| 摘要 |
<p>In a channel IC for a hard disk it is desirable that the write oscillator, but preferably also the read oscillator and the equalizer, can rapidly change their frequencies upon a change of zone on the hard disk while the stability and accuracy are maintained. The phase-locked loops in which such oscillators are included inherently respond slowly to a new frequency setting. According to the invention a rapid change in frequency is obtained, while the accuracy and stability are retained, in that by means of an analog multiplier/divider a substantial part of the control signal necessary to set the oscillators to a new frequency is derived from a control signal available in a second PLL loop, preferably the PLL loop of the servo circuit for controlling the read/write heads. The PLL loop of the write oscillator now merely has to provide the fine control.</p> |
