VCO CENTERING CIRCUIT

摘要

VCO CENTERING CIRCUIT A circuit arrangement for recovering data from a communications network includes a phase lock loop (PLL) with a voltage controlled oscillator (VCO) and a circuit for automatically centering the VCO. The circuit arrangement includes a counter that stores a changeable digital word. The digital word provides an adjustable current for driving the VCO. Initially, the VCO is driven so that its output signal falls within a predetermined frequency range. An error voltage representing the difference between a predetermined voltage range is developed and is used to change the contents of the counter until the VCO is centered. Thereafter the count that causes centering of the VCO is locked in the counter and normal PLL function is enabled.