Abstract: A charge pump circuit for connection to another circuit via an output node (614) of the charge pump and for causing a current to flow either into or out of the other circuit via the output node in dependence on a current output by first and second current paths (601, 602) in the charge pump, each current path comprising a current source and a current control device having two switched nodes, one switched node being arranged to receive a current from the current source, and a control node arranged to control a current flow between the first and second switched nodes in dependence on a voltage at the control node, the current control devices of the first and second paths being of the same type such that they are responsive to the same polarity of voltage at their control node to be conducting between their switched nodes, the charge pump further comprising a capacitive element (609, 610) having first and second capacitive plates and a switching arrangement (604-606, 611) arranged such that, during a first time

Abstract: A current generator for a phase-locked loop arranged to generate an output signal having predetermined frequency-relationship with a reference signal, the phase-locked loop comprising a signal generator arranged to generate the output signal, a divider arranged to receive the output signal and divide the output signal to form a feedback signal, the divider being arranged to vary the divisor by which the output signal is divided, a comparison unit arranged to compare the feedback signal with the reference signal and output a first error signal indicative of the phase-difference between the feedback signal and the reference signal to the current generator and a loop filter arranged to filter a current signal output by the current generator to form a control signal for controlling the signal generator, the current generator being capable of receiving the first error signal and generating a current in dependence thereon, receiving a second error signal indicative of an error in the feedback signal caused by the v

Abstract: A loop filter for a phase-locked loop that generates an output signal having a predetermined phase relationship with a reference signal, the loop filter being arranged to control a signal generator that forms the output signal in dependence on a phase error between the output signal and the reference signal by outputting a control signal for controlling the signal generator in dependence thereon, the loop filter being arranged to form the control signal to comprise a proportional component representative of an instantaneous magnitude of the phase difference and an integral component representative of an integral of the phase difference, the loop filter comprising a proportional path arranged to receive a signal representative of the instantaneous magnitude of the phase difference and form the proportional component of the control signal in dependence thereon and an integral path arranged to receive a signal representative of the instantaneous magnitude of the phase difference and form the integral component o

Abstract: A phase-locked loop arranged to generate an output signal having a first frequency that is a static value times the frequency of a reference signal, the phase-locked loop comprising a signal generator arranged to generate the output signal, a divider arranged to receive the output signal and divide the output signal to form a feedback signal, the divider being arranged to vary the divisor by which the output signal is divided to cause the output signal to have a frequency that is said static value times the frequency of the reference signal, a comparison unit arranged to compare the feedback signal with the reference signal, one or more current generators arranged to output current pulses in dependence on said comparison, a summation unit arranged to receive the current pulses output by the current generator(s) and form a single current pulse therefrom and a loop filter arranged to filter the single current pulse to form a control signal for controlling the signal generator, the phase-locked loop being arrang

Abstract: A phase-locked loop having: an oscillator for forming an oscillating output signal; a frequency divider connected to receive the output of the oscillator and frequency divide it by a value dependent on a division control signal; and a phase comparator for comparing the phase of the divided signal and a reference signal to generate a control signal, the operation of the oscillator being dependent on the control signal; the output data to form a divided signal a division ratio controller configured to, when clocked by an input signal, generate a series of output data for forming the division control signal; the phase-locked loop having: a first mode of operation in which the frequency divider is operable to frequency divide the output of the oscillator by a value dependent on the output of the division ratio controller; and a second mode of operation in which the frequency divider is not operable to frequency divide the output of the oscillator by a value dependent on the output of the division ratio controller

Abstract: A loop filter for receiving an input signal indicative of a phase-difference between a reference signal and a signal output by a signal generator and forming a control signal for controlling the signal generator in dependence thereon, the loop filter comprising a plurality of filter components that determine the frequency response of the filter, said filter components being arranged so that a first set of said components determines one or more zeros of the filter's frequency response and a second set of said components determines one or more poles of the filter's frequency response, each of said first and second sets of filter components being independent of the other such that the zero(s) and pole(s) of the filter's frequency response may be selected independently.

Abstract: A phase-locked loop for generating an output signal that has a predetermined frequency relationship with a reference signal, the phase-locked loop comprising a signal generator arranged to generate the output signal, a charge pump arranged to generate current pulses for controlling the signal generator, two control units for controlling a duration of the current pulses generated by the charge pump and a selection unit arranged to select either the first control unit or the second control unit to control the charge pump, wherein a first one of the control units is arranged to continuously monitor a phase-difference between the reference signal and a feedback signal formed from the output signal and to, when selected by the selection unit, control the charge pump to output a current pulse having a duration that is dependent on that phase-difference and a second one of the control units is arranged to, when selected by the selection unit, control the charge pump to output a current pulse of predetermined duratio