A fractional-n frequency synthesizer based on a charge-sharing locking technique

A method of charge-sharing locking for use in a PLL;

• the method comprising:
• providing a voltage pre-setting stage;
• providing an oscillator;
• providing a shared capacitive load operably coupled between the voltage pre-setting stage and the oscillator;
• selectively connecting the voltage pre-setting stage to the shared capacitive load during a first phase for applying an expectant voltage to the capacitive load, wherein the expectant voltage is pre-set on the capacitive load based on an expected output voltage of the oscillator;
• and
• selectively connecting the capacitive load to the oscillator for phase error correction during a second phase in response to a voltage difference between the expected voltage of the capacitor and the voltage of the oscillator.

A phase-locked loop (PLL) for charge-sharing locking;

• the PLL comprising:
• a voltage pre-setting stage;
• an oscillator;
• a shared capacitive load;
• and
• a switching network configured for selectively connecting the voltage pre-setting stage to the shared capacitive load during a phase of voltage pre-setting for applying an expectant voltage to the capacitive load;
• the switching network being further configured for selectively connecting the capacitive load to the oscillator during a phase of charge-sharing locking for correcting a phase error in response to a difference between the expected voltage of the capacitor and the output voltage of the oscillator.

A method of charge-sharing locking for use in a PLL;

• the method comprising:
• providing a voltage pre-setting stage;
• providing an oscillator;
• providing a shared capacitive load;
• selectively connecting the voltage pre-setting stage to the shared capacitive load during a first phase for applying an expectant voltage to the capacitive load;
• and
• selectively connecting the capacitive load to the oscillator for phase error correction during a second phase in response to a voltage difference between the expected voltage of the capacitor and the voltage of the oscillator.