Apparatus and method for duty cycle conversion

A cellular telephone comprising:

• a voltage regulator capable of receiving a supply voltage from a battery of said cellular telephone and generating a regulated output voltage;
• analog-to-digital circuitry capable of converting analog signal in said cellular telephone to digital signals;
• and
• a reference signal generator capable of supplying an output reference signal having a target duty cycle to said voltage regulator and said analog-to-digital circuitry, said reference signal generator comprising:
• a sawtooth generator capable of receiving an input reference signal having a reference frequency and generating a sawtooth waveform having said reference frequency;
• first comparison circuitry capable of comparing said sawtooth waveform to a reference voltage and generating said output reference signal, wherein said output reference signal is Logic 1 when said sawtooth waveform is greater than said reference voltage and said output reference signal is Logic 0 when said sawtooth waveform is less than said reference voltage;
• and
• feedback circuitry capable of determining a duty cycle of said output reference signal by comparing a first time period when said output reference signal is Logic 1 to a second time period when said output reference signal is Logic 0, wherein said feedback circuitry adjusts a value of said reference voltage to cause said output reference signal to achieve said target duty cycle.

A method of generating an output reference signal having a target duty cycle comprising the steps of:

• receiving an input reference signal having a reference frequency and generating therefrom a sawtooth waveform having the reference frequency;
• comparing the sawtooth waveform to a reference voltage and generating the output reference signal, wherein the output reference signal is Logic 1 when the sawtooth waveform is greater than the reference voltage and the output reference signal is Logic 0 when the sawtooth waveform is less than the reference voltage;
• determining a duty cycle of the output reference signal by comparing a first time period when the output reference signal is Logic 1 to a second time period when the output reference signal is Logic 0;
• and
• adjusting a value of the reference voltage to cause the output reference signal to achieve the target duty cycle.

A reference signal generator for generating an output reference signal having a target duty cycle, said reference signal generator comprising:

• a sawtooth generator capable of receiving an input reference signal having a reference frequency and generating a sawtooth waveform having said reference frequency;
• first comparison circuitry capable of comparing said sawtooth waveform to a reference voltage and generating said output reference signal, wherein said output reference signal is Logic 1 when said sawtooth waveform is less than said reference voltage and said output reference signal is Logic 0 when said sawtooth waveform is greater than said reference voltage;
• and
• feedback circuitry capable of determining a duty cycle of said output reference signal by comparing a first time period is when said output reference signal is Logic 1 to a second time period when said output reference signal is Logic 0, wherein said feedback circuitry adjusts a value of said reference voltage to cause said output reference signal to achieve said target duty cycle.

A cellular telephone comprising:

• a voltage regulator capable of receiving a supply voltage from a battery of said cellular telephone and generating a regulated output voltage;
• analog-to-digital circuitry capable of converting analog signal in said cellular telephone to digital signals;
• and
• a reference signal generator capable of supplying an output reference signal having a target duty cycle to said voltage regulator and said analog-to-digital circuitry, said reference signal generator comprising:
• a sawtooth generator capable of receiving an input reference signal having a reference frequency and generating a sawtooth waveform having said reference frequency;
• first comparison circuitry capable of comparing said sawtooth waveform to a reference voltage and generating said output reference signal, wherein said output reference signal is Logic 1 when said sawtooth waveform is less than said reference voltage and said output reference signal is Logic 0 when said sawtooth waveform is greater than said reference voltage;
• and
• feedback circuitry capable of determining a duty cycle of said output reference signal by comparing a first time period when said output reference signal is Logic 1 to a second time period when said output reference signal is Logic 0, wherein said feedback circuitry adjusts a value of said reference voltage to cause said output reference signal to achieve said target duty cycle.