Phase locked loop circuitry having switched resistor loop filter circuitry, and methods of operating same

摘要

Phase-locked loop circuitry to generate an output signal, the phase-locked loop circuitry comprising oscillator circuitry, switched resistor loop filter, coupled to the input of the oscillator circuitry (which, in one embodiment, includes a voltage-controlled oscillator), including a switched resistor network including at least one resistor and at least one capacitor, wherein an effective resistance of the switched resistor network is responsive to and increases as a function of one or more pulsing properties of a control signal (wherein pulse width and frequency (or period) are pulsing properties of the control signal), phase detector circuitry, having an output which is coupled to the switched resistor loop filter, to generate the control signal (which may be periodic or non-periodic). The phase-locked loop circuitry may also include frequency detection circuitry to provide a lock condition of the phase-locked loop circuitry.

主权项

1. A phase-locked loop circuitry comprising:
oscillator circuitry having an input and an output; switched resistor loop filter, having an output which is coupled to the input of the oscillator circuitry, wherein the switched resistor loop filter includes a switched resistor network including a plurality of resistors, a plurality of capacitors and at least one switch, wherein an effective resistance of the switched resistor network is responsive to and increases as a function of one or more pulsing properties of a control signal; phase detector circuitry, having an output which is coupled to the switched resistor loop filter, to generate the control signal; divider circuitry to couple the output of the oscillator circuitry to an input of the phase detector circuitry; and frequency detection circuitry, coupled to the output of the divider circuitry, to provide a lock condition of the phase-locked loop circuitry, wherein the frequency detection circuitry includes:
(i) circuitry to generate a signal which is representative of the frequency of the output signal of the phase-locked loop circuitry, and(ii) comparison circuitry to compare the signal which is representative of the frequency of the output signal of the phase-locked loop circuitry to a reference input to the phase-locked loop circuitry.