Method and system for calibration of a voltage controlled oscillator (VCO)

• US 20050040900A1
• Filed: 08/20/2003
• Published: 02/24/2005
• Est. Priority Date: 08/20/2003
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Ignowski, James S., Naffziger, Samuel D., Bostak, Christopher J., Poirier, Christopher A.
• Granted Patent: US 7,091,796 B2
• Time in Patent Office: Days
• US Class Current: 331/44
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence
• CPC Class Codes: H03M 1/1038 by storing corrected or correction values in one or more digital look-up tables H03M1/1057 takes precedence
• CPC Class Codes: H03M 1/60 with intermediate conversion to frequency of pulses

Abstract

A method for calibrating a voltage controlled oscillator (VCO) comprising applying a plurality of known voltages to the input of a VCO, monitoring, for each of the voltages, an output count from the VCO over a set interval, and storing the output counts for each voltage. Also disclosed is a system for calibrating a voltage controlled oscillator (VCO) comprising a plurality of known voltages, wherein the known voltage are connectable to the VCO, and a controller coupled to the output of the VCO, wherein the controller maintains a calibration table of VCO output counts for selected voltage inputs.

Claims

1. A method for calibrating a voltage controlled oscillator (VCO) comprising:

applying a plurality of known voltages to the input of a VCO;

monitoring, for each of the voltages, an output count from the VCO over a set interval; and

storing the output counts for each voltage.

2. The method of claim 1 further comprising:

providing a serial resistance ladder having a plurality of equal resistors, wherein the known voltages are available from between each of the resistors.

3. The method of claim 2 wherein the serial resistance ladder and the VCO are constructed on the same integrated circuit.

4. The method of claim 1 further comprising:

interleaving a VCO calibration cycle in which known input voltages are substituted for measurements of unknown input voltages.

5. The method of claim 1 further comprising:

repeating calibration operations for the same known input voltage at periodic intervals to compensate for variations in operating conditions.

6. The method of claim 1 further comprising:

applying an unknown voltage to the VCO input;

monitoring an unknown output count from the VCO over a set interval; and

comparing the unknown output count to a table of stored output counts.

7. The method of claim 6 wherein the unknown voltage is measured across a sense resistor with a known resistance, and further comprising:

determining the value of the unknown voltage by relating it to a known voltage that has an equivalent output count; and

calculating a current through the sense resistor using the known resistance and a value determined for the unknown voltage.

8. A system for calibrating a voltage controlled oscillator (VCO) comprising:

a plurality of known voltages, wherein the known voltage are connectable to the VCO; and

a controller coupled to the output of the VCO, wherein the controller maintains a calibration table of VCO output counts for selected voltage inputs.

9. The system of claim 8 further comprising:

a resistance ladder having a plurality of voltage taps, wherein the voltage taps provide the known voltages.

10. The system of claim 9 wherein the VCO, the resistance ladder and the controller are constructed on the same integrated circuit.

11. The system of claim 8 further comprising:

a plurality of VCOs; and

wherein the controller maintains a separate calibration table for each of the VCOs.

12. A computer program product comprising a computer usable medium having computer readable program code embedded therein, the computer readable program code comprising:

code for selecting a voltage to be applied to inputs of a plurality of voltage controlled oscillators (VCOs);

code for monitoring output counts from each of the plurality of VCOs over a set period of time, while the selected voltage is applied to the VCOs'"'"' inputs; and

code for storing, for each of the plurality of VCOs, a table of output counts associated with the selected voltage.

13. The computer program product of claim 12 wherein the voltage is selected from one of a plurality of voltage taps on a serial resistance ladder, wherein the voltage taps provide known voltages.

14. The computer program product of claim 12 further comprising:

code for interleaving a VCO calibration cycle during which with other VCO measurements.

15. A system for calibrating a voltage controlled oscillator (VCO) comprising:

means for applying a plurality of known voltages to the input of a VCO;

means for monitoring, for each of the voltages, an output count from the VCO over a set interval; and

means for storing the output counts for each voltage.

16. The system of claim 15 further comprising:

means for interleaving a VCO calibration cycle in which known input voltages are substituted for measurements of unknown input voltages.

17. The system of claim 15 further comprising:

means for repeating calibration operations for the same known input voltage at periodic intervals to compensate for variations in operating conditions.

18. The system of claim 15 further comprising:

means for applying an unknown voltage to the VCO input;

means for monitoring an unknown output count from the VCO over a set interval; and

means for comparing the unknown output count to a table of stored output counts.

19. The system of claim 18 wherein the unknown voltage is measured across a sense resistor with a known resistance, and further comprising:

means for determining the value of the unknown voltage by relating it to a known voltage that has an equivalent output count; and

means for calculating a current through the sense resistor using the known resistance and a value determined for the unknown voltage.