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US 6,426,680 B1Granted
System and method for narrow band PLL tuning
AssigneeBroadcom Corporation
InventorsRalph Duncan, Tom W. Kwan
Life of this patent
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Abstract
An integrated VCO having an improved tuning range over process and temperature variations. There is therefore provided in a present embodiment of the invention an integrated VCO. The VCO comprises, a substrate, a VCO tuning control circuit responsive to a VCO state variable that is disposed upon the substrate, and a VCO disposed upon the substrate, having a tuning control voltage input falling within a VCO tuning range for adjusting a VCO frequency output, and having its tuning range adjusted by the tuning control circuit in response to the VCO state variable.
Claims28
An integrated VCO comprising:
- a substrate;
- a VCO tuning control circuit responsive to a VCO state variable that is disposed upon the substrate;
- and
- a VCO disposed upon the substrate, having a tuning control voltage input falling within a VCO tuning range for adjusting a VCO frequency output, and having the VCO tuning range adjusted by the tuning control circuit in response to the VCO state variable
- wherein the VCO tuning control circuit includes
- a window detector comparing a signal derived from a PLL loop filter output to a fixed voltage difference between an upper and a lower threshold that define a window,
- a compensation circuit coupled to the window detector that simultaneously adjusts the upper and lower thresholds in response to temperature and process variations while maintaining the fixed voltage difference, and
- a tuning register coupled to the output of the window detector generating a VCO tuning range adjustment signal.
5 more elements
An integrated VCO comprising:
- a substrate;
- a VCO disposed upon the substrate, having an adjustable frequency output responsive to a control voltage that is variable within an adjustable tuning range;
- and
- a VCO tuning control circuit responsive to temperature and process variations and a tuning control voltage input falling within a fixed VCO tuning window, the window having a first threshold voltage in fixed relation to a second threshold voltage the first and second threshold voltages being adjusted in fixed relation to each other to modify an adjustable tuning range of the VCO.
1 more element
A method of controlling stability of frequency output of a voltage controlled oscillator (VCO) over temperature and process variations, the VCO having a tank circuit with a tank circuit resonant frequency, the tank circuit including switched capacitors and varactors, the varactors being responsive to a varactor bias frequency output control voltage, the method comprising:
- providing a temperature and process dependent moving voltage window, the temperature and process dependent moving voltage window defining upper and lower limits of a VCO voltage control range and maintaining a constant differential voltage between the upper and lower limits;
- deriving VCO control voltages from the temperature and process dependent moving voltage window;
- and
- applying the VCO control voltages to the switched capacitors to set a frequency tuning range for the tank circuit.
1 more element
A tuning process for establishing a range of VCO control voltages that establish a PLL lock condition comprising:
- evaluating a state variable derived from a PLL loop filter;
- comparing the state variable to a predefined sliding window comprising a fixed difference between an upper and a lower limit, in which the upper and lower limits change in response to temperature and process variations, while maintaining the fixed relationship between upper and lower limits;
- shifting zeroes through a shift register if the state variable exceeds the upper limit of the predefined sliding window to decrease a VCO tank capacitance;
- shifting ones through the shift register if the state variable is less than the lower limit of the predefined sliding window to increase the VCO tank capacitance;
- disabling the shift register if the state variable falls within the predefined sliding window while continuing to monitor the state variable;
- initiating a timer when the state variable falls within the predefined sliding window;
- timing the time the state variable remains within the predefined window;
- comparing the time the state variable remains within the predefined window to a predefined time limit;
- producing an inlock flag if the state variable remains within the predefined window for a predefined time;
- and
- disabling a control circuit upon completion of the tuning process.
8 more elements
An integrated VCO comprising:
- a substrate means for supporting the disposition of an integrated circuit;
- a VCO means for producing a range of frequencies in response to a changing voltage input;
- and
- a VCO control circuit means for changing the range of frequencies produced in response to the changing voltage input through the use of a temperature and process dependent sliding window.
1 more element
An integrated VCO comprising:
- a substrate;
- a VCO tuning control circuit responsive to a VCO state variable that is disposed upon the substrate;
- a VCO disposed upon the substrate, having a tuning control voltage input falling within a VCO tuning range for adjusting a VCO frequency output, and having the VCO tuning range adjusted by the tuning control circuit in response to the VCO state variable;
- and
- an adaptive bias circuit having a PMOS transistor with its source to drain coupled in series between a power supply line and the VCO.
2 more elements
An integrated VCO comprising:
- a substrate;
- a VCO tuning control circuit responsive to a VCO state variable that is disposed upon the substrate;
- a VCO disposed upon the substrate, having a tuning control voltage input falling within a VCO tuning range for adjusting a VCO frequency output, and having the VCO tuning range adjusted by the tuning control circuit in response to the VCO state variable;
- and
- an adjustable capacitance responsive to the tuning control voltage, including
- a first NMOS transistor configured as a varactor with its gate coupled to a second terminal of a first inductor and with its source and drain coupled to the tuning control voltage, and
- a second NMOS transistor configured as a varactor with its gate coupled to a second terminal of a second inductor and with its source and drain coupled to the tuning control voltage.
4 more elements
An integrated VCO comprising:
- a substrate;
- a VCO tuning control circuit responsive to a VCO state variable that is disposed upon the substrate;
- a VCO disposed upon the substrate, having a tuning control voltage input falling within a VCO tuning range for adjusting a VCO frequency output, and having the VCO tuning range adjusted by the tuning control circuit in response to the VCO state variable;
- an adjustable capacitance responsive to the tuning control voltage, including
- a first field effect transistor with its gate coupled to a second terminal of a first inductor and with its source and drain coupled to the tuning control voltage, and
- a second field effect transistor with its gate coupled to the second terminal of a second inductor and with its source and drain coupled to the tuning control voltage,
- whereby the tuning control voltage is applied at a virtual ground such that the adjustable capacitance formed is an adjustable capacitance in parallel with a series of switched capacitors.
4 more elements
Dependencies are inferred from the claim text.