Digital VCO calibration method and apparatus

A method comprising:

• asserting a first indication if a voltage controlled oscillator (VCO) gain is above a specified gain value;
• adjusting, upon an occurrence of at least a first cycle of a clock signal concurrent with providing the first indication, the VCO gain responsive to a comparator asserting the first indication, wherein said adjusting comprises a control circuit changing a digital code output therefrom, wherein adjusting the VCO gain is performed by adjusting an output current provided by a digital-to-analog converter (DAC) responsive to said asserting the first indication, wherein adjusting the output current causes a change of value of a second voltage;
• repeating said comparing, said providing the first indication, and said adjusting the VCO gain upon occurrence of each of one or more successive cycles of the clock signal until the VCO gain is below the specified gain value, wherein determining whether the VCO gain is below the specified gain value is performed by determining whether a first voltage is above a specified voltage;
• asserting a second indication and de-asserting the first indication responsive to the VCO gain is below the specified gain value, said asserting and de-asserting being performed by the comparator;
• and
• discontinuing said adjusting responsive to said asserting the second indication, wherein said discontinuing comprises discontinuing changes to the digital code output from the control circuit.

A non-transitory computer readable medium comprising a data structure which is operated upon by a program executable on a computer system, the program operating on the data structure to perform a portion of a process to fabricate an integrated circuit including circuitry described by the data structure, the circuitry described in the data structure including:

• a comparator configured to provide a first indication if a VCO (voltage controlled oscillator) gain is above a specified gain value, and a second indication if the VCO gain is below the specified gain value, and further configured to determine whether the VCO gain is above the specified gain value by determining whether a first voltage is less a specified voltage, wherein the specified voltage is defined by at least a reference voltage, wherein the comparator is configured compare the first voltage to the reference voltage in order to determine whether the first voltage is less than the specified voltage;
• a control unit configured to, upon an occurrence of at least a first cycle of a clock signal, cause an adjustment of the VCO gain responsive to receiving the first indication, wherein the control unit is configured to cause adjustment of the VCO gain by changing a value of a digital code output therefrom, wherein, upon occurrence of one or more successive cycles of the clock signal, the control unit is configured to cause corresponding additional adjustments of the VCO gain until the comparator provides the second indication, wherein the control unit is further configured to discontinue causing adjustments to the VCO gain responsive to the comparator providing the second indication, wherein the control unit is configured to discontinue causing adjustments to the VCO gain by discontinuing changes to the digital code;
• a digital-to-analog converter (DAC), wherein the control unit is configured to cause an adjustment of an output current provided by the DAC responsive to receiving the first indication from the comparator, wherein adjusting the output current of the DAC causes a change of value to a second voltage, wherein a frequency of an output signal provided by the VCO described in the data structure is dependent upon the second voltage;
• and
• a charge pump configured to cause an adjustment of the first voltage responsive to the change of value of the second voltage, wherein adjusting the first voltage causes the second voltage to return to its value prior to adjusting the output current.