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 a flow of a third current therethrough that varies with the voltage drop, wherein the first tuning bank includes a plurality of resistors, the first tuning bank is configured to generate the third current by selectively connecting one or more resistors to the voltage node in response to the tuning signal, and the third current is a function of the voltage drop and a resistance of the one or more connected resistors;
• 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 an 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 a flow of a first current through the one or more resistors that varies with the voltage drop, wherein the first current is a function of the voltage drop and a resistance of the one or more connected resistors;
• and
• fine-tuning the oscillator output signal based on the first current to track a frequency of the reference input signal.