Cadence Design Systems, Inc.
Dual path phase-locked loop circuit

Abstract:

Aspects of the present disclosure include a dual path phase locked loop (PLL) circuit with a switched capacitor filter topology along with systems, method, devices, and other circuits related thereto. The dual path PLL circuit includes an integral path and a proportional path. Both the integral path and proportional path include a charge pump and a loop filter. The outputs of a phase frequency detector (PFD) are sent to both charge pumps. The output of the integral path charge pump is connected to a capacitor, and the voltage on capacitor is used as the integral path control voltage for a voltage-controlled oscillator (VCO). A switched capacitor network is connected to the output of the proportional path charge pump and used to generate the proportional path control voltage for the VCO. Together, the two control voltages dictate the VCO's output frequency.