Xilinx, Inc.
METHOD AND APPARATUS FOR A PHASE LOCKED LOOP CIRCUIT

Abstract:

A phase locked loop (PLL) circuit includes a voltage controlled oscillator (VCO), a first loop circuit, and a second loop circuit. The first loop circuit includes a first loop filter configured to receive a first signal based on a feedback signal from the VCO and provide a first VCO frequency control signal to the VCO. The second loop circuit includes a compensation circuit configured to receive a reference signal and the first signal, and provide a second VCO frequency control signal to the VCO.