog coarse trimming signal to control the oscillator (1). |
