Calibration of a voltage controlled oscillator to trim the gain thereof, using a phase locked loop and a frequency locked loop
AssigneeSTMicroelectronics International N.V.
InventorsNitin Gupta, Ankit Gupta, Anand Kumar
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Abstract
Disclosed herein is a method of calibrating a voltage controlled oscillator (VCO) for a phase locked loop. The method includes prior to activating the phase locked loop, and prior to activating a frequency locked loop, causing a bias signal generator circuit to generate a control signal with a fixed control voltage for the VCO. The method continued with activating the frequency locked loop, and adjusting the bias signal generator to calibrate a transconductance of the bias signal generator while the frequency locked loop is activated. The frequency locked loop is then deactivated, and the phase locked loop is activated.
Claims21
A circuit, comprising:
- a controllable oscillator;
- a bias signal generator circuit configured to generate an oscillator control signal for the controllable oscillator;
- a first bias calibrator configured to control the bias signal generator circuit so as to calibrate a voltage of the oscillator control signal as produced by the bias signal generator circuit;
- a second bias calibrator configured to control the bias signal generator circuit so as to calibrate a transconductance of the bias signal generator circuit;
- a phase locked loop that utilizes the controllable oscillator;
- a frequency locked loop that utilizes the controllable oscillator;
- a first switch selectively coupling the first bias calibrator to the bias signal generator circuit;
- a second switch selectively coupling the phase locked loop to the bias signal generator circuit;
- wherein the first bias calibrator is configured to calibrate the voltage of the oscillator control signal in a first calibration step, and to enable the frequency locked loop upon completion of the first calibration step, thereby beginning a second calibration step;
- wherein the second bias calibrator is configured to calibrate the transconductance of the bias signal generator circuit in the second calibration step, and to disable the frequency locked loop and enable the phase locked loop upon completion of the second calibration step;
- wherein the second bias calibrator is further configured to close the first switch and open the second switch during the first and second calibration steps, and to open the first switch and close the second switch upon completion of the second calibration step.
A method of calibrating a voltage controlled oscillator (VCO) for a phase locked loop, the method comprising:
- prior to activating the phase locked loop, and prior to activating a frequency locked loop, causing a bias signal generator circuit to generate a control signal with a fixed control voltage for the VCO;
- activating the frequency locked loop, and adjusting the bias signal generator to calibrate a transconductance of the bias signal generator while the frequency locked loop is activated;
- deactivating the frequency locked loop and activating the phase locked loop.
A circuit, comprising:
- a PLL including an oscillator generating an output oscillation signal having a frequency set by a control signal;
- a bias circuit including a first current source having a control terminal biased by a bias voltage and a second current source having a control terminal biased by a control voltage generated in response to a phase comparison of the oscillation signal to a reference signal, the first and second current sources in combination configured to generate the control signal;
- a first calibration circuit configured to calibrate the bias voltage;
- and
- a second calibration circuit configured to calibrate a transconductance of the first and second current source.
Dependencies are inferred from the claim text.