Patent ID: 8031011
Filing Date: 2011-10-04
Classification: H03K,H03L

Abstract:
1. A method of adjusting an output signal frequency in an oscillator formed from a ring of inverters coupled to adjustable load capacitors, wherein each capacitor of the adjustable load capacitors comprises a plurality of parallel-coupled varactors, wherein each varactor of the parallel-coupled varactors has a digital control input operable to receive a digital control signal, comprising: applying a first digital control word formed from first digital control signals to a first of the adjustable load capacitors operable to direct that first capacitor to produce a first capacitance value, wherein applying the first digital control word to the first of the adjustable load capacitors comprises applying the first digital control signals to the digital control inputs of the parallel-coupled varactors of the first of the adjustable load capacitors; applying a second digital control word formed from second digital control signals to a second of the adjustable load capacitors operable to direct that second capacitor to produce a second capacitance value that is different from the first capacitance value, wherein applying the second digital control word to the second of the adjustable load capacitors comprises applying the second digital control signals to the digital control inputs of the parallel-coupled varactors of the second of the adjustable load capacitors; and ensuring that the first digital control word and the second digital control word contain respective numbers of logic high signals that differ by no more than one.