System and Method for Synchronizing an Oscillator Output Signal with Reference Input Signal

An oscillator circuit comprising:

• a current mirror including:
• a master transistor configured to generate a first current;
• and
• a slave transistor configured to generate a second current that mirrors the first current;
• a first tuning bank connected to the master transistor at a voltage node and configured to receive a tuning signal, to generate a voltage drop at the voltage node that corresponds to the tuning signal, and to allow the flow of a third current therethrough that varies with the voltage drop;
• a second tuning bank connected to the voltage node and configured to receive an oscillator input signal and to regulate a fourth current that flows therethrough in response to a voltage difference between the voltage drop and an oscillator input signal;
• and
• a current-controlled oscillator connected to the slave transistor and configured to fine-tune the oscillator output signal based on the second current to track a frequency of the reference input signal.

A method for synchronizing an oscillator output signal with a reference input signal, the method comprising:

• operating a first control loop in a frequency tracking mode;
• detecting a frequency difference between a reference input signal and an oscillator output signal;
• generating a tuning signal based on the reference input signal and the detected frequency difference;
• in response to the tuning signal, selectively connecting one or more resistors to a voltage node to generate a voltage drop at the voltage node and allow the flow of a first current through the one or more resistors that varies with the voltage drop;
• and
• fine-tuning the oscillator output signal based on the first current to track a frequency of the reference input signal.