| 摘要 |
<p>A voltage controlled relaxation oscillator (VCO) (510) includes a comparator (175) in which a ramp signal across a capacitor (152) is compared to a reference threshold (N1) from a hysteresis circuit (199). The frequency of the oscillator is changed by varying the hysteresis range of the threshold level (N1) and by changing the rate at which the ramp is generated. Current sources (124, 134, 136, 145, 166, 170, 172, 174, 187) internal to the oscillator are controlled by a reference potential (CS1) that is generated from an externally supplied band-gap reference potential (VBG). The VCO (510) is used in a phase-locked loop which includes a charge pump (514) that accumulates charge on a capacitor (728, 730) responsive to pulses (UP, DN) from a phase detector (512) applied to current sources (712, 714, 716, 718) which are controlled by the reference potential (CS1) generated in the VCO (510).</p> |
