Multi-mode crystal oscillator system selectively configurable to minimize power consumption or noise generation

A power supply configurable to alternatively operate in at least two modes of operation wherein in a first mode of operation, power consumption is minimized;

• and in a second mode of operation, noise generation is minimized, said power supply comprising:
• a switching downconverter for operating in said first mode of operation;
• and
• a series downconverter for operating in said second mode of operation.

A crystal oscillator having an adjustable frequency output, said crystal oscillator comprising:

• a crystal having first and second interconnection nodes;
• a programmable capacitance comprised of a plurality of capacitors that are programmably coupled to a selected one of said interconnection nodes of said crystal, whereby the frequency of said crystal oscillator is adjusted;
• and wherein
• said crystal oscillator includes a crystal having a series resonant frequency below a target frequency and said crystal oscillator is configured to operate in a parallel resonant mode at a frequency above said series resonant frequency and said circuitry for adjusting the frequency of said crystal oscillator causes the frequency of said oscillator to be programmably adjusted toward the target frequency.

A crystal oscillator having an adjustable frequency output, said crystal oscillator comprising:

• a crystal having first and second interconnection nodes;
• a programmable capacitance for coupling to a selected one of said interconnection nodes of said crystal, whereby the frequency of said crystal oscillator is adjusted;
• measurement circuitry for periodically measuring a frequency error signal wherein said programmable capacitance is adjusted in response to said error signal to cause said frequency error signal to decrease;
• and wherein
• said programmable capacitance is adjusted to minimize said frequency error signal over a series of measurements and said measurement circuitry periodically measures said frequency error signal by determining a baud timing error relative to an external reference.

A crystal oscillator having an adjustable frequency output, said crystal oscillator comprising:

• a crystal having first and second interconnection nodes;
• a programmable capacitance for coupling to a selected one of said interconnection nodes of said crystal, whereby the frequency of said crystal oscillator is adjusted;
• measurement circuitry for periodically measuring a frequency error signal wherein said programmable capacitance is adjusted in response to said error signal to cause said frequency error signal to decrease;
• and wherein
• said programmable capacitance is adjusted to minimize said frequency error signal over a series of measurements and said measurement circuitry periodically measures said frequency error signal by determining a baud timing error relative to a fixed reference in a communication protocol controlled by an external source.

A crystal oscillator having an adjustable frequency output, said crystal oscillator comprising:

• a crystal having first and second interconnection nodes;
• a programmable capacitance for coupling to a selected one of said interconnection nodes of said crystal, whereby the frequency of said crystal oscillator is adjusted;
• measurement circuitry for periodically measuring a frequency error signal wherein said programmable capacitance is adjusted in response to said error signal to cause said frequency error signal to decrease;
• and wherein
• said programmable capacitance is adjusted to minimize said frequency error signal over a series of measurements and said measurement circuitry periodically measures said frequency error signal by determining a baud timing phase error relative to a fixed reference in a communication protocol controlled by an external source.