Method for calibrating a VCO characteristic and automatically calibrated PLL having a VCO

摘要

A method is disclosed for calibrating the oscillation frequency versus control voltage characteristic of a voltage controlled oscillator (VCO). The method includes establishing an oscillation frequency of the VCO at a maximum target frequency value ft_H (point Q) when the control voltage Vc equals a predetermined reference voltage Vref which lies within the operating range of the control voltage Vc, and verifying that the oscillation frequency becomes a minimum target frequency value ft_L when the control voltage Vc is changed to a value between the minimum value Vclamp_L and the reference voltage Vref. An automatically calibrated PLL circuit including a VCO is disclosed which performs a calibration to set the oscillation frequency versus control voltage characteristic of the VCO.