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US 7,443,206 B1Granted
High-frequency linear phase-frequency detector with wide-pulse outputs
AssigneeSun Microsystems, Inc.
InventorFrancisco Fernandez
Life of this patent
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Abstract
A circuit and method are provided for detecting a phase difference between at least two periodic signals. The circuit and method disclosed herein provide pulsed output signals with wide output pulse widths well suited for use to drive a charge-pump in a phase-locked loop. The wide pulse widths of the output signals generated by the circuit and method allow the charge-pump to sink or source current with higher accuracy and therefore improve the operational characteristics of the phase-locked loop. Further, the circuit and method disclosed herein allow a phase-frequency detector and an associated charge-pump to operate at a higher operational frequency due to the wide pulse widths.
Claims16
A phase-frequency detector comprising:
- a first stage responsive to an edge transition location of a first periodic signal having a first period received on a first input node and to an edge transition location of a second periodic signal having a second period received on a second input node to drive a first output node with a first output signal and to drive a second output node with a second output signal, wherein the first stage comprises, a first sequential logic device coupled to the first input node and a second sequential logic device coupled to the second input node, and a first inverter coupled between an output node of the first sequential logic device and a data input node of the first sequential logic device and a second inverter coupled between an output node of the second sequential logic device and a data input node of the second sequential logic device;
- and
- a second stage responsive to an edge transition location of the first output signal and to an edge transition location of the second output signal to selectively drive a first output node of the phase-frequency detector with a first output pulse and to drive a second output node of the phase-frequency detector with a second output pulse, the first output pulse and the second output pulse each having a pulse width related to the edge transition location of the first periodic signal relative to the edge transition location of the second periodic signal, the second stage comprising a selector circuit to select between the first output node of the first stage and the second output node of the second stage, the second stage further comprising a first multiplexor and a second multiplexor responsive to the selector circuit to select between the first output node of the first stage and the second output node of the first stage,
- wherein each of the edge transition locations of the first and second periodic signals and each of the edge transition locations of the first and second output signals represent a point in time at which a related signal edge transition occurs.
1 more element
A phase-locked loop circuit comprising:
- a voltage controlled oscillator (VCO) responsive to an analog control signal to produce a periodic output signal;
- and
- a phase-frequency detector responsive to a reference signal received on a first input node and a monitored signal received on a second input node to produce a first output signal on a first output node having a first pulse width and a second output signal on a second output node having a second pulse width, the phase-frequency detector comprising a first stage that comprises a first sequential logic device coupled to the first input node and a second sequential logic device coupled to the second input node, and a first inverter coupled between an output node of the first sequential logic device and a data input node of the first sequential logic device and a second inverter coupled between an output node of the second sequential logic device and a data input node of the second sequential logic device, the phase-frequency detector comprising a second stage that comprises a selector circuit to select between the first output node of the first stage and the second output node of the second stage, the second stage further comprising a first multiplexor and a second multiplexor responsive to the selector circuit to select between the first output node of the first stage and the second output node of the first stage;
- wherein one half of a difference in pulse widths of the first and second output signals represents a detected phase difference between the reference signal and the monitored signal.
1 more element
A method of driving a charge-pump in a phase-locked loop to generate a current, the method comprising the steps of:
- detecting a phase difference between a reference signal and a monitored signal related to an output signal of a voltage controlled oscillator;
- generating in response to the detected phase difference a first pulse having a first pulse width and a second pulse having a second pulse width, the first pulse and the second pulse generated by a phase-frequency detector, the phase-frequency detector comprising a first stage that comprises a first sequential logic device coupled to the first input node and a second sequential logic device coupled to the second input node, and a first inverter coupled between an output node of the first sequential logic device and a data input node of the first sequential logic device and a second inverter coupled between an output node of the second sequential logic device and a data input node of the second sequential logic device, the phase-frequency detector comprising a second stage that comprises a selector circuit to select between the first output node of the first stage and the second output node of the second stage, the second stage further comprising a first multiplexor and a second multiplexor responsive to the selector circuit to select between the first output node of the first stage and the second output node of the first stage;
- and
- driving a charge-pump with the first and second pulse to generate an average output current, on a per-period basis, proportional to one-half of a pulse width difference between the first output pulse and the second output pulse.
1 more element
Dependencies are inferred from the claim text.