Offset cancellation of charge pump based phase detector
AssigneeInfineon Technologies N.A., Inc.
InventorsMichael A. Ruegg, Sasan Cyrusian
Life of this patent
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Abstract
A offset cancellation of charge pump based phase detector is disclosed. The methods and circuits disclosed cancel inherent with a phase detector and imbalanced charge pumps. The offset cancellation includes detecting the phase detector and the charge pump offset with a calibration signal and a reference voltage source, and applying a calibration current to cancel the phase detector and charge pump offset.
Claims20
A phase locked loop for use in a PRML based read/write circuit, comprising:
- a loop filter operative to maintain a potential at a loop filter node responsive to current flow at the loop filter node;
- a charge pump coupled with the loop filter and operative to control current at the loop filter node;
- a phase detector operative to provide a control signal to the charge pump where the control signal is responsive to a phase difference in input signals;
- and
- an offset cancellation circuit operative to cancel an offset in the control signal.
An offset cancellation circuit for use in a charge pump circuit, comprising:
- a reference voltage source operative to generate a reference voltage associated with a settled state voltage for a phase locked loop;
- a pulse generator operative to provide a calibration signal to the phase detector, the calibration signal propagating an offset voltage to a loop filter node;
- a comparator operative to generate a control signal associated with a voltage difference between the reference voltage and the offset voltage at the loop filter node;
- and
- a logic circuit operative to control an offset current source responsive to the control signal, the offset current source coupled with the loop filter node.
A method of canceling an offset in a charge pump based phase detector, the method comprising the acts of:
- generating a reference voltage associated with a settled state for a phase locked loop;
- applying a calibration signal to a phase detector, the calibration signal propagating an offset voltage to a loop filter node;
- and
- applying a calibration current at the loop filter node to cancel the output offset voltage, the calibration current corresponding to a difference between the reference voltage and the offset voltage.
Dependencies are inferred from the claim text.