US Patent 11671238 Secondary phase compensation assist for PLL IO delay

A line card of a network box receives a SYNC input signal and generates a first time stamp based on receipt of the SYNC input signal. The line card generates a system clock signal in a phase-locked loop and generates a SYNC output signal by dividing the system clock signal in a divider circuit. The SYNC output signal is fed back to an input terminal as a SYNC feedback signal. A time stamp is generated based on receipt of the SYNC feedback signal. The line card determines a time between the SYNC input signal and the SYNC feedback signal based on the first time stamp and the second time stamp. The timing of the SYNC output signal is adjusted based on the time difference using a coarse time adjustment by adjusting a divide ratio of the divider circuit and using a fine time adjustment in the phase-locked loop based on a residue of a remainder of the time difference not accounted for by the coarse time adjustment.