Patent ID: 7408415
Filing Date: 2008-08-05
Classification: H03J,H03L

Abstract:
1. A phase locked loop circuit, comprising: a voltage controlled oscillator that has a control input to which a variable control voltage is applied; a loop filter; a phase-frequency discriminator with an output connected to the loop filter to produce the control voltage; a plurality of discrete frequency tuning elements; and a switch array selectively activating and deactivating each of said frequency tuning elements in said voltage controlled oscillator to determine partial ranges of frequencies through each of which the oscillator can be tuned by a variation of said control voltage in a range between predetermined upper and lower control voltage limits, wherein a total frequency range through which said oscillator can be tuned is divided into a plurality of partial frequency ranges each defined by a different number of activated frequency tuning elements; an inhibiting circuit that is set whenever one of said frequency tuning elements is activated or deactivated to inhibit an activation or deactivation of further frequency tuning elements, and that is reset only after the control voltage has evolved away from said upper or lower control voltage limit by a predefined amount; and wherein the loop filter includes a filter capacitance and, during the set condition of the inhibiting circuit, the phase-frequency discriminator is functionally disconnected from the loop filter and the capacitance is selectively connected to a charge sink or to a charge source to reduce or increase the control voltage applied to the control input of the voltage controlled oscillator.