CHARGE PUMP PHASE-LOCKED LOOP CIRCUITS

摘要

A charge pump phase-locked loop circuit includes an active loop filter, an adjustable reference voltage source, and a charge pump. The active loop filter includes an amplifier that has a negative input node, a positive input node, and an output node. The adjustable reference voltage source is coupled to the positive input node to provide an adjustable reference voltage. The charge pump is coupled to the negative input node to provide a current to or draw a current from the active loop filter in response to a signal from a phase detector. The charge pump includes a first current source coupled to a first voltage and a second current source electrically coupled to a second voltage, the second current source including a resistor. The second current source is configured such that a current provided by the second current source depends on a resistance value of the resistor and a difference between the reference voltage and the second voltage.

主权项

1. An apparatus comprising:
a charge pump phase-locked loop circuit comprising: an active loop filter comprising an amplifier that has a negative input node, a positive input node, and an output node, in which a feedback path is provided between the output node and the negative input node, the feedback path including a capacitor; an adjustable reference voltage source that is electrically coupled to the positive input node of the amplifier to provide a reference voltage that is adjustable; and a charge pump electrically coupled to the negative input node of the amplifier to provide a current to or sink a current from the active loop filter in response to a signal from a phase detector, the charge pump comprising a first current source electrically coupled to a first voltage and a second current source electrically coupled to a second voltage, the second current source comprising a resistor, and the second current source is configured such that a current provided by the second current source depends on a resistance value of the resistor and a difference between the reference voltage and the second voltage, wherein the adjustable reference voltage source comprises a digital-to-analog converter to receive a digital input signal and output the reference voltage provided to the positive input node of the amplifier.