Device for calibrating the frequency of an oscillator, phase looked loop circuit comprising said calibration device and related frequency calibration method
First Claim
1. A device for calibrating the frequency of an oscillator having a first and a second input and generating an output frequency as a response to a first voltage signal applied at said first input and an output digital signal applied at said second input of the oscillator for calibrating the output frequency, said calibration device comprising:
- a counter having a first input frequency proportional to a reference frequency and a second input frequency proportional to the output frequency of the oscillator, said counter counting a time window number given by the ratio of the second input frequency to the first input frequency;
comparing means for comparing said counted time window number with a reference time window number; and
means for changing a value of said output digital signal if said counted time window number is different from said reference time window number and until said counted time window number is equal to said reference time window number.
1 Assignment
0 Petitions
Accused Products
Abstract
A device calibrates the frequency of an oscillator. The oscillator has first and second inputs and generates an output frequency responsive to a first voltage signal at the first input. The calibration device generates a calibration signal applied at the second input of the oscillator for calibrating its output frequency and comprises a counter. The counter has a first input frequency proportional to a reference frequency and a second input frequency proportional to the output frequency. The counter counts the time window number given by the ratio of the second to first frequencies. The device comprises a comparator that compares the counted time window number with a prefixed time window number. The calibration device changes the value of the calibration signal if the counted time window number is different from the prefixed time window number and until the counted time window number is equal to the prefixed time window number.
-
Citations
19 Claims
-
1. A device for calibrating the frequency of an oscillator having a first and a second input and generating an output frequency as a response to a first voltage signal applied at said first input and an output digital signal applied at said second input of the oscillator for calibrating the output frequency, said calibration device comprising:
-
a counter having a first input frequency proportional to a reference frequency and a second input frequency proportional to the output frequency of the oscillator, said counter counting a time window number given by the ratio of the second input frequency to the first input frequency; comparing means for comparing said counted time window number with a reference time window number; and means for changing a value of said output digital signal if said counted time window number is different from said reference time window number and until said counted time window number is equal to said reference time window number. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. A phase looked loop circuit, comprising:
-
an oscillator having first and second inputs and generating an output frequency as a response to a voltage signal applied at said first input, said voltage signal being a reference voltage signal during a calibration phase; a low-pass filter coupled to said first input of the oscillator during a phase-lock phase and structured to generate a low pass signal as the voltage signal applied to said first input during the phase-lock phase; a phase detector that determines a phase difference between a reference frequency and a frequency deriving from the output frequency of the oscillator and generating a signal as a response to said phase difference; a calibration device that generates a calibration signal applied at the second input of the oscillator for calibrating the output frequency, said calibration device including; a first counter having a first input frequency proportional to said reference frequency and a second input frequency proportional to the output frequency of the oscillator, said counter counting a first time window number given by the ratio of the second to the first frequency first comparing means for comparing said first time window number with a first reference time window number; and means for changing a value of said calibration signal if said first time window number is different from said first reference time window number and until said first time window number is equal to said first reference time window number. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
-
-
17. A method for calibrating a frequency of an oscillator belonging to a phase looked loop circuit, said method comprising
applying a reference voltage signal at a first input of the oscillator; -
generating a calibration signal applied at a second input of the oscillator; generating an output frequency of the oscillator depending on the applied calibration signal; counting a time window number given by a ratio of a first input frequency, proportional to a reference frequency, to a second input frequency proportional to the output frequency of the oscillator;
comparing said time window number with a reference time window number; andchanging the value of said calibration signal if said counted time window number is different from said reference time window number and until said counted time window number is equal to said reference time window number. - View Dependent Claims (18, 19)
-
Specification